Diagnosis help/opinions needed...

[78SilvAnniv]

I'll take a stab!
I think the radiator cap is rated for a particular psi to hold the pressure of the cooling system. If the cap is old and compromised, perhaps it is able to suck air? Or fluid is allowed to blow out?
I have heard of instances where a cap with too low or too high psi adversely affected the cooling system.
Heidi

 

[Dave Z]

I'll give it a stab too...

Within the pressure cap there is an outlet valve and an inlet valve. The pressure cap raises the coolant's boiling point. Coolant can't boil until until the pressure opens the outlet valve (at whatever PSI your cap is). If your cap is old, then the seals may be bad and not allowing the system to properly pressurize, or one of the valves may be inoperative...anyone?

 

[Bob Chadwick]

Water boils at 212. Add a pressure cap and every pound of pressure raises the boiling point (7 degrees if I recall correctly). Water boiling at 212 won't cool the car as well as water not boiling at 212.

Glad you got the car running Heidi. Could you ask Kenny to bring that book he used to rebuild 78 to the BBQ this weekend. I want to take a look at a couple of the installation and torque values. Thanks.

 

[76 Sting]

I'll give it a stab too...

Within the pressure cap there is an outlet valve and an inlet valve. The pressure cap raises the coolant's boiling point. Coolant can't boil until until the pressure opens the outlet valve (at whatever PSI your cap is). If your cap is old, then the seals may be bad and not allowing the system to properly pressurize, or one of the valves may be inoperative...anyone?

Thanks.. Heidi BTW congrats on getting the car back in line again. Nothing
worse than not having the car up to snuff.
Dave or anyone, Would it then make sense to buy a extra high pressure cap??
I do not know what the standard is, does anyone? Is there such thing as too
high?

 

[Bob Chadwick]

Thanks.. Heidi BTW congrats on getting the car back in line again. Nothing
worse than not having the car up to snuff.
Dave or anyone, Would it then make sense to buy a extra high pressure cap??
I do not know what the standard is, does anyone? Is there such thing as too
high?

Go with what the manufacturer recommends. At a certain point the car is overheated and damaged. A higher pressure cap won't do anything to prevent this.

 

[Jack]

Heidi:
Purge air as others say. BUT ... the overflow system can be a source of air in coolant. If the small OF hose / any of its connections has the slightest AIR leak ... it can suck air back into radiator as motor cools off. Leak can be so small that it does not push coolant out ... but still large enough to suck AIR in. One thing that can help as you purge air is to park car on an incline with front end up. Of course, anyplace that pushes coolant out is a place where air can get sucked in. G'Luck!
JACK:gap

 

[78SilvAnniv]

Could you ask Kenny to bring that book he used to rebuild 78 to the BBQ this weekend.

Will do. I'll tell Kenny about the front end up and overflow air leak suggestions when he comes home. During yesterday's test drive, everything went smoothly so I think we're good.
Heidi

 

[Bob Chadwick]

Thanks Heidi.

Jack is right. If the system has even the slightest air leak, coolant will blow out and air will be sucked back in. If it is air tight and the overflow tank is functioning properly, the air blows out and coolant is sucked back in.

Mine was getting air into the system when I first got it. My overflow system had a hose that ran from the cap to the coolant. The hose was missing and air was being sucked into the system.

 

[76 Sting]

Thanks Heidi.

Jack is right. If the system has even the slightest air leak, coolant will blow out and air will be sucked back in. If it is air tight and the overflow tank is functioning properly, the air blows out and coolant is sucked back in.

Mine was getting air into the system when I first got it. My overflow system had a hose that ran from the cap to the coolant. The hose was missing and air was being sucked into the system.

:ughOh boy!! Just when I thought I knew a lot about the car...Now I feel stupid. I just installed a new double row aluminum Griffin radiator, all new hoses and a new recovery tank. However, I never filled up the expansion tank....I guess this is why I have been running hot (over 225) and having to pull over to let her cool down, because of air in the system. Am I on the right path??

 

[Bob Chadwick]

Could be. The overflow tank allows the radiator to be completely full of coolant all the time. If you fill it that is.

