I first got my 1966 in March 1999. Temperature-wise it always ran about 165 (slightly above the mark between the 100 and 210 on the gage). Then, about a year ago, a few months after I replaced some hoses, it started running slightly hotter---edging up whenever I was stopped a few minutes. It's never overheated but I don't usually drive more 30 miles at a time either. On hot days (90 +) after a 45 minute drive in regular traffic it reaches about 215.

I've tested the thermostat and it's fine. I have not leaks anywhere. The coolant level is always full. The Aluminum Radiator has the original part number on it but I don't know if it's the original or been replaced. The car has 84,000 miles on it but sat a while some years ago.

I saw (and did not know this) in another forum post that having a greater than 50/50 antifreeze / water mix can hurt cooling ability. When I changed hoses, I know I only partialling drained the radiator and replaced it totally with the green stuff (Stupid me---I was was trying to conserve). Could this be the problem or is replacing the $800++radiator the choice I'm avoiding? I know flushing and changing antifreeze is an easy choice but if the 50/50 mix shouldn't affect the operating temp--which is my basic question---why waste the time. Thanks for any advice. Thanks.

 

Hello Vette1966,

I also have a 66. I have had mystery temp spikes before after filling the system, after not burping it properly.

The actual heat transfer capability of the fluid is significantly changed with the mix variation you are describing. The specific heat of the Prestone is 0.675 vs 1.00 [Btu/deg F/lbm] for pure water. The specific gravity of Prestone is 1.098, vs 1.00 [kg/liter] for water. So, the performance of your coolant will be approximately 81% that of pure water when you have a 50-50 mixture. If you go to, say, a 75% coolant mixture, you will have coolant performing at approximately 71% that of pure water. So you have lost about 1/8 of your cooling system's (original 50-50 mix) capacity. Not a great amount, and probably not the cause of the temp spike.

My questions would be:
1. Have you ever "burped" it at the thermostat and checked that it is freely operating?
2. Have you ever checked your pump's output ?
3. Could your lower rad hose be kinked or collapsed?
Anyways, there are a few places in the above to start searching.

Dyna


[Modified by Dyna, 10:18 PM 2/6/2004]

 

Before doing anything else, have your thermostat housing and upper hose "shot" with an I.R. gun and compare that reading with what the temp gauge says at the same time so you know what the gauge is really telling you; Corvette temp gauges are notorious for reading high, especially if the original sending unit has been replaced. :thumbs:

 

That burping thing is a pain in the butt. You can eliminate having to do this by drilling a small, .125 hole, in the flange of the thermo. That lets the air trapped in the block escape and prvents air locks.

 

Thanks for the great ideas---anything to avoid the Radiator rebuild is worth a try. this forum is the greatest!! :chevy

 

Just make sure you have at least a 180 stat in the engine. :thumbs:

 

ONE LAST COOLING SYSTEM QUESTION:

I am going to test the water pump, actual temp, etc. all you suggest but what's the best way to "BURP" the cooling system without drilling holes? Thanks to you all!! :confused:

 

I do it by disconnecting the top hose from the thermostat housing. Then I fill the radiator/block through the fill cap. I put a long screwdriver into the thermostat and GENTLY push down on the sprung section to let coolant/air escape until I see it start to get flooded inside the top of the housing. Then I put sealant for the upcoming hose installation onto the thermostat housing. (I have to do it at this point because it's the last time I will have two free hands) Replace the radiator cap at this time. Then I put as much coolant as I dare into the open hose end while holding it vertical. I then kink the open end slightly so a reduced amount of coolant will spill as I am quickly moving it into position and pushing it onto the thermostat housing. Clamp it up. Done deal.

Dyna


[Modified by Dyna, 7:54 PM 2/10/2004]

 

One more probably dumb question---is it not possible to "burp" the system at the expansion tank as the engine warms, thermostat opens, etc. It would seem eventaully all the air locked in the system would make its way there and be released---or am I just dreaming wishful thoughts? Thanks again for the help!!!! :confused:

 

promise me you will do like JohnZ suggested and borrow or acquire an IR gun and shoot the intake at operating temp to confirm that you are, in fact, operating at 215 or whatever your gauge says - I went through many steps, all good, to address a high temp condition (which I did have, mind you) and then agonized because I could not get it down to a steady 180 on all days. turned out I had gotten there, just that the gauge wasn't telling me so - 15 to 20 degrees off it was

 

Any idea what an IR gun should cost? Regardless, I promise I will do that one way or another.

P.S. any further thoughts on "burping" via the expansion tank? Can it work?

 

I bought a couple from the following site - best price and quick shipping - get the mini MT4....looks like about $75 or so. Great tool! Of course, my guage that showed overheating on my 65 A/C car was right on the money once I took a reading or two with my new IR gun - shoot the T'stat housing on the intake and you should be real close to what an accurate guage would read.

Good luck! http://www.tooldesk.com/shop/store.wml :cheers:

 

VETTE1966, You might want to search the archives for over heating discussions and read the HEATED discussions about proper timing! Did you happen to adjust it prior to the heat rise? I've got to hook up my new heater core for a cruise this weekend and will need to figure out the Burp too.

 

get the temp gun....i is useful for many,,many things.....i.e....shoot the exhaust manifold to check for misfires,,lean,,ect....intake for even dist....a good guy with one can diagnose a motor pretty damned slick!

 

I just Bot the MT4 IR gun--thanks to all for that input.

To 6T7L71CPE: I did not change any timing when the temperature rise started too occur. Assuming the gauge is correct, I'm still thinking I didn't "Burp" this system right when I changed hoses and there's air somewhere causing a problem. Haven't heard from anyone re: the effectiveness, or even if it's possible, to "burp" via the expansion tank.

Anyone have any thoughts or am I stuck with playing the game with the rad hose and thermostat housing?

Thanks to all. :confused: