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Overheating problem driving me crazy!!! Help!!!

1K views 18 replies 10 participants last post by  Jakesteramalamajama 
#1 ·
Ok I have replaced my radiator,water pump, and thermostat...
My Jeep is still getting too hot, It is running about 230 on the highway and I dont know what else it could be.
4.2L with mopar fuel injection and 4.0 head. I am just about ready to Junk this motor and swap in a FI LT-1 or something of that nature. Can anyone give me some fresh insight on this matter. Thanks :(
 
#2 ·
Well, here are a few questions that may have been already address. Is there adequate air flow? Is there a spring in the lower hose? (possibly collapsing the lower hose at higher temperatures) Where is the timing set? My buddy had the howell tbi on his 4.2 and it was advanced a few degrees too much and it ran 15* warmer all the time, sometimes hotter. We bumped the timing back down and it was all good. He had replaced all of the things that you have.
 
#4 ·
Hi Lowrangerider,

I have a thought for you. May not help but here it is.

On the 4.0 L there are two water pumps.

One is Normal Flow, the other is Reverse Flow.

Outwardly they look the same, except for the direction of the inside Propeller and the letter "R" stamped on the back of propeller plate.

Generally, engine equipped with a "V" belt use the Normal flow pump, and those with the serpentine belt use the Reverse flow pump.

That said, I DO NOT know if the 4.2 and 4.0 water pumps are interchangeable.

If they are, there is a possibility you have the wrong water pump from the parts store in your Jeep.

I have seen this problem on 4.0 YJ's and TJ's more then a dozen times.

Might be worth you checking out.

Frank
 
#5 ·
What year is it? Is it A serpintine system or a V-belt system.
Make sure you have the water pump that flow in the correct direction.
 
#6 ·
The Rockslut,
There is a spring in the lower hose.
Good air flow, I have a fan shroud on it and a flex fan that doesnt have a fan cluch so it is running all the time...
I will have to check the timing. I havent done that yet. (good Idea!)

hy_desert_4wheeler,
I dont think it is leaking, At least there is no fluid comming out there.

Daless2 and Johncm,
I told them everything I knew about the Jeep before I got the pump and when I pulled the old one out I made sure that the impellers were going the same way. So it should be right.


I guess the next thing I need to check is the timing. This thing is really making me :mad3: though.
 
#7 ·
Oh yeah, It is a '89.
 
#8 ·
Have you checked the temp using a manual gauge? It might just be that your sender or your gauge is fawked up and the engine is not running hot at all... I mean, every 258 I ever saw ran at 210-215 most of the time anyway so it might just be reading a little off...

HTH,
Jake
 
#9 ·
I havent done that but the temp gauge usually reads right but if I take it on the highway then it starts to overheat. It also likes to overheat if I am really pushing it trying to get up a big sand hill or other areas that require a lot of right foot.
 
#12 ·
Lowrangeride,

I'm guess here, but given you have a new water pump that you checked flows in the proper direction, new radiator, and new thermostat, good fan, no fan clutch and a fan shroud........

I'd replace the thermostat again. Wouldn't be the first time one of those units has been bad out of the box.

For a few $'s and 30 minutes of your time it might be worth it.

Frank
 
#13 ·
What about removing the thermostat all together? I know this wouldnt work for winter but what about summer? Would it be a problem with the fuel injection?
 
#14 ·


hy_desert_4wheeler,
I dont think it is leaking, At least there is no fluid comming out there.
have it tested to be sure it holds the correct pressure or just replace it you wouldn't notice it leaking because the water would go into the overflow..
 
#17 ·
Lowrangerider said:
What about removing the thermostat all together? I know this wouldnt work for winter but what about summer? Would it be a problem with the fuel injection?
The function of the thermostat is to get your engine up to the proper operating temperature quickly and then maintain it in a certain range. If you enigne doesn't reach this temp quickly...you'll have exessive carbon build up. Which leads to worn rings, improper valve seating, fouled spark pulgs, oil breakdown.

With EFI you'll have the above metioned and the ECU will run in open loop longer.

This might be a stupid question, but have you burped the system?
 
#18 ·
Goat said:

This might be a stupid question, but have you burped the system?
Burped the system?:confused:
 
#19 ·
Lowrangerider said:


Burped the system?:confused:
He's talking about making sure that there are no air pockets anywhere in your cooling system.

Here's a writeup I found using google:

."To burp the air, remove the surge tank cap. Then, turn the heater control to HOT (this opens a valve that allows coolant flow through the heating system). Use a siphon (or turkey baster) to add cooalnt to your surge tank until it is 2/3 - 3/4 full. NOT FULL. Then, slowly squeeze the LF radiator hose as flat as you can....3-4 hands are better than two! As the coolant rises in the surge tank, the engine will visibly "burp" bubbles of trapped air into the surge tank, and the coolant will fall in the surge tank. "

That applys to a Viper, but you get the idea... I'm sure if you looked, you could find a writeup that was more applicable to a 4.2.

To be honest, it probably isn't the root of the problem, but it's worth a try...

HTH,
Jake
 
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