[andyfields]

I have a 90 Seville. It normally runs at 203 if I keep moving with the ac on. However if I get stopped in traffic it heats up pretty quick. It has gotten to 230. I have read in a few threads about people replacing the thermostat with a 180 or a 160. Is this safe? Is there a downside? I live in Florida and maybe the temp range is ok but it seems hot compared to my previous vehicles. Any help would be great.

 

[Guy]

I have a 90 Seville also, and had the same temp readings as you, I live in Australia with similar climate to you, I replaced my thermostat last month with a 160, and she runs around 176-180 and in traffic gets up to 182/183.

The car runs much better, feels crisper on acceleration (bit like a cold night), but I am not sure whether it will still pass the emissions test.

Very pleased I changed. I had previously driven 85,000 miles in old configuration, wished I had changed it 6 years ago.

Regards

Guy

 

[El Dobro]

Personally, I wouldn't mess with the thermostat and would just use the factory one, which is a 195. The engine and the sensors were designed with that in mind, so lowering the temperature it runs at would make the computer think that it's still warming up and let it run at the colder temperature settings.

 

[elwesso]

I agree.....

If you put in a new Tstat and your still running hot, your gonna need a new radiator........ Or, you could get it cored....... Im not sure on the specifics on the process, but they take it off the car and really clean it out, restoring it to new performnace....... Id say average would be about $200, and probably less if you take it out yourself.........

 

[B. Fitzgerald]

I agree.....

If you put in a new Tstat and your still running hot, your gonna need a new radiator........ Or, you could get it cored....... Im not sure on the specifics on the process, but they take it off the car and really clean it out, restoring it to new performnace....... Id say average would be about $200, and probably less if you take it out yourself.........

ditto. Lower thermostat only hides the problem. (and can cause others) Better to fix the problem. bf

 

[Guy]

Thre reason Cadillac run the high temperatures is to make the Catalyic converter burn the emissions to pass the stringent laws, mainly in the US.
The disadvantage is that the intake manifold now is hot so this reduces performance, because the air is warmed as it passes through it, whereas cold air is the best, and especially in city driving the heat-sink effect is enormous, so when you nail it off the lights the performance is down, and if fuel quality is not so good you can get pinking.

By lowering the engine temperature, as I have done, does give better performance, and feels like driving on a cold night, even during a hot summers day in the city. The engine is not that cold, so ECM is not, or does not appear to be affecting the tuning of the engine. In fact I get slightly better fuel economy with normal driving.

Other advantages is that the oil temp is lower, which helps keep it together longer, plus the transmission oil runs slightly cooler, giving crisper changes.

I understand the reasons for not changing factory settings, and I normally totally agree, but in my case this has been enormously advantageous, but I must say, I live in Queensland Australia, and drive my car daily, we do not have the same stringent emission laws here, or at least they do not test them, so this needs to be considered where you live.

Guy

 

[maydog]

Last winter I replaced my stat with a 180 degree one. It really did not decrease my coolant temperature, it still stays around 190-195 even in subzero temperatures. If I ever have to drain the coolant again, I would probably put a hotter one back in.

A hot engine actually is better for power than a cold one. Guy is correct about the intake air temperature affecting horsepower, but the Caddies have plastic intakes and manifolds which reduce the heatsink effect - most likely nullifying the benifits of a cooler engine compartment.

Ignition of the fuel/air charge creates pressure and heat. If the engine is cool much of that heat can be absorbed by the engine thereby reducing pressure. Heat also helps atomization, so a hot engine and cold air is the best combination for power and economy.

There are several threads discussing this, here and elsewhere, look around you will find some good info. I doubt that you will notice any change if you swap stats.

 

[elwesso]

If you would really get THAT much better fuel economy and performance with a cooler tstat, why wouldnt the OEM use a cooler one!!! 20degrees wont do a ton for emissions........

 

[maydog]

Oops, maybe the 4.5 does not have a plastic intake. I was speaking for the Northstar.