Before I Get the Head Milled (Overheating)

[Cruzberg61]

Hi All,
I've got a 97 4x4 with about 180k on it. Bought in in Feb 2021 mostly stock, and have since slapped on a 3" lift and 33s. Never wheeled it very hard. Never had over heating issues (in fact it ran on the cool side) until the last trip, where it was running around 225 on highway on a 100+ degree day. On the way out it overheated (needle pinned and "Check Gauges" light came on) going up a grade. Immediately pulled over and let it cool down. Made it home without it overheating again but it's been running hot ever since (220 - 230).


Flushed the system with Prestone system flush, replaced fan clutch (shroud is still intact), t-stat, t-sensor and water pump, and confirmed e-fan kicks on when its supposed to. It stayed around 210 when I burped it and on surface streets but jumped up to 230 on highway. Replaced radiator and added a trans cooler. While I was burping it this time, and it was just sitting in my driveway with the hood open, temp climbed up to 225, worse than before. When I shut it off after 45 mins coolant boiled over. I used concentrate coolant and kind of eye-balled the ratios.



There's no smoke coming out the exhaust, no oil in coolant and no coolant in oil, so don't think the head gasket is toast. The only thing that started happening around the same time was a chattering somewhere in the muffler or maybe in the cat, but it's getting a little rusty so thought something might have come loose and is rattling around in there. Don't know if that could be a sign of anything.



Buddy thinks the head warped when it overheated. Before I tear the engine apart, wanted to pick your brains to see if there was anything else to try before heading down that route? Thanks!

 

[Cruzberg61]

Forgot to mention I replaced the radiator cap as well.

 

[clean96XJ]

Shot(s) in the dark,

*check new water pump specs.
make sure its not reverse flow.

OR

T stat not opening.

I might also remove the t stat and see how she runs without it.


Before tearing into the engine, there are (chem) tests for checking if exhaust gases are getting mixed with coolant.

GL

 

[RCP Phx]

Yes, I would certainly want to find the problem "before" tearing into the motor. The heater core is also suspect as the Jeep system is sized that close.

 

[Cruzberg61]

Yes, I would certainly want to find the problem "before" tearing into the motor. The heater core is also suspect as the Jeep system is sized that close.

What do you mean by "sized that close"? Could a clogged heater core really cause running hot?

 

[RCP Phx]

It's been reported before, but until you rule out all the possibilties.....

As stated above- do a sniffer test
do a pressure test
do a compression test
do a leak-down test
check for vacuum leaks
Have you put a scanner on it ???

 

[RCP Phx]

Even the AW-4 comes into play because of the heat they can introduce specially with bigger tires and no gear change to compensate for the load!

 

[Cruzberg61]

Even the AW-4 comes into play because of the heat they can introduce specially with bigger tires and no gear change to compensate for the load!

I did re-gear to 4.56. No codes on the scanner. I haven't run any of those tests but will report back when I complete them.

 

[75SV1]

Concentrate coolant? I try for a 50-50 mixture. I do run the Prestone Z05. You can mix it to I think 70%, for added heat protection. I am not sure with the present green stuff. You don't mention if your loosing coolant.

 

[Cruzberg61]

Concentrate coolant? I try for a 50-50 mixture. I do run the Prestone Z05. You can mix it to I think 70%, for added heat protection. I am not sure with the present green stuff. You don't mention if your loosing coolant.

Is the cooling capacity of the water greatly affected by the ratio for the concentrate? I didn't measure super carefully, but it may have a bit more concentrate than water.
It's definitely not leaking coolant. If it's losing coolant internally it's not obvious. No signs of it in the motor oil, and haven't noticed the reservoir drop.

 

[RCP Phx]

No codes doesn't mean a lot, I was refering to actual readings for injector trims and O2 outputs. I also would check for exhaust leaks and the cat is also a suspect!

