Tyler Boyce

Hey guys i have a 1998 xj and the damn thing runs hot always and over heats. I have replaced the radiator, t-stat, water pump, all lines, have an external oil cooler and trans cooler and has electric fans. Had the head sent out and cheked for cracks and warpage. Thats all good there. The thing still runs at 230 always. I can be on the highway going 80 at 2500 rpm still runs hot. Im not getting exhaust in the coolant or vice versa, thats all been checked out. Have done all the checks for coolant flow, and all the known xj problems.

EZEARL

WELCOME

So I take it you've other symptoms of overheating besides what your gauge shows? Did you have the problem before the mods?

Tyler Boyce

Well i got it for a good price with a rusted out radiator. So i fixed that and had the head checked cause the owner said he had over heated it a few times when the radiator cracked. But the jeep runs perfect other then being hot. Im at a loss here. Ive got no other checks i can do. Did leak down, compression, used the diy in the coolant to check of exaust gasses in the coolant. And i dont think the block has clogged water jackets.

EZEARL

What type of replacement radiator? Could be those electric fans are moving enough air. The OEM clutch fans move a lot. Takes a high dollar electric fan set up to equal or better it.

Tyler Boyce

Well see at those speeds fans are usless, you will have more air over the radiator then what the stock fans could pull anyways. I mean when the fans kick on they are pulling a lot of air. At idle the fans bring the engine back to 210. Once the engine gets up to the 1500+ rpm the temp slowly climbs no matter what speed.

Tyler Boyce

Also i have a 3 core rad

EZEARL

Gotcha. I thought you were having issues at all speeds.
As far as your radiator goes there has been an on going discussion about them here. Seems that because there is so little space in these XJ's with the 4.0 the radiator has to be thin to fit. Pics of the insides of 1,2,and 3 core XJ radiators show that the 3 core and most 2 core ones will flow less coolant due to passages that are narrower than the 1 core. What you think?

I run a completely stock system except for a heavy duty fan clutch and even with the a/c running and poking around our backroads on the hottest days I stay at 210. Goes down a bit when the auxiliary fan kicks on from the a/c though.

Martlor13

Have you verified the temp? The dash gauge isn't really known for being completely accurate.

andrewmp6

Most factory gauges can be legally off 20% so unless it acts like its over heating the gauge could be reading wrong and your really running right.

EZEARL

"thing runs hot always and over heats."

Sounds like it's more than just a gauge issue. I asked what other symptoms besides the gauge.

Tyler Boyce

Ok to be clear i have verified that it over heats, the dash temp reads 210-220 but with the thermo gun it is reading right at 235 at the temp sensor. It stays there almost always. In town it does not boil over but gets close. Highway i have to have the heat on just to get the temps to stay at 240. And out side temp has little affect on how it runs. It can be 60 in the moring or 110 during the summer still runs at 235 or higher just takes longer to get there when its cold out. I think this thing would over heat in -30 weather:d . It never stays at the 210 mark. Ive got 3.55 gears so im only hitting 2300k rpms at 80. But the xj runs perfect, no power loss, no signs of a problem. I check the oil and coolant every time i drive and they are always at the same level and color. I dont really know what else to do with this truck. I had a single row rad that i replaced with the 3 row and that changed nothing in the cooling ability.

andrewmp6

210 is normal temp for a 4.0 the factory themostat is 195 degrees your jeep is running normal.The 4.0 in these jeeps run warmer then most other engines and people not use to it think its running hot when its just hitting its happy temp range and is fine.

Tyler Boyce

Also i have bled the cooling, drilled the hole in the thermostat then berped it. And its not the heater core cause that puts out some burning hot air when its on.

Tyler Boyce

But its does boil over when doing light driving, i would never be able to hit any kind of hill let alone pull anything. There is no a this truck would be able to be sold if you cant even hold 3k rpm for 1 min in 70 degree weather with out it boiling over

Tyler Boyce

WAY*