Pfish

I recently bought a 94 automatic 4x4 XJ and it had a cracked radiator. So put in a mishimoto radiator, changed the thermostat, hoses, and got rid of the heater valve. After replacing all those with the better radiator the temp still climbs while driving(highway or city) around 230 before I crank the heat and it slowly drops down to a little above 210. I also got a new fan shroud for the fan clutch and the fan clutch doesn’t feel loose and stops before I can see it after I turn off the engine(when hot). The only other thing I can think to change would be the water pump, if there’s any other thoughts of what it could be please let me know. I know the transmission is adding heat to the system but with the better radiator I don’t think that should be a problem. I’m also in Arizona so the temps have been ~100.

Morat

Water pump is probably the next logical place to go, but before you do that make sure you've burped the system really well. If you're getting good heat then it can't be too low but it could be worth checking the level at the rad cap rather than the expansion tank. I had a similar issue after changing my rad, water pump, thermostat and found that despite the expansion tank being full, there was a load of air in the rad and the coolant wasn't being filled from the tank. So I filled it through the rad cap and it's back to normal temps again.

Did you get a new rad cap with the rad?

dave1123

You also need to check the hose from the radiator to the reservoir to make sure it's clamped with no air leaks. The system relies on vacuum created when the coolant cools down to pull refill coolant from the reservoir. Any air in the system will be expelled into the reservoir when it's hot, then be replaced by coolant when it cools. This action takes more than 1 cycle usually.

Based on your locality, I would strongly suggest and aux trans cooler. Also, if your trans isn't going into lockup at highway speeds, you're still building heat in the converter due to hydraulic slippage, normally about 10% of rpm.

TrailerTrash

All that has been said above is 90% of what I would say.

The air bleeding is crucial and should not be easily dismissed.

Is the electric fan coming on? It definitely should be if the temperature is getting that high.

Have you verified the temperature?

Is there a coil spring in the lower radiator hose?

Definitely get a new water pump. Dont waste your money on a "high flow" pump

Pfish

Alright, I will burp the system and replace the overflow hose with a new one. They gave me a new rad cap with the radiator. The overflow hose I didn't replace but it definitely should be so I'll look for one of them. I'm not sure how to tell if my trans is locking up at highway speeds. The electric fan does come on, I haven't verified the temperature as I don't have something to check it with. I don't have a coil spring in the lower radiator hose but that's because I replaced the hose and I read on a different thread that they don't need them because of how the rubber is made now.

TrailerTrash

I'm sure some radiator hoses are made sturdy enough that they wont collapse. The replacement I bought for mine was fairly flexible so i swapped the original spring into the new hose

Pfish

So the radiator was full of coolant, it didn't need to be burped. When I got rid of the heater valve I followed diagrams that had the hoses crossing each other so I fixed that. The temp still sits high and I cant use the A/C otherwise it gets hotter than I would like. One of my friends said that I might be using the wrong coolant but I don't think it really matters(Autozone brand premixed). I checked the fan clutch again and when it's hot and it stops quickly(maybe a quarter turn) although when I try and spin it although I don't feel much resistance. I don't suspect that the overflow hose is the problem but I still need a new one. The radiator hoses aren't kinked. The only thing I can think of still is the water pump or that I just need more cooling(aux trans cooler).

IJM

I never understood this. The system operates under pressure (up to 16 psi), so how would a hose possibly collapse?

doublechaz

The water pump sucks it flat at high rpm because it's the hose going to the input of the pump and the radiator has little teeny holes through it that restrict the flow into that hose.

I had that problem with my 76 Volare. Once it sucked flat it would often act as it's own worse restriction and stay flat. New hose with new hose stiffness fixed it. The old hose had gotten soft with age.

dave1123

There is one other idea that a guy in Arizona did, although it's "out of the box" so to speak. He hung another heater core in the heater hose near the radiator reservoir with an electric fan in front of it and manually switched it on when needed to help cool the engine. This works since on later models, the heater core is full flow all the time anyway and didn't heat up the cabin by turning the heater itself on. He explained he mounted it horizontally so the fan blew the heat out the bottom of the engine compartment so it didn't add to the overall underhood temp. I could see where just the fan itself might help.

cruiser54

I'm betting faulty stat.

The spring in the lower hose was only to keep it from collapsing when they added coolant to the Jeep on the assembly line using vacuum.....

dave1123

I can see that, but then again I've seen one crush on one of my Chevy trucks due to a plugged radiator, although it didn't close off all the flow, just most of it.