My turn for the Evaporator Party
 

1990 124 300E. AC won't hold a charge. Significant leak.

I've been told that the definitive confirmation for the leaking evaporator is to remove the blower motor and look at the evaporator. I did. The photos are below. You can see that one side is nasty and oily with lots of crud stuck to it. The other side is clean. Does anyone agree or disagree that this evaporator is leaking?

Of course, MBUSA told me awhile back that they never heard of a leaking evaporator in one of their cars so if mine is indeed leaking, it will, I guess, be the first one ever to leak. Just like the upper neck on my radiator was the very first one that ever broke off. :lol:

Everything is starting to look so old in there, I wonder if I should even do this job. It's the challenge I suppose. And there's no car payment. That's nice. The car still runs great and the general public doesn't even know it's 17 years old. I think these 124s still look good. And of course, it would cost as much to have this done as the car is worth. Probably more. OK, I've had this car a long time and I still love it.

So, a couple of questions before I start the Big Project. Should I just leave the blower motor out and proceed, or put the blower motor and wiper motor and all those parts back together first, before I forget how they go together? Any advantage to having the blower motor out already?

Is it better to remove the front seats or leave them in place?

Is it better to leave the car flat on the ground or to drive it up on ramps in the front to elevate the work area a bit?

Any other comments or suggestions? Did anyone ever do a complete DIY on this job?

Which evaporator is best for a replacement?

What questions have I forgotten to ask?

Thanks

Evaporator for 124
 

If it isn't leaking now, it will. I assume you did this effort as a result of insufficient cooling or none at all.

Replace with an ACM evap that has the expansion valve attached.

Replace receiver drier and make sure your pressure switch on the drier is the red one or you need to replace that at the same time. I have an extra on if you wish to purchase.

My water hoses were a bit difficult to disconnect, but I removed battery to get better access and got it. I ended up taking the battery tray out and cleaning and repainting. Ever read the book "If you give a pig a pancake"

Order a oring kit for your heater core and replace the o-rings as an extra preventive maintenance.

Yes take the fan out to help you remove the box.

Leave the seats in place.

Replace all the vacuum pods while you have the dash out.

Get the printouts from the CD for all steps.

Take digital pictures of every screw you remove, because there are probably 6-7 different types.

There is a caution on removing the leg room flap arm so the plastic piece is not broken.

Everything is just like the book says, straight forward and no MB tools or MB 40 hr training required.

Inspect the shifter bushings when you disconnect the speedo from the tranny.

Put a few drops of ATF on the fan motor bearings while it is out.

Replace cabin air filters.

Use a pry bar like a Super bar to release the box from the firewall

You will need to replace the weatherstripping around the evap box. Cannot get this from MB. I went to Lowes. I think I used 3/4" wide and maybe 1/2" thick. I would not use plumbers putty as the sealer as it is not intended for plastic and non-stainless parts (unless you find a less acidic type). I used silicone based caulk - little messy if you aren't careful.

I never found the plug for the center vent dial light, so I cut the wire and reattached.

There are a lot of plugs to disconnect, so make sure you reconnect them all. I had forgotten the cigarette lighter and I had to remove the console again to find it.

I am sure I left something out, but plan well and take your time.

PS I have just completed mine and I think I might have damaged my ignition switch as a result of not removing it per the instructions. See my post on my fan acting irratic.

http://www.peachparts.com/shopforum/tech-help/176064-94-e320-acc-fan-irratic-after-evaporator-replacement.html

Olin

Hi
I did mine about three months ago. Olin made very good comments already. The job is not that difficult, but time consuming (22 hours). BTW, everyone will be impressed after you show them a pic with everything disassembled. The car is better left on the ground. I'd leave the front seat in. But removing the steering wheel helps. This is also what the manual recommends. I took pictures from the vacuum lines and how they are connected. I screwed the fasteners back to their place where possible or attached them with tape. Be careful when disassembling the heater box, there are some clips and plastic that can break.
Good luck, Bruno

I am a DIY'er and I did it a few year back...
 

