I picked up a used plate/fin evaporator from my friends vehicle, and it was caked with a sticky dirty mess on the front side of it. It didnt look like it was leaking from the o-rings, but it was hard to tell. It could have been leaking from the end of the block style txv, but again hard to tell. I cleaned up the core really nice and it looks almost new, but I am worried the core itself could have a leak in it. I dont want to go through the effort of insalling it if it could have a leak in it. Is there any way I could bench test the evaporator for a leak before installing it? A new OEM unit is upwards of $250, and I do not want an aftermarket unit. Thanks.
Pull a vacuum on and see if it holds, or charge it up with about a 100 PSI of nitrogen.
One can also fabricate fittings for the core and place it in a dunk tank.
The evaporator should be flushed prior to testing. Residual lubricants can mask a leaking evap. Suggest both a vacuum test and charge test. The vacuum test could indicate no leaks and a charge could reveal a potential problem.
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Sticky, dirty mess--- as in oil? and you don't think it leaks? How did the sticky oil get there? There are those that leak due to pinhole leaks caused by acid rain corroding the air inlet face of the evap....you can pull a vacuum all day long and swear it doesn't leak, and it will loose a complete refrigerant charge in about two weeks.
Bottom line if that sticky stuff is oil or grease-- you have a bad evap- it is refrigerant oil that catches all kinds of dirt in the air path...
This failure mode was extremely common on Caddies and H, W, N, J cars in the GM line up prior to 1994....
I'd go with aftermarket evap- just over a $100 will do just fine...
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
Edited: Mon August 06, 2012 at 10:22 PM by GM Tech
OK thanks for the tips guys. You convinced me to skip the time money and effort of getting it flushed and tested. Found a new OEM Denso evap (same exact evap that the dealer sells) for 1/3rd the price.
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