4 litre cherokee overheats after replacing complete system

[roelcha]

:-[ hi i bought a 97 jeep cherokee 4.0 auto about 3 months ago and had no issues with overheating until summer, and have since replaced the waterpump, thermostat 3 times, had the radiator flushed, replaced all hoses, and the cap, clutch fan, and yet the motor is still overheating. if anyone has any ideas i am very interested

[Cpage66]

You'll get some more specific replies from our XJ owners but what I do know is that you are experiencing something that nearly ALL XJ owners face in regards to your model.
It stems from the Cherokee being originally built with a small four cylinder and a small V-6 and that is what they were designed to take. When the 4.0 ltr. straight six came along, they stuck it in under the bonnet and it wasn't designed for it. Hence, lots of heat, very little airflow underbonnet and so on and so forth.

[Steve F]

When you say overheating what is the gauge getting to as they do run hot normally. Also does it overheat on the freeway or sitting at the lights? If it's at idle it could be the electric fan, it should kick in at 105C and turn off when the temp drops to 100C, if it isn't kicking in then it can overheat at idle in summer.

Does it actually boil over, water coming out of the overflow bottle?

Cheers
Steve

[roelcha]

hi thanks for the prompt reply
the water does boil and there is steam coming from the overflow bottle , however there is no water pouring out of the bottle.
the guage does go into the red very quickly when it is on the freeway or in traffic, but is not that bad around 105 when driving about 80 km per hour although large hills bring it up high quickly

[Bear]

Just an idea, when you flushed the radiator etc. did you think to chemically de-scale the water ways in the head and block.

Bear.

[ACJ]

head gasket maybe?

[Wooders]

What fluid are your running?
Checked the radiator isn't blocked with mud?
Do your hoses have the metal spring in them? (these prevent the hoses sucking "shut").
Head gasket is a very real possibility, but try to eliminate all other items first cause it's not really a fun job.

[roelcha]

the hoses that i am using do have springs and do not shut when the engine overheats.
there is no water in the oil or oil in the water, so please explain what you mean by head gasket?
i am running nulon coolant as the manufacturer recommends but have tried various combination's of coolant with no luck.
a friend suggested to check the timing but was unsure of the best timing for the engine does somebody know please?
the fan does switch on and of at the temperature that it is supposed to.
thanks for your help

[Steve F]

Hmmm, I was thinking head gasket as well but no oil in water or water in oil probably means it's safe. To double check I'd take the radiator cap off and run it and confirm no air bubbles at the filler. If there's none then all is good in that regard.

I'll have to think some more on this, sounds strange. Is the XJ stock?

Oh, and ignition timing is not adjustable on the XJ.

Cheers
Steve

[roelcha]

as far as i know entire car is stock

[Jaffas]

Seems you have covered most things... only thing I can think of to check is whether the radiator fins are full of mud/dirt and reducing cooling capacity.
If it is all stock it should be running a touch hot, but not boiling all the time. But XJ's definitely have a overheating issue.
After I nearly melted mine on stockton one time, I had it checked out and was so full of mud, rad was basically stuffed. Had it replaced with a slightly bigger metal-cored one and hasn't missed a beat since. I also have bonnet vents in mine, and on hot days, esp when hill climbing offroad you can see the heat pouring out of them.

[roelcha]

hi everybody

i took your advice and had the radiator checked out again and this time he removed the tank, and not just a flow test and found that there was significant blockages in the radiator caused by small bits of rust from the dirty coolant that was in the system before i bought the car. the last week it has been very stable between 95 and 105 degrees.

but i still wanted to ask if the electric thermo fan is supposed to switch on at all if the a/c is off ?

[Steve F]

The electric fan will come on at 105c even if the aircon is off, it then goes off again at 100c I think. So yep, on a hot day underload it will cycle on and off even with the aircon off. Oh, glad you got it sorted.

Cheers
Steve