The only thing I have to add is: use zip-lock bags to label and separate your bolts and smalls parts I would check the compressor and old the AC lines since if the evaporator goes, the compressor is not far behind (do a search on black death). I did not remove the steering wheel, I just extended it as far out as it would go...same thing with the seats, bring them as far back as they would go...

I've found this procedure to be like dealing with a hundred little jigsaw puzzles. As I go along, I am always impressed with the engineering expertise that went into this car. Like a fine watch.

Anyway, this little puzzle I have not figured out yet: See the piece of ductwork in the photo with the yellow "X" on it? After you remove the one screw in the floor, how do you get that out?

Just curious, has anyone experienced a failure of their replacement evaporator?

Thanks

carefully,you have to make old brittle plastic give just enough to get it out. going back is the fun part.

OK, I figured out that to remove the ductwork above, you have to first remove the piece below that goes under the seats. No easy task. The plastic was not brittle at all, though, even after 17 years.

My toughest puzzle so far...the dash would NOT come out. Why? It seems that the guy who replaced my windshield a while back glued parts of the dash in for me. No extra charge.

I did not remove the steering wheel. I was going to but couldn't get the bolt loose. I figured I'd come back to it later but it turned out that it was no problem. I did remove the ignition switch.

I used a bit of compressed air to blow out the heater core so I wouldn't spill coolant in the car.

I've ordered ACM evap w/expansion valve and all new pods and a dryer and pressure switches.

I haven't broken anything. The drain hoses are one thing that deteriorated over time and have to be replaced.

It sure feels like I've gotten up close and personal with this car!

For the drain hoses...
 

You can get something better. I replaced them with plastic/rubber hoses from the plumbing department at Home Depot. it will outlast the car for sure...:D

I found the following interesting post on one of the newsgroups....Perhaps blaming it on mites is easier than admitting copper does not play well with aluminum. Our maybe mites really do eat Mercedes-Benz evaporators. Who am I to say?

I've seen and replaced the evaporator core on countless 140 body Mercedes.
It is a problem that Mercedes-Benz is aware of and has released an
"unofficial" explanation for: the Southeastern US has a particular variety
of mites that apparently "eats" and "digests" the bare aluminum. The result
is a hole that develops in the evaporator core and allows the R134A
(refrigerant) to leak. The new parts that are being installed are "mite
resistant" - no kidding. The parts are dipped in plastic and coated with
chemicals. By the way, the 124 body Mercedes has had this problem for
years. I have heard some new Mercedes have actually lost the refrigerant on
the new car lot before it was sold. If your car is out of warranty there is
no alternative for repair payment. If you have an extended warranty, that
company should pick up the expense. If you have any other questions check
us out at www.peachparts.com.

Benzmac

As my wife says, I have completed my Journey to the Center of the Earth.

The evaporator pics are below.

Obviously leaking on the left side. Tough to tell exactly where, though. I expected to find the leak at one of the copper/aluminum joints but I don't believe that is the case. Looks like the leak is probably out in one of the tubes near the top.

There's less copper in the evap than I expected. Only the parts in the pics. The other end was completely aluminum. Maybe it was mites after all!

I have the MB Climate Control service book. While it does give procedures to replace the heater core and is quite thorough with all the AC items, there is no mention of replacing the evaporator. The heater core can be replaced with the box in the car but replacing the evaporator is a really huge job because it is absolutely buried. It really does seem like MB never expected these evaporators to be a problem. Surprise, surprise!

significant damage? or not?
 

New parts arrived today. ACM evaporator with expansion valve installed.

Problem is, one of the tubes was bent in shipping. I know the tubing these are made of is thick and the passageway is small. I'm concerned about an obstruction here. This one might be closed entirely. In the pic below, what do you think? I'll have to wait another week to get a new one but I'm afraid this evap might freeze across the middle because of the obstruction. I do not want to do this job twice because of a faulty part.

Also, the expansion valve says R134A on it. Does that mean it will work with both R12 AND R134A, or ONLY R134A? Mine is an original R12 system and is going to stay that way.

Thanks!

It's damaged you need a new one. I don't know who you're dealing with but they should be able to send a new one out right away and credit you for the old one when they get it back.

Do you think that dent happen when it was made? That's kind of what it looks like. Was the packing material damaged in the area of the dent?

