98 Cav overcooling, yes, I replaced the thermostat

[Timmy390]

So this is driving me nuts. Most of the time, you have it the other way with overheating.

The gasket around the thermostat started leaking so I replaced it. Seems the wrong one was in it to start with. Put it all back together and it started overcooling. So, I replaced the thermostat as I should have done while I had it apart the first time. Still overcooling.

It was fine before I took it apart. It's find around town as long as you stay under say 60MPH. Get above that and the temp gauge dropps like a rock. I replaced the temp sensor thinking it was the problem, still overcooling. I know it overcooling because the heater starts blowing cooler air as the gauge drops. On the highway, running 70 and 80MPH, the temp drops to below normal on the gauge and the heater blows cold. Take an exit and slow down, it starts heating backup.

It's not cold here in AR, 40's 50's and 60's for the past two weeks.

Got any suggestions? Could it be air in the system maybe?

Thanks Tim

[Asus2006]

Very good ? I have a 2000 CAv. One day on my route, about 300 miles of constant driving and city traffic, I noticed the temp a bit above normal. So I stopped at a gas station to check the level. It was low, I filled it to its recommended level, maybe slightly above. Anyway, I took the express way home, it was about 20-25 degrees, doing about 75 mph, and the temp gauge fell to just above 100, and it was cold. Even if I turned the heater completely off, it still didnt warm up. Normal driving around the city or waiting for a traffic light will cause it to go back to around 180. So im thinking that the recommended level is off. So I will keep taking little bits of coolant out of it and let you know what that brings. Good luck.

[corning_d3]

Yes, nice and warm in N.E. AR today, huh? Just guessing, but you are using the proper mix of fresh water/antifreeze, correct? Too much water in the system can cause the coolant in the radiator to begin to freeze at cruise speeds, then unfreeze when slowed down. If you are using the right mix, and it's fresh, try covering 1/4 to 1/2 of the radiator with cardboard. Also you may want to make sure you have a 195 degree thermostat installed....

[Timmy390]

Originally Posted by corning_d3

Also you may want to make sure you have a 195 degree thermostat installed....

That's a darn good ponit. The one that I removed was a 180 (installed by the PO I'm guessing and it had the wrong rubber gasket) and the one the parts store gave me was a 180. Looking at my trusty Haynes, it should be a 195 like you say. Guess I'll be changing that. They ask what engine and I said 2.2 but I guess they gave the the one for the 2.2 OHC and not the 2.2 OHV. I'll also check the coolent mixture. Maybe I have it out of wack.

It held some heat this afternoon driving home but it's like 70 outside. the temp was in the normal area but just. I took my exit and stopped at a light and it heated up to where it should be then started cooling back down the minute I was on the move again.

Tim

[RahX]

what a curse eh? lol anyway i would do the cardboard trick. if its overcooling in 50ish weather freezing isnt the problem. but yea, cover half the rad with cardboard. i dont know if it would matter side to side or top or bottom. try diagonally

[corning_d3]

cover 1/4 to 1/2 of the side....lol, diagonally!!

[cdru]

Originally Posted by Timmy390

That's a darn good ponit. The one that I removed was a 180 (installed by the PO I'm guessing and it had the wrong rubber gasket) and the one the parts store gave me was a 180. Looking at my trusty Haynes, it should be a 195 like you say. Guess I'll be changing that. They ask what engine and I said 2.2 but I guess they gave the the one for the 2.2 OHC and not the 2.2 OHV.

The Haynes manual is incorrect, at least for my '97. It does indeed say 195 degree thermostat for a 2.2. OHV, but my offical shop manual says that both the 2.2 and 2.4 for my year use a 180 degree thermostat. Unfortunately I discovered this the hard way as I was just finishing up replacing my thermostat, with a 195 degree one, and just happened to see that in the shop manual while I was seeing at what temp the fans kick on (>223 degrees BTW).

[Timmy390]

Well, I DID change the 180 out to the 195 this past weekend. It helped the problem but it's still running cooler than it should. It runs just a bit hotter with the 195 around town (which is to be expected) but get out on the highway and it cools off. It did hold more heat yesterday but it's not what I consider cold here in AR. 40's in the morning and 60's in the afternoon.

The temp gauge did stay 1/4 up into the normal area for the drive home (running 70 and 80) but it sits at half way when driving around town or sitting at a light. I suspect when it cools off here, it will run too cold again but time will tell.

Could a bad pressure cap be causing some of my trouble? I've changed everything but the water pump and the pressure cap. Do these cars just run cold?

Tim

[cdru]

What I'm saying is that the 195 thermostat is the incorrect one. It really should be replaced.

There was a thread from about a month ago (originally started over a year ago) started by DeadBird with exactly the same problems. The replaced a variety of things and actually when through 6 different thermostats, all from Autozone sold under the Duracraft brand name. Every one had the same problem. Ultimately he replaced it with a 7th thermostat, this one from Napa, and the problem was corrected.

I beleive he suspected that the Duralast thermostats had a weaker spring holding it close and would open up under pressure during higher engine speeds. Stop and go city driving used lower speeds as well as reduced air flow through the radiator, allowing the temp to increase.

[Timmy390]

Cdru, I wasn’t saying 180 was not correct. Just saying I replaced it (already had it before I saw your post about 195 being wrong) and the problem didn’t go away. I searched earlier and didn’t find that thread on topic but searched now and found the thread you mentioned. It helped that I searched on “duralast thermostats” and not “overcooling”. Seems the motored thermostats are crap and that’s what I’ve been replacing with.

Guess a trip to NAPA is in order.

Will post my results.

Tim

[Timmy390]

Well, went to NAPA over the weekend and got the NAPA brand thermostat as recommended. Problem seems to be solved. It holds heat on the highway now. Funny, it runs cooler than it did in town and hotter then it did out on the highway. The gauge never gets higher than straight up on the highway and around town, it cools down to ¼ into the normal.

Anyway, I have heat for the morning drive and the wife is happy.

Thanks for all the help.

Tim

[Cavalier2000]

well it is a problem that most people have. No matter what thermy u put in there it will still run cold. Mine does and it even has a slightly colgged rad. U can do the cardboard trick!

[kirby747]

the 180 is fine cause those things are bad for blowing head gaskets just get a good one from napa, the sping is too weak in the motorad ones, as soon as engine revs the water just pushes the thermostat open and circulates thru the rad whether engine is warm or not, learned that on here, have to find the original post and thank them