Chuck, thanks for sharing your experience in Evaporator and Heater core R&R. With some pics this is a good candidate for DIY sticky.

 

Thanks for the time you are taking to detail this procedure. Its only a matter of time before this sad fate befalls all of us ! :crying

 

Thanks, Chuck.

You must be into some serious self abuse to do this.... :eek

Dan

 

The Labels and Bags

OK, here we go.

One important piece of advice is "do not trust yourself to remember anything," at least until you have done a dozen of these jobs. I labeled every wire harness and vacuum line that I disconnected. This was important in my situation because someone had been in there before me for an aftermarket stereo install and there were several connectors sort of dangling. So with the tape, I had a record of sorts of what I disconnected and re-connected.

When I took pieces out I labeled them, unless they were totally obvious (like the dashboard), especially if they had a right or left. I used yellow masking tape and a black Sharpie.

I left all the labels in place when I put it back together.

I used plastic bags to hold fasteners and other small components as I took them out. I labeled them with tape and the Sharpie. I did this sort of by major component or area. Here, in no particular order, are the bags I ended up using. I suggest you make up a set before you start.

Air ducts and cross-strut
Light switch
Parking brake release
Dash screws
Dash vents
Steering wheel
Case to firewall and support bracket
Hose clamps
Spectacle case (bigger screws in back)
Console
Center vent
Under-dash
Wiper and firewall
Speakers

Pictures are OK but they don't tell you what screw goes where. I found the tape labels and bags to be very helpful.

 

Very descriptive and sounds so strait forward. Only stating to remove this or that leaves out the how it is done technique. There is always a secret technique to get her done I don't know!

I have needed to do this on my car for 2 years, I just keep filling with Freon until I have to have her vacuumed down and recharged. I have also just retired and may find the time to start this one now, if my back holds up to all the positions I need to get into!

Thanks and look forward to seeing the pictures if they arrive.

Glenn

 

Glenn,

If your car is leaking down over time and not catastrophically, you should consider using a sealant.

This is not snake oil stuff, and is in use both in automotive and stationary AC systems.

My 1995 S500 (W140), which is one of the "known" cars in the list to be prone to evaporator failures, had a leak that wold drain the whole system in about a month. Rather than submit to the ordeal of replacing the evaporator, or paying someone to do it for more than the car is worth, I used sealer, and it's worked great.

It's been over a year since I did it and the system has held a charge and not required any topping off. I know another BW member who lives nearby that did the same 3-4 years ago and has the same experience.

I highly recommend this approach. If your car meets the criteria for use, you'll have $40 invested for the sealer and the cost of an evacuation and refill.

The manufacturer was very helpful with the use and application of the product. I called to speak to someone about it and ask some questions. I spoke with an engineer who was very helpful and took time to explain the process and how the product worked, what it would and would not do, etc.

I'm very pleased with it.

Dan

 

I seem to remember Matt Smith doing a similar DIY a few years back.
I think also he used a technique in the photos, some thing like a gas that glowed green, to show the leaks.

I'm not sure if it's still available because he might have deleted it after a dispute with a fellow member, then leaving the forum!

 

Some photos and info survived, but video was deleted

http://www.benzworld.org/forums/r129-sl-class/1414818-r129-air-conditioning-evaporator-r-r.html

 

Hi James I managed to find a vid of the work Matt Smith did on the evaporator

.
Hope it helps.

Cheers.

 

CT, impressive work and writeup.
How many hours/days did it take for you to replace the Evaporator?

Carl

 

Around 40 hours, but as I will explain, probably 12 of that involved three specific problems.

 

Evaporator replace pictures 1

Pictures of the initial work on the console and dash.

Again, important to have the Alldatadiy for the car. The diagrams are a little hard to read and the instructions a little cryptic, but there is nothing in this part that can't be figured out.

Some help:

- The spectacle case may have a false back in it concealing phone wiring. If you take the two screws out and the case won't move, fish the back out and you will find two more screws.

- The storage compartment in the console may also have a false bottom with four screws underneath it. There are two electrical connections and a vacuum connection in the rear of the console that need to be unhooked.

