I should have known better than to try to bring the GM R4 compressor back to life - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 06-29-2015, 02:31 PM

A couple weeks ago my brothers '85 300D threw the A/C belt, and he asked me to fix it. I told him the cost for a Sanden retrofit, but decided to try and save him some money by trying to resurrect the R4. It was replaced a while back, but the system had a leak that we could not find. He kept on adding 134a until it threw the belt. The compressor was not frozen, so I put a new belt on it and took it to the A/C shop to get leak checked and recharged. We found a bunch of small pinhole leaks in the low side hose going into the cabin. I went back home and made up and replaced that hose. Back to the shop and the system checked out leak free and was charged. It worked fine (with the exception of a bad Klima relay, so the compressor was hot-wired) for the next week or so. Fast forward to Friday, when his wife was driving it on the freeway when she heard a VERY LOUD BANG and HISS. Thinking she had a blowout, she prepared for a ride. When nothing happened but the cold air quitting, she proceeded on. After getting home and telling my bro' about it, he investigated it. Upon opening the hood he observed green oil everywhere in the vicinity of the compressor. This is what he found:

It appears that the case of the R4 exploded. Trying to figure out what caused it, we came up with a few ideas. It could have been excess pressure from the condenser fan quitting, or something like that. The other thing that I thought of is that it may have blown up from too much oil in the system, and the compressor was compressing more oil than refrigerant. The hose that was bad did not look oily in the least. I suspect that every time the system was charged, more oil was added. The leaks in the hose were not large enough to let oil out, but only refrigerant. Whatever the cause, I am NEVER going to work on another R4 again! It is just not worth the money and effort to get these compressors to work. At least that has been my experience. I should have bit the bullet and just put a Sanden in for him. Yes he would have not liked the extra expense, but he would have working A/C now!......Rich