Over Heating....

[brendan88mj]

My radiator got punctured (did not drive without coolant in it) and I replaced it, refilled it. Ive flushed my coolant several times before so I know how to do that. But now its running a little hot. Maybe 10-20 degrees. Nothing too terrible but I don't want to drive it like that. Any ideas would be greatly appreciated!

[cruiser54]

Thanks for your post.

 

We’re here to help but you must understand that all Jeeps are not the same. 

In order for us to give you more accurate advice and help, we must know the following, along with detailed information as to the symptoms/problems etc:

 

Year

Model

Engine 

Transmission 

Transfer case

[carnuck]

Brendan has an '88 (according to his handle) and my first question would be original used or aftermarket new rad? Used rads can be clogged. Especially Blackstone which had cooling tubes too small from new.

 

Did you convert to open system? (if 4.0L)

 

Did you loosen the temp sender to burp the motor?

[cruiser54]

What temp is it running at? 

 

The original style replacement caps can cause issues. The best replacement cap for an 87 to 90 is a Napa 703-1396.

 

FWIW, I have NEVER had to burp a Renix Jeep's cooling system. and, neither did my techs at the dealership. Granted, the cap needs to work properly..

 

From the factory service manual.

 

 

Check this out from the FSM

 

This system does not have a radiator pressure cap. Instead the pressure cap is mounted on the coolant pressure bottle. System coolant flows directly through a fully pressurized Hot-Type expansion bottle. Coolant flows through the pressure bottle at all times during engine operation whether the engine is cold or at normal operating temperatures.

 

Larger coolant volume caused by thermal expansion during engine operation is absorbed by the expansion chamber in the bottle. Air trapped in the system is purged through the pressure cap vent valve during maximum coolant expansion..

[carnuck]

That's because Jeep used the GOOD thermostats with the hole drilled in them to allow air through so they don't vaporlock. By '92 they went to a thermostat housing that didn't trap air like the Renix ones did.

 

http://www.lunghd.com/Tech_Articles/Cooling/BurpAirMod.htm

[brendan88mj]

I have a 88 MJ 4.0 5spd manual (BA-10) and a np231 transfer case. The cap does make a hissing noise but its always done that and never caused any problems. I'm using a used radiator which I assumed in perfect working condition.I have a new one on order and I'm hoping that will solve my issues. I did not loosen the temp sending unit but I will do so when I replace the radiator.