Thread: V8 - Where's your temp run

Originally Posted by Traco

Continuously sits slightly below half way, irrespective of how warm or cold it is outside. 3.9 V8 runs an 88 degree thermostat.

Do not fit a thermostat rated below about 82 degrees.

Reason is the enrichment signal to the ECU from the temp sensor does not cut out until engine temp reaches around 81 degrees. If you run a 74 you'll always have rich fueling.

Ahhh, thats probably why the exhaust fumes make my eyes sting.

Given there is a 74, 82 and 88 degree thermostat, I now know not to run a 74, but what does the factory specify for the 1995 3.9V8, I'm guessing from what I can see it is 88 degrees? I'm assuming it is good practice to stay with that temperature? Sorry for such basic questions.

Do not fit a thermostat rated below about 82 degrees.

Reason is the enrichment signal to the ECU from the temp sensor does not cut out until engine temp reaches around 81 degrees. If you run a 74 you'll always have rich fueling.

well, not exactly true, but can happen.

As others have said, the thermostat is mainly for fast warm up, most engine wear occurs when cold. It fully opens at rated temp, but, the engine will continue to warm to 'normal' operating temps. This is a factor of design, (and weather), size of radiator, water pump and condition of engine. etc. etc.
So no, it will not continue with rich fueling if a 74 is fitted. Normal operating temps above 90-110 deg.

BUT, under extreme conditions, for example, outside air temp is around -5 to -10 deg. ie. freezing winters, and maybe coasting downhill in a snow storm, The engine may over cool, then the thermostat will close below rated temp to maintain the set temp......not good if it's too low, (74) and yes, then the engine will go into rich mode.

Very unlikely in Australia, but in Europe it is a factor. (maybe Canberra too, he.he.). In some climates they cover the radiators to prevent icing and overcooling.
As said, standard thermostat for 3.9 is 92deg. Most fit 88's here in Aus.

In some engine designs, ie. huge stationary diesel motors, or earth moving machines that are constantly slow working, the radiators are designed to overcool the engine, They have massive radiators, in such cases the thermostat controls and maintains the set temps.

Hope this helps.
Ron.

Fantastic, thanks for this Ron. Interestingly, the climate here is very very close to that in Canberra. I might just put an 88 into it in that case. Thanks.