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Hey, has anybody ran into any problems running the 160° thermostat without switching the pcm on the 96-99 Bonneville's?
I've been looking around and really only issue's was with the 2k+ Bonneville's running into the P0128 code.
With this heat and no signs of letting up I figured I would use a lower thermostat to extend the longevity of my motor.
Thanks guys.

Do you even have the fan turn on temperatures dropped to utilize a 180*?

I don't believe the system even goes closed loop until 170*, so you will be fighting a rich burn.

If I recall correctly, the only person that I recall running a 160* was Willwren in Greenzilla, but even then he wasn't too sold on it.

No I haven't made any modification to the fan over-ride switch or PCM. Any recommendations or just stick with 195° thermostat?

A 180* with a pcm fan tune will do you just fine. 160 is too cold for performance/mpg.

01bonneSC wrote:A 180* with a pcm fan tune will do you just fine. 160 is too cold for performance/mpg.

Forgive my ignorance but why the fan tune?

A 180 stat would be useless with out it really because the car would still run at 195-210*......because the fans wouldn't kick on earlier to help regulate the temp.

Realistically, just the t-stat is gonna open at 180* but isn't gonna make the car run any cooler, that's up to the fans and ambient air temp for that.

LakevilleSSEi wrote:A 180 stat would be useless with out it really because the car would still run at 195-210*......because the fans wouldn't kick on earlier to help regulate the temp.

Realistically, just the t-stat is gonna open at 180* but isn't gonna make the car run any cooler, that's up to the fans and ambient air temp for that.

Aahh I see, makes sense, Thanks Lakeville!

As long as the engine is in good shape and has no LIM gasket issues, 195* is no issue. Lots of cars run 195*F or warmer routinely. Normal for my Cruze was 220*F before a tune lowered it to 200*F.

What these guys said lol

Or if you did the man override you could turn them on yourself. Actually that would be the really way you could see a diff if you have a better gauge than stock or an Aeroforce.

01bonneSC wrote:What these guys said lol

Or if you did the man override you could turn them on yourself. Actually that would be the really way you could see a diff if you have a better gauge than stock or an Aeroforce.

Aeroforce FTW.

You can put an override switch in, yeah, but getting a tuned up PCM with the 180 option and gaining some throw back at the same time seems more logical to me, I dunno what your financial situation is tho.

Aeroforce gauge is on the "to get" list for sure.
I don't really want to do anything more performance wise, just make it reliable and be able to possibly hit the 300k mark, and thought that this small mod might be beneficial to hit the goal.
Yeah I replaced the LIM gasket and fixed a few other small leaks and odd noises, first time in a long time that I've had a leak free car, but if the 195° thermostat will be fine I will leave well enough alone and shoot for the Aeroforce gauge.

I run a drilled, 160°F thermostat on my 97 Ei. I live in Texas and with the heat outside 100+, the engine only get's to 175°-180°F The only difference I notice is the pick-up-and-go seems a little better. I gave up on MPG's for the most part - I drive 55 tops whenever I can.