Identifying the air cond. low pressure line and end color

[Gusfazekas]

On a 195 SL500, can anyone explain how to determine the location and color of the low pressure line on the air conditioning piping? I need to check the system and might want to use a sealer. Has anyone successfully used a sealer to plug a leak in the evaporator? I posted this on the SL forum but got no replies. Thanks, Steve

[Matt L]

I doubt that you will have any luck with the sealer, but if you do use any, be sure to know exactly what you are putting in and label the system very conspicuously to warn future service technicians.

The stuff sold at the big-box parts stores will almost certainly not help at all. Especially be wary of so-called "o-ring conditioners" which can cause leaks where none existed previously.

Cryoseal is one product that might actually work. This is something that you get installed at a shop, rather than attempt to do yourself. They shrink-wrap the service ports to prevent disasters in the future. But still, although it might work, I would bit the big bullet and pull the dash.

That is, if you are 100% sure that you have an evaporator leak. There is a test fitting which bolts on in place of the expansion valve to charge the evaporator with nitrogen.

[Gusfazekas]

I took my SL500 1995 out for a spin after placing a block/heater core sealant into the heater core last week. It is still leaking a small puddle of green, kinda thick slime after the car sits or is driven. When I did the heater core, I replaced the thermostat because it was giving me trouble and the antifreeze. The car had Prestone (which is green) in it and I flushed everything out and installed the Zerex brand (which is kinda light yellow) Since the green slime is still dripping out, I am concluding that this is freon/dye residue. The car still cools well. The dealer says that the hose that this stuff drips from (located in the trans/drive shaft tunnel) is coming from the heater core/evaporator compartment and if it isn't antifreeze, it has to be the freon/dye leaking out. Anyone have any thoughts? Agree or disagree? To remove the dash and replace the evaporator is about a $4K job at the dealer. The price on the MB dealer evaporator is $800 alone. So I would be inclined to use a sealer if that might work. I welcome ideas at this point. How about the MB service techs weighing in on this?

[Matt L]

If it is dye, it will be fluorescent. Aim a UV lamp at it and see if it glows. Now, just because it is dye doesn't mean that it definitely came from the AC system, but dye is routinely added there and not normally added anywhere else.

I realize how difficult it is to change the evaporator in that car. Sealer is used for situations like this, but mainly for an owner who does not plan to keep the car very long and thus doesn't care much how many more years of AC it has left, as long as it runs for a season or two. If this does not describe your relationship to your car, stop thinking about sealers.