Question for the master mechanics

[Rodney Bullock]

If a cars temp gauge goes up the faster the car goes what is wrong. If you slow the speed down to about 55 the temp hits around 190 degress, if you spped up and run it 75 mph the temp goes up to about 220. What could be happening here, car is a V8. The fan blade pulley is not loose and the lower radiator hose is not collapsing, don't know about the top hose:rolleyes: I had the radiator cap off and ran the car and when the thermostat opens the water really flows. You can see it rolling.

[knuckleharley]

There are a couple of possibilities.

One is that that water is flowing too fast to properly cool the engine. We know this isn't happening because you have a thermostat.

The second is that either your water jackets or your radiator (or both) are so clogged with rust scale that the water has a tougher time flowing. It might flow enough at low speed to cool properly because the lower RPM's create less heat and because the pump spinning slower might not stir up so much crap.

I'd suggest taking the car to a radiator shop to have the cooling system reverse flushed. If that doesn't do the trick you will have to have the radiator "rodded out" to remove the obstructions. You still need the reverse flush before the rodding process because you want to flush the scale out of the water jackets.

[Frank Blackstone]

Just strap him to the fender and have him check for that collapsing lower radiator hose at 75 mph. Coatney is out of town or he would probably do it.

[greg g]

hot at speed is a coolant flow or low coolant problem. If your up to level, you probably have a blockage somewhere. remember after about 35 mph, your fan is just making noise. What are you running for coolant? You might try draining the system and running plain water for a while to see if it makes a difference. the 50 50 mix is good for winter, but anti freeze doesn't have the thermal capacity of water. I noticed mine was runig a bit hotter than normal the other day. Level had gone down so the top of the core was showing. Don;t kow where it went no visible leaks any where.

I run 75% water 25 % coolant. usually I never run over 170.

[wayfarerstranger]

I HAD a car do that checked everything nothing worked ! turned out to be a bad radiator cap ,,, CHANCE

[TodFitch]

This was already answered well by previous posters, but I just have to get my word in too.

Your engine is only 20% or so efficient. So 80% of the energy in the gas turns into heat that needs to be dissipated. The power required to move your car goes up as the 3rd power of the speed. So if you double your speed your power needed goes up by a factor of 8 and your waste heat also goes up by a factor of 8. Which your cooling system has to get rid of. Some of that heat is lost directly off the engine. Most of the heat is moved to the radiator via the coolant and transferred to the air by the radiator.

Fortunately you are going faster so there is more air flow through the radiator. But there might not be enough coolant flow because of blockages. Collapsed lower radiator hose could be a blockage, rust and scale blocking passages in the radiator is another "popular" problem. And, especially in our older cars, rust and scale in the block can cause issues.

But there can be another issue: If the engine is not tuned properly it will not be as efficient. Then more heat is being generated for the same output power and that might be enough to overload the cooling system. So you should also check your mixture and your spark timing.

P.S. We had a car in the 1960s that developed a over heating problem that eventually was traced to the fact that a gas station attendant had sold Mom on a new radiator cap of the wrong pressure rating. So while I don't understand the physics of that I concur with CHANCE that it can happen.

Edited May 23, 2009 by TodFitch

[dezeldoc]

Another thing people don't think of is the coolant going to fast through the system and not getting a chance to stay in the radiator long enough to get heat transfer. plus in a non pressurized system the coolant boils at a lower temperature. in our race motors we don't use a thermostat we use a restrictor, basicly a plate with a hole in it to slow the coolant down.

[Rodney Bullock]

I am so glad I know you guy's, all suggestions are very sound:) The radiator is a recore, I have changed the cap because the other (new) was leaking. I had a problem with finding antifreeze on the ground when I arrived at shows, found out that I had to much antifreeze in the radiator and it was coming out of the overflow tube. The motor was rebuilt last year however Blockage in the water jacket is always a possiblity because scale is everywhere. One thing comes to mind right away coolant mixture, I know this is very important however I just put water and antifreeze in the car until it was full. I don't have a clue if it's the right mixture or not. I know the radiator content is green:rolleyes:sometimes I think it's a wonder any of these cars I have run at all.

