thelinux

When
1. I have brand new Champion 1" 2 row champion aluminum radiator.
2. I have electrical 2 12" cooling fan with matching aluminum shroud. Fans are wired for 2 speeds and working properly
3. Water jacket flushed many times with distilled water. Filled with 50/50 mix of new coolant and bleed cooling system many times.
4. Tested for head gasket leak with combustion leak tester. No sign of carbon dioxide in the coolant.
5. New 185F thermostat which is working properly (overheats even without thermostats anyway)
6. New radiator cap 16lbs.
7. The car still has the air dam under the radiator to air cool the engine (Though I removed the factory radiator shroud to install new radiator and shroud. So I don't know how efficiently air cooling without factory shroud).
8. Pressure tested cooling system at 15psi and there's no pressure loss.
9. Both upper and lower coolant hoses are new.

Also when,
Driving on freeway only.


Yes, the car overheats on the freeway. When driving on local streets or when idling, the temp gauge stays at around 200F and no overheats.
But when I take it to freeway the temp goes over 220F and into the red zone.

The next thing I can throw in is a new water pump. But seems like my current water pump works fine. I opened radiator cap while the car is running. I can see that the water flows well. (But I don't know how fast is fast enough)

In fact, I installed a cheap ebay aluminum radiator originally, then my mechanic said the radiator is not cooling properly after he used IR thermo gun to check the coolant temp at upper radiator hose and bottom hose. So that is why I replaced it with Champion radiator. But it's still the same.

I checked temperature at both radiator hose myself after installing champion radiator but I don't see much difference in terms of temperature between these two hoses. I feel that the reading from IR gun may not be reliable.
Especially for the lower hose, if I check the surface of the hose facing the engine it's hot but if I check the side not facing the engine, it's cool. The difference is about 30F between these two sides. Maybe the heat from engine makes the hose surface facing the engine a lot hotter than the other side?

I also used IR thermo gun to check the temp of radiator surface. The top is about 30F cooler than bottom????

Anyway, I can at least tell that the temperature difference between top and bottom hoses are pretty much non exists.

How can it be? The electric fans are running fine. I don't get why I can't see temp difference between two hoses.

Maybe my water pump is not efficient enough somehow?
The other thing I can think of is that the car is running lean maybe?

The engine is a rebuilt one and these are the part numbers.
Head : 3932441
Block : 3970010

I don't think these parts are not meant for my corvette. If so, can this be the reason for over heating. By the way I have
Edelbrock Performer EPS 2701 intake and 1406 Performer carburetor.

Also, if I am going to replace water pump, should I get short version or long version? My research tells me that I need a short one but my engine block is not original.

Other notables are:
1. No white smoke from exhaust. But when I put my hand close to the tail pipe, I can feel that the exhaust gas has moisture.
2. Even the coolant is new and combustion leak test says negative, the coolant is contaminated by very little with something that feels like oil.
3. Heater core was removed by connecting a hose directly between water pump and intake.
4. Currently no AC compressor.
5. Nothing is blocking radiator and I am test drove the car even without the hood.
6. Coolant does not move back and forth between radiator and coolant reservoir. When the engine cools, radiator does not suck back the coolant from the reservior nor spit out coolant to reservior when hot. (Bad radiator cap? But I have a new one!!!)
Any advises please?

rcread

Have you checked your timing? Is your vacuum advance working? A lean condition can cause an engine to run hot. How do the plugs look?

thelinux

I had a shop to adjust the timing and vacuum advance but I don't feel like they know these old engines very well. I don't know much about carburetor engine either. I think I will do some study and check it myself. But if that is the case, why is the engine overheats on freeway only???

0Willcox Corvette

Is the car spewing over antifreeze when it gets hot?
Did you replace the temperature sender when you built the engine?
Have you verified the temperature gauge in the dash is reading correctly.
Is the electric fan turning the correct way (seen this before).

If you replaced the sender it's possible the dash unit isn't reading correctly so check it. Use your IR gun and verify the temperature of the engine to the dash unit.

