Originally Posted by allan5oh

You probably have multiple problems, and you might have solved a few of them already. The fan clutch will only get air while the engine is running, so it is not a "loss of air while parked" problem.

You've covered a lot of fittings, but have you really hit every single one? What about the fittings in the dash, on ABS relay valves, on top of the transmission, on the firewall, etc..

After that absolutely cover every single air bag. I once had a hole right in the middle of one. Couldn't hear it. You also have to check exhaust ports on all the valves, as well as the arms coming out of leveling valves. Another possibility is the quick drain cocks on your air tanks. Sometimes they need to be snugged a little more.

As far as your air dryer pissing off every 10 seconds, that's a serious problem that should be addressed. Are you losing enough air pressure during these 10 seconds (say from 120 to 100) to cause your air compressor to turn on or are you barely losing any air? If you are losing that much air you need to get it fixed. That could put you in serious trouble, plus air dryers can only handle a compression event every 120 seconds or so.

If it's not an air leakage problem, it may be the governor, air dryer or the air compressor itself. There are valves in the air compressor that can bugger this up. Look closely for any leaks on the lines going to and from these 3 items.

IMO you should absolutely get rid of ALL quick disconnect fittings and replace them with compression fittings. That's what I'm doing. I've finally got my truck to compress every 20 minutes or so. It's been a battle. I've probably changed about 20-25 fittings so far, and I'm just going to change the rest(some of them cannot be changed to compression fittings due to their design, blasted Volvo!).

After all this is done (checking all fittings, valves, relays, drain cocks, sensors etc..) you have to look at air actuated systems that could possibly drain internally due to bad seals, like transmissions. I've heard of the range splitter actuator leaking right into the tranny.

Originally Posted by allan5oh

The small line going to your air compressor is losing its charge, that is causing the compressor to compress very quickly, but you have a quick decompression since the governor is hitting the psi limit(that you were at anyways). Make sense? The small line is the signal line, it's leaking somewhere.

BTW if your fan clutch is leaking while off, it may be the air actuator is internally leaking as well.

Originally Posted by rank

I'm not understanding how a fan clutch that leaks air can cause the engine to over heat.

I help change a fan clutch on an M11. Or was it an N14? I can't remember. But it was a bugger. Not much room to work without taking the rad out. IIRC, we cut a section of the fan shroud out so we could remove the fan. With the fan out of the way, there is room to work. Then we pop riveted the piece of shroud back in place.

Me, I don't like air leaks. I figure every time that air dryer sneezes, my compressor dies a slow death.