Help settle a thermostat bet

[hotrod preacher]

really doesn't apply to t-stats, but it applies to engine cooling.......

if an automobile is running a complete system-antifeeze, thermostat etc. and the engine temp runs "normal going down the hiway and only overheats sitting in parades or traffic, then more than likely you have an airflow issue and not a coolant/t-stat issue

simply put the heat can't leave the radiator without airflow--some think a fan shroud is only to keep you from loosing a finger, but if working correctly it helps to pull the air through the radiator....i know many ratrods use an electric fan and that's fine, however the size of the fan is usually dictated by space confinements, with no consideration for how much airflow is needed to keep the engine cool....


....all i'm sayin is.....don't forget airflow in the cooling equation

 

[jfg455]

Your "car" will only run at the temp that the cooling system is designed to handle. To small of a cooling system and it will run hot no matter what the temp T stat is in it. Too big (efficiant) system and the car will maintain the temp that the T stat is designed to do IE: 160 T stat will run right around 160 and 195 will be around a 195.
On the circle track cars it is a different story. You would run a restrictor in place of the T stat and runn a slower water pump due to the fact that a regular water pump is not designed to run at 6-8K rpm constantly and will cavitate. If the pump cavitates then you will over heat due to the fact that you are not moving any water. just my $.02

 

[rainman]

Its not just cavitation you can pass the water too fast through the rad. to dissapate heat. Look at a 160 degree stat and then a 190, the 190 should have a slightly larger hole, therefore in open posistion water will travel through the thermostat faster= higher temp. If you have a cavitation problem the only way to completely solve that is to slow the pump or use one designed for high rpm. I hope I said all this like I was thinking it. lol

 

[Sam_Fear]

Apparently the coolant moving to fast through the radiator idea is false. Cavitation may be the real problem - not just at the waterpump,but also at critical points inside the motor.

Detailed article. http://mgaguru.com/mgtech/cooling/cool_200a.htm

This wound up a can of worms!

 

[Willowbilly3]

I think it's a great thread with lots of good information and opinions.
Another theory, which would be hard to prove is this;
If you have a low pressure area such as a restriction might cause, the oxygen may seperate from the water and cause bubbles. Bubbles in cooling will cause the coolant to not transfer heat. Also remember that straight water cools more efficiently than antifreeze does. If you live in a warmer climate you could go 75%-25% instead of 50-50 on the mix and pick up a little more efficiency. If you decide to run straight water, add some rust inhibitor. Also there is a product called water wetter that helps water transfer heat better. I suppose it is some kind of surfactant that breaks down the surface tension of water.

 

[jfg455]

This wound up a can of worms!

No no, no, no. A can of worms inherantly will run no more than 98.7 degrees F. sheesh! everyone knows that!

 

[Sam_Fear]

^^^

Willowbilly3 - You seem to have a grasp on this.

Will running without a T-stat actually cause higher temps?
I've never witnessed that, but always understood it to be true. After reading that article and a little strained thought, the only thing I could figure is that increasing the speed of the coolant would be a plus until at a certain point the speed of the flowing coolant would start to bubble along the surfaces (cavitation) and transfer heat less.

 

[Willowbilly3]

^^^

Willowbilly3 - You seem to have a grasp on this.

Will running without a T-stat actually cause higher temps?
I've never witnessed that, but always understood it to be true. After reading that article and a little strained thought, the only thing I could figure is that increasing the speed of the coolant would be a plus until at a certain point the speed of the flowing coolant would start to bubble along the surfaces (cavitation) and transfer heat less.

There isn't anything carved un stone but I have seen many engines overheat without the T-stat, not all though. For some reason the first thing a lot of people do is remove the T-stat when they have an overheating problem. Kinda getting off track but the most common overheating problem I had come into my shop were just a bad pressure cap. I've seen some weird stuff too. I had a customer with a 2.8 S-10 that we couldn't get any heat out of with the T-stat completely blocked off.

 

[donsrods]

A friend of mine has a 29 roadster with a sbf in it. It ran warm regardless of what thermostat or no thermostat he ran. He finally put a restrictor plate in it that just had a small hole in the middle, and it started running a lot cooler. So I guess every car is different and you might have to play around. Right now for breaking I have no thermostat in the sbf in my 27 because the radiator is so small it needs all the help it can get, and I found during the 7 years I drove it that no thermostat happened to work better in that particular setup.

Looks like there is no one clearcut answer.

Don

 

[Willowbilly3]

I think you nailed it Don, every system is different and there are so many variables.
I do like to see those engines hotter though. Anything less than 180 or so on the temp guage is not hot enough IMO and I see no problem at all with an engine that runs well over 200 if the coolant is staying in it.
Back when electric fans started showing up on production cars, I had a Celebrity come in for an overheating issue. It had a guage and in traffic it would go into the red. I dug into it and found that the fan thermostat didn't turn the fan on until 108C which (IIRC) is 232F. Nobody made a different one, all GMs had the 108C. The car wasn't boiling over but I couldn't convince the customer that was the way the car was engineered so I finally cobbled in a fan-stat from a Chrysler product and got the fan to come on around 195.

 

[donsrods]

I know. I rented a new car on a business trip a couple years ago and it ran at 210-220 normally! I just get nervous when my temp gauge starts going north of 180, and living here in Florida that isn't hard to do at all.

They tell me the newer Mustangs electric fan doesn't even come on until 221 degrees.

Don

 

[jfg455]

Most all late 70's to mid 90's GM temp gauges read lower then the actual temp in the engine as well. The engineers didn't want the public to know that they run the engines that hot abd are designed to do so. Most people even now think that anything over 200*F is overheating. Cadillac northstar motors will run at 230*F all the time. High speed fan doesn't turn on until 232*F.

 

[imnezrider]

I know. I rented a new car on a business trip a couple years ago and it ran at 210-220 normally! I just get nervous when my temp gauge starts going north of 180, and living here in Florida that isn't hard to do at all.

They tell me the newer Mustangs electric fan doesn't even come on until 221 degrees.

Don

Used to be with Saturn. I know in their mid-90's cars, the sensor turned the fan on at 226 degrees. I went back one day when a tech was checking a car on the shop computer and watched the fan come on at precisely that temp. I was impressed with the built-in accuracy.