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Old 08-18-2002, 02:19 PM
Posts: n/a
AC evaporator leaking/134 conversion

The AC evaporator on the 124 is leaking and the cost to replace is high as all know.

I am considering changing over to R134 and using a leak sealant to save money as I have other repairs that need attention too that I will be doing.

Seeking words of wisdom here before I start something that will create more problems than it will solve.

Any thoughts appreciated - Ron

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Old 08-18-2002, 02:36 PM
Posts: n/a
Sorry to hear of your misfortune. I cross my fingers every spring when I start relying on my 124 a/c. So far I have been lucky, knock on wood.

I have always been a skeptic of chemical cures for leaks and other mechanical ills. I also know that the 124 car is a very poor candidate for converting to r134. You will lose cooling capacity big time on these cars.

As Steve Brotherton states best, R12 is the least expensive component of your air conditioning system, why is everyone so intent on changing it?

In your case, R12 is REALLY a small expense as a percentage of the repair. You can now buy R12 for about $29 per can. If you have the evaporator changed by a shop the R12 will probably be less than 10% of the expense.

I recommend that you bite the bullet, change the evaporator, evacuate and charge with R12. I would personally not consider ANY alternate refrigerant for this car.

My $0.02,
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Old 08-18-2002, 03:14 PM
Posts: n/a
Larry - thanks for your insights. If I had not already spent $1,000 on the ac manifold and other hoses, it would be easier to take.

ACs are a weak link in all vehicles. Since they need constant attending when they get older, that is why I would convert to R134. At least I can do the work myself. For the cost of one repair, you can outfit yourself decently with the equipment and it would pay for itself when you have 2 or more cars in the family. If you hand onto your vehicles like I do, it would pay for itself.

Thanks again - Ron
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Old 08-18-2002, 04:07 PM
J.HIDALGO's Avatar
Registered User
Join Date: Jul 1999
Location: Jax, FL
Posts: 1,785
Too bad Rod!

The AC manifold hose can be rebuilt by your local pressure hose supplier. About $100-150 to replace the rubber portion only. If the evaporator is leaking it will cost you pain in your walet if you go to a professional or, pain in your body if you do it.
'86 300E
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Old 08-18-2002, 04:46 PM
Join Date: Dec 2001
Location: Southern California, U.S.A.
Posts: 8,538
I've read many times on this site that the shop time to replace an evaporator in a W124 is 22.5 hours.

I agree with Larry. Stick with R12. Yeah, it may be cheaper to recharge the system with r134a if you develop a leak, but your a/c will never blow as cool as it will with R12, and you'll regret it.

Trust me - been there, done that.
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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Old 08-18-2002, 05:00 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
I almost jumped on this one until I read Larry's post and then the others.

I read your question differently. I think you are asking if we think its reasonable to not replace the evap but instead to hit it with stop leak and use 134 since even if it leaks you will be a good guy.

If thats your question then I have a couple pieces of advice. First don't use it if you have long term plans for the car. it's possible that the stop leak can cause some serious problems. it works using a silica compound that in the presence of moisture turns to glass beads. My partner tried some in his old 140 body last summer after adding refrigerant every monthfor a while. I noticed that he had some added Friday for the first time since last summer. He had never let the system get empty and probably had no moisture in it. It seems to reason that a system with moisture in it could have some catastrophic problems it the stuff started turning to glass beads inside the system.

The second point is that R134a has smaller molecules and leaks faster than R12.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 08-18-2002, 07:15 PM
R Easley
Posts: n/a
Adding to Steve's comments, there is also an ethical issue associated with the use of sealers. Do you have the responsibility to tell a repair facility that you have used leak sealers in your A/C system if you go to them for repairs? I would say absolutely "yes."

Evidently, some shops are finding that these sealers are damaging their refrigerant recovery units and the manufacturers of these machines are beginning to void warranties if the machines have been used on a car that has been exposed to these sealers. See
System Sealers Void Warranty that says, among other things:

"Vehicles found or suspected of having an A/C refrigerant sealer in the system should be serviced as a refrigerant system containing a contaminate. Visteon approved refrigerant system flushing equipment/agents may not remove the refrigerant system sealer from a contaminated system, and replacement of the entire A/C refrigerant system is recommended."

Unfortunately, there's no such thing as a free lunch. I, too, have a 124 in a hot climate (Central Texas) and keep my fingers crossed on the evaporator. I, too, have considered using a sealer if the evaporator should develop a leak. However, I have decided that if a leak happens, I will bite the bullet and do the replacement myself. If that happens, while I'm working, I'm gonna try not to think about how quickly Steve and some of the other pros out there could do the job!

I agree about the recommendation of continued use of R-12 in a system originally designed for it. Those in the north will not understand, but every 1/10th of a degree counts down here in the south!

Also, I really do think that we've seen or are seeing the peak on R-12 prices -- there are simply too many shops that insist on converting incoming R-12 cars to R-134a. Now, where is that R-12 going? By law, it cannot be vented and a shop would be foolish to do so anyway, so this R12 is being recycled into the market (see this site for example). Couple this with those that are hoarding it and also consider the reduced number of vehicles on the road with R-12 and you have a classic case forming of supply eventually exceeding demand. Bodes well for those DIYers that want to stay cool . . .

Richard Easley
Waco, Texas
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Old 08-18-2002, 07:23 PM
Posts: n/a

I now know why my skepticism of this cure is warranted, there's nothing like glass beads circulating with your refrigerant to ensure a healthy compressor!