I think that expansion valve will also work for R12.

EPC lists two different expansion valves for 1990 W124:
201 830 06 84 for R12 only
140 830 04 84 for R134 only

the 134a valve works fine with r12 you will not notice any diff.i would not install that evap make them replace it.btw i looked at the pics of the old evap and can see where the epoxy dissappeared where the copper fits into the aluminum.benz did not know that long term the 134a would compromise the epoxy[neither did anyone else]but they knew that aluminum would transfer heat much better than copper and was half the weight.

The new ACM core came in a sealed box that looks like it was probably a factory box with an official-looking ACM label. Unfortunately, they just put it in the box, the fit was very loose and the core was able to bang around inside the box. There was virtually no packing material in the box...only one piece of thin cardboard that wrapped around the core. Damage was almost inevitable.

Meanwhile, the much less delicate and much less expensive dryer came in a specially-made box that held it place very, very securely.

Regarding the 134A eating the epoxy, mine has always been an R12 system. Wonder what went wrong?

How much oil should I add back to this system? Replacing evaporator, expansion valve and receiver/dryer.

The manual (83-525) calls for 50ml (or 60ml when system was emptied by leak)
 

40ml for the evaporator and 10ml for the receiver/drier. This is for part exchanges. An extra 10ml is added when refrigerant (and some oil) was lost due to a leak. Total volume of the system is 120ml (4 ounces).
Bruno

External corrosion due to mold. Mold will form corrosion 'cells' that will 'eat' right through the aluminum--probably where the 'South has aluminum eating mites' comment came from.

While I have been very impressed with MB engineering, fit and finish as I've worked through this project, there are a couple of things that have been lacking, IMHO. One of them is the AC condensate drains. The originals are delicate foam with springs inside to support them. You can see the remains of one in the first photo. You can also see the consequences of it leaking onto the floor under the mats. I went to Lowe's plumbing dept and bought some plastic tubing, 3/4"ID and 1"OD. See the second photo. The fit is perfect. Be sure to warm the hose up a bit in hot water and installation is a snap. I am confident that this will not leak. Cost was $1.13 total as opposed to about $11 per side for the original foam hoses.

I can't believe that you're bastardizing such a fine car with " Lowes " parts. :D
Sure give you a lot of credit for your courage, tackling this project. ;)

The first sentence in the quote above is INCORRECT! Not ALL 124 evaporators will leak. Yes, this is most definitely a terrible achilles heel of the 124 MB, but that DO NOT ALL leak or eventually develop leaks. My 88 300E still has the original evaporator and it is still tight. I have had and repaired other leaks and at those times it was difficult to keep from assuming that the problem was the evaporator but it was not.

One time, the expansion valve was leaking and the other time the condensor was leaking.

DO NOT replace a 124 evaporator without CONFIRMING that it is leaking. Use a sniffer and UV dye both. BE SURE!

Oh man!!! I hope that when you put your benz back together it will still drive quiet like a benz without the squeaks and rattles that haunts other makes. I really feel sorry for you already.

There will be no rattles. There will be no leftover parts.

Actually, the way this thing is engineered, I think it would be hard for anything to rattle, especially if reassembled with reasonable care.

larry,i agree that not all evaporators will leak.mine did but only after i made the mistake of trying out one of the blended refrigerants that contain mostly 134a.3 days after filling with fr-12 mine lost it all .tracked it down to the interaction of 134a with epoxy used to seal the u tubes at the ends.moral----if you dont want to change an evap stick with r12.

A few odds and ends for those who do this job...

Not really necessary to remove the steering wheel. I could not get the bolt loose even with an impact wrench.

Do remove the ignition switch from the column. It's easy. The retaining pin fell out of mine so watch out. You will have a rough time getting the heater box out with the ignition switch in the way.

The A-pillar trim is removed by pulling straight toward the back of the car. The two clips hold it firmly. Replacing it requires attention. I had to remove the visors and lower the top molding to get it back under at the top. Don't worry, the VIN tag that has to be bent forward will bend right back into place after you replace the A-pillar trim.

I used an ACM evaporator. It almost fit. The difference was mostly in the area of the expansion valve...it sat further back than the original. I had to loosen the clamp that holds the low-side pipe and slide it towards the firewall. The inlet and outlet pipes were a bit different. I had to use a bit of sealer in the gaps.

Pay attention when disassembling the heater box. Tons of screws and clips. There's more to it than you would expect and by the time you get to that part of the job you are in a hurry to finally get that damn evaporator out! Just remove everything from the outside of the box and it really will split open so you can get to the evap. Just take it easy and DON'T force anything. The heater core stays in place unless you are replacing it (you can replace the heater core without removing the heater box from the car). As everyone says, replace the vacuum pods. All of my dual-chamber pods were bad; all the others were ok. You can probably not bother with the footwell and diverter flap pods if yours are good. The diverter valve seems to rarely operate and the footwell is not too hard to get to in the car. Certainly do the center flap pod or you will be sorry if you have to replace it later, unless you have the hands of a munchkin. Test all the new pods with a MityVac. Then test them again right before you reinstall the box in the car. Being cowardly, I replaced ALL my pods, BTW.

You cannot take too many photos. I was SURE I had taken plenty but I still missed some things.

Leave the seats in. Put the car up on ramps and it will be easier all around.

Evidently the center vent light wire comes right out of the harness and has no end connector. Some people cut it. I removed the wheel from the center vent and left it in the car.

Be careful removing and fitting the dash and pay particular attention to easing the dash over the defroster outlets on the heater box.

One of the tougher puzzles on reassembly for me was the driver-side lower dash under the steering wheel. A word to the wise...put the black plastic front part in first. Hold your mouth just right and get everything positioned just so and get the fasteners in before anything moves. The passenger side is much easier.

When removing the floor ductwork, there is a secret little tab on the piece that goes under the seats. Gently bend it up to gain just enough clearance to get the two sections apart.

Toss the drain hoses and replace them with clear vinyl hose from Lowe's. 3/4" ID, 1" OD fits perfectly. I just saved you an hour - now you don't have to take the bottom of the case to Lowe's and try all the different ones.

When you drain the coolant, drain about a gallon out of the bottom of the radiator. Disconnect the driver-side heater hose and use compressed air to gently blow the coolant out of the heater core. This will save you from making a mess in the car.

Repair all the broken metal tabs on your AC vents with JB Weld. Reinforce the ones that have not broken yet with JB Weld.

The row of push buttons under the center vent? Remove the rocker switch on the right and the trick is...you remove the little panel by pushing it IN, not pulling it out.

There are FIVE NUTS that hold the heater box in.

Go ahead and remove the wiper for access. It will be easier than trying to get the blower power cable out of the firewall while you are trying to balance the heater box on its way out of the car. If you also remove the blower motor you will be able to see the evaporator to verify the leak and the box will be a bit lighter and a bit easier to remove.

I had plenty of bags ready for my fasteners but did not use the bag-and-label method. I simply replaced each fastener as I disassembled things and I think that is the best way to go.

Replace any burned out light bulbs while you are in there.

Go ahead and buy a little telescoping magnet to pick up those fasteners that get away.

Disconnect the battery and remove it for access to the heater hose on the right. Of course, you were going to disconnect the battery first thing, right? Good.

The panel with the window switches tilts to the side and stays in the car when the center console comes out.

Try to order your parts in advance so there will be no delays. You can forget a lot of assembly details while waiting for parts to arrive. Order the evaporator (w/expansion valve), pods, and drier. I replaced the pressure switches on the drier, too. You can test the pods before you ever take the car apart right through the glove box opening and determine which you need, if you are daring enough not to replace them all. If you buy an ACM evaporator, tell the seller to open the factory box, verify there is no damage and add packing material. Mine first one came with inadequate packing material to protect the evaporator.

I removed the center console first, before the dash to avoid damaging the top of the center console with the two bolts that stick down out of the dash.

No matter how careful you are, there will be times when you have to go back and disassemble what you just put together because something else needed to be assembled first.

When you restart the car, the coolant will be reluctant to flow thru the heater core. I ran the engine briefly up to about 1500 RPM and started the flow.

