Fluctuating temperature

[sdf]

Greetings:

We recently replaced both the radiator and the thermostat on my 1989 Cherokee Laredo. The radiator leaked, so we initially only replaced it. Immediately afterwards the temperature would drop to 100 before climbing back to 200 or so (highway driving). We then replaced the thermostat, and now the temperature bounces between 150 and 200. The temperature changes over a 20-60 second period.

Any ideas that could be causing this? The jeep has a new serpentine belt, no water is leaking anywhere, it has a new overfill container, there is plenty of fluid in the system.....any suggestions appreciated.

Thanks

Sean

 

[redrooster]

You have an air/steam pocket in the system. Let it cool and then open the cap and start the engine. Once it gets warm enough to open the thermostat you eventually notice the coolant level dropping.
When the steam or air passes the temperature sensor it causes a spike on the gauge then it goes back to normal. Spikes usually only last a minute or so.
Sometimes it requires getting the vehicle pointed uphill to get the air out of the system.

 

[LBR]

You have an air/steam pocket in the system. Let it cool and then open the cap and start the engine. Once it gets warm enough to open the thermostat you eventually notice the coolant level dropping.
When the steam or air passes the temperature sensor it causes a spike on the gauge then it goes back to normal. Spikes usually only last a minute or so.
Sometimes it requires getting the vehicle pointed uphill to get the air out of the system.

Exactly as stated........... LBR