Need some help/advice with engine overheating. I took my car out for a spin today, very cool weather, to see how the car runs on the freeway. In the past, on warm days, my car would overheat when on long drives on the freeway. Stop and go traffic made it overheat as well. Today, I noticed that my car would run around 200 degrees and it was a cool day. The engine is stock with a non stock cam. If it was a warm day, I'm sure the car would have overheated. Here's a silly question, during my search for wheels and tires, I've been told the 255/50/17 would maintain stock tire height of 27 inches. I noticed that on my stock rallys, the tires are 235/60/15. Is that a much shorter tire than the 27 inches and could it add to the overheating problem? I want to make my car dependable on long drives without worrying about overheating. Any thoughts out there?

Thanks in advance,
William

 

First, 200*F is nothing to that engine. And, if you have a 195*F thermostat in it, that temperature is NORMAL.

When on the interstate, the engine temp should NOT increase very much on the temp gauge. If it does, there are two likely possibilities:

1) the anti-collapse spring in the [lower] suction radiator hose may be missing or may have decomposed from rusting...so that when the pump is running at elevated rpm's, the lower hose collapses and limits coolant flow to the pump/radiator. Squeeze that hose near the middle of it. If it squeezes closed (at all), that's part--or all--of your problem.

2) a C3 MUST have a lower front valence (air dam) on the car. If it does not, your radiator will get little airflow at speed and it will heat up.

Also, your thermostat could be defective and not opening completely. If that's the case, it will show up when you are at higher speeds.

 

Shorter tires will effect your RPM range a little but that would mean your engine is turning faster. The problems you are listing seem to be flow related and not tire related. What year car is it, engine, and last time the coolant system was really serviced. Also if the factory seals between the radiator and radiator support frame are not there or deteriorated has a huge effect on corvette cooling.

 

This is where I would start and that would be to replace the FAN clutch and thermostat, along with some new coolant. The fan clutch is often overlooked and can very well be the culprit. Took a minute for my brain to process the problem. KISS method at its best.

 

the car is a 72 coupe. New fan clutch. Bottom radiator hose spring is firm. Front valance is on the car. Radiator seals are there as well. Currently not running a thermostat, was running a 160 degree before with it still overheating. Would adding a front electric fan help? Thought about adding one to make the car dependable and not overheat on long drives. This would be temporary until I make the major changes of motor, overdrive tranny, and new cooling system. This is years away though, so I want to be able to enjoy the car the way it sits. Short term, I plan on redoing the seats and seat foam along with putting on new wheels and tires. I was just wondering if the shorter tires along with my driving habits (speeding) was a major cause of the overheating. Any other options that I'm not aware of?

Thanks

 

Define overheating. A fully warm engine should run about 200F. Absolutely normal.
Use a 180F thermostat. Running no 'stat will cause your engine to take damn near forever to warm up, and wear excessively*, with dismal fuel consumption, along the way.

*Had a friend in college who had an old Plymouth that ran well. Then he removed the 'stat, based on someone else's terrible advice.. A year later, the engine was burning one quart of oil every 90 miles!

 

Like he said.....180* 185* thermostat.

It couldn't hurt in stopngo traffic to have a 1,600 to 2,000 CFM pusher slim-line electric fan on the front of the radiator if it will fit controlled by a 35 amp relay with a 200* coolant temperature switch to activate the relay.....I'ts about a 4 hour task that you won't regret!

Just make sure it's not a gummed-up radiator/bad water pump that is causing the problem before you invest $150 in an electric fan kit

 

i have run many cars without a thermostat but, i always used a restrictor made by removing the guts of the thermostat leaving a disc with an opening in the center. it is "possible" the water is moving too quickly and not cooling the water.with no thermostat you shouldn't have an air bubble, so i would check coolant flow. i had a pump impeller that slipped that took a while to figure out. I'm just kind of thinking out loud so to speak, but you have a lot of areas to check. good luck

 

Where is your timing set? If it's not at least in the 10* or more initial range it's gonna run hot. Stock settings were pretty retarded for emissions.
I would also use manifold vacuum vs ported vac.

 

Install either a 160 or 180 thermostat. Check the flow in your radiator after wards by the following. Start the car cold with the radiator cap off. Watch the temp gauge to get close to tstat temp range and make sure you have good flow. Other than that who knows. Needing to add an electric fan is not right.

I can leave my original BB with standard fan idling for 30 minutes or run it down the road as hard as I want and never get over 200.

 

Engine might be running a tad lean or maybe timing would add to the heating, Also can the shroud ring be added (for AC cars) http://www.ebay.com/itm/1970-1975-CORVETTE-FAN-SHROUD-EXTENSION-/271430178891?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f327fd84b&vxp=mtr

 

1)Are you running a fan shroud?
2) what's your timing set at?
3) what thermostat do you run?

 

I always thought that the more advance, the hotter. I don't have a timing light, so I'll have to pick one up. Are the snap on lights with the advance adjustment accurate? Or should I just pick up a simple timing light without the advance adjustment.

 

It's easier with the advance timing light, but I don't have one and it didn't take much to measure the balancer and mark my "target" and time to it with a standard light.

Make sure you can see through the radiator. Shine a light in it and really look through it to see that air can get through it. On the highway you should have plenty of air moving through it and it should easily be able to cool the coolant. But put the thermostat back in. Believe it or not, it helps to keep the coolant in the radiator just a bit longer to cool it more.

 

Snap-On makes professional grade equipment. If you could get your hands on one, I'm sure you'll be in good shape.

 

A digital timing light is a great tool. You can pick one up at Sears for about $100. I know a bit expensive, but sooo much better than anything else I've owned in a timing light. With a digital you don't need any marks on the balancer other than 0*, so lots easier to use as well.
Timing set too retarded will actually cause your headers to glow red it gets so hot. Timing set too advanced can cause detonation which also will get the engine hot and cause damage to the piston and or cylinder and head. Too far advanced timing is one of the causes of run-on or dieseling as well.

I have my initial timing set at 19*. That seems to be the number that makes it happy. total timing is at 34* and cruise (with vac advance) is at 51*.
Most cars like around 36* total and 52* cruise with vac advance, with those numbers on an HEI your initial usually is 16*.

 

First off, drill 3-4 3/16 holes in your t-stat flange, allowing extra flow but not too much the temp rating of the stat only tells when the stat OPENS, once it's open, that's IT.....the flow is the same......over the years they have reduced the large opening in most stats, to the size of the 195f stat, so no matter what you buy, it still runs at 195f or so.....now, in my car, the gauge is a cap tube deal, screwed into the cyl head on the driver side....the reading on the head is 10f less than the gauge says.....very consistent......so check that with your thermocouple or IR gun that you know are accurate....I cal mine in a pot of boiling water on the stove....212 is 212, or it's steam, close enough, eh???

as stated before, the airflow rubber forcing the air through the rad, instead of around it....very important....I use that pipe wrap from Lowes Despot....

I set my timing at 10 initial, but I have a speed density FI setup....
computer controls the HEI.....

not that it matters to the temp, but I have a serp drive, and dual spal fans.... the radiator is from a '89 F body

 

I agree with ctuinstra , start simple. Check to make sure the radiator is clear , is your coolant new and mixed properly and up to level ? Does the radiator need to be flushed.

 

My 73 w/ AC and 180 thermostat would always run over 200 until i did a inspection of the radiator/ac condensor and found everything from plastic to pine cones wedged in between the too. After a good cleaning the temp dropped to 180. Just something to think about!

 

I had cooling issues with my 77 and started with timing. That didn't fix it so moved on to flushing the rad. That didn't fix it so I extended the air dam on the front. Made a little difference at speed but still hot at idle. Replaced clutch fan. Small improvement. Still too hot, so did an aggressive rad and cooling system flush. Although rad looked better it didn't cool any better.
Then I installed electric fans. Finally, temps came down at idle.
But not good enough to suit me. So I bought an aluminum radiator and that was the ticket. Now it runs as cool as I need it to, which is right at the thermostat temp until it gets around 100* out side with air on then it hangs around 200* water temp.
So it's a process, eventually you'll get there it just may take lots of tries to nail down the offending item that is causing the high temps.