Cooling System

[Joe C.]

Re: Cooling System

Leif------


My recommendation on this is quite simple: obtain a DeWitts reproduction of the GM #3155316 radiator and return your cooling system to completely stock configuration. Yes, the radiator is expensive but it's the only configurationally and functionally correct way to go.

Trying to "Rube Goldberg" the already "Rube Goldberg" set-up you have is foolhardy.

I should have expected such a response.
After all..............you've got to "know your audience".
Maybe the poor fellah can't afford to shell out for a new radiator, and actually the one he has will do the job as long as it's in good condition.
That said, the directions I gave above will result in a fully functional "closed" system.
But, my oh my, it won't be "korrekt" mein Freund!
Achtung!

[Michael W.]

Re: Cooling System

Leif------


My recommendation on this is quite simple: obtain a DeWitts reproduction of the GM #3155316 radiator and return your cooling system to completely stock configuration. Yes, the radiator is expensive but it's the only configurationally and functionally correct way to go.

Trying to "Rube Goldberg" the already "Rube Goldberg" set-up you have is foolhardy.

Alternatively, the system could be easily converted to resemble a car with a copper/brass rad. It appears there is no overheating issue to cure, so the existing rad is adequate in that respect. Not correct for judging, but fully functional.

[John H.]

Re: Cooling System

Leif -

Suggest you read the article at the link below to understand how your Corvette cooling system is designed and configured, how it works, and how to diagnose it.

http://www.lbfun.com/warehouse/tech_...em/cooling.pdf

[Leif A.]

Re: Cooling System

Duke,

DeWitts is recommending a model 941 radiator...your opinion?? What is the difference between the model 316 and the model 941?

[Joe L.]

Re: Cooling System

Duke,

DeWitts is recommending a model 941 radiator...your opinion?? What is the difference between the model 316 and the model 941?

Leif------

I'm sure Duke used '316' as an abbreviation for the GM # 3155316 radiator. The specific version of that radiator applicable to 1965-72 Corvettes is the DeWitts model 941. Minor differences of this same GM part number were applicable to 1963-64 and that radiator is the DeWitts model 942.

The DeWitts model 941 is the best choice of ANY radiator for your car. Yes, it's expensive but on an inflation-adjusted basis, no more expensive than if you had purchased a GM #3155316 way back when it was last available from GM. And, the DeWitts is actually a better radiator.

[Duke W.]

Re: Cooling System

What Joe said... Before you buy you should thoroughly audit the current configuration. Compare it to the AIM (including C60 section) to ensure that the core support had not been modified and you have the correct top mounting bracket and fan shroud, and also compare it to a car that's known to be correct.

Be sure to order new top (one) and bottom (two) mounting grommets. These are required to electically isolate the radiator to prevent galvanic corrosion.

With proper installation and maintenance it should last at least 30 years. My SWC was missing the top grommet from new and the radiator succumbed to galvanic corrosion in 15 years.

For a nominal extra fee and longer delivery you can order a date coded radiator. Both the part number and date code are easily visible and are a judging item. A date coded DeWitts typically has no judging deduction. It's exactly as original.

Duke

[Leif A.]

Re: Cooling System

As always, thanks to all for great advice and insight. After double checking, the lower nipple (closest to the tank) does lead back to the radiator and the upper nipple is vented to the atmosphere. While driving the car doesn't heat past the first marker on the temp gauge (the one between 100 and 210). But, if let to sit and idle for more than 10 minutes, that's when she pukes. Going to monitor over the next week and make a decision on the DeWitts radiator ($895). Thanks for clearing up the 316 vs 941.

[Joe C.]

Re: Cooling System

If it doesn't overtemp while driving, then that means that the radiator is not at fault. The engine is making a LOT more heat while under a load than while idling. The problem has more to do with lack of sufficient air flow across the radiator while static, and/or ignition timing. Could be a myriad of other things as well, but the radiator seems to have the cooling capacity given the proper airflow. First things I'd look at is the fan clutch, fan shroud and baffling as well as seals, proper fore-aft fan positioning of 50/50 in and out of the shroud, and static timing with vacuum advance.

[Michael W.]

Re: Cooling System

It could simply be that the system is overfilled. I'd get rid of the pseudo recovery tank and call it good.

[Leif A.]

Re: Cooling System

Joe,After reading your PM to me, I checked the fan clutch (new and functional) fan shroud (new and in proper location and sealed), proper fore-aft fan position (approx. 1/2 inch or more extending outside the fan shroud. Haven't checked the static timing and vacuum advance yet. Engine purrs like a kitten and has tremendous throttle response and runs like silk...but, I will still have the timing and vacuum advance checked.Really appreciate all the time and input from everyone attempting to help me figure this out. It will get fixed!!!

[Joe C.]

Re: Cooling System

It could simply be that the system is overfilled. I'd get rid of the pseudo recovery tank and call it good.

The way he has his system plumbed, it is exactly like stock, so the tank is not a "recovery" tank, but a stock "supply" tank.

[Stephen L.]

Re: Cooling System

Leif, I assume the fan clutch is tight, no more than 2-3 turns on shutdown of engine. I've seen fans that are installed backward. There is a notation "front" on the fan. Front actually faces the clutch.. Something to check which could show up while idling. Fans don't do much when running down the road.

[Michael W.]

Re: Cooling System

The way he has his system plumbed, it is exactly like stock, so the tank is not a "recovery" tank, but a stock "supply" tank.

Depends on what's been done with the cap on the rad.

[Joe C.]

Re: Cooling System

Leif said that he has typical stock open system caps and both 15# (RC15 or RC26 IIRC). The tank is not isolated from the radiator, so it's always at the same pressure (through the heater hose tee).

The only cap which should relieve to the atmosphere ("boil over") is the cap on the tank. He never stated which cap is blowing off. As insurance, I'd put a generic 18# "closed system" cap on the radiator, as I stated in an earlier post, just to ensure that there is no blow off to atmosphere other than at the supply tank cap.

[Michael W.]

Re: Cooling System

Leif said that he has typical stock open system caps and both 15# (RC15 or RC26 IIRC). The tank is not isolated from the radiator, so it's always at the same pressure (through the heater hose tee).

The only cap which will relieve to the atmosphere ("boil over") is the cap on the tank. He never stated which cap is blowing off, As insurance, I'd put a generic 18# "closed system" cap on the radiator, as I stated in an earlier post, just to ensure that there is no blow off to atmosphere other than at the supply tank cap.

How would air (if any) in the rad vent to the supply tank at less than blow off pressure?