'87 SDL Heater Core and Evaporator

[BlueTank]

Hello All,

The diesel gods decided that I have had enough rest. The 87 300SDL has 200K+ miles and I picked it up to add to the fleet this past October. It has some rear suspension issues and some full power performance issues, but those will have to wait.

Yesterday on the way home from work I started to hear some hissing, smelled that unmistakable odor of coolant and the windows started to fog up . After turning the climate control temp dial to max cool to get the flow of coolant to shut off and stop the fogging, I was able to complete the COLD ride home.

I believe I have to take the entire dash apart to get the heater core out (right?) and I will also replace the heater core pipes and the vac pods. My question is - what is the history of the AC evaporator in these cars? Should I replace it too (it is around $200)?

Thanks

Richard

[TX76513]

The W126 history is more favorable than that of its cousin the W124. However I would take a serious look at the AC Core while you are in there and make a decision from there.

[BlueTank]

Originally Posted by TX76513

The W126 history is more favorable than that of its cousin the W124. However I would take a serious look at the AC Core while you are in there and make a decision from there.

Thanks! I assume I am looking for corrosion/physical damage?

[TX76513]

Obvious stuff. Seriously the 126 isn't as bad to get at if it's working - leave it alone.

[Hit Man X]

Wait until you see it, it's going to need a serious cleaning.

[BlueTank]

Originally Posted by Hit Man X

Wait until you see it, it's going to need a serious cleaning.

Hello All,

It took me quite a while to finally put almost everything back together, but things have been working great for the past 2-3 weeks!! It’s nice not smelling coolant anymore. I don’t have all of the driver side lower trim back on because I’m going to tackle the AC/Kickdown issue before buttoning it all back up.

A big reminder for everyone! The cause of my heater core leak was not the heater core itself; it was the “3 pipes”. Whoever serviced the car before must have yanked on the heater hoses instead of being careful. There were cracks in all of the pipes!!! Do yourself a favor and be very gentle with those heater connections! Oh – and the evaporator was fine and VERY dirty.

The procedure for R&R of the dash is well documented in the DIY section. The job is not difficult, but unless you have done stuff like this before it will take you a lot longer than you think. Also, if you are like me you will need to get away from it once in a while to keep from getting frustrated and breaking some of the 20+ year old plastic parts.

As advised by others, I spent the extra money to replace all of the vac pods that are attached to the heater box – especially the one for the center vent. I have no idea how that would come out without taking a bunch of stuff apart – and if you figured out how to get at the little bugger, those little screws would probably cause insanity! I also replaced the cruise amp while I was in the area.

I spent a lot of time cleaning up everything – it was very dirty from the leaking coolant and the accumulation of 20+ years of crud and degrading foam. The foam seals are the reason I’m writing this.

I hated the “blast of fuzz” every time the defroster came on so I decided to fix it, and as usual that lead to fixing all of it! I purchased some 1/16” ECH closed cell foam from McMaster Carr – the softest available. The stuff is expensive for foam but is only surpassed for heat/chemical resistance by viton foam. I figured the heat resistance will translate into long life and the stuff is said to resist compression set very well. It is not as soft as the original foam but seems to do the job. If I did the job again, I would get thicker foam – I did not realize that the foam on the “outside” air door was a lot thinker than on the other doors. All I did was use multiple layers.

I removed the footwell doors (they are loose anyway when you take the box apart) and the outside air door. I did not remove the others because I was afraid I would break the parts. Use your own judgment about which ones to take out. I scraped the old foam off with a razor blade paint scraper tool and lighter fluid. It is slow work but not hard.
For the parts that I could spray, I used the 3M Super Trim adhesive left over from my hood liner installation and it worked very well. For the parts still in the box, I used Goop auto adhesive and it also worked very well. The only problem is the odor of the Goop hung around for a week or so, but is gone now.

I can’t say that the foam improved anything greatly but the center vent seals completely now and the recirculation works to keep out the “hit skunk” odor that is becoming very common right now. I also don’t hear the doors slam shut anymore. The best part is not having little pieces of foam blow out, but I could have achieved that by just scraping all of it off. Overall, replacing the foam is worth it if you already have the box out and are going to keep the car.