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Overheating issue/tried several things...

B

BUGMAN99

NAXJA Forum User
Location
christiana pa
I have searched this forum and am at the end of my rope...not sure what the problem is. Here is the list of things I have done and my XJ still overheats.

98 XJ 4.0, automatic
replaced: Heater core, Evap Core, thermostat, rad. cap, head gasket, had head resurfaced, water pump.

Coolant was a rusty orange color. Cannot find the petcock on the radiator, I just removed the lower hose and flushed it out until it was clear.

I know this is my first post as I have been lurking for a while, and hate posting for help without helping out first but this problem has me frustrated. Thinking about just replacing the radiator as maybe it is clogged up.

I do have the heater core bypassed for now until I flush the rad again, and the hose may be slightly kinked.


Any help is greatly appreciated!!!!!
Howard
 
What kind of commercial flush did you use?
 
BUGMAN99 said:
Prestone superflush.
Click to expand...

Wasn't that the 10-15 minute flush?

Better job is done with the Super Radiator Cleaner, put it in and drive for 3-6 hours--that can be over multiple days.

The 10-15 minute stuff is good for a bi-annual flush on a well maintained system.
 
BUGMAN99 said:
I have searched this forum and am at the end of my rope...not sure what the problem is. Here is the list of things I have done and my XJ still overheats.

98 XJ 4.0, automatic
replaced: Heater core, Evap Core, thermostat, rad. cap, head gasket, had head resurfaced, water pump.

Coolant was a rusty orange color. Cannot find the petcock on the radiator, I just removed the lower hose and flushed it out until it was clear.

I know this is my first post as I have been lurking for a while, and hate posting for help without helping out first but this problem has me frustrated. Thinking about just replacing the radiator as maybe it is clogged up.

I do have the heater core bypassed for now until I flush the rad again, and the hose may be slightly kinked.


Any help is greatly appreciated!!!!!
Howard
Click to expand...
Sounds like you have all your bases covered but the rad
 
i would replace that radiator
im sure the fins are all bent and everythings clogged
make sure you flush the entire system drain plug and flush from the top as well
you could also look into hood louvers after the radiator
 
I don't think hood louvers are going to be his answer, this time of year in PA (or CO).

Lets back up and start over.

When does it overheat? Be descriptive.
 
It overheats almost right away after getting up to normal operating temp. Before I blew head gasket and now after putting it all back together.

And for some reason I keep getting different answers when I search for petcock location on a 98xj.

Thanks
Howard
 
i didnt say hood louvers would solve the problem just saying i installed them after i overhauled my entire cooling system and they made a great difference with underhood temps
do you have a fan shroud?
what about your electric fan? is it kicking in when it gets hot?
might sound stupid something as simple as a fan shroud but with a closed cooling system it will make a big difference at idle
 
BUGMAN99 said:
It overheats almost right away after getting up to normal operating temp. Before I blew head gasket and now after putting it all back together.

And for some reason I keep getting different answers when I search for petcock location on a 98xj.

Thanks
Howard
Click to expand...

Petcock is in the radiator tank, passenger's side, lower. Be careful, they are plastic and notorious for breaking when disturbed. Pulling the lower hose is the best way.

Well, you have a new thermostat and water pump, so if the mechanical fan is working then that leaves a plugged radiator, if the head isn't cracked.
 
Damn, sounds like me two years ago. I replaced everything in the coolling system, including the radiator, thermostat housing, fan clutch and ALL the hoses.

Still kept running too hot. Replaced the head gasket and milled the head.

Still kept running too hot. Ran a pressure test. Turned out the new radiator cap wasn't holding pressure.

Suggestions:

o Get an infra-red thermometer. Use it to scan the various components of the cooling system. Specifically check for inflow and outflow temperatures at the upper and lower hoses.

o Lower radiator hose must have a good spring inside or it will collapse.

o Check operation of both the mechanical fan and electric auxiliary fan.

o Run a pressure test to look for leaks.

o Put thermostat into pot of boiling water on stove and check operation.


Report back.
 
Thanks for all of the suggestions. I probably won't be able to get back to working on it until next weekend, so I will let you know how things go.

Thanks,
Howard
 
I agree with Andy's advice. Are you using any coolant? If so, that would accelerate the need for more testing. Pressure testing is something quick and easy to perform. My gut feel though is that this may be radiator related.

New (newer) components can and do fail so don't rule anything out. Cardinal rule of troubleshooting.

BTW, I wouldn't touch that radiator petcock. Safest/easiest to just drop the lower hose when changing coolant as Joe mentioned.

Whatever you do, don't let a serious overheat occur again......is that what led to your headgasket/head repair??
 
Last edited:
Yeah that's what led to all the repairs. Heater core was completely clogged so I am figuring the radiator is the same way. Figured since I replaced all the other stuff might as well just replace it instead of trying to flush it for the 5th time.
When I do flush it out it comes out clear, but that doesn't mean it's not clogged up because the water will take the path of least resistance, correct?
 
And the electric fan works properly. As for the mechanical fan clutch I am not sure, don't know where or what it is to be honest or how to check if it's working.
 
Easily overlooked items:

Filling the XJ with coolant properly can be tricky. You can get an air pocket. It happened to me once. I had a mechanic tell me he usually fills 4.0's through the hose that attaches to the thermostat housing holding it above the engine. That way he's filling it from the highest point possible.

Also make sure your coolant is no more than a 50/50 mix. Coolant doesn't cool as effieciently as water and if you haven't diluted the coolant enough it will overheat.
 
Check your catalytic converter. Mine was clogged nearly shut and causing overheating after I had replaced every component.

I found out by touching the floor over the cat while driving... hit a bolt for the passenger seat and burned myself. Took it to a shop and confirmed.

Just something to think about.
 
Viscous fans can't be checked. Replace if older than 5 years.

My next step would be to replace the rad. Not much left. Be sure there isn't air in the block. The thermostate should have a hole in it with the orientation of it at the top upon installation. It helps the air to escape out of the head. I live on a steep hill and park it uphill when filling. I also squeeze the return hose to check for air with the cap off.

After doing all that, let it idle up to temp and watch for bubbles in the overflow tank. You know you are ok if you don't see any and after cooling, the rad is full when the cap is removed.
 
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