I'm having a pressure problem in the coolant of a 93 6.5 and I fear it is the head. I replaced the thermostat, but the coolant reservoir slowly fills and doesn't return to the radiator. Seem like a slow compression leak at this point as there are no other classic signs of a blown gasket; no water in the oil; no white smoke on a cold start. Could it be anything else?

Sounds the same as my 95 was, head gaskets only leaked into the water jacket pressuring up the coolant jug, started out slowly but by the end of a week i couldn't keep up with adding coolant. (2 gallons/100 km's)

Did you do the R&R yourself? If so, what kind of time did it take? This would be a larger project than I've done before, but not that much bigger.

If not, what is the ballpark cost?

Yes i did the R&R myself with the help of everyone on this board, they were GREAT when i needed some information. If its just gaskets your cost would be low, head gaskets, head bolts, intake gaskets and some misc other gaskets. If you read through my Digging into the 2000 6.5 most of you questions should be answered there.

Quantum Mechanic does alot of refering to rock auto for parts and they seem pretty fair on prices if your in the US and can wait for parts, i ordered mine more local and picked em up from DSG in Saskatchewan, but then again i did more than just replace head gaskets.

You'll need a torque wrench too! Get yourself a piece of cardboard that you can push the bolts you take out into then you can label where they came from for easy install later too. Mark all wires and plugs with tape and name tag. I'm sure everyone here would be happy to help you out as you go.

You might want to get cooling system checker and test radiator cap ,I had same problem and it was a bad cap!

My first test for bad head gasket is, cold engine, remove radiator cap, make sure radiator is full, start engine and look for bubbles. A small leak will have small bubbles and big leak will have lots of big bubbles. This is almost always a sign that the head gaskets need to be replaced. No oil in water is very good sign. Northern auto parts is very reasonable for felpro gaskets and head bolts. Don't spend much time worrying about cracks inbetween the valves on the heads unless there is coolant build up at the point of the crack.:grd:

In addition to Dcam's info, if you want to know which side is leaking, remove water pump drive belt, drain coolant 'til below the water crossover, remove the crossover, fill it back up with coolant to the top of the holes in the head and observe the bubbles. Don't run it long with no coolant circulating, just start it cold and look for bubbles. Fred

Thanks for your help. I have Jim Bigley's repair guide that has a good description of replacing the head gasket. With all the useful posts on this site, it shouldn't be too much of a burden. The Digging IN post looks very helpful.

Strange. I had the coolant checked for combustion gasses. Nothing there. the truck was hot and had the chemicals in the radiator for close to 30 min. Nothing. Is there anything else that could cause excess pressure in the coolant system? Maybe a blocked coolant line in the lower end? It has a new radiator cap and thermostat.

It is possible that your head gasket is just starting to go and that it doesn't leak combustion gas until boost is developed. Do you notice any bubbles in the coolant? Early signs sometimes are bubbles the size of a pin.

Mine does it too. I don't think my head gaskets going but I get a pressure buildup at start up. I found a leak around the thermastat but havn't havn't put on a new gasket yet.

I've never been able to get "Bloc Check" liquid to change color on a diesel engine with a combustion leak. I think it's because there just isn't enough CO and HC in diesel exhaust. I don't know exactly what gasses make the blue liquid in the tester turn green or yellow but, I know a diesel doesn't produce enough of it.