I took my 87 260E into a local shop (******** West in Mission Viejo, CA) GREAT PLACE BY THE WAY!! Very honest and cool guys, chatted for quite a while with them...

I took her in for them to find where the A/C was leaking from.
It leaks out after about 1-2 weeks. They charged it and told me they checked all lines, found nothing, but when you pull the carpet back on the passenger side, the lines are a little rusted and there was some "old" dye there which leads him to believe the evaporator is the cause of the leak.

Also, he said that I was getting some odd #'s...50 on the low and 250 on the high side. psi?? He said it should be more like 30-100/150 which could be a blocked expansion valve. The A/C worked (as I knew), but it was not blowing as cold as it should do.

There are plenty of posts about the evap removal...so my question is on the Expansion Valve. Does his psi #'s sound like the Exp valve is the cause of this?

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It could be. If you like and trust the guys, if it makes you feel better, yeah I'd say do it. On top of that, if you are doing the evap, it sort of makes sense just to replace it, there would only be the parts cost, the labor should be no additional, and since you have it in your hand....why not just do it?

I would wonder though, if the high side pressure is high due to the expansion valve, maybe just the o rings are leaking? I'd throw that out there just to see if they might agree that the joint between the expansion valve and evap might be the only leak?
Gilly

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Thanks Gilly,

He said he probed it and found no leak. I looked at the FSM and it looks an easy replacement for ~$26. Since there is no gas in there right now it would be a good time just for the heck of it. Maybe I should do it then fill her up again. I've got a ton of R134a cans + oil that would be an easy fill to test before tearing everything open. Would probably be a smart decision...

Makes me wonder if it could be the same issues on my 300TE. It blows cold fine, but it really struggles at above 90F outside. I can't tell if its just the small evap the way it was designed + R134a instead of R12, or if there is an issue?

I will be doing the work myself. I just took the car in because I don't have the knowledge or leak detection machines to properly find a leak. I "tried", but failed at finding "where" it was leaking from so I just handed it off so they could find it for me.

I've also heard you can see the condition of the evap by removing the blower motor? Anybody confirm this? Maybe I can pull it off (after replacing expansion valve) put some dye in and use a UV detector and watch in there? Is there enough space to do this? Seem a good idea?

I can't wait to start tearing off everything Looks like fun...
Can't get my head around if pulling the transmission out covered in oil or doing this job...which one is worse LOL

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The 250 high side number is normal for an MB, depending on the outside temperature. It has to be pretty darn chilly before the high side will see only 150PSI. What was the ambient temperature when he was working on the car?

The low side should be 25-30, but only when running the engine at 2000RPM. At idle, it will be up around 45.

Assuming the weather was cool, I think it's overcharged. Both the low side and high side are too high. A bad expansion valve causes one side to be too high and the other side too low (depending on whether it is stuck closed or open).

I'm not convinced the expansion valve needs replacing.

UV dye is good for DIY, assuming you have somewhere dark to work on the car (ie a garage where the door can be closed). It's hard to see the UV dye in bright light, but is pretty easy if you can dim things down.

You can more or less see the front of the evaporator by pulling the blower motor. There's no guarantee you'll be able to tell if it is leaking or not. But with your 2 week leakdown you should have a lot of dye at the leak site(s), so I'd guess there's a good chance you will be able to tell.

My $.02.

Don't know your temps.. .you need pressures and temps to know.

Anyway, if the low and high side pressures are high- your system is overcharged. The 86-89? cars had only 15 cc compressor where later ones are 17 cc's. I wouldn't use R134a, I'd use either R12 or an R12 subsitute for better performance. That being said- you should be fine to about 100F where things really break down.
The idle performance can be dreadful with a converted car.

What is the condition of you FAN CLUTCH????? Is there leaves or part of the raditor plugged with bugs?? I'd bet the new fan/fan clutch would make the world of difference. Less stress on your headgasket by keeping the engine temp rock-solid @85F. The pressures could easily be not enough airflow over the condensor. Did they run a water hose over the condensor when checking pressures???????