If you be careful and pay attention you really can do this job. I had the luxury of spending over three weeks on it, off and on. It is not a job I would want to be rushed on. Twelve days of that was spent waiting for parts and then replacements for damaged parts. It is a BIG job, no doubt about it. I had my trunk full of parts and the roof and truck lid covered with parts. It is a very satisfying job, though, and the labor savings are very significant. Replace your evaporator and you will surely feel like you have accomplished something.

I have lots of pics. Let me know if you need a pic of anything.

I have not replaced my evaporator, but I went all the way down to it in order to replace the vacuum pods and heater core. This was almost two years ago so I don't remember every detail.

I would suggest, however, that to prevent the problem in bold above, simply lay out the parts in order. I don't mean every little screw, but when you remove a piece, lay it and all the associated pieces at one end of the garage wall or somewhere. Then the next piece and it's hardware are laid down after that until you have a trail of pieces. Then when you go back together, you will put everything back in the correct order.

I have done this with most all major jobs over the years and it helps a LOT to keep from getting something on, only to have to remove it for the addition of another subassembly of some sort.

Also, it is unfortunate that brewtoo could not remove the steering wheel bolt. It is normally it only takes a minute to remove the steering wheel and get it the heck out of the way. ALWAYS, however, disconnect the airbag connector under the right floor mat FIRST. Also, lay the airbag down with the soft portion up. If it were to somehow go off, if the hard part is up, it will be a projectile.

Also, when loosening the steering wheel center bolt, hold the steering wheel with one hand and the wrench or ratchet with the other to prevent putting this load on the locking mechanism.

My $0.02,

All good points, Larry. Regarding the statement above, I would also suggest first turning the key to unlock the steering wheel, just to be sure the load cannot be transmitted to the locking mechanism.

And that's a good idea on the "trail of parts," too.

OK, time to replace the drier.

I removed the left headlight since, IMHO, it makes it SO much easier to get to the drier, fittings and wires. It just takes a minute to get the headlight out. I also removed the air filter housing so I could remove the intake ductwork.

I replaced both pressure switches.

For those doing the evaporator replacement...be sure to order ALL the o-rings that you will need in advance. I missed a couple.

I have a few R134 conversion questions that I have not found answers to in my search of this site.

The coil on my 190 has a leak and it needs to be replaced. My indi recommended that since the coil needs to be replaced and the cost of R12 is going up and up that I might as well convert to 134.

The indi told me that I would need to replace the coil. Dryer/receiver and expansion valve but not the hoses. I was under the impression from some of the things I have read that the hoses need to be replaced with 134 friendly hoses due to the fact that the 134 molecule is smaller than R12. So, do the hoses need to be replaced or not?

Most of the threads I found were a bit dated so I will ask this (I have a feeling I probably should not but what the hell), does anyone know how this will affect the cooling? I live in TX. I saw one thread where someone had a 190 and felt no ill effect as a result of the conversion.

Thanks

I just replaced my evaporator and I did NOT convert to 134. Did not even consider it.

I would think long and hard about converting. The condenser is too small, you will have to be sure that all the o-rings are the green ones rather than the original black ones. It is true about the 134 molecules being smaller but the hoses should be OK anyway, but not the o-rings. You have to be SURE to flush out all the original oil as it is not compatible.

I had a 300E that had been converted and it never did get very cold, although it did start eating compressors after the conversion. I had that one done by professionals. After the third compressor failed, they gave up and refunded my money.

With a conversion you have a good chance of not being happy with the performance. Especially in Texas where you need all the efficiency you can get.

R12 is what that sysem was designed for. You can't beat that wonderful 38-40' air coming out of that AC in the hot summer! 45-50' just ain't the same.

It's not worth the risk, IMHO, of course.

if you convert to 134a you will have about 70% of the efficiency that you had with r12.the cooling should be fine until the ambient temp goes above 94f then the condensing requirement of 134a goes off the scale.to convert properly you need to oversize all components by at least 50% and fit the barrier hose so that you wont need to fill the system every year.good luck finding a condensor with the required capacity.stick with r12,it's a much better refrigerant.

Thanks for the info. I guess the man thing I am concerned about is long term. I am planning on driving the car till the wheels fall off or I go broke. Which come first at this point is still somewhat of a debate. The car may cause me to go broke but I guess that belongs in another thread.

