180 degree thermostat

If you replace the Intake manifold with the newly redesigned ( in 1999 ) one, the car should be alright then and shouldn't need a lower degree thermostat.

========= Harryface =========

1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~275,982 miles_~_~_ ~_~_

Keep the OEM. 180's a worthless.

why is it worthless? I put one in my bonnie and it runs fine.

Why would OBD II be any different? If anything it would be more sensitive to those changes.

It runs fine, but what good does it do, very little if anything at all. All it does is make your ECM think that your car is not all the way heated, all of the time. Thus burns more fuel, all the time. You want to add fuel to your mix, hit the accelerator, or find a way to add more air density (ie cold air) and/or volume (ie cold air intake or air induction).

They are all alike, in that the car won't go closed loop until fully warmed up. I don't know what temperature your car uses, but I did have one factory shop manual that actually gave a number. It was 90C, which is 194F.

after I fix the upper plenum and lower intake coolant leak (great design GM, jacka%@). My question is I have always heard with the computer controlled cars that the thermostat is critical to gas mileage because at 180 the computer still thinks the engine is not fully warmed up therefore, it increases the fuel to the cylinders because like we all know a cold engine requires my fuel to make the same power. Is this still the case with the obd II or was it just with the earlier cars?

>

"Joe" wrote

I'd like to see that manual. I think that folks give out some incorrect info on when the vehicle goes into closed loop. It's much quicker then you think.

For example, on the original posters car, (using a 98 manual, as the manuals I have access to don't go back further then 98), the temp at which the engine will go into closed loop is 20C/68F. In other words, a 180 degree thermostat will have no bearing on whether the engine goes into closed loop, as the engine should go into closed loop way before 180 degrees is achieved.

Still, you achieve nothing by using a 180 degree thermostat, and in the case of the OP's car, lower coolant temperature has "nothing" to do with the intake manifold design problem. It won't help the problem, as the problem is not related to coolant temps but to EGR gas temps coming up from the lower manifold up thru the plastic manifold.

But of course, myths will persist.

Ian

Actually the computer will fall back on a time delay if proper temperature hasen't been reached by that time. It won't continue to add fuel all day in a futile attmept to warm the engine up. What is beneficial is if you have a supercharger the lower temperatures will allow the PCM to have maximum spark advance which might get you a little more power. Most who go with a 180t-stat will opt for the drilled stat. It has 4 small holes drilled in the housing which allow a small amount of coolant to constantly blow past it. This is available from

as well as other Bonneville performance websites.

The thermostat regulates flow, not temperature. Is this correct? When the thermostat goes open at 195, 180 whatever, the coolant loop is expanded now to include flow through the radiator so that heat transfer can take place. Do these engines really run cooler with the 180 t-stats after the engine is stabilized at rated operating temperature?

-- markwb

2001 Bonneville SLE

Barely, but yes. What you really want is higher/colder air mass to cause the introduction of more fuel, not a confused ECM.

In today's weather, yes they will. If you're stuck in a traffic Jam on July

4th, they might not. At 200 degress both thermostates are wide open, so of course they're no different.

Unless you plan on doing several mods, a 180 stat will give you nothing,except for more fuel use.Also if you live anywhere it gets some what cold,you will get very little heat.