Engine Running too Cool?

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EmersonC

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So a while ago my engine was constatly running too hot. I replaced the thermostat and now it runs far on the cold side. Is this a problem that I should worry about? Or just be happy its not running hot anymore?

I have a 66 dart with a 273
no A/C
Thermostat was replaced with a 160F I believe
My temp gauge could be faulty, I have never replaced it
 
I would much rather my engine run cool than hot. I also replaced my thermostat with a 160 my car runs about 160-170 during the winter and right at 200 in summer when it gets to 110+ outside here in so cal. You shouldn't worry
 
If your temp gauge is running about one needle width off the cold side of the normal temp range, that is normal. Mopars don't run in the middle of the gauge. That's how the gauge is set up to run. Before fuel infection, cars came from the factory with 180 degree thermostats. 195s came along with that mess....
 
grumpuscreature said:
If your temp gauge is running about one needle width off the cold side of the normal temp range, that is normal. Mopars don't run in the middle of the gauge. That's how the gauge is set up to run. Before fuel infection, cars came from the factory with 180 degree thermostats. 195s came along with that mess....
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Ok, that makes me feel a bit better. Though I am more like two needles width off the cold side.

What about what jimmyjimjim said. Can anyone second that or expand on it?
 
Before you get to worrying too much one way or the other, check it with a thermometer. Then decide on a course of action that will keep it in specs. Any sort of wear from too much or too little heat is all relative. Even the amount of time it spends in certain heat ranges, like warming up or cooling off all count. If it could go 500,000 miles and you only get 470,000 does it really matter?
 
yup he is pretty close ,as a colder engine does not burn the fuel as complete and the extra ends up going out the exhaust and into the oil . it causes the oil to get thin between oil changes and thinner oil doesnt cushion the parts as well speeding up engine wear . as far as running its best at 195 it depends on the engine but between 180 and 195 is fine to burn off harmful deposits left by the combustion process
 
EmersonC said:
What about what jimmyjimjim said. Can anyone second that or expand on it?
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I've always heard that a cold running engine (ie: not operating within the temp range it's designed to) accelerates wear too (but not overnight). Don't know exactly what the scientific reasoning is behind the declaration. However, I can say that since an engine is a big heat pump it needs to run at upwards of 200* for efficiency. Also, you need higher temps to burn off condensation that forms inside the engine - amongst other things. I'd make 180* the minimum.

It's also a common belief that if a car overheats with a 195* stat, then switching to a 180* or 165* may cure the problem. Assuming the 195* unit was opening correctly, switching to a cooler thermostat won't fix anything. It'll just take the engine longer to overheat. Best to investigate why.
 
Very true 70dust440, I would like to know exactly why I was over heating. I still have the old thermostat and ill pit it in some hot water to see if it opens all the way.

I'm also now wondering if my temp sensor is still good. As far as I knor it is the original one. I might replace it. Probably is not too expensive, I hope.
 
It's possible there's an issue with the sender or gauge but after ruling out the thermostat I'd be inclined to check the radiator for plugged passages, the condition of the radiator cap, and ignition timing.
 
The purpose of the thermostat is not to keep the engine cool, it's to get the engine up operating temperature quickly, and to keep it there.

I read once that 95 percent of engine wear occurs before an engine reaches operating temperature. And that is why it's not uncommon for NTC taxis to get 1 million plus miles, they are constantly at operating temp, and therefore not causing much engine wear.

Another consideration is wether the oil is getting hot enough to burn off the moisture in the oil.

I run a 195 degree thermostat in my 72, and even in an Austin summer where the highs are usually 100+, I never have an issue with overheating.
 
70Duster440 said:
It's possible there's an issue with the sender or gauge but after ruling out the thermostat I'd be inclined to check the radiator for plugged passages, the condition of the radiator cap, and ignition timing.
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The radiator cap seems fine, no corrosion and the spring still works.
How would I check the radiator for plunged passages?

I'm thinking today after work... I'll take the cap off, bring it up to operating temp. See if coolant is moving in the radiator (letting me know if the stat is starting closed then opening) and stick a thermometer in there to check the temp. The temp of the violent at the radiator should be the same as the temp at the sensor right (give or take a few degreed).

As far as timing, if the timing is off won't that make the engine run hot, not cold?
 
EmersonC said:
How would I check the radiator for plunged passages?

As far as timing, if the timing is off won't that make the engine run hot, not cold?
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If the level is low enough or the coolant clear enough you'll be able to see whether there are white calcium deposits in the ends of the tubes.

Retarded ignition timing can cause it to run hot.
 
I'll take a look after work today. I think my timing is about 10* reterded.
 
EmersonC said:
So a while ago my engine was constatly running too hot. I replaced the thermostat and now it runs far on the cold side. Is this a problem that I should worry about? Or just be happy its not running hot anymore?

I have a 66 dart with a 273
no A/C
Thermostat was replaced with a 160F I believe
My temp gauge could be faulty, I have never replaced it
Click to expand...

Remove the 160 stat and replace it with a 180 or 195. Problem solved.
 
About the timing... The stock timing should be 10 degrees BTDC unless it is a California engine with cleaner air package (CAP). The CAP engines were set 5 degrees ATDC. They also had a vacuum control valve, that switched the vacuum source to manifold vacuum off idle, to advance the timing to near normal. The carbs were specially calibrated with air bleeds in the throttle plates and changes int the idle circuits. The distributor had different mechanical and vacuum advance components. While it worked OK as a system, if some parts are removed or changed with non-CAP components, may lead to tuning problems. Some change to a standard carb and distributor with good results.

+1 on 185 degree thermostat.
 
This is a great thread! i love playing with cooling systems. There is lots of great information in these posts. Engines do make power at 200 degrees, one of the first automotive lessons I ever learned. One of these guys mentioned the 95% rule as to when damage occurs, he's correct. The argument between 180 and 200 degrees is bunk though. One thing I havent seen in this thread is that there are several points within an engine and cooling system to measure temp. Who or where creates the baseline?...YOU do...Also hardly any measuring equipment are gonna measre the same at different points. Simple math tells you if your motor dont register 170 minimum, you are inefficient. And when you go over around 225 with a 22 lb or lower cap, you got issues. Weather, ambient temp, fan cfm, radiator capacity, driving style, other air conditions, etc all affect the results.
 
Just a heads-up, going to a lower temp. thermostat will NOT solve overheating problems. In fact it might make it worse because it puts more strain on the cooling system in trying to get rid of more heat than before. A cooler T-stat is only good for performance engines (high compression, etc.) that need the extra heat dissipation.
 
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