Anyway, I am concerned about R12 either going away entirely or being so bloody expensive that it is not worth. The argument being used for the conversion is that since I have to have it all replaced anyway (coil, dryer…. Etc) why not do the conversion now rather than maybe having to do it somewhere down line. If another component fails and I loose the R12 I have to get more.

Last summer, the car kept me comfortable in the TX heat. If I switch to R134 and I am not cool, I will be pissed and there will be a good chance that some crazy SOB on the freeway will piss me off and get shot in the process (I do not tolerate pin heads on the freeway very well…. Anger issues I guess) and then I go to jail, become someone's b!tch, loose the car, the wife, house, 5 cats and 1 dog, you see where this is going right? Ah, decisions? I guess I will make an appointment at the indi and pick their brain while they are giving me an est.

One more question. I thought I read here (forgot what thread) that the coil on a 190 can be accessed through the firewall, the indi said he did not think it could be. I have the shop manual at home (have not looked at it yet), does anyone know the answer? Will it say in the shop manual?

Thanks for all the input.

As others here, I am NOT a fan of converting to 134. I live in Texas, so all the capacity I can get is needed.

R12 is getting LESS expensive, not MORE! The vehicles that require it are at an age that they are hitting the wrecking yards in record numbers, thus the demand is decreasing. You know, supply and demand determining the prices?

I bought a 30 pound bottle of R12 from Refrigerant Supply in Colorado two years ago for, I think, about $400. At that same time 134 was going up in price. I expect that you could buy a 30 pound bottle now for less than $400. Check it out.

You will need a 609 license, but you can take an online, open book test for $15 in less than a couple of hours.

Good luck,

A mechanic said to me that when r134a first came out it was less efficient in original r12 cars. He had wanted to convert my 420sel but I respectfully refused. I told him that I wanted a/c that was cold not cool. He told me that the r134a that is made now is more efficient in cooling and that he could make a conversion now that would be just or almost as cold as r12. He said that maybe two years ago the coversion would leave customers unhappy.

E150GT,

I respectfully suggest that your mechanic is FULL OF IT! Saying that 134 has changed is like saying that the law of gravity has changed such that water will now pour up hill.

I expect that if you took him up on it, he would put one of the junk coolants in the system behind your back and tell you that it is 134. Find a new mechanic.

agreed,the formula for 134a has not changed.refrigerants work because of the heat required to change state from liquid to gas.no magic just pure physics.heat is measured in btu's and 1lb of 134a will require 30% less heat to change from liquid to gas than will 1lb of r12.the only way to make 134a do as much work as r12 is to make the components about 50% larger and or more efficient.

Hi All -

I've been there, done that. During the winter of 2003 I replaced the entire a/c system of my 1987 300TD wagon. Evap, condenser, compressor, manifold hoses, etc. Just got tired of chasing leaks every year and decided to fix it right.

I used a synthetic refrigerant oil compatible with both R-134a and R-12. I initially charged the car with R-134a. Given the price of R-12 I wanted to be certain there were no slow leaks.

I drove it that way until about the end of July. And I live in Dallas. Surprisingly, the R-134a did an acceptable job of cooling. I recovered the R-134a and changed to R-12 more out of curiosity than any lack of comfort. At the time I posted a writeup with a comparison of vent temps and such, it can likely be found via a search. As I recall there was little or no difference in the final vent temp produced by each refrigerant. But the R-12 seemed to cool down faster - the air was noticably cold by the end of the driveway, as opposed to half-way down the block.

My theory is the lack of cooling has as much to do with the dirty/bent/broken fins on the evaporater and condenser reducing the heat transfer ability of each as to any inherent differences between R-12 and R-134a. With fresh parts the R-134a worked OK.

- JimY

Good and interesting point which makes me wonder...when you do a conversion, why do you put in LESS 134a than you would if you were still using r12?

you put in less because it requires less heat to go from liquid to gas and therefore find an equilibrium.

Yes if you are charging with 134 by weight in a converted system, you put in .85 times the specified R12 amount. If you are topping off a system, however, it gets more touchy than that. Even when charging an empty, converted system by weight there can be a little black magic involved in getting the charge right.

