Mississippi-Mud Forums

As some of you know my Jeep overheated during the Laurel run and I had to pull out early due to what I that was a blown head gasket.
I have done a compression check which was fine ( 150 psi on every cylinder).
I also run 125 psi to each cylinder using the compression tester and had no bubbles in the radiator.
There is no water in the oil or oil in the radiator.
All test were done with the motor cold, I know it is suppose to be hot, but I was so sure about the gasket.

The symtoms are as follows:
It is a 258 6 cylinder.
I have installed a Chevy HEI distributor from D.U.I.
I can run it about 10 miles before the temp.slowly gets to 250, where it seems to stay.
I'm not losing any water and it cools off very quickly by running water over the rad.
It is also miss firing but not consistanly.
The motor has less than 2000 miles on it.
I have installed a Chevy HEI distributor from D.U.I. before the rebuild.

I could use some help. Thanks, Terry

Water pump ( could be wrong rotation ).
Radiator ( have flushed ).
Thermostat ( pull and try it without one or take a old thermostat and knock the guts out).
Timing ( not likely but can cause one to run hot ).
Check temp drop across the radiator if you have a temp gun. I can help you Friday when I get in from offshore.

does it have a clutched fan? is the fan cluch locking up and turning the fan like it should? if not a fan problem then its probably the wrong water pump or faulty thermostat.

I agree with the wrong w/p or t-stat, w/p turning the wrong direction being meant for a v-belt sys in a serp belt sys or vise versa, t-stat could be stuck partially closed. on a lot of radiators (with the cap on the rad style) you can see the flow when the t-stat opens. I dont think its the fan clutch because they usually engage when the ambient temp in the engine comp. reaches a certain temp. you can test the rad cap as well.

another thing to try is the actual flow through the block and the radiator.

I am leaning toward the fan clutch because wetting the radiator is cooling it off. That tells me that water is pumping and flowing through the t-stat. An inefficient radiator may be the cause if it is partially blocked or has heavy deposits on the inside.

If it does not run hot going down the road but does on the trails, I would look hard at the fan, radiator and shroud.

mike327 Wrote:If it does not run hot going down the road but does on the trails, I would look hard at the fan, radiator and shroud.

I would tend to agree with Mike... But i would try and pull the thermostat out and see what that does...

thats a no brainer..............Buy a nissan!!!!!.......i hope you get it fixed soon

Lastest update.
At the time that I wrote the thread the distributor, plugs and valve cover were off the engine, I have since put them back on and will try more of your suggestions, but I had to go to work.
I took the thermostat out when it over heated the first time, and the waterpump is correct and new but I know that doesn't mean anything.
Also it is running hot going down the road, I don't know about the trails because I got scared and went home.
Most of the test suggested require the motor to be hot so I will try them Thursday morning. Thanks, Terry

how hot is it getting?
are you sure your temp gauge is working properly? most 6cyl jeep engines have a 195 degree thermostat so the guage will read 200 or so most of the time. radiator could be partially stopped up too