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Can't seem to fix leak on R4 compressor connection

webbch on Wed July 03, 2013 10:25 PM User is offlineView users profile

Year: 1990
Make: Chevy
Model: K2500
Engine Size: 5.7L
Refrigerant Type: R12

My truck's compressor blew up a couple weeks ago. I've replaced the compressor, condensor, evaporator and accumulator, flushed the lines, added 3 oz mineral oil to the compressor, 1 oz to the condenser, 2 oz in the accumulator and 2 oz in the evaporator for a total of 8 oz. I re-attached the lines to the compressor, pulled a vacuum, then added 1 oz of R134a and pressurized to 100 psi with nitrogen.

I've been sniffing the lines with my tek-mate to look for leaks before I recharge with R12. All of them check out except the lines at the connection to the compressor. The sniffer goes off every time I stick it under the connections. I've sprayed some big blue on them as well, but don't see any bubbles. I even put in a new line, connected it all up, and it STILL sets off the leak detector at the same place. Any ideas on what I'm doing wrong? I really want to make sure the system is tight before I charge up with R12. Thanks.

I've torqued the compressor connection to 26 ft-lbs (specified in service manual), and given it just a little bit more on subsequent attempts to ensure it wasn't too loose for normal sealing. New sealing washers came on the new compressor that were identical to the old ones, so those are new as well. I lubed them with a little refrigerant oil before installing.

Chad

Edited: Wed July 03, 2013 at 10:29 PM by webbch

webbch on Thu July 04, 2013 7:19 AM User is offlineView users profile

For reference, the sealing washers I have look just like Sealing Washer Kit

I'm using the green one (discharge port) and the gold one (suction port). The old compressor had similar depth ports and was also using these same colors. The connection to the compressor appears to be even. I've seen many recommend the use of the red sealing washer. I can use that one as well in conjunction with an even thinner washer (looks more like this) and keep the connection block flat, but alas, still have the leak problem.

I'll have to keep looking. I did notice that the leak I was detecting on the discharge line side went away after I tightened the connecting block substantially more than the required torque spec. However, the suction side still had the leak. Is nylog recommended on these sealing washers, or refrigerant oil?

Edited: Thu July 04, 2013 at 7:23 AM by webbch

GM Tech on Thu July 04, 2013 8:18 AM User is offline

I use the red on discharge and a standard silver on suction- works every time-- sealing washers go on dry,

don't be afraid to torque it down- I've never used a torque wrench on thast connection- but be sure the manifold is flat/parallel to the pump.

-------------------------
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......

webbch on Thu July 04, 2013 7:23 PM User is offlineView users profile

OK, I think the problem this whole time is brake cleaner. At one point, I cleaned off some oil from the compressor ports by spraying some brake cleaner on a paper towel and wiping down the compressor ports.

To verify this theory, I took a connection that had previously shown no sign whatsoever of a leak with my tek-mate, sprayed it with brake cleaner, dried off the fitting and allowed it to dry. Now the sniffer sets off any time I go near that fitting that I KNOW is good. So I'm guessing that all this time I've been chasing a phantom leak brought on by brake cleaner fumes.

wptski on Thu July 04, 2013 7:57 PM User is offline

Quote
Originally posted by: webbch
OK, I think the problem this whole time is brake cleaner. At one point, I cleaned off some oil from the compressor ports by spraying some brake cleaner on a paper towel and wiping down the compressor ports.

To verify this theory, I took a connection that had previously shown no sign whatsoever of a leak with my tek-mate, sprayed it with brake cleaner, dried off the fitting and allowed it to dry. Now the sniffer sets off any time I go near that fitting that I KNOW is good. So I'm guessing that all this time I've been chasing a phantom leak brought on by brake cleaner fumes.
That's used a lot as it flashes off and I "think" some have used it as a flush.

GM Tech on Fri July 05, 2013 2:16 AM User is offline

Once you spray- you can never go back and leak test-unwritten mechanics rule #13 - carb cleaner, brake cleaner whatever--even dead birds will set off a leak detector

-------------------------
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......

wptski on Fri July 05, 2013 7:51 AM User is offline

Quote
Originally posted by: GM Tech
Once you spray- you can never go back and leak test-unwritten mechanics rule #13 - carb cleaner, brake cleaner whatever--even dead birds will set off a leak detector
What cleaner can be used that won't set off a leak detector?

GM Tech on Fri July 05, 2013 11:42 AM User is offline

water

nothing with propellant in it..

-------------------------
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......

wptski on Fri July 05, 2013 1:44 PM User is offline

Quote
Originally posted by: GM Tech
water

nothing with propellant in it..
Water alone won't clean much of anything.

webbch on Fri July 05, 2013 3:06 PM User is offlineView users profile

24 hours later, after baking in the sun yesterday and this morning, the "test fitting" that I sprayed with brake cleaner is only detectable on the "high" setting. I'm guessing this is why you leak check on the low setting, and only use the high setting to hone in on a suspected leak area.

webbch on Wed July 10, 2013 5:59 PM User is offlineView users profile

There does not appear to have been a leak. I've only been running it a few days now, but it's cooling great now. Only time will tell for sure. I suspect the thick green sealing washer used in conjunction with the thinner gold washer was just fine. However, I currently have the red washer (slightly thinner than the green) and the silver washer (thinnest of them all) installed.

Learned to avoid using brake cleaner on things I plan on leak testing with an electronic leak detector!

Cussboy on Tue July 16, 2013 4:21 PM User is offline

Some brake cleaner formulations use chlorinated/halogenated solvents so they can be "nonflammable". However, even minute traces set off the electronic leak detectors, which basically pick up any volatile materials that have different thermoconductivity than "air".

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