I'm old enough to remember when cars didn't have overflow tanks. When it got hot, the car puked out coolant. Did this a couple of times and then would stabilize with the coolant at some level below the top of the radiator. Then came overflow tanks. You wouldn't see the car puke coolant anymore because it would go into the overflow tank. As the car cools, the cap would allow the coolant to suck back into the radiator filling it for the next time you went out.

I've never had a car with an expansion tank but I think the principle is the same.

When the car is cool, open the cap and look in the radiator and see if the radiator is full. Fill the expansion tank to the cold level, run the car through a hot/cold cycle and see if you have less coolant in the tank than before.

Unless you are down alot of coolant I would start to look elsewhere. Your car shouldn't get that hot in RI during the Winter just a little low on coolant with that radiator. Did you put in all the seals around the radiator? Is your shroud in place? Is your chin spoiler in place? All of these items control the direction of air flow through the radiator. If not in place, the air will want to go around the radiator.

Post some more information about the driving you're doing when the car gets hot.

Here is a good article from JohnZ, our resident expert, on Corvette cooling.

 

[RodsnRides]

76 Sting -

Yes-you are probably correct. However, now that you have made the upgrade, accept it and the fact you can probably go anywhere, any time of day. Idling at stoplights downtown at noon comes to mind. Most Vettes (any car, for that matter) hate that. While mine is finally sorted out (shroud, fan spacing, water wetter), I certainly wouldn't mind the aluminum radiator upgrade.

Heidi -
I like to run the Robert Shaw Hi-Performance 180 degree thermostat. Quality part, available at (sigh) AutoZone. Sorry about that. Really good for highway running at 70+. I have them in all my cars and never a problem. I would also suggest Red Line Water Wetter. I run 2 bottles in mine, also a 350, w/auto. I get that product at Advance Auto Parts. I'm pretty sure Summitt Racing offers both products online. Suggest checking your fan to shroud spacing (blades of fan about halfway in/out of shroud. Another good check is to hold a red rag (like a bull matador) in front of the radiator while it's idling-the rag should pull towards the radiator and indicates good fan suction-pulling air through the radiator.

Finally, I put an Edelbrock aluminum water pump (yeah, it's kinda pricey) on my 383 stroker in the '70 Chevelle wagon-along with the other items (thermostat, RL WW) above. Works great - did not bust 190 degrees all the way to Pullman, Washington last July 6 on a new (100 miles) motor-including Lolo Pass in Idaho. Now, that's cooling performance! Any new motor I build/install will get that pump and the other goodies.

Rick

 

[76 Sting]

Unless you are down alot of coolant I would start to look elsewhere. Your car shouldn't get that hot in RI during the Winter just a little low on coolant with that radiator. Did you put in all the seals around the radiator? Is your shroud in place? Is your chin spoiler in place? All of these items control the direction of air flow through the radiator. If not in place, the air will want to go around the radiator.

Post some more information about the driving you're doing when the car gets hot.

Here is a good article from JohnZ, our resident expert, on Corvette cooling.[/QUOTE]

Thanks Bob great article soon to be read. Spoiler OK, shroud in place perfect spacing between the fan and shroud. Unfortunately it does not leave the garage in the winter..when it get to be 50 deg I might take it out a bit. Heavy traffic is causing the engine to get hot once I am 15-20 MPH steady it cools right down. I did also check the timing and OK.

One thing I do not have is the seals around the shroud not even on the top where the rad brackets are. I have a stinger hood which prevents the seals from working contacting the hood. Also coolant/water always seams to disapear, but no noticable leaks ever.

 

[76 Sting]

Hey Rick..
As I was just mentioning to Bob she does not do well in heavy traffic, which is why I upgraded to the Griffin double core alum rad. i forgot to ask Bob if the seals around the rad could make that much of a difference in heavy traffic?
BTW. The water wetter stuff works awesome, my driving problems were so much worse before I stared using that product, but only a bottle of it. By you comments it looks OK to use 2 bottles.

If anyone is having problems overheating and have checked just about everything. At the point of giving up and dealing with it like I was, try that product.....unbelievable

 

[RodsnRides]

76 Sting -

It is my opinion that air is not passing THROUGH the radiator like it should. Rather, it is taking the path of least resistance and traveling everywhere else. Highly recommend you get all the seals. I am not sure about the top of the radiator area and a BB hood, though, but there must be some sealing methods. I would put in the latest and greatest updates (say, '67 big block stuff, versus '65 BB). And, as mentioned, Red Line Water Wetter works for me.

