1987 300TD HVAC system overhaul thread

[Aquaticedge]

Well, It's decided.. my HVAC system is one of the last things left on my car that doesn't work. I've ordered a compressor, I've also will be ordering a Receiver/Dryer. I've been reading on the forum about the Condenser behind the dash going out... So I have a few Questions about it,

1) Should I go All out and just replace it and only have to yank the dash once or just try to use whats there? Currently the Evaporator holds vacuum but I want to head off any problems,

2) I think the compressor just seized, whats the likelihood that it grenaded out into the system?

3) I'll be using babymog's 124 Dash removal turtorial (thanks for writing it!) located here 124 Dash Removal Turorial (sans photos)

4) How should I Flush the AC system? I do believe that it's prudent to do giving that the compressor could have grenaded into the whole system

I will also be overhauling all my Vac pods in the dash too, I'll rebuild what I can and replace what I cant..

is there anything I missed?

If your interested in the process, I'll be posting pictures as I go, I plan on this taking a month about and hopefully at the end of it I'll have a Working AC and heating system for awhile.

In spite of what many on this forum believe, not ALL 124 evaporators fail. I have an 88 300E that still has the facory evaporator and still has no leaks. I've seen several posts stating that all 124 evaporators either have failed or will fail. I don't believe that, especially since mine is well over 20 years old and the car has a half million kilometers with no evaporator problems whatever.

That said, since you are doing a podectomy, this is a decision only you can make. You are faced with roughly a 15 hour job. Replacing the evaporator would takn only another hour or so. The problem is that if your evaporator is NOT leaking, you are taking a chance by disturbing it.

I did a podectomy on mine about 6 years ago as I recall and I did not replace the evaporator and I'm glad I didn't. It's a tough decision to make.

To answer some of your other questions, the way you flush the system is to break all connections and blow flushing agent through the hose or component and THOROUGHLY blow it all out with compressed air. Then replace all o-rings and coat them with Zylog upon assembly.

In the event of a failed compressor, thorough system flushing should NOT be considered optional. In fact I don't know of any compressor mfg's or rebuilders who will warranty their compressor unless the system is completely flushed and the r/d replaced. Since you say the compressor siezed, there is no doubt whatsoever regarding debris being in the system. It's THERE, PERIOD!

Have you TESTED the pods yet? It is a pretty simple procedure to test them and WELL worth it when faced with the job of a podectomy. If there's no need to replace them, you DON'T want to go through it, believe me. It sounds as if you've already tested the evaporator.

If you haven't tested the pods, let us know and we will tell you how to do it.

[Aquaticedge]

I've tested everything UP to the pods, Some work while others revert to defrost, I'll know more in the coming week

The easiest and best way to test the pods individually is to remove the glove box and look to the lower right for the switchover valve. Remove the hoses one at a time from this manifold looking thing and use an auxiliary vac source to make sure they don't leak.

If none of them leak, there's no need to pull the dash. If even one of them leaks, my advice would be to replace them all.

[Aquaticedge]

I'm sure one or more are shot. Someone told me they are rebuildable so, I'll see whats available, Thanks for posting

[babymog]

Someone here tried the rebuild kits, could've been sixto or gsxr, and the diaphragms for the dual-chamber pods were not large enough for full travel.

Hard to say on the evap, and should you have a new heater core too? Probably leave them alone if they're okay. I have two spares, pulled from cars, hold nitrogen pressure well. Apparently they don't all fail?

I might not know what I'm talking about on this part, I have HVAC work done by a trusted professional, who tells me that a grenaded compressor requires a new filter/dryer and a flush through the condensor and to the filter/dryer, everything else is fine. Sound correct?

Anyone coming through NE Indiana who can take a dash to Florida?

[Aquaticedge]

I know my heater core is good, it practically Roasted me out of the vents that mostly work lol

[vstech]

on the condenser flush out. you have to disconnect the lines from the reciever dryer, and the input of the condenser, and flush with flushing agent from the reciever connection out the discharge connection. I have not pulled the connections apart on either my parts car or my newly acquired 87TD, so I don't know yet, but be SURE there is no screen, and if there is one, pull it and clean it or replace it. the reciever should prevent any debris from passing it, so the line from the reciever to the evaporator should be clean, but if you get gunk out the condenser, it takes very little time to disconnect the line from the expansion valve to the reciever and flush it as well.
the next thing you have to do is flush from the expansion valve connection of the suction line, through the evaporator out the suction line that goes back to the compressor. this will be harder because the line is larger, and the debris will not as easily be flushed out.
personally, I'd go to a welding supply shop and pick up a 40 or 80C Nitrogen tank and a regulator. to flush it all out. using compressed air will work, but it will also introduce water into the oil residue that is in the lines, and it's nearly impossible to get it out once it's in.

[Aquaticedge]

where is the dryer? I've looked all over for that bugger.

[vstech]

on my TD, it's right behind the drivers headlight.

[babymog]

Yep. You'll see only the top from above, I believe that you need to pull the panel under the oil cooler to get it out.

[Aquaticedge]

hooboy, that ought to be fun

[babymog]

It's a plastic cover, like the fender liner, pretty simple. As I'm thinking about it, ... might be part of the fender liner on the turbodiesel 124s.

[Aquaticedge]

I'll take a note of it, and when I get that far I'll see whats there

[Aquaticedge]

Ok, I got the dash out.... Aaand I'm dismayed... I have to fix other peoples Fixes and decipher the non color coded Vacuum tubes... some are factory, some are not.....some of the vac pods are cracked, some are disconnected. it's a nightmare... Over the next week I expect to accomplish

1) See which pods are shot
2) try to find color code vac lines
3) gut the other car for parts I need
4) yank the radio. It sucks.
5) yank the center console
6) replace light bulbs... most of mine are shot
7) Repair wiring and prep for AC work

Questions for you:

What holds the center console down? the front is free, I diddnt try to move the rear section

When you select Gears, should there be a moving indicator that shows you what gear your in like in most modern car with the needles or is it just positional in the shift gate with no indicator light? Ie a moving red/green led with the shifter

Do you know where I can get color code vac lines

if I need to drive this car... Can I without the dash? (I currently have it parked.)

And as a side note, Thanks babymog, your Tutorial on the 124 Dash removal is invaluably helpful