A Cautionary Tale---81 300D w/84 Powertrain---R4 A/C Compressor Explosion

[iladelf]

Howdy all,

Just had work done on my '81 300D (that has an '84's engine and tranny) to replace a bad R4 A/C compressor. The new one...exploded. Yes, exploded. My mechanic says it blew the case. Was frightening and I believe had someone been in or near the engine bay at the time of occurrence, serious injury would have likely been the result. Now, the details.

So, my mechanic replaced a bad R4 with a new unit. Along with that, there was a cut in a hose (the A/C Manifold hose---either part # 13-029 or 13-030 in my father's ancient Performance Products catalog, from Fall/Winter 2008). Before he could replace the R4, my mechanic had a difficult time finding the part; I found a local Napa which repaired the rubber hose with new. The repair looked very sturdy and capable of holding the pressure of an A/C system. After receiving it, repair was all systems go.

Upon picking up the car, he told me the car's A/C ran around 50 degrees, but that it probably wouldn't cool the best in town due to what he thought was an incorrectly working front auxiliary fan. Believe he said it was sucking air in instead of blowing it off the condenser. The final price tag for the repair was somewhere between cheap and expensive, a repair that, after hearing the final total (included replacing a rusted ball joint) made me think to myself that I've spent a lot of money on an older car. Oh well, it was time for the test drive.

Driving it around town...was...not so good. With the windows closed on a 90 degree day, the air coming out of the vents in MIN position was cool, but not cold. I also noticed a severe loss of power with the A/C on. I decided to drive it to a town 30 minutes away; figured I needed to check it via highway, if it still didn't work very well, then go to Plan B (talk to mechanic about solution to issue). I thought I noticed a bit of metal-to-metal rattling as I drove, but wasn't sure. The cooling was better, but not enough to use on a regular basis. Also, my coolant temp gauge rose to a needle's width above the 100C mark as I drove on the highway; the highest it has ever been.

Upon arriving, pulled into a a shopping center parking lot, and opened the hood. Immediately, I noticed the engine was severely loping and shaking, almost to the point of near shutting off. I decided to turn off the A/C, and the car returned to normal. Looking around in the engine bay, I saw nothing out of the ordinary, but knew full well things weren't right. Oh well, let's go get a bite to eat, I thought.

So, I pulled into a restaurant's parking lot, and decided to look at the A/C again. Now, I started hearing that intermittent metal "screeching" sound I thought I heard on the highway. I opened the hood to look around; saw nothing out of the ordinary. Decided to get back into the car and shut off the A/C. I found a thermometer I had in the car, and turned the A/C back on. After about 30 seconds (a minute?), the temp dropped no further than 77.5F, which I knew could not be right. So, I shut it off, and decided moments later to turn it on one more time. At this point, I had my driver's side door opened, my left foot on the ground outside of the car, and moments later...BOOOOOM! I felt something (Freon gas? a rock? a part of the compressor?) hit me in the leg. and then I saw fumes rise up from the engine bay (I had the hood up). So, after being stunned momentarily, I decided to check on what happened. There was green goo all over in the bottom front driver's side area of the engine bay, and then I knew...it was likely the compressor. You can see the immediate aftermath in the pictures below. Later, I checked underneath to make sure it wasn't the new hose; nope, it was intact.

After discussing with my mechanic (I was level-headed; after all it's a 35 year-old car), he believes it could have been a plugged condenser. Now that I'm looking at a condenser and an aux fan on top of what I've spent, I'm ready to punt and move to the Sanden. Might as well go modern if I'm going to have a reliable system. But that's for next year.

Of note, my mechanic says he'll refund me; that of course is good. His diagnosis? The compressor's case blew; you can still see a gasket hanging on the outside of the unit. However, when he mentioned to me that the system didn't have a high side port (it does, which he found after the blowout) and that there are no real pressure checks in the system, this may be a job for someone more familiar with these cars. I'm glad no one was hurt; he or anyone from his crew could have been injured rather severely, I believe. He also stated those compressors are supposed to have some kind of pressure relief valve, but it apparently didn't work or this one did not have one.