- Once the storage compartment is out, there are two screws on each side that hold the rear of the console in place. The cassette case or cup holders need to come out to get at the middle screws. Then there are two more screws at the very top of the console.

- The air bag in the steering wheel is removed by unscrewing two Torx 25 fasteners accessed through holes in the back of the wheel. The fasteners stay in place after the air bag is removed.

- Once the steering wheel is removed, align holes and remove two small screws to release plastic cover, then remove three screws that hold cruise control and multifunction switch to wheel hub. Pull out the above and just let hang down on wires. Once the dash is out, you can put them back in place to keep them out of the way.

- You can remove the instrument cluster without the hooks by reaching up under the right side and pushing it out.

- Once the three screws securing the dash are out, the biggest challenge is lifting it up enough to clear the defrost vents, which are what really hold the dash in place.

Time for these steps, about 8 hours. This includes a wasted hour because I didn't know about the false back in the spectacle case.

 

Evaporator replace pictures 2

Clearing up a few details on the inside, then time to move under the hood.

- If you look at the picture of the dash removed, you'll see that both lower plastic covers need to come out, along with the driver side bolster. The passenger side bolster can stay. The passenger airbag stays in the car.

- There are air guides on each side of the heater case that need to be removed, along with the cross-strut. There is a large electrical connector on top of the center vent that needs to be detached, but it's not necessary to disconnect the halves.

- All vacuum lines need to be disconnected. Alldata says to to this at the connector in the passenger footwell area, but this means you will drag out a tail of plastic lines along. I disconnected them at the vacuum elements and labeled the connections on the elements. For example "Red/Gray." I then tied them out of the way.

- The defrost vents need to be removed. They are held on by little clips, and the ones on the front side are difficult to access. I used a long thin screwdriver.

- Inspect the case closely because there are a variety of electrical connections that need to be unhooked. Label each one, don't trust your memory. Don't forget to pull out the evaporator temp sensor on the lower left side of the case.

- Finally, the four 10 mm nuts that hold the case to the firewall need to be removed. They are all accessible with a ratchet and a long extension. There is a fifth securing point. It is a small L bracket that also holds a relay at the middle bottom part of the case. It's marked in the "Lower tunnel detail" picture.

Done inside, time to go under the hood for a while.

 

I did this to my w124,not hard just time consuming as heck! I replaced all vacuum pods also!

 

The next steps are to remove plastic grilles around the base of the windshield, and the wiper motor and the plenum case. This is to gain access to the heater and AC connection.

The grilles are straightforward, but don't make the mistake of un-clipping them. The phillips screws can be accessed through little slots.

The Alldata instructions for the wiper motor removal are written as though it's being replaced so it includes disconnecting the electrics in the control unit case. I disconnect the electrics, but I think the only reason is so you can remove the lower plenum housing. You might, however, not need to do this. Just remove the motor and plenum(see below) and set them aside rather than completely removing them from the car. If you choose to remove them, you need to remove the engine control module to access the wiper motor connection.

Remove the top of the cabin air plenum and the filter. Disconnect the vacuum lines. Remove the screws that hold the bottom of the plenum, and remove the plenum or set it aside if you left the wiper motor connected.

All of this is needed to get access to the expansion valve and heater hose connections. You don't need to remove the blower motor.

Having drained the radiator, you can disconnect the large and small heater hoses on the right side, and the large hose on the left. If you can, blow any remaining coolant out of the heater core into a container.

Remove the screw in the middle of the plate that holds the hoses to the expansion valve, Now, follow the big AC line forward to the fuel line cooler. There is a clamp on the big AC line that needs to be removed to be able to pull the AC lines back to clear the expansion valve. I could not get the line to move with the fuel hoses connected to the AC line, so I . Tie the hoses out of the way. Remove the two tiny hex-head screws that hold the expansion valve to the evaporator plumbing.

