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Is this normal? Engine cools down when driving

 
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Old 12-18-2010, 10:31 PM
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Is this normal? Engine cools down when driving

When I leave my lude on idle, the temperature slowly creeps up to the 3 bars to the middle.

However, I start driving and even at just 30mph, the bars go down to the min temperature.

I know it's freezing out here in Detroit and so maybe that's contributing. Before, during the fall, I would drive at freeway speeds and the temperature gauge would fall to minimum.

The other car I usually drive, the temperature gauge goes to the middle and stays there.

Is this normal or is something out of whack here?
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Old 12-18-2010, 10:59 PM
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Re: Is this normal? Engine cools down when driving

sounds like you have either no thermostat ,or one that is stuck open
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Old 12-18-2010, 11:24 PM
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Re: Is this normal? Engine cools down when driving

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Originally Posted by apex1972 View Post
sounds like you have either no thermostat ,or one that is stuck open
Thanks. The symptoms are typical of stuck open thermostat.

I should replace it soon since I would love for some heat instead of freezing my ass off. I'm having some problem with the gas pedal sticking (I was thinking PCV but it rattles fine) and now, I'm thinking it's the low temperatures that's gunking up the system instead of being burnt off.

Wish I had done the coolant flush before the snow came but I guess I'll have to do that also.
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Old 12-19-2010, 03:11 PM
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Re: Is this normal? Engine cools down when driving

The bars go down because your coolant cools itself through convection (radiator). The more cold air flowing at the radiator, the cooler your coolant is; therefore, your engine cools down.

Then again, I could be completely confusing my physics (being I haven't had it in a few years) and be completely wrong
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Old 12-19-2010, 08:37 PM
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Re: Is this normal? Engine cools down when driving

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Originally Posted by RandallSharp View Post
The bars go down because your coolant cools itself through convection (radiator). The more cold air flowing at the radiator, the cooler your coolant is; therefore, your engine cools down.

Then again, I could be completely confusing my physics (being I haven't had it in a few years) and be completely wrong
My OBD tool says my coolant temperature is 50C (122F) whereas the optimal temperature is around 90C ( 195F).

From what people are saying, low engine temperature can
- lower fuel efficiency
- cause quicker engine wear because engine oil is not warm enough to burn or boil away contaminants
- carbon deposits since some stuff aren't burnt away

And, of course
- discomfort in the winter due to low heat
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Old 12-20-2010, 12:22 AM
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Re: Is this normal? Engine cools down when driving

Quote:
Originally Posted by RandallSharp View Post
The bars go down because your coolant cools itself through convection (radiator). The more cold air flowing at the radiator, the cooler your coolant is; therefore, your engine cools down.

Then again, I could be completely confusing my physics (being I haven't had it in a few years) and be completely wrong
Your physics is right, but coolant control isn't...as suggested, the engine's designed to operate best within a certain temperature range, so the thermostat regulates flow through the radiator to maintain that temperature. Stuck thermostat = too much cooling = engine cools down.
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Old 12-22-2010, 03:03 PM
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Re: Is this normal? Engine cools down when driving

Changed the thermostat as described here. Got the Slant Superstat 180 degree one (45878) since they said that's OEM temperature.

Since it's so cold out there, I didn't do a full coolant flush. I will change timing belt when it's warm out so I will have to go on with the old coolant in there. Bled the system like described here. While bleeding couldn't get the coolant temperature above 185 on idle. When driving the coolant temperature stayed around 215-220.

I've only driven a few miles on the car so I'm hoping no overheat issues. But, looks like it was a bad thermostat that was the problem.

I wonder if it was the engine temperature being too low that I was getting a lot of gunk in my intake and sticking my pedal? I checked the PCV valve and it rattles fine when shaking. Hmm, we'll see if that solves the sticky gas pedal problem. I would clean the intake and it would get gunked up the next day.

Also, really happy I have heat in the car :)
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