Michael

Don't we also replace the receiver/dryer if the system has been open to air?

You can see some of the evap when the blower motor is removed, and see all the dirt caked to the fins. I used FrostKing Air Conditioner Cleaner spray foam on that mess, and gently rinsed it out. I did this for my TE converted to r134 by the PO, and for the E300 because it was filthy (the pics below).

Also, if dye has leaked out of the evap where the copper meets the aluminum, that dye will trickle down to the base of the evap, and into the heater box under it. The dye will be visible.

Attached Thumbnails

       

When you cleaned it, did all the dirt go down into the footwells?

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No.

I learned from replacing an evap in another 124 that those foam "hoses" that go from the heater through the floor can disintegrate. So I checked the cars before doing the clean job.

All hoses were intact in the cars, so no water in the footwells.

My foam drain hoses were disintegrated on my 1995 E320.
If the leak is bad enough in the evaporator, you will see some dye dripping off the drain hoses (provided they are functional).
My bet is that you need a new evaporator.
I removed the transmission, rebuilt it (my first auto rebuild), and reinstalled about 2 years ago.
I then replaced the evaporator. It was a lot of work removing the dash and everything involved. If I had the choice, I think that I would pick the transmission job over the evaporator replacement.

Having said that, I know that you can handle it. Just be prepared for a lot of hours inside your Benz.

I did have 1 other comment on low cooling.

There is another problem. The system could be overloaded with oil. There is a point, before hydro-locking where the dryer is full of oil(mostly full?). I've experienced this in my truck. I knew it was charged a little high with oil. I blew out the condensor and replaced the dryer.
For poor performance, the thermal cycling switch is a thermal couple- they can go bad. MB set them to cycle pretty warm. You can add a shunt resistor and bring it down from 48F toward 38F and see better cooling.
It's weird- I would have thought the electronic system would push systems closer to 32F. But when I researched the web- it looks like all the electronic cycling switches are higher. I've done this mode to american cars too.

Fred- what a comment would rather almost do a transmission job!

Michael

Thanks everybody.

Fred -- Was it "fiddly" or more time-consuming? Upon reinstall did you have any issues fitting everything back in? Did anything NOT fit back in "quite" right? My only concern is upon re fitment because I understand 20 years in the sun is bound to have warped the plastics. I definitely want it to look like it had never came out.

I should be expected to replace -- Evap, Heater core, Drier?, Vac pods...anything else? I want to do the job right...$ is not so much of an issue since I will be doing it myself.

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It was fiddly and time consuming. I went by the detailed write up that I found on this site as well as the repair CD. I had no problems with dried out plastic that was warped or broken. After you get everything apart you will look at your "baby" and wonder if it will ever look the same again!

Actual removal of the condenser/heater housing assembly was tricky and took some force to break the sealant, and finagling to get it out.

The evaporator normally comes with a new expansion valve attached. The drier is inexpensive and should be replaced when ever the system is opened up. I bought all new o-rings for the a/c from the local MB dealer. Didn't want to take a chance with possibly not having the correct size.

All of my vacuum pods were working so I chose not to replace them. I also didn't replace the heater core as I hadn't heard of them being a problem.

This is a good time to add a little oil to the blower motor bearings.

Take your time when reassembling the dash as there are a lot of electrical connections and vacuum hoses that must be reconnected. Would be a good idea to take a lot of pictures so you can remember how wires are routed.

Very satisfying job when it is done and everything works as it should.

I'll just do the same as I do with any big job...Lots of ziplocks, and for this case, lots of labeling tape. I'll put a step # and what it goes to that way I go backwards upon reinstall and never miss anything.

I thought I heard the heater cores leak too after a while? Maybe I read wrong? Obviously that would be good news as a new core is ~$250 and that would cut the cost of the repair in half practically.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

The heater core probably depends on how gentle you are with it...

There are o-rings between the core and the heater manifold which I'd guess would be a leak point.


M