Hey guys, I picked up a real clean 94 dually RWD IDIT for 1500 bucks. I bought it because he had paperwork for a Jasper E40D rebuild that is still under warranty. The truck is getting parted out, but the original problem was that it developed so much coolant pressure, that it blew the neck off of the radiator! I figured it was head gaskets, or the dreaded cavitation, but I got it home and put a scrap radiator in it, and the things runs perfect. No oil in the water, no water in the oil, but it still build pressure from the radiator. It immediately, when started blows a stream of fluid out of the overflow tube, and when the coolant level gets low enough, it blows bubbles from the tube. The bubbles don't smell at all like exhaust, and there is no smoke produced from them. The motor sounds and runs perfect. The water pump is leaking slightly from the weep hole. My question is, Could a water pump back up in such a way, that it blew pressure back into the radiator? Nothing else seems to be unusual about the way it runs. It doesn't overheat while idling, and there is no moisture or coolant smell from the exhaust. I need to buy a compression gauge and check that, but it runs too well to think head gaskets, and if it were cavitation, I would think the bubbles would smell like exhaust, and they don't.

Your thoughts? Thanks,

Mac.

 

are you running coolant, or are you running water? Once I ran water while trying ot diagnose a similar problem, and once it got up to temp, it would bubble like you said. no exhaust smell. I even captured a bunch of the gas, then took it to a clean area. Then opened the jar. No exhaust.

I ended up theorizing that the water was boiling in the block once it got to temp, thus making it appear like bubbles. Once I ran fleetcharge,the bubbles disappeared.

 

put a small wire under the rad cap over flow valve and put overflow hose in bottle with water if it blows bubbles it is head gasket or perforated cylinder wall, it will do it cold and maybe worse if warmed up, put the truck in gear and put a load on it.. if it bubbles more its more proof its a compression leak of some kind..if the head gasket blows it only ocationaly leaks oil into the water, not every time.

 

Gen, I am running coolant, and it is not a boiling problem, because it starts immediately at cold start, before the truck could ever produce that kind of heat. Speed, I don't have a relief valve radiator cap, I have decided to do a compression test before I pull it. I'll know more then.

 

Going to say 95% certain it's a head gasket. That's what happened to me; I could even feel a sharp "pulsing" in the upper radiator hose at idle. Replaced the gaskets, everything's fine!