Why on Earth is my truck overheating????
 

2000 D2, having problems for the past few weeks. To recap:

Truck overheats. This is the 4th time in as many weeks.

New T-stat - aftermarket
Blew out heater core - no blockage here
New radiator
Water pump is 1.5 yrs old - aftermarket
Most hoses new - all but lower rad to t-stat
New cap for expansion tank

Pressure tested a couple of days ago - 16 PSI for 15 minutes

Ran it in the driveway for about an hour yesterday, half hour the day before. Took it out around town, no issues. Had heat the entire time - hotter than ever.

Today, I warmed it up in the driveway for about 5 minutes. Drove 2 miles, before overheating (again). Had heat in the truck the entire time. After engine temp rose, pulled over, shut it down, did not notice any leaks, the hoses were rock-hard.

What is causing this? I've replaced everything in the system. I've read about aftermarket water pumps failing, but after 1.5 years, is that likely?

What else could it be? Another blockage somewhere?

Thanks in advance,
Steve

If the hoses are rock hard, then the pressure cap is probably working correctly. Also you either are getting air in there from a head gasket, or inproper bleed. Have you bled the system of all air?

Rock hard hoses doesn't sound good. Are you positive the system is completely free of air? No gurgling from under the dash? Other than air in the system, which isn't consitent with the radiator hoses being rock hard, the overheating could be a failed head gasket which can be consistent with the hoses being rock hard.

is the thermostat facing the correct direction? do you have the updated T connection? sound slike there is pressure in the system hoses should stay soft

Wow! That was quick!

I bled it, for sure. No gurgling. I don't suspect head gaskets. I did a pressure test, 16 PSI @ 15 minutes, with no leaks.

What I did to bleed it was:

1. Filled the reservoir.
2. Started truck
3. Held tank above motor
4. brought engine to running temp
5. refilled tank, once t-stat opened
6. opened up bleeder screw
7. waited until a got steady stream of coolant out of bleeder screw.
8. repeated 5-7 four times.

Am I missing something in the bleed process?

The bleed procedure you described above sounds textbook to me. Atleast, thats what I followed in the past and I haven't had any issues to date, knock, knock, bang on wood. What instrument are you using to determine the overheating? Ultra Gauge or something similar, besides the factory temp gauge?

Just the idiot gauge. Haven't purchased an Ultra Gauge, yet. Been too busy wrestling with these repairs (3 kids, all play basketball, wife, work .. :-) )

I'm just not sure that I'm going to dump any more money into the truck if it's head gaskets. It's got 192K miles on it and needs a few other things, like ball joints, tires, and some other things.

I might do it (HGs), though, just for the fun of it.

A couple of things, never turn off a vehicle with an aluminum engine if it is not leaking, you will toast it.
Second, you only bleed the engine when stone cold and never with it running if you want it done right.
As for your trucks issue, if it keeps happening over the next day, send me your number so I can walk you thru what to check and quit driving it if it even tries to over heat again.

I would also say your bleed process is incorrect. You bleed the truck when its cold and then afterwards you start it.

Temp sensors trippin?

If your hoses are pressurized and you are 90k+ miles -
you may need a head gasket.

If you start to get misfire codes on 1,2,7 or 8 cylinder # that will point to a head gasket eventually too.

I have bleed my D2 by running it at 1,200 rpm for 8 minutes with the coolant tank raised as high as it will go and the cap off.

This is NOT recommended and you can get scalded if not done correctly.

Right after I replaced the head gaskets I did this bleed below.
Before I replaced the head gaskets, I could never bleed it.
The bleed would not hold.
And, there was the water fall sound when taking off from spotlights.


But, I did this type of system bleed in March 2012 in Boulder, CO
and I have not had to bleed again.
I did just replace the head gaskets too.