Changed thermostat temperature. My assumptions...

[gr_diver]

I always used an 82*C (180*F) thermostat, because this is what I found in the car after I got it from my father. The gauge, while warming up, would slowly get to just below the 3/5 (middle) mark (see attachment with gauge), then when the t-stat opened it would go back to 2/5, and then hovered between the two during driving, up to the middle during load.

Today I installed an 88*C (190*F) t-stat, which was the closest I could find to the 87*C (189*F) that Opel recommends. Now the engine, while warming-up, slowly gets exactly to the middle mark, AND WILL STAY THERE with no variation at all. Once it gets there, engine temperature will stay stable all the time. The only exception was during highway driving, the needle only got a hair past the middle mark, and this could well be due to radiator needing a little more flushing than I did to it about 2 months ago.

My assumptions are that is a much more healthy t-stat for my engine. So far the engine would only under serious load reach 90*C (middle), and as I've heard the 85-90*C (185-195*F) range is the ideal operating temperature for CIH engines. Previously it would drive between 75-85*C (167-185*F) (these are estimates from the gauge of course).

Also, and this is what I like most, is that the engine during warm-up does not now experience sudden temperature changes, as it did going from the middle to 2/5 (approximately from 90*C/195*F to 70*C/160*F) and back and forth, with the t-stat opening and closing repeatedly, until it stabilized about 20 mins after start-up. In addition, the oil gets hot faster (pressure starts to drop about 5 minutes faster), due to the steady & higher engine temperature. This will be good for the following winter months, when I expect temps to now be in the normal range rather than the "a little towards cold side" they used to be...

In general engine temperature is far more stable under all conditions, and withing the ideal range.

I don't know if these are of any value to people, but things like this might come useful to somebody for cooling system troubleshooting.


For the record, climate here varies from -10*C/14*F (winter) to +42*C/107*F (summer). Both behaviours described above were for these days that we have approximately 28*C/82*F. I am pretty sure that this t-stat will be in there until it goes bad. From personal experience on my engine, I don't think it will suffer by it at any season during the following years...

[2 Fast 4 U]

I have the same experience with my temp reading, will go to the middle of the gauge and go up a bit while driving on the highway [speed +/-100 kmh]

[gr_diver]

Happy to hear that! I also usually go 100-110km/hr on the highway, so the little temp increase could even be normal.

[Lindsay]

Using a 180 degree thermostat in my re-cored GT radiator for several years. There is no temperature gauge sweep cycling. Think I am using an all brass thermostat.

Tried a 160 degree thernostat and GT gauge would sweep back & forth.

Need to install an overflow bottle ... someday!

Attachment from classicopels.com

Lindsay
71 GT

[gr_diver]

Oh, that overflow bottle. It always is my "next thing to do" but mysteriously always something else overtakes it...