4.0l XJ overheating? Start here - the basics!

[Oli-dogg]

Originally Posted by sbk930

The radiator is pretty much new...

I'd still be trying another radiator, preferably an Adrad #JEE9001.C/A2 with the extra tubes.

http://www.go.jeep-xj.info/HowtoRadiatorFitting.htm

[sbk930]

Hi Oli-dog

Did an ebay search and found the radiator I installed it is an FF Dynamics triple threat, item no.161185791684

Today I installed high density foam around the radiator and between the grill so all air has to be directed entirely through the radiator.

Willing to try anything.

[94xjeep]

hi there again, Don't use ultra blue sealant or silicon.
I only use gasket cement 3 pond or the Holden head stud sealant in a small can. Repco sell it put it is a little pricey but will last a lift time if stored properly. It's yellow 3 bond and the holden stuff a little lighter. Remember every time you boil the engine the scale will transfer into the rh radiator tank. Steam is the best cleaner.

[94xjeep]

HI RHD drive XJ's have the engine fan as we know on the outlet end of the radiator so as they heat up at low speeds half the core is only doing the job till the little fan cuts in at about 107 Degrees I think and it has to deal with the HOT coolant from the engine first. This little fan is flat out doing this. The engine fan is clutch type and it's only as good as the core. If the core is blocked opposite the bimetal spring then it will not engage and spin at engine speed. Remember the thicker the core the more aggressive(pitch and speed) the fan must be pull air through the core. It's now more of a restriction at lower speeds. They can also block up with debris quicker to as the air speed is slower through the core. Less core(rows) and less fins per inch keep air speed up (velocity) to help blow the dust through the core. It's like a good vacuum cleaner to one with a blocked bag, the core is the bag.

[94xjeep]

Hi LHD Xj's have the engine driven fan on the inlet side of the radiator as they have no steering box to get in the way. This fan being larger and driven all the time deals with the HOT coolant first as long as the clutch is OK and the smaller electric fan has to only deal with cooler coolant which it should do. The heavy cores are good for high speed, high engine rpm (water pump speed) and high air pressure and velocity to maintain cooling. In the slow off road stuff you wont as much air through the core as possible(electric fans on all the time) to help take heat away.

In January this year we went up to Lake William Hovel in the ZJ jeep and it was 45-47 degress C. I have replaced the radiator with a plastic tank alloy core single row type and I watched the temp like a hawk the whole way. We towed the camper and the jeep loaded, the trans in 3rd and sat on 80 kph all the way. the temp would come up to 110 and the you could hear the engine fan cut in and it pull it back down to 100 in no time flat then disengage. it did this all the way up, the needle waving at me but that's all it did recovered the temp over and over again like the fan is meant to. No boiling or bubbling in the overflow bottle

[94xjeep]

On that trip up to the lake I also had the A/C on. This jeep still has it's 333,000 km factory water pump on it. The XJ suffers from as we know, cant get a good size fan in the engine bay to help pull the air we need to get heavier cores to work well unless like said before electric fans running all the time in the slow stuff. So this large single row radiator is working well and this winter the bottom hose is always cool to the touch even at highway speeds and idling in the driveway it is pulling the heat via the fan very well. The fan in this cold air is not locked in and roaring either(only when first started like normal) The engine sits on 100 all year around.

I have given up on the copper brass Adrad radiators as I cant get more than a month out of them before they let go on the hot header tank. The tubes are pulling through. I put up with a leak for 12 months as the first radiator htye repaired it 6 times and it would fail over and over again. Now I have a single large row cheapo off E bay and it works well and it has not leaked yet. Time will tell I guess. New genuine thermostat and the gauge is up and down on the thermostat all the time like the Adrad. The Adrad worked well very well but the material quality is Bad.

[junglejuice]

A month from a radiator! You have a problem....