What I call "black magic" is probably the "equilibrium" as David more correctly puts it.

Man, this keeps getting more and more difficult.

Given the current discussion I am leaning toward staying with R12. I do not want to risk loosing efficiency on my system. The temps in Dallas are too extreme for me to risk it.

Given that most of the system will be replaced, are their any incidentals that should be replaced as well. I would like to just have this done one time.

Some mentioned the O-rings, and someone else mentioned the low pressure hose. What else? Can/should a compressor be overhauled or maintained? The condenser (in front of the radiator) is only about 4 years old.


thanks

Ah, don't interpret my post as encouraging you to use R-134a, that's not the intent. I wanted to point out that performance perhaps does not suffer as much as one would be led to believe based on postings here. The cost difference between the two refrigerants is insignificant in the context of all the other work, so use the good stuff!

As for what to replace. The basics are evaporater, expansion valve, and dryer. If the car has the original manifold hoses (to/from the compressor) it's probably time for those as well. (Some shops can rebuild these, saving you a ton 'o dough.) O-rings are good, they are a prime source of leaks when they get old and brittle, say after 20 years of service. There are also two electrical switches which thread into the dryer, they have been known to leak on an occasion or two.

Compressors are expensive; I'd only replace if it's original or if there are obvious problems - funny noises or leaks.

If the condenser is 4 years old, it can stay. That's practically brand new as far as this car is concerned. :)

- JimY

See the text in bold above. THAT is a statement of wisdom.

Since you are in Dallas, the best automotive a/c place I've ever dealt with is McCains in Richardson near the Floyd Rd. TI Plant. Their address is on Floyd Circle. Mark McCain will give you advice. Sell you what you need and not try to sell you something that you don't. They also do a/c work and are good and honest.

Good luck,

if you are going to use 134a,take out the condensor,block the pipes from moisture,get some of the strong acid used to clean mag wheels and spray it on the condensor and remove the black paint until the pipes shine.this will aid your condensing by approx 40%[the big prob with 134 is condensing]

Yes, condensor capacity is key. I did not know though that removing the black paint would help so much. That sounds like a GREAT alternative to fitting parallel flow condensor.

larry even if you are running r12 this makes a nice improvement of 20-30psi on the high side pressure on a 100deg day.

As a testimonial against converting to r134a, we used to have a 1993 Nissan Quest, and I had it converted over to r134a. It completely failed to blow cold air. The difference between its performance and that with R12 was so great, that a few days later I had it converted back.

My advice is to stick with R12 if your car was designed to use it.

I used to own a 1993 300E (3.2) "E320", which was the first year it came with r134a from the factory, so it was designed to use this refrigerant.

I sold it JCE's son two years ago (in 2005), and the a/c system was completely original, it even had its original charge, and it still had ice cold a/c, even on a 110 degree day in Las Vegas. It had the coldest a/c of any car I have ever owned.

I just don't understand what all the noise about converting to r134a is. I just converted my wife's '78 300D and it will freeze you out of the car. Granted, I upgraded the York to a Sanden, but that doesn't change refrigerant efficiency. My '82 300DT has been converted and I can't run it at full-cold in the summer. The first vehicle I converted was an '88 MErkur XR4Ti done in 1999 and my buddy who did it couldn't believe how cold it blew (44 degrees) and again I couldn't run it at full cold during the summer. These conversions have all been done here in hot 'n' humid central Florida. Other than those three mentioned I've converted about nine other vehicles of various makes since 1999 and they've all performed spectacularly.

All I can imagine is that those that have experienced poor results are getting either poor workmanship or inferior materials. Just my $.02! :nice:

BTW, great write up on the W124 evap service! :thumbsup2:

It's ALIVE!
 

Getting back to the original part of this thread, it has gotten warm enough for me to really test the system since the evaporator replacement.

38-degree air from the vents. No leaks. What a relief.

Sounds like you're in good shape. I keep a dial thermometer in the vent of my 300E all the time. The Climate Control seems to regulate the temp to 38 F. When it starts getting slow to reach 38 is when it gets my attention.