Isuckatusernames

Hi i have a 92 xj that has brand new radiator a new thermostat and all new hoses but it continues over heat it has a mechanical fan that works as it should but no electric fan i had on the trails today and my heat temp light came on so i shut it off and turned on the heater and when did i heard the coolent at a steady boil and it was literally boiling out the reservoir im at my wits end and have no idea where to go from here does anyonehas any suggestions?

tech

How old is your water pump ? and look at your a/c condenser to make sure the fins are clean and air can flow though .

Scott91370

Are you sure the thermostat, even though new, is opening?
Water pump is a good spot as well. Why not replace the electrical fan? I'm sure having more air moving over the radiator would be a good thing.

gat

Replace the cap with a new radiator. I have a 1992. The last time that I replaced the coolant I removed the sensor in the rear to fill, then still had to top off the system for weeks after that. I learned from ChrisFix on YouTube that you can drill a small hole in the side of the thermostat. It helps to purge air, but it also allows a small amount of fluid to always circulate. You can rig the heater hoses so that the heater core is always functioning as a smaller secondary radiator since you only have the one of two fans.
If the boiling coolant is in the reservoir, then it is coming from the overflow which is released via the radiator's cap. Coolant is supposed to be pressurized and hot which means that it would be boiling as soon as it is released from a pressurized environment. It could just be that your old cap isn't putting enough pressure on the cap for the system to function well.

Isuckatusernames

the pervious owner said the water pump was brand new but you know how people lie about **** ill definitely pull it out and check it as for the ac condenser is definitely brand new so it should be fine do you think not having electric fan could cause it to over heat to such a degree

tech

yes my xj uses the electric fan a lot on the trails and in traffic .

Isuckatusernames

Cool thanks for the help man i figured that since i had 3 core radiator it would compensate for the lack of a fan i didn't put it on when i swapped the radiator because it has very little clearance but ill have the find a nice puller fan that will fit in there

tech

I running a Champion All Aluminum Radiator 2 row and , I don't overheat any more . the radiator is now over 2 years old . I did change the fan clutch when I put in the radiator . the electric fan is the OEM fan .

Isuckatusernames

mine is a csf 3 core radiator its all steel which might be part of the problem

Isuckatusernames

It should be how would i check that short of pulling it out?

third coast

Hoping there was just remaining air in the system as others have mentioned. Definitely get an aux fan. At low speed, such as on trails or stopped in traffic, you don't get much air flow through the radiator without it.
One possible cause of your symptoms is a bad head gasket or head problem that is allowing combustion gas into the cooling system and venting out the overflow tank. A couple of quick checks can be done. You can rent a combustion gas tester from AutoZone but you may have to buy the test fluid from NAPA. AutoZone did not carry it the last time I checked. This is a simple and quick indicator if it is likely you have combustion gas in the radiator. Another less certain check is if you see bubbles or fluid surging at the radiator fill cap. With engine cold and radiator fill cap off start the engine and let it warm up. As the thermostat opens if you see a lot of bubbles or tendency to aggressively overflow out of the cap this is a hint there might be a head issue. This method is not definitive, just another investigation tool. Be very careful of the potential for hot antifreeze coming out of the fill opening.

Note: A correct thermostat should already has a small bleed hole in it. Maybe some low cost generic thermostats do not. The correct orientation is with the hole facing up, or at 12 o’clock position. Make sure the gasket or any gasket sealer used is not interfering. This helps bleed trapped air after cooling system work. Of course you have the spring end is positioned into the block.

Scott91370

Without pulling it and putting it in water on the stove you can't. But I suspect it is the lack of electric fan.

Isuckatusernames

Thanks for the info man i really hope my head gasket isnt blown but it is i have a new one in my shop the auto zones where i live do in fact have combustion test fluid if my head gasket is blown do you think i should just rebuild the engine she has 191k on the clock and as far as i know the engine has never been apart, im just happy my old xj got through the fringed colorado winter again

Isuckatusernames

i've never been into any of my past xjs engines but i have been in many many old vw and subaru engines i suppose the head gasket on the 242 wouldn't be any harder than on an ej? Just a lot bigger im gonna test for exhaust gas in the cooling system soon ill get back to you all with the results

third coast

I would not be in any hurry to rebuild the engine unless you have known problems. They have been known to go 300k or 400k miles. Someone on this forum just recently hit 400k.

The head is not a terrible job - it just takes some time to do it right. It is especially heavy if you put it back on with the manifolds attached, which I very much recommend as that is about the only way to get the manifold bolts properly torqued.

Regarding the combustion gas test - follow the directions and take care not to contaminate the test fluid by getting antifreeze sucked up into the tester. Also keep the tester/fluid away from exhaust so as not to risk a false positive reading.