since we are all guessing and i know you offroad it

is the exhaust ok, any restictions that could be causing the exhaust to not flow correctly is the cat glowing red when the overheating occurs.

is it possible that you "pinched" the radiator causing fluid not to flow

i had an older i-6 and it had a valve on the exhuast that would open and close, i guess to help it preheat, this was on an 84 model. this kind of goes with my exhaust restriction.

the fan really on helps in stop and go, if this overheating does not occur at highway speed then the fan is a possibilty.


does the problem happen when the a/c is on or off or both. does it happen if the truck is in neutral idling?

 

hey dave i had one of those vavles on my 87 dakota .pain in the a$$. if you didnt lube it. would get rust up shut. it had a little thermostat that was suppose to control it, that never worked. i overheated a few times around town because of that. this guy has a 95 i think everyone got rid of that stlye valve by early the early 90s

 

That valve didn't restrict the exhaust - in only redirected it around the intake to preheat that air. The valve on the driver's exhaust manifold of the V8s would actually block up that side, but not the one on the I6s.

 

i once installed a new thermostat only to find that it was bad also.

 

Thanks again for all the input, I really do appreciate it!!!

First, on a side note, running the heater on full helps quite a bit.

I've just finished letting the truck idle for probably 45 minutes. It is very hot but not boiling over.

I checked the exhaust and I do not see any problems there. Air flow should be fine.

I dont understand the fan clutch concept, but as I've said before the fan is spinning just as I would expect.

I might try a highway drive this evening, but I'd hate to boil over and have to pull over on the side of the road to cool off. But I'll probably give it a shot. I can tell you that when I first noticed the persistant issue, I had driven 10 miles (mostly highway) to a concert. On the way home, I ended up taking non-highway roads. It was on the way back I had a problem. Or at least that's when I noticed it anyway.

I dont know about the A/C as I don't use it. But I might try and see what affect that has.

I dont know if they pressure tested the radiator cap or system. I know they verified the thermostat was opening and the problem has occured through 3 different radiator caps.

The hoses are difficult to squeeze at this moment, after ideling for so long.

I dont know if there has been a lot of steam when the problem occurs, but I can tell you that I have had the overflow tank boil over as well.

I dont know about gravity check, fan clutch testing, or boil temperature. It was Meineke so I would be surprised.

 

If you don't find the problem otherwise., my bet is you need a radiator.
Reason, the lower section crossflow tubes are blocked shut.
This reduces the cooling area of the radiator even though the side headers are large, clear and open. Even will drain without a hint of blocking but it's lack of cooling area that make it act this way.
On the road it may take some time to overheat but go to a hill and it will act up very quicky from the exta load and heat. Add higher ambient temps and it all happens faster.

 

well my vote goes to one of the head gaskets. Menekie is on the right track with the exhaust gas tester. You can have a blown head gasket and not have antifreeze show up in the oil.

I wouldn't think those temps would be hot enough to boil antifreeze even with no pressure in the system. Are you running straight antifreeze or a mix?

 

I agree with supersoic491 - the lack of steam from the overflowing tank, and the instant pressure on the hoses tells me something OTHER than overheated coolant is overpressurizing the system. I expect the dissolved-gas test to fail.

 

Alright, I have some new information to share.

I was doing some fan clutch testing, had the engine going and getting hot, when I noticed the puddle of antifreeze. But theree was no leaking from the radiator cap, overflow, Nor hoses.

I discovered a good sized leak coming from the water pump (The water pump is connected to the fan and fan clutch right??)

So what are the chances I just need to fix a leaky water pump gasket? Would that cause everything I've described so far including the apparent pressure issues? Or am I just overly optimistic? Maybe I'm completely nuts and this is how a blown head gasket might show up?

Here's a link to a poor quality video I shot of the leak

http://s68.photobucket.com/albums/i2...t=MyMovie1.flv

 

No, unfortunately a leaking WP wouldn't account for the other symptoms. But overpressure in the cooling system could have damaged the WP seal.

What was the result of the dissolved-gas test?

 

No dissolved gas test. Meineke couldnt get ahold of the tool and since they dont do engine work, decided I Should go away. LOl.

Seriously though, I really really needed the truck last weekend so I was happy to get it back. I drove it very carefully to Lowes and back to pickup some large remodeling items.

 

Replace the water pump - if it is leaking, it is bad...

Overpressure of the system would damage the seal ? Don't think so, unless the radiator cap and overflow pathways are completely blocked.

I'm betting the water pump is bad, followed by the plugged up radiator theory.

It is very unlikely that the gasket for the water pump is leaking - they usually just start leaking around the shaft, right past the seal.

Don't let anyone monkey with head gaskets until you are certain the water pump and radiator are good to go. If the head gasket is leaking into the cooling system, it will definitely cause cooling issues. But on the likelihood scale, the water pump and radiator are more likely.

A compression leak-down test will reveal a blown head gasket too.

Don't take the 1st diagnosis as certain, unless you can see it for yourself.

 

The kit is ~$50 from NAPA and takes all of 30 sec. to use. You can probably get it even cheaper off a tool truck like Snap-On or Cornwell...