The Idea of reverse flushing the system sounds like a great idea. after the week end is over I think I will try that, I have been playing with the timing. It's advance quite a bit however it is not pinging.

The hoses are another issue;)they are new however one might be giving me a problem .......Where is Don right now? Frank you think we can get a bungy cord big enough? That's to good!

[Rodney Bullock]

I went out this morning and got some radiator hose with spring, removed the spring and incerted it into the upper hose on the car. I also added some water to the mix. I will drive it later on today and see if there is any change. I think the hose is collapsing at high speed:confused: Oh boy these cars atleast childen grow up and leave home:cool:

[billwillard]

Rodney,The upper hose WILL NOT collaps. Put the spring in the lower hose.

[radioguy7]

For a $3 possible fix, change out your thermostat with a new one, if stuck open you will have similar symptoms as you are describing.

[gnoub1948]

Rodney:

My brother had a similar issue. It was the radiator being clogged, and it had recently by restored.

Gary

[Don Coatney]

For a $3 possible fix, change out your thermostat with a new one, if stuck open you will have similar symptoms as you are describing.

Stuck open? Did you mean to say stuck closed?

[Joe Flanagan]

Rodney,

I had a similar problem on my 87 Toyota pickup. Temp was fine until I got on the highway and ran it up to 65. Then the needle spiked. Then after a few seconds of driving, it would come down. I assumed my thermostat was sticking and replaced it. That solved the problem.

[Rodney Bullock]

Oh boy:confused: after I got back from the cruz spot yesterday something told me to look at the heat riser. It's closed. I pulled the flap back with a piece of wire and the exhast pipes sound great I guess I was working one side of the system. I went out to the sunday morning spot and the temp was at 180 all the way there, takes 50 mn. to get there with no change in temp on the way back it took 70 min with the temp at 188. I am going to check my mixture because I think I have to much anti freeze. When I ride into a real cool area there is no change in the temp it should read cooler.

I now see why it would get hotter the faster I went, the heat riser closed the exhast system generated more heat kicked back onto the motor. as if it was 30 degress outside this heat riser would heat up the motor. So without the cold the heat riser was doing it's job to well. I will not remove it instead I will unhook it in the winter.

[Frank Blackstone]

The local gearheads tell me that mixing the different colors would cause a glob to form. Sounds like a potential restirction to me. How would a color blind person tell the difference between yellow and green? Certainly not by taste. Rodney I hope your solution works. I'd hate to use mine and lose Don.

[Rodney Bullock]

Rodney,The upper hose WILL NOT collaps. Put the spring in the lower hose.

Thanks Bill, I did not know that, there are things that even I don't know:) How is everything. That spring was hard to get inside the hose, where were you when I needed to know the upper hose could not and would not collaps:rolleyes:

[radioguy7]

Stuck open? Did you mean to say stuck closed?

Stuck open, the faster the engine RPM the faster the flow and LESS cooling since the water does not have enough time to transfer any heat from the block. Try removing your thermostat and running on a hot day, you'll be sitting on the side of the road over heated. Been there, done that

[Don Coatney]

Stuck open, the faster the engine RPM the faster

the flow and LESS cooling since the water does not have enough time to

transfer any heat from the block. Try removing your thermostat and running

on a hot day, you'll be sitting on the side of the road over heated. Been

there, done that

I understand your theory. Back in the 50's my neighbor had a circle racer

powered by a flathead furd with dual waterpumps. He welded a restriction

washer in both goosenecks to prevent just what you are talking about. In

those days the track speed rarely ran higher than 40 MPH and he was always

running behind someone with the engine floored. So in this case restricting the

flow was benefical. However in a 55 chevy running 75 MPH on the open road with

an upgraded radiator I dont think excessive flow due to a thermostat sticking open is

the issue. If the thermostat were sticking closed it would be an issue.

