4.0L TJ overheating

blazerbrad · 05-14-2011, 10:03 PM

Neighbor has an '99 TJ 4.0L. It suddenly overheated on him while driving down the highway yesterday. He put a new thermostat in it and supposedly let it sit and idle for almost an hour before it overheated.

The coolant looks pretty nasty with lots of rust in it. I thought maybe he just had an air bubble so pulled the radiator cap and had him turn the heater on. It idled for about 30 minutes with a rock steady temp reading and then overheated. Pulled the t-stat just to make sure it wasn't sticking and had him hop on the highway real quick and it got hot.

Planning on looking at it tomorrow so just wondering if there are any common issues with the 4.0L with this type of overheating. Water pump is dry but wondering if the fins are rusted out?

Can you typically see flow through the radiator cap on these?

05-14-2011, 10:03 PM	#1
blazerbrad - CORE Member - Join Date: Feb 2007 Posts: 831 Images: 6	4.0L TJ overheating Neighbor has an '99 TJ 4.0L. It suddenly overheated on him while driving down the highway yesterday. He put a new thermostat in it and supposedly let it sit and idle for almost an hour before it overheated. The coolant looks pretty nasty with lots of rust in it. I thought maybe he just had an air bubble so pulled the radiator cap and had him turn the heater on. It idled for about 30 minutes with a rock steady temp reading and then overheated. Pulled the t-stat just to make sure it wasn't sticking and had him hop on the highway real quick and it got hot. Planning on looking at it tomorrow so just wondering if there are any common issues with the 4.0L with this type of overheating. Water pump is dry but wondering if the fins are rusted out? Can you typically see flow through the radiator cap on these?