Thermostats

[El Tigre]

Nothing reduces air bubbles like pressure.
Replace radiator cap at least every couple years. That's really as long as they're good for.

 

[df2x4]

I run OEM GM 195 degree thermostats in both of my '97s. ACDelco part number 131-151. I'm in MO so not really "northern" so much as central US, but it gets pretty cold here and I do not notice any fluctuation like what kenh described in the original post. Temp rises to 200 or so, then drops 15-20 degrees and stays there.

They're more expensive and sometimes a pain to get but I prefer to use OEM thermostats when possible. They just seem more stable and reliable to me.

 

[studigggs]

Does anyone ever drill a small hole in their thermostats? I have in the past on other vehicles. I also run cardboard in front of my radiator when the temp drops. Beer case cardboard seems to work the best for whatever reason.

I drilled one in mine. On the TBI in my ‘90 the coolant is always circulating from radiator to block through heater core and back to radiator so it doesn’t affect warm up time.

 

[Schurkey]

And yet...GM, Ford, Chrysler, AMC, and plenty of others managed to build millions of vehicles every year that didn't have holes in their thermostats, with essentially zero problems.

 

[El Tigre]

Yet, it doesn't seem to make much difference. I will say that thermostats get "lazy" over time. They tend to open later ,more slowly ,and not as far. 180 stats. are a good compromise in my opinion ,and are what I use/recommend. Plenty of wintertime heat, yet doesn't cook the underhood rubber/plastic during summer months.

 

[studigggs]

And yet...GM, Ford, Chrysler, AMC, and plenty of others managed to build millions of vehicles every year that didn't have holes in their thermostats, with essentially zero problems.

True. They also likely use pressure/vacuum to leak test and fill the coolant system at the factory, so they dont have to use a special funnel or spill a quart of coolant on their floor burping the system.

 

[kenh]

Trying to apply some logic to my T-stat..... I think it may have been mentioned but having the t-stat separated from the temp sensor almost has to have consequences. The temp sensor in the head will see more heat than the t-stat every time. Especially when the engine is "cold". The head will get warmer way before the t-stat sees the same warm water because of very little/low coolant flow with the t-stat closed, hence the temp spike. As the engine warms up the t-stat will open somewhat and thus more coolant flow and a more constant temp in the engine.