AC repair and recharge questions

MCBMW
Sun, 22 Jul 2012 22:12:17 +0000
Maintenance/Repairs

Ok, this post is full of bad ideas so go ahead and shout at me if you need to.

I have a 1985 BMW 318i, 5 speed manual.

So, I had this crazy idea that since it’s pretty much been 100 degrees every day since April I need some AC in this car.

Now, some background info. I have no idea how long this car sat or how long it had been since the AC was last serviced. I have been very successful DIYing everything from timing belts to half shafts to… pretty much anything but a transmission issue, but I decided one must learn somewhere.

Some more background info, in order to retrofit this vehicle it is recommended that you replace the compressor as the original equipment model is not 134a compatible, but I have it on good authority that dumping a little in will get you some cool air but burn out the compressor more quickly and you should not mix the oils.

Ok, so, with this in mind and the idea that this would be the last summer I’d be driving this car, I went ahead and simply purchased an adapter for the low side valve and some 134a. I know this is not a proper retrofit, but I found that the car held no pressure, and I simply don’t care if the compressor burns out after a week, because that’s about how long I need the AC to run anyway. Longer story, won’t go into it. Anyway, before charging I looked for obvious signs of damage and leaks, cleaned the condensor and checked to see if the clutch would engage and if the condensor fan was running. I came up good on all counts.

So, I decided there wasn’t much else to do but to start adding my 18 oz can of charge and see what happens. So, I began charging. The low side pressure started to rise and got as high as about 25 psi and then dropped back to zero, the compressor had kicked on, so I guessed that was a good sign. I added the rest of the can and the pressure never came off zero. I read that these cars had required about 2 pounds of R12, so I figured I’d start another can and see what happens. I began adding the second can and the pressure began to come off zero psi finally. I got it up to about 10 and decided to feel at the vents. It was barely there, but it started cooling down just ever ever so slightly. So, I squeezed in a little more, checking the gauge I was at about 11 or 12 psi on the low side. I began to add more, and that is when things went terribly wrong.

I heard a loud pop and suddenly found myself in a white cloud. I released the trigger on the can. Stepping back I watched the low side gauge climb to just at redline very rapidly. I stepped back fearing and explosion and shut the car down. I gave things a minute to settle and with the gauge on the low side still at red line I removed the hose from the low side fitting. I could still hear gas escaping, and I located the leak. The rubber line that runs between the low side line and compressor had been resting on one of the rails of the car and had simply worn through. I missed this on my initial inspection. Once the line came up to pressure, it blew through completely, but it is absolutely plainly obvious that the leak was due to this line of wear from contact with metal.

So, I have two questions oh wise ones.

1. How the hell do I remove this line at the low pressure line? It seems like I just unbolt from the compressor, but the other end? Any ideas? Seems like it should be easy, but I’m not so sure.

2. I have access to proper R12 now, but given the spike in pressure on the gauge, did something else happen as well, or is that just a result of a leak on the low pressure line? Given this scenario, is that pressure reading “normal”? If so, aside from replacing the line and pulling a vacuum is there any other step I should take to start riding cool?

Thanks for your help, as this community as helped me so many times.

37 posts - 10 participants