Willcox

toobroketoretire

I suggest throwing the 12" fans and shroud into the garbage and put the original fan shroud and 7-blade clutch fan back on. The little 12" fans may look "cool" and work okay at idle when the demand for cooling is at it's least but at highway speeds the 12" fans and shroud cause an enormous restriction to air flow and that's why it gets hot at the higher speed.

thelinux

What do you mean by "spewing over antifreeze"? Spewing out from overflow tank? No it does not. I think something wrong is going on with this area.
No I did not replace the temperature sender and many tests I did reveals that the temp gauge is working fine.

thelinux

Well, my car was overheating with all original shroud and mechnical fan. That's why I installed electrical fan. Interstingly, when I had factory setup, it was reverse. Car overheats on the local streets but cools down at high speed on freeway.

I did not install the electric fan for look but for more efficient cooling.

Jeff_Keryk

You should have sufficient airflow on the freeway, due to speed. I would suspect radiator efficiency.
I understand your radiator is new, but this is the classic example of an undersized radiator.
I have never used a Champion radiator. Did they recommend the model you purchased? Perhaps give them a call.
I am running the stock radiator in my 68 BB Roadster. It is the original Harrison; I had it recored and they soldered the tags back on. Never overheats. The only non-stock parts are Flow-Kooler pump and aftermarket steel fan and thermo-clutch.

0Willcox Corvette

If the car is over-heating, then odds are it's going to spew antifreeze. I would verify the dash unit is reading correctly if you don't have any spew... wouldn't that be a shame if you replaced all this because the dash unit wasn't reading correctly. This could be an issue with the sender or the dash unit.

You can check the out put of the sender easy by knowing what thermostat is in the car. If you have a 180 in there.. hold your hand on the upper hose and when the water starts flowing look at the dash unit and see what the temperature is....

I have the factory required input for the temp gauge on my repair and help site... so if you have a potentiometer you can double check the dash unit.. my money would be on the sender having an issue.

IMHO

Willcox

thelinux

With the original setup, the car was already overheating. Though it helped when driving on freeway.
I saw a lot of people liking champion radiator. Mine is their Eagles series which is rated for over 600hp and it is the correct model for my car. Though I don't really buy that 600hp thing this radiator is 2 core, 1 inch tube.
Anyway I already throw in two new aluminum radiator so I hardly think it's the radiator. Maybe the fan is not sucking in air enough?

thelinux

Thanks. I will try to do that test.
Anyway I found one obvious problem just a moment ago.
I have a crack with the plastic tube inside of the overflow tank cap. The root of the tube where the tube meets the inside of the cap is almost broken and dangling there. This explains why the radiator is not sucking in the coolant when it cools down. It must be sucking in air instead of coolant!!!!

That is also why I've been noticing low coolant inside of the radiator even after proper bleeding and engine cools down.

I just ordered a new cap and will report back the result.

BTW what is the proper coolant temp range for my car??

SH-60B

LOL! This should be your signature!

mikep3

I am with Wilcox,
Electric fans are turning in the wrong direction.
Electric fans are not turning in the same direction.
Timing.

65GGvert

IF everything you said is correct, the fans are probably blocking the air flow, They shouldn't even be running at highway speeds. You don't even need fans at highway speeds. After all you've done, I'd pull the fans out and run down the highway, if it still overheats, you can eliminate that.

JimLentz

or the shroud is blocking some airflow at highway speeds. Some people have added flaps to their aluminum shrouds for their electric fans to help with this.

capevettes

A stock clutch fan and shroud coupled with a Dewitt's aluminum radiator may be the answer to your issue. You are running warmer than you should but not overheating. I run a stock setup on my 68 BB and all of my older Vettes with a Dewitt's aluminum radiator and they run cool.

Swiftrider08

Lower radiator hose - does it have a spring in it? If at highway rpm, the lower hose can be sucked shut and then at lower cruising speeds, it opens back up. The symptom for this is just as you describe. Fine around town and overheats on the highway. Most replacement hoses these days do not have a spring in them to keep from collapsing as they say the advanced rubber these days does not need them. Might check this area.

thelinux

The fan is on the engine side of the radiator and it is pulling in the air to the engine room.

thelinux

Flaps? Can I get some more information on this? I am trying to modernize my vette and have no intention to keep it stock. So I am keeping the aluminum shroud if possible and I am sure I can because there are many people doing this.

rcread

If you go to Dewitts page, here, you can see how they do flaps on their part # 4139063M.