You did not say if you have a fan clutch or not, nor how many fan blades on your fan. Another item worth checking-when was the system flushed? Is the coolant 50/50? Sediment likes to sit in heater cores, too. Suggest removing the hoses and running a garden hose-back flow-through the system. Finally-suggest a 180 degree thermostat. Best of luck,

Rick

 

[76 Sting]

Thanks a million to all!!

 

[RodsnRides]

Okay-I think I get it...

Hey Sting -

Sorry-I got the posts mixed. Anyways, now that I look close at your mods-make sure you are not running too lean! It may be a matter of jetting. The Edelbrock is easily enough changed. The book that comes with these carbs is quite useful for jetting.

But, definitely, airflow THROUGH the radiator is important. Use my "bull matador" example for Heidi-you want that fan to pull that rag flat against the radiator. I see you have a fresh motor-did you flush the heater box, too? Feel the hoses as they come in and go out. And, run a 180 thermostat. It helps.

If you can swing it (~$160)-get the Edelbrock pump. It works. Here...

www.edelbrock.com


Rick

 

[Vettehead Mikey]

I've never had a car with an expansion tank but I think the principle is the same.

When the car is cool, open the cap and look in the radiator and see if the radiator is full. Fill the expansion tank to the cold level, run the car through a hot/cold cycle and see if you have less coolant in the tank than before.

Must disagree here. An expansion tank is a very different animal from an overflow recovery tank- operation and purpose is VERY different. The two terms are not interchangeable.

First off, no Corvette newer than a '73 was built with an expansion tank, only an overflow recovery tank. They just don't need them with a stock config. radiator.

If the poster has retro fitted one to his '76 it would be of benefit only if was matched to a radiator that needed one, ie. a radiator that did not have an internal expansion tank, typical of pre-73 aluminum rads. The tank would also have to be plumbed correctly (in line with the heater hoses) to be functional. If that's the case then the overflow/recovery tank would need to be plumbed downstream of the expansion tank to catch the excess coolant. Whether the radiator cap and tank fitting would be capable of sucking back the coolant after cool down is another big maybe.

Pre-73 Corvettes had either an external expansion tank (as mentioned above) or an internal expansion tank. One or the other but not both. Typically the copper/brass radiators had an internal expansion tank. The tank(s) run vertically at each end of the radiator and across the top in some cars. The idea is just to provide room internally to the radiator to allow expansion.

In either case, they puke excess coolant until they reached their own level. A common mistake is for owners to constantly attempt to replace lost coolant by topping them off completely, and are then surprised when it keep puking.

Hope this helps.

 

[76 Sting]

Must disagree here. An expansion tank is a very different animal from an overflow recovery tank- operation and purpose is VERY different. The two terms are not interchangeable.


Ok guys I am learning more and more (thanks to all of you ) and my mistake for calling it a expansion tank. It is a recovery tank. So first I will try the rag trick that RodsnRides mentioned, will this work OK with the hood open:confused , it seam to defeat the purpose? Now will the recovery tank suck back the overflow once it cools down. Also did I make a big boo boo by not filling the recovery tankin the first place? The tank never had a mixture in it since I did the swap and I am worried that air was sucked back in and caused more overheating concerns.

Cheers

 

[Bob Chadwick]

With a recovery tank my example is correct. Go out and open your radiator cap (cool engine only) and check the level. If not full, fill it and then the overflow tank to the cold mark.

Make sure all the plumbing is in place on the overflow bottle. Some of the tanks have the plumbing connect to the bottom. Others to the cap. If it connects to the cap there should be a hose that runs down into the coolant otherwise it can't siphon the coolant back into the radiator.

I suspect your real problem will be the lack of seals around the radiator.

 

[76 Sting]

I suspect your real problem will be the lack of seals around the radiator.[/QUOTE]

Thanks Bob!! I will try your sugestion and I too am leaning towards the seals

Thanks again to all for your continued support, now if i could only get my co-workers to be so helpfull.