I don't understand your comment about doing it yourself. If you can do 134 yourself, you can do 12 yourself. As a matter of fact, a set of R12 manifold gauges are cheaper than r134a gauges. You can go online and take the 609 certification test so you can purchase R12, it costs $15 to take the test. You then go to the shop and have them recover the R12, then repair the system, buy the R12, evacuate and charge.

I will reiterate Steve's wise advice; "R12 is the least expensive component in the system." And to reiterate Suginami's warning, he said he'd "been there, done that."

Again, the 124 MB is NOT a good candidate for an alternate refrigerant. I am quite sure you will be disappointed if you spend all this money and time, stay with 134 and find that if you're lucky you will have a marginal a/c system.

Good luck and I hope you make the right decision,
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Old 08-18-2002, 11:41 PM
Registered User
Join Date: Aug 2001
Location: Huntsville AL
Posts: 12
Question Hydrocarbon refrigerants

I've been looking on the web, and the claims for Hydrocarbon Refrigerants are too good to be true. Better cooling than R-12, compatible with existing hoses, lubricants and components, enviro-friendly and no license required.

I see you guys are gung-ho on R-12, but any advice on these refrigerants ?
Michael H
1986 300D W124 5-spd manual 250k miles
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Old 08-19-2002, 07:23 AM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,577
do a search Mike

I am running something other than r12/r134 in my 300D but that is my choice. I do not want to start a long, drawn out thread discussing the pros/cons of the other "refrigerants" - this discussion has already been covered in other threads and that is why I said to do a search.

With my "keeper" car (the 300TD) I am going to go with r12 just because I was able to purchase alot of it from a company going out of business that was selling it for $15/can. Also, I plan on totally overhauling the a/c system in the 300TD - rebuilt hoses, new compressor, new dryer, etc... I have not even started troubleshooting why the system in it is not working but it may just need "recharging" . That is all that seems to ever need to be done to a/c systems in used cars that are being sold BG - LOL . Yea right .
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Old 08-19-2002, 08:33 AM
Posts: n/a
Flammable refrigerants are illegal. Non flammable blends cause problems whenever a leak occurs. The different elements leak at different rates necessitating a complete recharge.

I suggest that you look around for a deal on some R12 like Jim did.

Steve Brotherton has wisely pointed out that R12 is the least expensive component in the a/c system.

The other reason is that with all these alternative refrigerants being put in cars all over the place, it is accidentally getting recovered into containers of R12. This contaminates that entire container and requires it to be destroyed. The only R12 we have is what is on the shelf yet to be sold and what can be recovered. Every time an alternate refrigerant is put in a system it opens one more chance that it may contaminate our remaining R12 supply. Please don't do this.

Most of these fancy named alternatives look too good to be true. In my experience when something looks too good to be true, it usually is.

My $0.02,
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Old 08-19-2002, 01:36 PM
the_good_fellow's Avatar
07 E320 Bluetec 7 pistons
Join Date: Jul 2001
Location: Houston, TX
Posts: 170
Since you guys are talking about R12 A/C performance in hot southern climate. Hope you guys don't mind if I jump in with these unsual experience on both my 87 300SDL and 91 300D. It happened to me twice on my SDL and once on my 300D.

This happen once on my SDL, it was parked under the sun for a while and it started pouring. I got into my car and started it up, drove for about 10 minutes and the A/C compressor got cut off. blower was working but there wasn't any cold air. the dial was set on 70F and the outside temperature was about 85F. I pulled over at a gas station, checked on all connections and fuses(with engine running). I didn't see anything wrong. So I keep on driving until I got to my destination and turned it off. about 20 minutes later I got back, startedit up and it went back to normal...

these happened to both SDL and 300D while driving on the (sunny side 85F+) of freeway and I got got into a rainny area. A/C Compressor got cut off in the rain .... Again, parked for a little while, restarted and nothing happened. I'm wondering if this is the outside temp sensor having problem with certain quick drop in temperature??

Larry, Richard & Steve you guys are in the south. Have any one of you experienced this problem?


09 GL320 Bluetec 65K+
07 E320 Bluetec 43k+
05 Nissan Frontier NISMO 4X4 72K+

07 Kawasaki Vulcan 900 5k+ gone
87 300SDL 158k+ gone
91 300D 113k+ gone
83 300SD 220K+ gone
89 300E sold
87 190E sold
83 380SEL sold
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Old 08-19-2002, 01:45 PM
Posts: n/a
Good Fellow,

Most likely what happened was the rain caused the belt to slip. There is a sensor that cuts off the compressor upon slippage. It then works after restarting.

Have a great day,
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Old 08-19-2002, 06:02 PM
Registered User
Join Date: Aug 2002
Location: Milwaukee, WI
Posts: 126
More refrigerant banter........

Interesting thread - nothing like R12 vs R134a to get the opinions flowing.

Until very recently, I bit the bullet and used R12 for my four cars that need it. Yes, I'm certified to purchase R12.

However, it is illegal to sell R12 in anything less than the large cylinders that the 609 license does NOT cover in Wisconsin. A 30lb cylinder is now running $1000. R12 is scheduled to be illegal to sell after the end of this calendar year in the US, I've been told.

So, my decision is to go ahead and convert to 134a when faced with the next major A/C service or if recharge is needed. In the long run, it makes the most economic sense.
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Old 08-19-2002, 07:07 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
My position has changed over the years. I see no end to freon and have seen no such laws. I see no reason to change till one is repairing and there IS no freon.

If you repair this year with R12 then by all rights it should last a few years hopefully many. When its next a decision, reassess the situation. I see no point to doing something now for a future possible reason. It can always be converted, you never loose that option. It won't work as well and all possible leaks will occur in at least half the time. the compressor will have its life shortened by the same ratio maybe more.

Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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