vank

I've got a 94 4.0L with a 5 spd and its running hot (220 to 230) on the highway especially going up hills. Around town or stop-and-go traffic it will stay atound 215. Things I've done:

-New head gasket
-machined head (was .012 out of flat)
-pressure tested the head (no cracks)
-tested the block to check for cracks (block tester rental from autozone)
-new 195 thermostat
-hesco high flow thermostat housing
-hesco high flow water pump
-new hoses, lower does have spring in it so it's not collapsing
-new temp sensors
-aux fan out of later model Cherokee wired to in-cab switch
-new max cooling HD mopar aluminum 2 row radiator (had csf 3 row previously and it was getting even hotter)
-new 16 lb radiator cap
-50/50 coolant mix

All this has been done in the last thousand miles or so and I'm still having issues. Fan shroud is in place, fan clutch is newish but since I'm overheating on the highway its not really suspect..What am I missing?

Firestorm500

Does the exhaust seem like it's flowing freely?

vank

Yes, I forgot to mention. I did suspect a plugged cat and just welded in a new high flow. The rest is 2.5" from the cat back. I even pounded that dent out in the down pipe after the manifold.

Thanks for the suggestion though!

dans98xj

Could there be a small air pocket in the block or head? It might be worth burping the system a little more to see if anything works its way out. I have also heard of problems with the 2 row radiators. Were the first and second row will do the cooling at low speeds but at high speeds the air flowing through the grill and radiator goes over the first row but heat soaks the second row causing the temp to rise from insufficient cooling. Try spacing the back of the hood a bit to see if pulling some of the hot air out will change anything.

vank

It's possible there is an air bubble but I didn't think that was an issue with the open cooling system? Any air should work itself out after a few stop/start cycles right? If I pull the sensor at the back of the head coolant will bubble out when at a cold idle, no air.

I do want to install hood vents but haven't done that yet. I could space the hood for now and see what happens.

CCKen

Is it actually reaching the indicated temps?

vank

So at first I thought it wasn't and an IR thermometer on the thermostat housing does indicate a bit cooler but when I shoot the head with the IR gun I'm seeming temps in the 220s. It's hard because it doesn't heat up when stopped so in order to verify I have to get it warm on the highway, stop, lop the hood, run out and check quick. It cools down real quick when stopped.

Firestorm500

I don't think cracking the hood open at the back is going to help much, if at all.

There is plenty of space for hot air to go down under the vehicle. Especially at highway speeds.

If it cools down real quickly at idle, as you say, then you have a restriction to flow at higher engine speeds.

It's not going to be an air bubble.

I have a Jeep that ran hot before and after a complete engine rebuild. Head had been magnafluxed, too. Long expensive story short, I ended up putting a third head on it. That solved the overheating problem.

Eisenschwein

Mine runs in the 220 range a lot of the time but never goes over 230. I installed hood vents and nothing changed in terms of engine temp. I didn't really expect it to and installed them so all of the other components wouldn't be getting cooked. It is pretty cool to see the heat waves boiling out of the vents in traffic, especially when the e-fan kicks on at a light.

I would say do the vents, because they are a good thing to do but don't expect it to have much effect on engine temp, especially when moving.

vank

Did you have signs of a cracked head? I have none of that now. No coolant in the oil, no coolant smell in the exhaust, great compression on all cylinders, and no oil in the coolant. Plus the block tester didn't indicate exhaust in the coolant.

As you said I'm thinking there is a restriction somewhere, but where? I just had the head off and replaced all freeze plugs so I know water jackets were clean. Head was cleaned when they pressure tested and machined it. Lower hose isn't collapsing. I replaced the csf three row with an OEM 2 row since I heard of restriction problems with the CSF..

vank

I have read this before and as you said was more planning to do this so the brittle under-hood plastics dont get heat soaked.

I know XJs can run warmer (220-230) but since everything is brand new now (and OEM or better) I figured I'd get back to stock running temps. I'm just feeling frustrated. Guess this is why all my buddies have JKs now lol

Eisenschwein

Ya, but you'll keep your XJ because you don't wear a skirt.

vank

Haha true, what is the most likely next course of action is finally putting the LS6/tremec I've got into my other project and ripping the csb 350 and 700r4 out of it and dropping that into my XJ (with a milder cam). I'll miss the ax-15 though.

Eisenschwein

Nice. SBC in the XJ... gonna pop some wheelies.

vank

Not with my D44 and winch/bumper in the front. That's some heavy s***.

For now, anyone have any other ideas?