77 CJ5 304 overheating problems continue

[winecountryjeep]

40k Miles,

12 year old rad

New water pump (and yes its pushing water the correct way)

New thermostat (fail-safe 180F)

New rad cap (16lbs)

Bottom rad hose not collapsing

Goes from cold to almost hot in under 5 min at idle.

Coolant does not seem to be flowing, because the rad top return hose is cool to the touch and seems to be full of air.

No expansion tank. I ordered one, but it hasn’t had one for decades and there hasn’t been an issue until recently so I do not think it’s the issue.

Where do I look next? I’m at a loss.

 

[PistolDave]

I would verify that the t-stat is actually opening, heat some water on the stove to 200 degrees and dip it in, see if it goes open. I have had 2 bad t-stats right off the shelf. Also, make sure the stat is facing the correct direction so that the element is immersed in the water coming from the manifold and not the other way around. I have seen that a few times. You might try running without the stat even installed and see if your upper hose gets hot or see water dumping into the radiator from the upper hose just to verify that water is actually circulating.

I bet some more folks will chime in shortly with other ideas.

Dave

 

[Torxhead]

Do a thermostat ck like Dave suggested. With a new thermostat, there could be air in the system also. I drill a hole in the thermostat housing when I install one just in case. A back flush might be needed here if there is no record of one.

 

[mriplaybass]

Do a thermostat ck like Dave suggested. With a new thermostat, there could be air in the system also. I drill a hole in the thermostat housing when I install one just in case. A back flush might be needed here if there is no record of one.

After rebuilding the engine, it overheated within just a few minutes. After trying everything else, I drilled a small hole in the thermostat to allow air to purge. The engine has run at normal temp ever since.

 

[winecountryjeep]

I also think the air in the system is a problem. I will pull the Tstat this evening and test it.

So torxhead drilled a hole in the Tstat housing and mriplaybass drilled a hole in the Tstat itself? Wouldn't a hole in the housing leak coolant?

 

[mriplaybass]

Not in the housing! Drill a hole in the flange of the thermostat itself. Didn't read Torx's post carefully enough. I am sure that he didn't mean the housing itself.

 

[Lumpy Grits]

Get rid of the 'fail-safe' t'stat.
I would look into have'n a 'rod-out' done on that radiator.
Are you using the OEM temp gauge for engine temp? If there is any type of GND issue with the dash. Your engine temp will show a false higher reading and your gas tank will show lower than it should.
LG

 

[Torxhead]

Not in the housing! Drill a hole in the flange of the thermostat itself. Didn't read Torx's post carefully enough. I am sure that he didn't mean the housing itself.

Yeah, the flange would be a better description, use a 1/16" drill. After cooling system work, driving it up and down steep hills after warm up can help flush air out also.

 

[exheep]

I will agree with Lumpy . Lose the failsafe thermostat. It fails in the open position but remains open as it will catch on some tabs.You can check for flow by simply removing the rad cap and watching for coolant to begin moving. In my neck of the woods a 12 year old rad could be due for a replacement. Once the fins become thin or loose from the rods it can't wick the heat away.
Hope you get it figured out .

 

[Turbogus]

I was struggling with overheating a few years back myslef and I realized that the winch was blocking airflow through the grille enough to impact cooling efficiency. I ultimately went with the Contour/Mystique dual fan setup and all has been well ever since.

 

[Lumpy Grits]

I have an 8274 Warn on the front of my '7', never an overheat issue ever. I also run the OEM fan with a SHROUD. I do have a electric pusher fan inside the grill that does help with reducing vapor lock by keep the air moving for a spell.
OP-Are you running a shroud? You really should. What are you using for a fan?
Pull the t'stat and go for a drive. Any difference??
BTW-when things get sorted out. Your engine will like a 195* t'stat much better than a 180*.
LG

 

[Turbogus]

Just sayin' I went with electric on account of the P.O. had a hack job of an efan when I first got BB. the wiring was good though, so I went with it. I was going to go O.E. and went as far to buy and fit a stock shroud but went with the Contour/Mystique efan setup ultimately. If this system fails however, I'll try the stock O.E. route.