How to find AC Leak... need advice... please! - PeachParts Mercedes-Benz Forum

SlashJoe · #1 06-19-2008, 11:28 AM

How to find AC Leak? ... need advice... please!

Oh no! Not another AC thread! I know! But I need help.
So here it goes... AC didn't work since I got my 85 300D. PO's mechanic said compressor leaked. That was about 2 years ago. I decided to try and fix the it. The system didn't have any pressure and before I started, I applied 20 psi of air to the low port and it leaked in no time. I was able to hear the leak at the compressor. So here what I did:
1. Removed compressor, expansion valve, and dryer.
2. Flushed all lines, evaporator, condenser, and pushed compressed air to push it out. Messy job!
3. Replaced o-rings at: expansion valve, dryer, hose junction next to the low port.
4. Installed new expansion valve.
5. Drained and added 2 ounces of PAG oil to new compressor ( that's all it can hold without dumping it all while installing ), and installed it. What a pain! I was able to only torque the hose manifold to the compressor using only about 20 ft-lb. My big torque wrench won't fit. The instructions with the compressor said 25 ft-lb. Used green seal washer on discharge side and NAPA TEM 407279 on suction, no pilots.
6. Added 4 ounces to new dryer and installed it.
7. Added 2 ounces in the suction hose near the low port.
8. Closed the system.
9. Applied vacuum for about an hour. It reached 29 after a few minutes. But it won't hold the vacuum. When I stop the pump, the vacuum will drop slowly, but you can see the gauge move looking at it for a minute. I disconnected the hoses and let it sit overnight just to rule out the manifold tool. In the morning it had 0 vacuum.

So what now? Any idea's? Any way to find the leak without needing to eventually remove the compressor in order to drain it and add the correct amount of oil?
I can't think of any way to find the leak while on vacuum. If I add compressed air and try to hear the leak, will I need to flush the system and replace the dryer?

JimFreeh · #2 06-19-2008, 11:36 AM

Anytime a compressor has sat for an extended period (and 2 years qualifies), the shaft seals can and often go bad.

Jim

tangofox007 · #3 06-19-2008, 11:39 AM

Quote:

Originally Posted by JimFreeh

Anytime a compressor has sat for an extended period (and 2 years qualifies), the shaft seals can and often go bad.

Jim

That might explain why the old compressor leaked.

SlashJoe · #4 06-19-2008, 11:41 AM

True, but this is a new compressor that I installed.

tangofox007 · #5 06-19-2008, 11:49 AM

SlashJoe,

You have obviously invested a lot of time and money in your a/c system. After I did the same thing a few years ago, I (slowly) came to the realization that an electronic leak detector was an essential tool when doing major a/c work.

Also, the new style sealing washers on the compressor can be problematic. I found that I needed to add some spacers to the bracket that bolts to the compressor; otherwise, the bracket put a side load on the sealing washers and caused a leak there.

Matt L · #6 06-19-2008, 11:51 AM

Find a shop who will charge it with nitrogen and 4oz of R22 to check for leaks with an electronic detector. It is legal to discharge this mixture into the atmosphere.

SlashJoe · #7 06-19-2008, 12:31 PM

Forgot to mention it had been converted to r134a at some unknown date, no sticker.

dmorrison · #8 06-19-2008, 06:52 PM

If you running it R134 then put a can of freon in the system and use a Freon detector (sniffer)to find your leak. Check the entire system. when it comes to checking the evaporator, sticking the sniffer in the line hole to the case will let you know if it is the evaporator.

Dave

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92514