Hot at highway speeds

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roccodart440

roccodart440

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So my GVOD controller took a ****. I have a new one on order. This has however exposed a cooling issue.

My car has 4.56 gears with 28" tall tires. It has a GPS speedo so 55mph is 3,000 RPM.

Around town, at idle and slower speeds with fan on it's fine. 180ish.

On the highway it will go to 200, even approach 210. If I turn fans on it will come down slowly. Get into town and leave fans on the temp comes right down.

This was not an issue witht he GVOD and lower cruise RPm.

What would cause a temp increase at highway speeds when traveling at more RPm?
 
Fan blades not turning (turned off) may be blocking airflow. Also check airflow going around radiator instead of thru it at highway speeds. I just fixed a Corvette with the same problem by sealing the top of the rad to the hood, fender to fender.
 
Had a 69 Roadrunner that did the same thing, highway driving , and it would run real hot. In town driving , no problem. Took the radiator out to the radiator shop and they cleaned it out, and no problems after that. That car went on to be the Mopar Nationals Grand Prize give a way car in 1992, and I think it is on ebay right now for $42,500.
 
If this just started when the Gv took a crap, it could be running the engine at those rpms doesn't give the coolant enough time to cool.
 
furyus2 said:
If this just started when the Gv took a crap, it could be running the engine at those rpms doesn't give the coolant enough time to cool.
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It did.

My thought is does it have a thermostat in it? If not it needs a restriction ring. This may sound stupid but I parted ways with this car for a while after I built it.

69MOPE said:
Fan blades not turning (turned off) may be blocking airflow. Also check airflow going around radiator instead of thru it at highway speeds. I just fixed a Corvette with the same problem by sealing the top of the rad to the hood, fender to fender.
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What did you use to seal it?
 
Probably normal for the added RPM. 210 is not overheating.
 
you basically doubled your cruise rpm. that is what is going on. the motor is making more revolutions and creating more heat for the same amount of air flow across the radiator. you have a couple options. fix the overdrive. go bigger on the rad. or get more air thru the rad. I am in the process of sealing my rad to the core support and blocking off areas that air could go around the rad.
 
69MOPE said:
Fan blades not turning (turned off) may be blocking airflow. Also check airflow going around radiator instead of thru it at highway speeds. I just fixed a Corvette with the same problem by sealing the top of the rad to the hood, fender to fender.
Click to expand...

I would try this first, do you have the rubber piece that mounts to the hood and lays across the radiator support when the hood is closed? Also check any where that air can go around the radiator and close it off some how.
 
roccodart440 said:
It did.

My thought is does it have a thermostat in it? If not it needs a restriction ring. This may sound stupid but I parted ways with this car for a while after I built it.



What did you use to seal it?
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Thick foam rubber. Give me a measurement(width - thickness and length) and I will send you a piece.
 
RustyRatRod said:
Probably normal for the added RPM. 210 is not overheating.
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I know 210 isn't overheating but I don't like it.


younggun2.0 said:
you have a couple options. fix the overdrive. go bigger on the rad. or get more air thru the rad. I am in the process of sealing my rad to the core support and blocking off areas that air could go around the rad.
Click to expand...

I just bought a http://www.summitracing.com/parts/b...I76MIWd1vYm7mYJ6UOaLgHCAH44L7rflUmRoCo9Tw_wcB

I am fixing the OD.
 
roccodart440 said:
So my GVOD controller took a ****. I have a new one on order. This has however exposed a cooling issue.

My car has 4.56 gears with 28" tall tires. It has a GPS speedo so 55mph is 3,000 RPM.

Around town, at idle and slower speeds with fan on it's fine. 180ish.

On the highway it will go to 200, even approach 210. If I turn fans on it will come down slowly. Get into town and leave fans on the temp comes right down.

This was not an issue witht he GVOD and lower cruise RPm.

What would cause a temp increase at highway speeds when traveling at more RPm?
Click to expand...