OK. Time to remove the evaporator case. It helps to have an assistant. The case comes out by pulling maybe 3/4" back to clear the studs in the firewall, then pulling and twisting the right side to clear the heater pipes, then raising the right side and pulling back to get the evaporator pipes to clear the firewall and lift it out in one graceful motion. If you didn't blow out the coolant, be careful to keep the pipes pointed up so you don't spill coolant on the carpet or seats.

Surprisingly, the case isn't heavy, just awkward.

There. Put it on the bench, and take a break.

 

Pictures from previous post.

 

There has been a lot written about this job, mainly how difficult and time-consuming it can be. I was asked by a local shop to take it on for a very nice low-mileage 1995 SL500. They didn't want to do it because it would tie up their best tech for a long time and they were concerned about something going wrong and having to eat a bunch of time. Being retired, I didn't have that concern, so I agreed to take it on for a fixed price.

I would say that I enjoyed about 95% of the job. Nothing was very dirty or heavy, and the only reason to go under the car is to drain some coolant. Most of us hands-on types wouldn't be concerned about any of the steps in the job, but this is a case where the whole got greater than the sum of the parts. So if you are driving around this summer with the windows down because you have no AC, consider doing the job - it's not as difficult as it's reputation. Just take it one step at a time.

Here are the steps for disassembly as I recall them:

-3. Remove or have removed, any R134 in system.
-2. Get Alldatadiy subscription for vehicle.
-1. Put soft top down.
=========================================
1. Disconnect battery. Remove ACC controls radio, ashtray, shifter surround, shift knob and finally console wood and switches.
2. Remove center console.
3. Remove center vent and spectacle case
4. Remove dash speakers and side vents
5. Disconnect/remove parking brake handle/surround and light switch
6. Remove air bag and steering wheel.
7. Remove instrument cluster
8. Unscrew combination/cruise control levers and let hang down.
9. Remove under-dash covers on both sides, carpeted bolster on driver's side.
10. Remove dashboard by lifting it up from defrost vents and pulling it back.
11. Remove defrost and side vents from heat/ac assembly, remove four nuts holding assembly to firewall and bottom center bracket (two screws).
12. Disconnect and label all vacuum and electrical connections. Remove foam drain hoses.
=========================================
13. Drain radiator.
14. Remove grilles around windshield
15. Remove air filter and housing
15. Remove wiper and wiper motor
16. Remove large firewall "pan".
17. Disconnect heater hoses both sides.
18. Slacken clamp holding big AC hose, undo plate holding lines to expansion valve, pull lines away from valve, and remove valve.
=========================================
19. Remove evaporator/heater assembly. First, pull it back to clear the studs in the firewall. Then lift and pull on the right side. As the heater pipes clear the firewall, pull out the left side and lift assembly out. There will be coolant in the heater core, so be careful not to allow the pipe to point down. Ideal to cap pipes before lifting out of the car.
20. Remove top of the heater/AC box, remove the heater core, and then the evaporator.

The road back.

21. Install the new evaporator assembly, the heater core (with new o-rings), and put the top of the box back on.
22. Re-install the assembly in the dash. First line up the left side and position the right-side heater lines to go through the holes in the firewall. Alternately move the left and right sides forward until the assembly is on the studs on the firewall. This is probably the most challenging part. There is a foam seal on left side that is clipped to the evaporator pipes. It is very easy to dislodge this seal as you are maneuvering the assembly into position. If this happens, you won't have a good seal against the firewall and it will make the connection of the pipes on the engine side to the expansion valve difficult.

The rest of it is pretty much the reverse of the first 18 steps.

I will continue this thread with some pictures and helpful hints for each step as time permits.

Cheers,

CT

text me I need mine done ASAP I’m in nc 704223 2831

 

Very interesting. My son has a W201 190D 2.5 and the heater core sprung a leak. He was on COVID lockdown on full pay and did the replacement just as described here. Methodical, carefully, with every wire and pipe being labelled appropriately.

The result was that everything worked with the exception of a connection to the instrument cluster that was easily resolved. He'd never undertaken anything like this and it has greatly increased his confidence to tackle almost anything.

One day this will happen to my 300CE and I hope we shall have the opportunity of tackling iit together.

Best to all.

RayH