My truck has taken to leaking about 3 cups of coolant from the pass. side of the engine roughly between the water pump area and the turbo....but only once a day after about a 8 mile run. Have pressure tested the coolant system at 20psi for an hour with no luck, no real visible traces except for the coolant on the driveway.

The water pump and thermostat were both replaced back in march with cummins parts along with the upper and lower hose and the freeze plug behind the turbo, since then I've put a little over 20K miles on it with no problems. Truck runs great with steady coolant temps around 180 or so after it gets done cycling. No signs of coolant in either the oil or tranny fluid.

Am thinking possible suspects could be water pump, Lower hose adapter O-ring, oil cooler gasket, thermostat seals or maybe early signs of head gasket failure.....Does anyone have any other thoughts....I really don't want to have to trade the thing in on a yugo..........

 

I got A 1st gen. 12 valve and it's A common problem for them to leak from the head gasket in that area. I got A friend who's has been leaking there for years.

 

Not so wierd, pretty common if it is coming from the head gasket below the thermostat. A Cummins mech told me it would do no harm, but after awhile it bugged me so much I changed the gasket (295k). It was easy to see on the gasket where the coolant had traveled, and true to what the mech has said, no damage to the engine. I did take the opportunity to change the valve springs to 60 pounders (for the 3k GSK) while the head was off. Way easier than trying to do it under the hood. I also replaced the valve seals while the springs were out.