Zjcherokee

96 xj 4.0 auto, fresh rebuilt head now overheats quickly
Took head off again today thinking gasket was installed wrong.
But it was good, went back with new gasket finished it up and
It still does same sh@@. Water pump is good and has new radiator.
Help please ready to shoot it and put it out of it's misery.

1991Jeep_Man

Thermostat? Rad cap? Hoses not collapsing? Is the engine steaming or are you going by the gauge?

tiwvr1

Did ya burp it? Thermostat put in right? How quick does it heat up, over heat only at idle or at speed to? Fan kicking on?

djb383

I understand "new radiator" but "water pump is good"??????

Jakeshain

First off, check your fan clutch, if that is bad you main fan will spin but not well enough to ensure it's pulling air through. Check your secondary fan as well, if thats bad then when you're stopped for a while you'll see the gauge slowly climb. If it's over heating while driving down the road then it's something to do with your coolant flow, either thermostat, waterpump, and so on. Even if you get heat through the vents this is no indication that your thermostat is working as your heater runs coolant through with out needing your thermostat. If you do all this and it's still over heating then you may need to flush your coolant lines running through your head to ensure there is nothing blocking it.

Jakeshain

I've never heard of water pump being good, no real way to tell this even with a new water pump.

Firestorm500

Did it run hot before the head was rebuilt/replaced?

Willys55

hopefully the OP will log back on for the help he asked for

Jakeshain

Also, don't forget to check that both your temp sensors are hooked up, one at the front of the engine and another at the back side!

Zjcherokee

Thermostat is good, water pump has been taken off and inspected.
All blades look new and spins freely with no leaks. System has been
burped to the best of my ability, I filled with coolant thru the thermostat
housing which is the highest point on the system, ran at idle in garage
till stat opened up then went for test drive. At idle it dosent overheat but
under a load it heats up quickly to 230 then cools off to 200 or so at steady
speeds. Both fans are working correctly and checked water jackets for clogs
when I had the head off this morn, even blew thru the ones in the head with
compressed air. I think it must be air locked but cannot get it all to burp.
Thanks for your help.

Zjcherokee

No it wasn't but gasket was burned thru between 1 and 2 cylinders.

Zjcherokee

Both are hooked up and operational, also added a mechanical gauge. The fact gauge reads about 40 degrees hotter than the new mech gauge.

lookin2wheel

Upper and lower hoses new? You might have a hose collapsing under load restricting water flow. One of the hoses is supposed to have a spring in it to prevent collapse. Even if the srping is partially missing, the hose can and most likely will collapse. Just dont know right off hand if it the upper or lower hose that is supposed to have it.

djb383

Which gauge reads 230?

Zjcherokee

Mechanical reads. 230. Oe is pegged out. It has never boiled over with cap on but has spit some with it removed.