92 BMW 318i, first time learning AC work. Replaced the compressor (broken magnetic clutch), dryer, flushed the lines, replaced the o-rings. When I turn on the vacuum pump I can hear a whistle from the block at the firewall where the lines go into the car. If I disconnect the high side hose and just suck low side, I can hear it. Same if I suck just high side with the low disconnected. With both connected and sucking, the whistle is about twice as loud.
I removed the lines to reseat the o-rings, no help. I played with the Schrader valve to see if it was sticking open (or maybe a faulty R134 adapter), no change.
Any advice on how to isolate this? So far AC work is not my favorite.
The low side and high side are connected, so if one is open you will be pulling air into the system. Do a lot of that and you'll need to replace your drier again. As for the leak, put in a token charge and use soapy water in the area you are hearing the sound. If the leak is audible, it shouldn't be too hard to pinpoint.
From where you said you hear the whistle, sounds like time to look under the dash.
Hope it is not the evaporator.
My car has a thermal expansion valve that bolts to the block and the part of the evaporator that sticks through the firewall. I had a leak there was well, it was from the o-rings slipping off while I reached my hands through 30 feet of engine bay to get to the bolts. Just make doubly sure all your o-rings are still where you put them as you tighten everything. Otherwise, it sounds like your evaporator is wonky...and in that case, I pity you. My wife's car has a clogged evaporator, and I am NOT looking forward to disassembling the entire dashboard (and front half of the interior) to get to it.
I know that this is going to be a stupid question, but I'll ask it anyway. If I hear the leak near the firewall, then that is where the leak must be? I can automatically ignore connections at the condensor, dryer, compressor, etc and just focus on that one area?
