Thread: How much coolant temperature variance is considered normal on V8?

Howdy Boys and Girls,

I have been monitoring my engine temperature with a ScanGauge II plugged into the OBD connector on my 1999 Discovery Series II V8. Using the gauge, I am able to read the coolant temperature in degrees Centigrade.

I notice that when I'm doing an easy, steady cruise at highway speeds, the coolant temperature gets as low as 93 degrees Centigrade. When I'm stopped at the lights, it can climb all the way to 98 degrees. Then when I take off, after a short moment, the increased revs and airflow causes the temperature to drop off to around 95 degrees. Then I come to a stop and it goes up again. So, in summary, the temperature variation can be as wide as from 93 to 98 in stop start driving driving.

When a friend of mine uses the same ScanGauge on his Prado TD, the coolant temperature is rock solid - no fluctuations whatsoever.

I've only started to monitor the coolant temperatures after my engine slipped a liner about 12 months ago, so I bought the ScanGauge II. After the rebuild, the engine suffered a subsequent head gasket only 10,000 kms after the rebuild. So I'm wondering if the fluctuations could be the cause of the slipped liner and the follow on head gasket failure....

Any insight would be greatly appreciated.

Thanks,

Lawrance

Mine (brand new 4.6 HC with less than 3,000 km) varies from about 93 on the road to 105 in traffic, measured on Scan Gauge. The vehicle has a new water pump, new thermostat, near new radiator and all new hoses. On Sunday, in Canberra, OAT around 17 degrees, inlet temp 39, stuck in traffic, it hit 105 but the Disco gauge stayed firmly centred. Go figure!
Cheers,
Terry