Car: 1991 560 SEL with R12 system with a working compressor
Problem: A/C not very cold.
Test: injected UV dye with additional Freon

Upon putting a blacklight on the compressor, I found it is totally covered by the yellowish dye. I mean the whole compressor lights up like some one painted it one side with this UV dye. I am going to spend some more time tonight to study the leak a bit more and I need your advise.

How should I go about checking if the dye is just from the connectors on top of the compressor? What could explain the fact of large area of even dye deposit?

Thank you.

Probably the o-rings that seal the hose manifold to the compressor.

Dye is all over the engine side, right? comes around to the bottom and crawling up the fender side?

Leak test, likely the two 0-rings are shot, blowing freon and oil out. Naturally, it's almost impossible to reach the engine side to test, and you will have to pull the compressor to replace them, but otherwise this is a very easy job. You won't have to pull the clutch or anything, just the hose maifold (four 6mm allen screws, probably). Get new 0-rings for the hose connection too, just to be safe.

Peter

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

How long ago did you put in the dye? Oil has a tendency to migrate along surfaces. If you're still unsure of the origin, see if you can wash it off and try to catch it earlier next time.

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95 E320 Cabriolet, 169K

Warm water and a gel shampoo .. 50/50 mix ..
Whip the mix up real good with a 1' paint brush and apply the foam to the head of the compressor..
You will see the leak as it will blow out a bubble as large as an orange..

Kids Bubble mix works well too.
They make leak spotter liquids , but I have been using shampoo for years ... I use it for pinpointing after I have located the general vicinity with my GE Halogen leak detector..

Hi, Arthur. Thanks again for coming to the rescue. Since this time the leak was so bad that the clutch wouldn't engage no more. Shoudl I ask the shop to blow nitrogen in there to check leak as you subscripe? Also, is it ture that I will have to get a "new" compresor if the leak is found to be from teh compressor itself?

You have to have pressure to make the leak show up, so even if there is not enough to trip the compressor , there may still be enough to show on a bubble test.
Where the leak is and what is needed to fix it can not be determined till you find the leak..
Push the schrader valve in for a sec to see if there is still pressure and then try a soap test where you found dye...
If it's empty, forget it til you get some pressure back in there .
I just add a little refrigerant to get a few psi and go leak hunting...

Hi, Peter. It is actually on the fender side. If I shine the blacklight from the top of the engine bay, I would not see anything. If I put the blacklight right in front of the driver side front tire and shine it toward the engine, I will catch the whole side. Nothing from front nor from back seal. With regular light, I could see there are oil where there are UV active.

It seems to started right below those two allen screws whose housing has an S mark. Since I don't think oil will go down rather than up. I will attach a picture tomorrow with daylight. Hopefully it is just the oring.

Thanks.