a problem my 1988 sse has had for ages is that the egine doesn't seem to come up to proper operating temperature.. the gauge barely moves up which creates a couple of problems.. one is barely any heat.. and second is the engine thinks it'* not warm yet.. so it runs rich and gas mileage is very very poor!!!
Through some research and taking apart a friend'* thermostat housing on his bonneville to see if he had something I didn't... I noticed he had a sort of rubber o-ring which sat just above the thermostate and inside the thermostat housing.. do you think this would make the difference? I've taken mine apart.. put a new stat in it.. but mine never had that o-ring. If anybody has any ideas or suggestions.. please help? I can't go through another winter up here with minimal heat like that!!!!

Its your gage man, I gurantee you that the engine is coming up to operating temps. Motion generates heat. And no cooling system in the world is going make your engine run that cold.

Pop the hood after driving, it should be hotter then hell under there. Also, let the car idle, once it reached 200F the fans will come on. You probably have a bad Coolant Temp sensor or the gage is faulty. Quite possible when a car is going on 16 years old.

As to you fuel effiency prolems? Check o2 sensor, get your TB cleaned, get your fuel lines and injectors professionally conditioned, check your plugs/wires, and use higher octane fuel. Do some experiments.

You do not want water getting around the thermostat. Your symptoms are a classic sign of a thermostat stuck open. Make sure all o-rings are there.

What if you let the car sit there and idle? Does it ever warm up to 200?

All of my cars have 180F Stant "Superstats" (about $6 at Pep Boys).There is just ome seal (O-ring) around the thermostat housing though there was a TSB around 1989 that said for owners compaining of poor heat to add the second seal on top of the thermostat.

The first quater mark on the temp guage seems to be at 190ish (my cars all operate under this mark.

That said the ECM goes closed loop when the coolant hits 146F and heat should be decent at anything over 160F. Sounds like you are running under 140 and are a candidate for a new thrermostat. Just be glad it didn't fail closed.

hey everybody. thanks for the suggestions.. first of all. thermostats have been replaced.. two of them as a matter of fact.. so they check out ok.. and when i say the temp gauge barely moves. i mean barely. in the summertime.. it comes up quite nicely to about 1/4 way up the gauge.. as far as the car being older.. i've owned the car since 1990 and it'* done this since i've owned it. so it'* nothing new.. over the years i haven't put a lot of milles on it. but now i'm driving it a lot more and would like some heat and some proper fuel mileage out of it. motor has been tuned.. injectors cleaned and so far all testing points back to something not letting the engine temp come up..I'm gonna try to find if that o ring i saw on another bonneville inside the therm housing is available and give that a try.. just in case coolant is getting by the thermostat .. this is the only thing i can see that may help unless there is anybody else who can suggest something else.. i'd appreciate it.

I'd connect a scan tool first to verify coolant temp below 150F.

If so check out Buick technical service bulletin 89-6-03 dated Nov 88 which calls for thermostat sealing gasket 2553539 (may not still be a good number) that goes on top of the thermostat and under the water pipe (you still need the O-ring).

While apart, verify that the thermostat is not stuck open (common).

I had the same problem on my '87. The guage never moved. I got fed up with it and went ahead and changed the coolant and thermostat. I noticed the problem still wasn't fixed (i should note that I never got ANY heat at all) so then I went to the parts shop and got a thermostat O-Ring for my car. I didn't know my car needed one or didn't need one but my chilton'* wasn't very specific and all it said was to replace the gasket. It turns out my car is supposed to have an 0-Ring but no gasket. So I opened up my upper engine coolant inlet and noticed it was just a thermostat dancing in there. So what I did was put the new thermostat in there, then put the o-ring over it, then put the inlet pipe, then the radiator hose. It took care of the problem. Strange how someone might leave things like that out. Anyway it was hard to tighten the bolt that holds the inlet pipe over the thermostat and at first it leaked a little because I had under-tightened it. Never the less just tighten it well and make sure no green drops from it probably better to undertighten it first and then tighten it more and more until leaking stops if you're not sure) and your problems will be gone. My temp guage did the SAME thing. I was like, "Damn my engine is running smooth and cool!" but really it was just screwed up by too much coolant flowing.

Mike Diaz

Should mention a couple of things here. First the "C" 3800 (88-90) just has one bolt on the water outlet housing. This is because the bolt just holds the outlet in place, it does nothing to seal it. The sealing is done by an O-ring that fits in a groove in the part of the outlet that fits down over the thermostat. As long as the manifold and the groove in the water pipe are clean, when the outlet is in place, the O-ring will seal.

Until November 1988 there was also a paper gasket under the thermostat the was supposed to keep coolant from seeping around the thermostat lips. Either it did not work very well or the general got in a load of undersize thermostats (is supposed to be 44 mm in diameter) because part way into the 89 model run the paper gasket was replaced by a conical rubber ring that goes on top of the thermostat. You do not need both.. In any case you still need to O-ring that goes onto the water outlet.

Do not try to install the water outlet just by tightening the bolt, the water outlet will **** in the manifold. OTOH a little angle won't hurt anything providing you really cleaned the walls of the hole. I genally coat the surface of the O-ring with some never-seize (silver stuff) and work the outlet in as far as possible by hand. Then I use a big screwdriver to push down on the lip of the outlet opposite the bolt while tightening the bolt. It will slip down pretty evenly until it bottoms.

Once the bolt starts to bottom, you do not need to play Godzilla, as I said, the O-ring makes the seal, the bolt just holds the outlet in place. Snug it down about like a valve cover bolt. Coat the bolt with never-seize also & it will be easy to remove when flushing time comes around.

Don't have to but I always replace the O-ring whenever a t-stat comes out. For a few dracmae I keep a handful around.

Long time ago I learned that surface preparation is everything in engine building even if you are just replacing a water pump. Unless there is a problem I just apply a slight film of wheel bearing grease to gaskets before clamping everything up (friend of mine insists on applying gaskets dry but I want them to swell a little in use. Once that is done, just the factory torque on the bolts will seal everything. OTOH if the surfaces are not cleaned properly, bolt breaking torque will not seal properly.

Do keep some Permatex around - the silver stuff I just mentioned, threadlocker blue (not red) for when I need to be certain a bolt will stay in place, and aircraft gasket sealer (aka #3) for hanging blind gaskets when I need to tack one side in place. IMNSHO #2 and blue death are kludges.

BTW I have had very good luck with Stant SuperStats (plug).

hey.. thanks for those last couple of posts.. i think we're on the right track here.. over the last couple days. i tracked down that o ring that i can try putting either under or over the thermostat.. i also got another o ring that is the one that came on teh 89 and later therm stats and with those housings.. although. i believe i did try one of those last winter and it didn't do much. i'm gonna make the attempt at the larger o ring under the thermostat to help seal it and not have any coolant seep by.. cross your fingers.. i'll post results when i get some time and get the job done. thanks again everybody!

so I got a rubber o ring the same diameter as the theremostat.. and i placed it nice and flat in the manifold so it sits under the theremostat.. i cleaned all surfacesand reinstalled the thermostat housing.. filled with coolant.. and bingo.. !!! up comes the temp nicely and I have heat!!!.. I also have much better fuel mileage also! wonderful how this works! Thank you everybody for your help and suggestions