Potentially Overheating - researched and repaired ...

'93 XJ - Guys, I've read the old posts and re-read and have done it all I think, but still, without the electric fan, my 4.0 would boil over sitting in traffic. Short of testing the accuracy of my electric gauge I have:

- put in the 3-core radiator
- changed the fan clutch
- experimented with thermostats (have 2 holes drilled in current)
- changed hoses, pump
- flushed system a couple of times
- experimented with various amounts of antifreeze
- changed sensors
- changed rad cap, burped and burped some more

Normal temp runs about 210. After 5 minutes of idle the temp runs up and the electric fans kicks in, probably around 225. Temp pretty much returns to normal, electric fan ceases, temp runs up, electric fan kicks in ... Running the heater helps, but for God sakes, I kind of like to run the AC in July sometimes, instead of the heater.

I am getting another boat and will be towing this summer. So, before I blow up my sweet 4.0 out of ignorance, I humbly ask your advice.

Final comment: I have run without a thermostat and although it's slow to warm there wasn't overheating potential. I am going to drill more holes in the existing tstat and see if a little more flow helps. My guess is the tstat is restricting the amount of flow needed to maintain normal running temp in Summer.

Am I missing something here?

Brian

What brand thermostat ? and are the holes you drilled located at the 12 O'clock position, facing up ?

The thermostat might be a Gates. I remember trying two or three at the beginning of last summer, one was a cheap one and the one in now I asked for over the counter. (I do remember the cheap and more expensive one both being stamped "Made in Isreall" Thought that was interesting.)

The holes are probably drilled on opposite sides.

The GDI 3 core radiator flows water slower but has more capacity then the stock radiator. The stock radiator cools better with smaller capacity but when your pumping hot water like crazy is doesn't cool as well and gets warm (220-230). The GDI has the opposite effect. It cools very well until your driving down the road with the engine running at 3000 rpm. My temp stays at 210-215 because it moves the water too slowly even though the water pump is pumping like crazy it cant dissipate the heat I am producing without moving more water. I think the pump cavitates the water when It cant push it through the radiator. I think the XJ needs a 3 core 5/8 to 3/4 inch tubed alluminum radiator to cool anything mildly built. They are available and I will be going to it when my GDI takes a dump.