Could it be as simple as the ET & cap? I bought this particular truck as a basket-case with the heads already off... Put new HG on it and it runs great- no coolant in the oil, no white smoke. I can drive it all day, but it loses coolant through the ET cap and overflow.

Thoughts?

I plan to do a leak-down test on it tomorrow to check for exhaust gases in the coolant.

 

My worst fear is a cracked block, as I KNOW the HG job was done EXACTLY right and by-the-book... (I did it myself, with the help of a very accomplished mechanic friend!)

Looking for some insight or feedback on similar experiences!

 

another option is to do a dynamic pressure test, install a coolant pressure tester on the ET when cold and do not pump it up. http://www.mityvac.com/user_manuals/MV4530.pdf

From the Mity-Vac pressure tester instructions:

An immediate and rapid pressure buildup is an indication of
a breach between a cylinder and the cooling system, most likely
due to a blown head gasket. Immediately turn off the engine and
release the pressure in the system by pressing the Pressure Relief
Valve located on pump hose near the quick-connect coupler.
Disconnect the test equipment and replace the head gasket.

If no immediate or rapid pressure buildup is indicated, operate the
pressure pump to bring the system to normal operating pressure.
If the needle on the pressure gauge vibrates rapidly, this is an
indication of a smaller compression or combustion leak into the
cooling system possibly caused by a damaged block or head.

 

Some Discos just like to drain out some coolant. Mine always drains down until it sits about an inch below the 'full' line. I was constantly filling it and trying to find the leak until I realized it doesn't lose any more fluid once it drains down a bit.

I haven't topped it off in months and it's at the same level.

 

Yeah, today she pretty-much emptied the entire coolant reservoir over the course of about 30 miles non-stop of mixed-use driving... I've heard of trucks wanting to run an inch or so below the cold-level line, but this one wants to empty the tank!

 

Is it running hot?

Have you replaced the coolant reservoir cap?

 

It's not actually running hot at all... I talked to Will Tillery a few hours ago, I'm going to replace the expansion tank & cap to start.

 

"expansion tank & cap" is the best place to start. if i remember correctly there was a huge price difference between 00-02 and 03-04 expansion tanks, but the do interchange.

 

Swapped the cap from my '04 to the '02 today... slightly better. Still spews coolant from around the cap but never overheated, even in stop and go traffic and with the AC on max! Didn't lose as much coolant as yesterday though, and took the truck on the same 30 mile loop...

 

Hmm. I'm not sure what I think of that. I guess we're back to my "some Discos just like to drain out some coolant" statement. So I'd check it before and after every drive and run it a bit to see if it stabilizes.