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Hey, I recently replaced my radiator due to a crack in the end tank. First and foremost, there are absolutly no leaks anywhere in my cooling system, or in the entire car, for that matter. I own a 1991 Plymouth Acclaim 4Cyl, 2.5L.

Anyway, I recently owned a Toyota Camry, but that was totaled when another car slammed into it from behind while it was parked, so I had to buy this. The reason I told you that was because my temperature gauge on that car was always dead center, give or take. In the new car, my engine seems to run a lot hotter.

Here is my temp gauge:

C ( /...|...........|.. \ ) H     The ! represents the needle.

After about 8 minutes of driving normally, the needle rises to about:
C ( /...|...........|.!.\ ) H

Sometimes it sits there for about 4 minutes before the thermostat lets the coolant flow.

After my thermostat lets the coolant through, it sinks down to about:
C ( /...|...!.......|...\ ) H

From here, the needle sits pretty high until the car is running for a while, and then it sits back around the cool side for the rest of the trip.



My question for you is: Is it abnormal for the car to run so hot for the first 10 or so minutes of driving? Keep in mind, I just replaced the radiator and hoses with brand new, as well as the thermostat, and there are no leaks in the car.
I heard from my uncle that this is normal, but that was after being described in words, and he didnt have the visual aid that i provided you guys with.

Thanks a lot  

if you have the plymouth....   i bet it only does this hot cycle thing when you have the heater on....


how did i know...  the cooling system bypass in that motor involves circulating some of the coolant through the heater hoses and returning it through the other hose...  when the heater core is restricted..  the coolant flow in the bypass system is reduced close to 0...  the thermostat is a long way from where the heat is made in the engine..  so the coolant temp has more time to pick up more heat before it can boil the wax in the bottom of the thermostat to push it open..

if you have blocked off the heater  or the heater control valve that returns coolant...    or the heater control valve is corroded closed...    it will cause the problems you describe...

continued thermal cycling will cause your cylinder head to crack.. and the head gasket to fail...  

you should also check the radiator cap... the little disc in the middle (size of a dime)  that seems to hold the rubber on...  if that disc flops loose..  change the radiator cap...   replacements are available with a spring loaded disc...

this disc holds pressure..  so the cooling system builds pressure quickly..  that cap was designed for systems that can splash coolant up against the disc to close it..   it was a bad idea..   get one that is spring loaded..    i have had to change a bunch of heads and head gaskets do to just that cap disc being loose..  and the system not building pressure..  

Actually, it happens no matter weather or not the heat is on, but thanks for the reply, because you did give me ideas of what to check, and I didnt even think about the fact that you have to give the wax in the thermostat time to boil, which would indeed cause the engine to get hotter for the first couple minutes of driving, and it also explains why the engine always stays cool when the car has been running. Thanks for the ideas, I appreciate it.

But the question still remains weather or not it is good for the engine to run at such a high temperature for that first couple minutes... Excuse my lack of knowledge of older cars.  

you really do need to verify that you have heater core flow... or the heater control valve is actually installed correctly so when the heat is not called for... it is bypassing the coolant..

this is simple.. but it gets screwed up sometimes.. because it really is not written down.. except in a few technical service bulletins somewhere..

i have found the hoses stuff with dowels to stop the water from getting to the heater control valve as it was leaking..

the both heater hoses will get hot before the top radiator hose will.. if they system is working properly..  

Was the cooling system properly bled of air after the repairs were made? If so then there is a problem. Temp. should never be any where near the red line or the top end of the range. A faulty thermostat may be the cause and is a cheap fix. If the car doesnt show any signs of actually running to hot (knocking or poor idle) then it may have a bad temp. sending unit or gauge.