 

[Anak]

Air pockets can be an issue. I went for years without any issue, but then I drained and filled my system with the Jeep pointed slightly downhill and created an issue for myself.

My method now is to first make sure the Jeep is at least level, ideally pointed uphill, and second I remove the heater hose from the T-stat housing and fill the radiator until I have brought the coolant level up to the very lip of the heater hose fitting. That seems to make it clear that I don't have any air pockets in the engine. Put the heater hose back on and then resume filling the radiator. Squeezing the upper radiator hose also seems to help chase air out of the system.

 

[RCP Phx]

The +97 doesn't require burping since the heater constantly flows coolant(or is supposed to) past the t-stat from the highest point in the head that's one of the theory's on the bad heater coil! Having no/bad flow creates hot spots in the head!

 

[RCP Phx]

I should have added that it also causes cavitation from the pump that just makes things worse!

 

[Cruzberg61]

Air pockets can be an issue. I went for years without any issue, but then I drained and filled my system with the Jeep pointed slightly downhill and created an issue for myself.

My method now is to first make sure the Jeep is at least level, ideally pointed uphill, and second I remove the heater hose from the T-stat housing and fill the radiator until I have brought the coolant level up to the very lip of the heater hose fitting. That seems to make it clear that I don't have any air pockets in the engine. Put the heater hose back on and then resume filling the radiator. Squeezing the upper radiator hose also seems to help chase air out of the system.

My method's similar to yours, but I remove the t-sensor and fill the radiator until I see it at the lip of the threads. My nose was pointed up hill. Is it normal for the coolant to boil over when I shut off the Jeep after burping?

 

[75SV1]

Is the cooling capacity of the water greatly affected by the ratio for the concentrate? I didn't measure super carefully, but it may have a bit more concentrate than water.
It's definitely not leaking coolant. If it's losing coolant internally it's not obvious. No signs of it in the motor oil, and haven't noticed the reservoir drop.

I would think near 50-50 is OK. Also, I think the Green Stuff if HOAT or OAT, same as the Z05. So, a bit stronger shouldn't hurt.
Also, I was wondering if it was at Highway speeds only or not. From you post, its at any time. I was thinking if the torque converter was not locking up in OD. I am aslo wondering if you are going by the dash gauge or have measured with a temp thermometer or such? Try changing the temp sensor???

 

[Anak]

The coolant should not boil over after burping.

If you are running the engine without the radiator cap in place then a boil over might not be surprising, but if the system is properly sealed then the coolant should never boil.

 

[boncrshr]

For what it's worth I recently replaced my timing chain due to a leaking front cover and it had a noticeable effect on cooling. The FSM says to change at 1/2" of deflection and mine was definitely more than that. My XJ was at 190K miles when I changed it.

 

[Cruzberg61]

I would think near 50-50 is OK. Also, I think the Green Stuff if HOAT or OAT, same as the Z05. So, a bit stronger shouldn't hurt.
Also, I was wondering if it was at Highway speeds only or not. From you post, its at any time. I was thinking if the torque converter was not locking up in OD. I am aslo wondering if you are going by the dash gauge or have measured with a temp thermometer or such? Try changing the temp sensor???

I did replace the t-sensor. Going by the dash gauge and my BlueDriver OBD2 tool. When I replaced the rad cap, water pump, and t-stat it ran at 210 while burping and on surface streets but ran hot (220 - 230) on highway, but didn't overheat. When I changed the t-sensor and radiator and added tranny cooler, it ran at 225 while burping. I haven't taken it out on streets since.

 

[Cruzberg61]

The coolant should not boil over after burping.

If you are running the engine without the radiator cap in place then a boil over might not be surprising, but if the system is properly sealed then the coolant should never boil.

To be clear, it boiled over when I had the burping funnel attached and had shut it off after burping it for 45 mins. During this burping event, it ran at 225. I have not replaced the rad cap and taken it for a spin since, because if it ran hot at idle with the hood open I anticipate it'll run hot once I get on the street.