water pump locked up on my 96 cherokee sport 4.0 ltr Inline 6 , replaced pump,started running hot within 5 miles,not redlining but close, replaced tstat with 160 degree,still got hot ,flushed radiator ,verified no water in oil,and both fans are working ,drove it about 12 miles and it did fine until i got on it for a few seconds to pass a slow car and then it started to get hot on me again, turned on heater and it helped it to cool off a bit,not sure what the problem is,any advice would be appreaciated.

 

First, start by replacing the heater control valve. As they age corrosion builds up on the inside and can cause the valve to malfunction and restrict coolant flow. It is a $20 part and a good starting point. Second, check and or replace the upper and lower radiator hose, as they age the rubber becomes weak, especially when running hotter than normal, and can collapse restricting flow. Third, replace Radiator if needed. Mine was cooling fine as long as I stayed under 60 mph, but could not flow well enough for highway speeds. Again, that's an age and mileage thing with these Jeeps. And last, if this is a new to you vehicle. How many miles does it have, and did it sit for any length of time before you bought it?

 

Your jeep was running fine before the pump went out right?and all you did was change out the pump and tstat,are you sure it has enough water in it,on mine if there is not enough it will flucuate on acceleration and deceleration just from water moving around and not being full. I would also replace your tsat with one that is 195,engines actually enjoy running warmer it improves combustion. The other thing is did you get your belt tight enough?

 

How hot are we talking? What is the condition of the hoses, raplace the radiator cap, use 190 deg Tstat. Normal temp is 205-215 deg.

 

jdcooley,

If I read right you have have ruled out the following:

1.) Water pump
2.) T-stat
3.) Radiator
4.) Bad Head Gasket
5.) Main and Auv. Fans

Sounds to me like you have a good old fashioned air bubble problem. Not to insult your knowledge of your rig but, after doing any cooling system maintenance, you need to run it with the radiator cap off until it reaches normal operating temperature and the T-stat has fully opened. You need to be able to look into the radiator and see coolant flowing through it. Add water until it is full while circulating. I normally let it run for an additional 5 minutes, with the radiator cap off, while circulating to get all of that pesky air out. I top it off one last time and take it for a test drive. I hope this helps.

 

Oops, forgot. I always fill the overflow tank to the "Hot" line, as well, as part of this evolution. Before going for the test drive.

 

it sat for about 2 and half months ,i did have to replace heater control valve when i did the water pump b/c it just broke into peices (brittle i gues from age) its got 140k on it ,but how can you tell if the hoses are collapsing?

 

just have ruled out head gasket with a pressure test and the radiator and the hoses are now coming into play since i just bought a radiator i'm gonna go ahead an try that.

 

okay i have replaced the heater control valve water pump ,tstat,serpentine, and radiator,had a pressure test and head gasket is fine,but when i get in traffic it still tries to get hot on me and both fans are working any suggestions ?

 

did you 'burp' it? As was suggested above, you may have some air in there. Is it overflowing when it overheats? And how hot is hot? Mine will sometimes run a notch on the hot side, but doesnt seem to be too big a problem

 

Also, just because the mechanical fan is moving doesnt mean its working right. if the fan clutch goes out, it can still move the fan, but its not moving enough air.

 

It has been asked several times... How HOT is it getting?? Where are you, outside temps may have a role here?

 

gettin about 240 in traffic i live in gray court south carolina so its hot here right now.