[martybose]

Stuck open, the faster the engine RPM the faster the flow and LESS cooling since the water does not have enough time to transfer any heat from the block. Try removing your thermostat and running on a hot day, you'll be sitting on the side of the road over heated. Been there, done that

Not always true. My 47 is running a pump with the later 6 blade cast impeller and no thermostat or restrictor. It runs at 160 degrees around town and 170 on the freeway, according to my recalibrated temp gauge. The only time it heats up more is when it is sitting still, since I don't have an engine-driven fan anymore; it heats up to about 180 degrees and then the electric fans come on.

I've been driving around in 95 degree weather with these results.

Marty

[Rodney Bullock]

I understand your theory. Back in the 50's my neighbor had a circle racer

powered by a flathead furd with dual waterpumps. He welded a restriction

washer in both goosenecks to prevent just what you are talking about. In

those days the track speed rarely ran higher than 40 MPH and he was always

running behind someone with the engine floored. So in this case restricting the

flow was benefical. However in a 55 chevy running 75 MPH on the open road with

an upgraded radiator I dont think excessive flow due to a thermostat sticking open is

the issue. If the thermostat were sticking closed it would be an issue.

I should have mentioned what car I was talking about, nice pic Don however it's not the 55 Chevy. It rarly runs hot with that aluminum radiator. It's that blasted Studebaker hawk. I drove to WV yesterday to get a trim spear for the fender and it stayed at 180 all the way up. It ran at 190 all the way back. I ran faster and it was hotter on the way back. That was driving it from 8:00am til til 2:30 almost non stop. so I guess the heating up problem was in the heat riser. Nice ride and land scape:)

[Joe Flanagan]

This is an interesting subject. I guess it's one for the engineers. I was always under the impression that removing the thermostat would allow for more cooling. I overheated one summer day in a 1974 Dodge Dart coming back from New Hampshire. Pulled over and removed the thermostat. Don't remember anymore why I focused on that. It was a long time ago. Anyway, I got home to Boston just fine after taking it out. Never heard the greater-flow-lesser-cool theory, but I see the reasoning.

Rodney, when are you going to pick up that Saratoga?

[chopt50wgn]

Some things to know about cooling systems.........when running a water based coolant, when the motor gets hot, cavatation can form in the pump and in the block. That bubble will move eventually, that' why you will see the temps start to rise, only to fall fast due the bubble being broken. Another thing is the so called "dwell time" in a radiator, Any time coolant flows through the radiator it is being cooled. The temps of the coolant coming back through the suctions side of the pump is what is important. If the fan, pump and rad are doing their job correctly, then the coolant coming back should be 10-15 degrees cooler than what the gauge is reading. Lastly, the sending units for temp gauges are usually at the front of the manifold, right near the thermostat housing. So the coolant temps are being gauged as the coolant is LEAVING the motor, not what the temps are in the motor.

[radioguy7]

I understand your theory. Back in the 50's my neighbor had a circle racer

powered by a flathead furd with dual waterpumps. He welded a restriction

washer in both goosenecks to prevent just what you are talking about. In

those days the track speed rarely ran higher than 40 MPH and he was always

running behind someone with the engine floored. So in this case restricting the

flow was benefical. However in a 55 chevy running 75 MPH on the open road with

an upgraded radiator I dont think excessive flow due to a thermostat sticking open is

the issue. If the thermostat were sticking closed it would be an issue.

LOL, knew that would get a response from you, just to disagree

[Rodney Bullock]

This is an interesting subject. I guess it's one for the engineers. I was always under the impression that removing the thermostat would allow for more cooling. I overheated one summer day in a 1974 Dodge Dart coming back from New Hampshire. Pulled over and removed the thermostat. Don't remember anymore why I focused on that. It was a long time ago. Anyway, I got home to Boston just fine after taking it out. Never heard the greater-flow-lesser-cool theory, but I see the reasoning.

Rodney, when are you going to pick up that Saratoga?

Hey Joe, I was at the guy's house yesterday. I had to drive to WV for a part. The Saratoga isn't there anymore he may have found a buyer. can't blame him as he is moving and needs the money.