Another [I]HOT[I] question

jwinkler · #1 (**permalink**) 02-01-2002, 07:22 PM

Got a new heating problem that's just showed up recently. When I start the car, it gets up to temp, and then keeps on heating up until I get underway. I've got a 180 degree thermostat, and temp will keep going up to 220+ before dropping back to normal running temp (roughly 190-195). Once temp drops back to normal, it'll stay there while moving, and get a touch warmer if sitting, but otherwise behaves.

Then, if I make a short stop (10 minutes or less), when I start the car, temp immediately shoots back to 220+, once again, until I get underway.

So - do I have air in my radiator, or somewhere in the system? Does bringing the revs up when getting underway get water flowing and drop the temp? I'm planning to drain the radiator and refill, as well as check the thermostat, but I doubt the thermostat has failed, mainly because once the temp drops after spiking, it stays in the normal zone. The problem only happens on startup.

Any suggestions, help, or ideas are greatly appreciated.

Thanks,

JLW

ERA535 · #2 (**permalink**) 02-01-2002, 07:51 PM

Water temps going above normal after a restart for a short time is normal. Does this happen after a cold start as well? I would first check the accuracy of your temp guage.

Cobra20646 · #3 (**permalink**) 02-02-2002, 03:31 AM

I really don't see much of a problem. What kind of cooling fan are you using. Does it run all the time or come on at some preset temp?
The only problem I see from your symptoms MIGHT be a sticky thermostat...... opens, but later than 180 degrees, and that's stretching the point, or a fan that has the preset temp set too high.
You said "Then, if I make a short stop (10 minutes or less), when I start the car, temp immediately shoots back to 220+, once again, until I get underway. " this is indicative of electric gauges and is normal. When you shut down the engine, the water does not move through the system (well not much anyway) and the temperature of the water in the block rises. The temp gauge, being electric, when turned on by the ignition switch will then shoot up, and then return to normal after the water has a chance to start circulating again. A manual gauge will do the same thing, but you can watch it while the engine and the ignition is off.
With my own car, when the engine is running and I'm sitting still, the temp will rise over 200 to about 210 and stay there... even with the electric fan... and then return to normal after getting underway again, with better air flow and higher RPM at the water pump.
The only reason to drain and refill the radiator is if your unhappy with the "type" or condition of the coolant. You won't gain anything if your just tring to expel air.
- Jim -

Bob Putnam · #4 (**permalink**) 02-02-2002, 05:16 AM

You might need a small hole drilled in your thermostat flange to allow a little flow all the time. Without heater flow, water will stagnate a bit next to the thermostat so it doesn't open immediately.

jwinkler · #5 (**permalink**) 02-02-2002, 06:16 AM

Thanks for all the suggestions - the reason I'm concerned is that this is a recent development. It used to not spike past 210 or so. The car does tend to sit for a while between outings (sometimes a couple of months - I know, I know, a pre-oiler's on my list). Could this contribute to this change in behavior? Would the fact that it sits for so long cause a problem with the thermostat?

Thanks again,

JLW

Michael C Henry · #6 (**permalink**) 02-02-2002, 04:21 PM

Check the thermostat bypass ,that short hose between the manifold and water pump.If that is plugged there is no circulation near the thermostat untill it is much hotter in the heads and the hot water causes the thermostat to open usually violently.I've seen the metal nipples rust and I found the hose to have a blister inside that chocked off the flow,but was not visable from the outside.