7.3 overheating and excessive cooling sytem pressu

GregKneupper · March 25, 2009

I have a 2001 7.3 with a complaint of overheating. The customer has already replaced 2 thermostats and put a fan clutch on it. The radiator is a few years old and the water pump is pumping. The customer removed the thermostat so it currently does not have one in it. I have not duplicated the overheating yet but there is some serious cooling system pressure that builds up in the cooling system after only a few blocks of hard driving. The hoses get rock hard. The temp at the t stat housing is only getting to 168 degrees so the engine is not overheating at this time. I feel that it has blown headgaskets or a cavitation problem. Has any one seen this before and how would I go about diagnosing the head gaskets. We have already tried a block tester and that showed nothing. Thanks for the help.

Brad Clayton · March 25, 2009

I have had cracked injector cups over pressurize the cooling system.

GregKneupper · March 25, 2009

Was there always fuel in the coolant when this happened? I have seen quite a few 7.3 liters with cracked injector cups but there was always fuel in the coolant. There is no fuel in this one.

Brad Clayton · March 25, 2009

Yeah, you make a good point there.

Brad Clayton · March 25, 2009

Had a tow truck one time which would overheat quickly on a hard run. Ended up being an oil cooler. Used a temp gun to help pinpoint. Removed the cooler and the bundle only had two tubes that could flow coolant, and there is a bunch in there.

Fredsvt · March 25, 2009

I had one '01 a long while back doing the same thing.

Mega pressure in the cooling system, and lots of steam coming out of the oil cap (not blowby) when it was hot. He complained of constant fan clutch cycling when towing and pushing out coolant after pulling hills.

The guy had run a very high hp chip in it while towing it's whole 110k life. It cavitated right at the bottom of the bores on 2 cylinders. The pits were in the ring area when the pistons were at BDC. When I pulled the valve covers the "jelly" was evident, even though it wasn't visible on the stick or oil cap.

GregKneupper · March 25, 2009

That is what I am thinking may be wrong with this truck. I drained a little coolant out of it and the only thing I got out of it was pure water. No green color to it at all. He told me it was low on coolant and added some to it. But the only thing in it is water. I think that they may have run it low on coolant and overheated it and then maybe added water to it at some time and now the engine is ruined. I am going to see in the morning if it builds pressure when the engine is cold. If it does I believe that will be a pretty good indicator that there is a major failure.

Mikill · March 25, 2009

The only time I had something similar it turned out to be the radiator. Cold spots on the radiator and the truck would only overheat carry a trailer and coolant would come out of the degas bottle.

Mekanik · March 26, 2009

Is this engine using coolant?

GregKneupper · March 27, 2009

I cannot tell you if it is actually using coolant or not. I do know that when it does start to overheat it blows coolant out the bottle he say. But there is not alot of tracer evidence around the bottle to suggest it happens all the time like we see on the 6.0. The fact that he did tell me it was low on coolant and could not find a leak tells me that it probably is using coolant. I pulled that radiator and the water pump off yesterday and the pump was good. I believe the radiator to be good as well as there was a temp difference from the top to bottom. I wanted to send it off and have it checked but the customer did not want to pay for it. I do not believe the radiator to be the cause anyways. He took it today. I do believe that it has an engine issue. I contacted the hotline and the guy that I was dealing with says that it is possible for an injector cup to crack and not put fuel in the cooling system. Either way the customer did not want to spend any money on the truck anyways.