Mine also does this and I don't like seeing 210 either, even if it isn't technically overheating. It runs 3100 ish rpm at 60 too. I'm running an electric water pump so obviously no thermostat. I've put a restriction washer in but I think it actually made things worse. The reasoning behind it (I think) is because the restriction washer is actually causing the coolant to shoot through the washer at a high velocity and thus creating aeration (this I can see). With all the aeration in the coolant, this leaves less surface area when it goes through the radiator and does not cool as efficiently. At least that's my theory. I'm probably going to end up taking the restriction washer back out. Sealing around the radiator would be another good idea. I've also been suggested to add a front air dam (kind of like a lot of newer cars have). This will create an area of low pressure behind the radiator and help pull air through it. But unfortunatly our old cars don't always look right with an air damn up front and it's not like you can just go buy one and bolt it right on that I know of.
 
roccodart440 said:
I know 210 isn't overheating but I don't like it.
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Do you like having moisture and contaminants build up in your oil? That's what happens if your engine does not run hot enough for a long enough period.

The fact is, as long as an engine will cool back down after slowing down, it is not overheating. Overheating by definition is when an engine gets to the tipping point and cannot recover to a cooler temperature. Yours is obviously not doing that. You are simply creating more heat without the OD unit by spinning the engine at a higher RPM. 210 is your new normal for now and it will not hurt a thing. In fact, it is a very healthy temperature for your engine, whether you "like" it or not.

Most modern engines don't cut the electric fans on until around 230 degrees. That's because over time, engineers have learned that boils impurities, contaminants and moisture out of the oil. You don't have a problem. My advice is don't make one.
 
Get an infra-red temp gun,, when you think it's hot,, shoot the temps at the rad inlet/outlet fittings,, the diff should be min. 40*,, if less ,, your rad isn't losing enuff heat..

also try shooting across the front of rad, half way down,, any cool areas are plugged tubes, the bigger the cool areas,, the bigger your prob..

Here's a very similar link,, with all the suggestions he tried,, it was the rad..

http://www.forabodiesonly.com/mopar/showthread.php?t=312573

hope it helps..

PS. RRR is right,, new fans don't turn on till 230*..
 
roccodart440 said:
What would cause a temp increase at highway speeds when traveling at more RPm?
Click to expand...
Simple... the engine is producing more power so the heat output goes up. There is no more power needed to push the car body through the air or to roll the wheels and tires at the same highway speed, BUT there is more power in torque converter and trannie losses, and the engine itself requires more power; as a self-powered air pump, turning more engine RPM's raises pumping and frictional losses, and thus it needs more power.

So your cooling system will have to push more heat out, and all parts of the cooling system have to get hotter to do that if nothing is changed: coolant, radiator, etc. The suggestions to lower the temps by sealing off the rad to the core, etc., make the radiator more efficient by 'connecting' it better to the air with more airflow. You could do the same with a larger radiator or one with more rows.

Or, just fix the OD....like you plan!
 
RustyRatRod said:
Do you like having moisture and contaminants build up in your oil? That's what happens if your engine does not run hot enough for a long enough period.

The fact is, as long as an engine will cool back down after slowing down, it is not overheating. Overheating by definition is when an engine gets to the tipping point and cannot recover to a cooler temperature. Yours is obviously not doing that. You are simply creating more heat without the OD unit by spinning the engine at a higher RPM. 210 is your new normal for now and it will not hurt a thing. In fact, it is a very healthy temperature for your engine, whether you "like" it or not.

Most modern engines don't cut the electric fans on until around 230 degrees. That's because over time, engineers have learned that boils impurities, contaminants and moisture out of the oil. You don't have a problem. My advice is don't make one.
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Well said Rusty! tmm
 
clinteg said:
Wow that's a nice one. You'll have to let us know how that works out.
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I will. I pulled it out of the box. It's a piece of art. It's the largest one they make and is rated for 1,000hp so it should be just big enough right? lol
 
nm9stheham said:
Now the t'stat will really being doing its job....
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I suspect a "spoiler by randy" would help that situation a bunch. I`ll be ordering one for my barracuda after I get done playing w/ the suspension, it pretty low in front, so we`ll see . :coffee2:
 
famous bob said:
I suspect a "spoiler by randy" would help that situation a bunch. I`ll be ordering one for my barracuda after I get done playing w/ the suspension, it pretty low in front, so we`ll see . :coffee2:
Click to expand...

I've wanted one of those for a while.
 
My 67 Dart used to run hotter above 70mph, moded a early Dakota air dam to the lower bumper with the opening in the Dakota air dam help forcing air into the lower part of the rad, no more issues at speed.
 

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