hey everybody,
i have had this a/c leak in my 86 420sel since i bought it last year. i had it filled with dye and bought a uv light but could not find any leaks. well now its been humid here in texas and my ac has been leaking water on the drivers floor for some time now and i havent looked under there until today. i was expecting to maybe replace a hose that was dripping on the floor but as soon as i put my hand on the carpet it felt oily and wet up by the top of the gas pedal and i instantly saw lots of dye. when i pulled back the carpet i couldnt find the drain hose but i saw two hoses, one was blu and one was covered in what looked like rubber going into a little aluminum looking block of metal. there was clearly dye all over the blue lines fitting and all aroud the immediate area. other than below that fitting i didnt see any other dye anywhere else so i tried to tighten that fitting as best as i could (which wasnt very good because i have no room and probably could have used better tools). anyway we will see if the leak stops later but another thing is condensate was forming all over the place down there and it doesent seem to drain off any where except to drip on my carpet. should there be some way to keep the condensate from destroying everything down on the floorboard? i had planned on this as a long term toy but i cant justify 1800 dollars on the a/c plus a rotted out interior from moisture.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

As you know, this does not look good.

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2012 E350
2006 Callaway SC560

First question I have is why is the dye leaking inside the car? Sounds like an evaporator core/fitting is loose. Does the AC work when you charge it?

I have had success on my 87 560SL with a sealant called cryoseal (as of right now the AC works great - but time will tell). Everyone on the forum thinks it's cheating....but if the AC works......especially in Texas....does it really matter? Even if it's not a permanent fix - it delays a costly removal of the dash to get to evaporator core.

You do have to replace some parts to make sure this stuff works - the expansion valve and receiver drier....system MUST be really clean too.

Give it a shot.....

I expect that the evaporator is leaking, and the drain hoses have deteriorated, letting the condensate drain onto the floor. Those drain hoses are flimsy foam with springs inside.

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2012 E350
2006 Callaway SC560

I suspect the TXV (expansion valve) has a bad O ring. More common than evaporator failure on a 126. Condensate drains can be replaced with vinyl hose or such. Clean out the openings to the drain a bit, first, to make sure debris isn't clogging them.

Replacing the TXV is a physical job, requiring crowsfoot wrenches, leaning upside down, but, for a young man, not too bad. I'm old and find it not too difficult. You MUST read up, in the archives here, or in the factory service manual if you plan to DIY.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

My a/c works great but it looses its charge after a few months. it looks as though that fitting is leaking, and I tried to tighten it as much as possible, but i need to buy another set of crows feet as all of my tools were stolen not too long ago. As far as the drains go the water drains pretty good on the ground but it also soaks up on the floor. Is it possible to see the drain hose on the drivers side by just removing the little tray under the steering wheel and peeling the carpet back? or do i have to remove the center console because of that plastic on the side where the carpet goes over wont come out? on the 420sel does water drain onto the ground from two drain hoses?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

You need to remove the side carpet at the trans tunnel to get to the drains. If you're careful (and use judicial amount of brute force) you can slde them out from under the console "lip". At least on the generation I W126.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

I slid the carpet back but faced plastic on the other side of it.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

The carpet is attached to the black plastic as one piece on mine. Check for release fastener (black plasic screw on mine).

Here's a picture of the drain in post #8. W126 87 300SDL Mysterious Sopping Wet Carpet

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

if the expansion valve has a bad o-ring, do i need to replace it or just put a new o-ring in it?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

We're surmising that it's a bad "O" ring (God forbid it's a bad evaporator/tube), so just replacing the o ring sounds good. Many folks find the job hard on their back, so they replace the TXV while there, so they don't have to stand on their head again. TVX is not too expensive.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

IF it's an o-ring it would be foolish to remove the expansion valve and not replace it (the expansion valve) with a new one while it was out.

At least I would not do it.

Sometimes the expansion valve itself will leak.

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2012 E350
2006 Callaway SC560

well i am going to replace the expansion valve, drier, and the little leads that go from the drier to the fan while the refrigerant is evacuated. hopefully after some finger crossing i will have the first non leaking and working air conditioning of any car ive ever owned. (knock on wood trim)

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual