Cooling

[Annivette]

I've replaced the fan clutch which caused the problem with my waterpump, I've also replaced the thermostat and yet i'm still over heating. I'm pretty sure that its not the radiator because the pump is getting fluid. The hoses are knew too, I'm lost.

 

[MaineShark]

How old is the radiator? Even if it still flows, there can be a lot of scale and corrosion on the insides of the core, after 25 years. If the radiator is original, it's probably in poor shape internally, even if it looks okay on the outside.

Also, are you having problems all the time, or only at high speed? When driving on the highway, the Corvette draws air from underneath, with the aid of an air dam. If the air dam is not in good shape, it won't "scoop" enough air into the radiator.

Joe

 

[Nut]

Annivette.... check your hoses. If they are old (and soft) they will collapse under load and restrict water flow. Cheap and easy fix.

Good luck.............. Nut

 

[78SilvAnniv]

Kenny and I struggled for YEARS...

...with the run-hot problem.
We finally solved it by installing a flex fan. It has been mentioned that changing the original design of the cooling systems is not always the correct fix, but it worked for us.

Our problem was running hot at any speed in the summer. Idling and slow speeds in town to over 65 on the highway. AC...temp shot up to 240 degrees!
We changed our fan clutch almost yearly, with no results.
Belts, hoses, water pump, t-stat, fan shroud, radiator...everything we could think of. When we installed a new engine we still had the same problem.

Nothing changed until we installed a flex fan two years ago.
Now I can drive at any speed AND use the AC at any of those speeds, in-town or sustained hwy driving...and she never gets above 195.

Now, you state your problem is overheating...
Is it overheating (boiling over) or is it running hot?
Is all of the molding for the front air dam and fan shroud present?
Heidi

 

[cruzer99]

Check to make sure the fins aren't clogged with bugs and etc. Use an air hose to blow out any obstructions.

 

[JBWeaver]

Go Aluminum

I put a Griffen aluminum rad, in my '77 and has never run cooler. got a good deal from corvette central too. Cost more than stock, but how much is your baby worth to you? It looks real cool also.

 

[mvftw]

Does the new bottom hose have a spring inside it? It should...it will stop it from collapsing at high speed.

 

[cmegga]

i would also recomend checking the air dam, plays a very big role in cooling these cars !

If the radiator is shot, speedway has a 2 row aluminum for $169. ! its a great price and will do wonder over the stock one.

 

[tx73vette]

Also check that your shroud is covering your radiator too. with all the foam around the shroud. Hope that this helps.

 

[SwaveDave]

Make sure the radiator seals are sealing the sides of the radiator good. Have you given the system a real good clean and flush opening the block and radiator drains too ? Dont use anymore than 25% antifreeze in the system. Did you powerwash the a/c condensor and radiator (back and front) ? While at idle, rev the engine to 3000 rpms and watch the lower radiator hose...does it get sucked in ?? Is the shroud fitting tight against the radiator ? How is the water pump belt .. does it slip ? Look at all these things and make sure they are all ok. Then, until you find out what the problem is...id remove the thermostat entirely which will circulate max. water thru the engine/radiator for cooling. This will help lower your temps.

Dave

 

[78SilvAnniv]

...until you find out what the problem is...id remove the thermostat entirely which will circulate max. water thru the engine/radiator for cooling. This will help lower your temps.
Dave

This does not mean it fixes your problem. "...until you find out what the problem is..."
You will still have a cooling problem until it is located and rectified. Removing the t-stat allows your engine (in the summer) to operate cooler until you CAN find the problem.

Good luck and keep us posted. Who knows...maybe another, or future, member will have your same problem and what you found to work for you, may work for them, too!
Heidi

 

[SwaveDave]

True 'Jackie' , it doesnt mean it fixes your problem...but it will help your present overheating situation ; its a temporary bandaid so you can keep driving your Vette but you need to get to the root of the problem.

You may be in need of a new water pump too ; if thats the case, look into Stewart Water Pumps ; i got one and i noticed immediately a difference over my old stock water pump.

Dave

 

[78SilvAnniv]

...its a temporary bandaid...

That's what I meant...I'm sorry I'm not clear about things when I'm trying to clarify.
See what I mean? :crazy

What kind of difference did you notice with the Stewart water pump? More water volume circulation?
I wonder if I had used a high-flow water pump if it would have solved my run-hot problem without having to do away with the fan clutch and using a flex fan...but we went through sooo maaany clutch fans!
Heidi

 

[ironmoo]

Both times I had cooling problems it was traced back to the radiator. (This was after looking at the waterpump, lines, fan, clutchfan, heater core and electric fan and was still having heat issues.) Simple to remove and replace with a few hand tools, took the old radiator to a local radiator shop and they went through it. Cost about $50, for a nice repaint and internal repair/weld of tanks.
Also you may wish to check the condition of the fins on the front surface area. Rocks, insects, etc and hit the forward area and make indentions or holes. These can adversely affect cooling when the water flow is restricted.

Good luck!

 

[MaineShark]

A word on thermostats...

Assuming you have the correct thermostat (195 stock, 180 for a nice upgrade - colder than that can reduce reliability), and that your engine is running hotter than that temp, the termostat is sitting open once the engine warms up. Unless the temp is dropping below that level (in which case there wouldn't be a cooling problem), the termostat is sitting wide open, so removing it won't solve the problem. It will yield a small increase in flow rate, but that's not going to make the difference between overheating and normal driving.

The thermostat serves two functions: to speed warm-up, and to prevent over-cooling. In a car that's overheating, this isn't an issue. The thermostat does not impact your cooling system once it is open, and switching the thermostat temperature won't coll the car down, if the radiator, pump, etc. are not capable of exchanging the right amount of heat.

Proper coolant mix (25-50% coolant, distilled water for the rest), proper sealing (all shrouds and gaskets in place), proper airflow (air dam and fan), and a clean radiator (externally and internally) are the keys to cooling.

Joe

 

[SwaveDave]

Joe,

I beg to differ with you on the thermostat issue ; even after the thermostat is wide open ... there is a big restriction still left from the body of the thermostat. Removing the thermostat drastically increases flow thru the engine/radiator even if there is a problem elsewhere such as the waterpump. Im only suggesting that the thermostat be removed as a temporary assistance to the cooling problem at hand.

'Jackie' ,

The Stewart Water Pump made a huge difference in how often my radiators electric fans kick on. I have the fans thermostat set for 200 on / 190 off with a 180 f engine thermostat ; after the Stewart Pump was installed, i found if the temp outside is no higher than 75 f . and im going at least 40 mph (in 4th gear)...the radiator fans never turn on. Plus...if im at a stop light , the radiator fans do not come on unless its a very long stop light.

Dave

 

[78SilvAnniv]

The Stewart Water Pump made a huge difference in how often my radiators electric fans kick on. I have the fans thermostat set for 200 on / 190 off with a 180 f engine thermostat ; after the Stewart Pump was installed, i found if the temp outside is no higher than 75 f . and im going at least 40 mph (in 4th gear)...the radiator fans never turn on. Plus...if im at a stop light , the radiator fans do not come on unless its a very long stop light.

Dave

Very cool. I don't have electric fans on the 78.
So it appears the Stewart Pump moves plenty of fluid through the system, enough to make the secondary cooling accessories not need to be utilized constantly.
'Jackie'

 

[SwaveDave]

Thats a big 10-4 Jackie....the electric radiator fans (2) dont kick on nearly as much as before which in turn gives me some added h.p. gain due to the electric fans being off, more. Plus it will make my fan motors last longer, but more importantly...it will cool the motor much more efficiently and effectively. My philosophy is : If the water pump has over 40,000 miles on it, its smart to change it out anyways ; who needs it to go out when your on an out of town trip . Youll pay a bit more for a Stewart Pump, but it is a high quality pump and mine has 6 impellers in it. (You can go as high as an 8 impeller pump, but thats a big overkill). Go to Stewarts website and you can log onto thier Discussion Group between consumers and a Stewart engineer regarding various cooling system topics. Its a wealth of info.

Dave

 

[MaineShark]

As far as I can tell, the thermostat really isn't a big restriction. I mean, look at it this way: it would be very easy to make a zero-restriction thermostat (think: oversized water neck, thermostat unit enlarged so that the orifice is the same diameter as the outet pipe), yet I can't recall seeing anything like that for sale. If it offered any significant improvement, someone would be making it.

Speaking of thermostats and water pumps: has your Stewart pump interfered with your thermostat? I've heard that some of the high-flow pumps require a special thermostat, so that the pump won't force the thermostat open too early.

Joe

 

[SwaveDave]

Joe,

When the thermostat is fully opened, it is a disk that is pushed opened perhaps a 1/4-1/3rd of an inch ; when the water comes along...it has to hit the disk, experience cavitation, then make a radical angle flow around the disk . Thats restriction. The reason they make thermostats the way they do, is because they need em to be fully closed for engine warmup as fast as possible . Frankly, if i lived in the south , i wouldnt even run a thermostat during summer months because the engine temp is up to normal operating level in no time anyway ; running without the thermostat gives the engine an edge in continual severe high ambients . I have experimented running with and without a thermostat , and i can lower the cooling system temp by as much as 30 degrees from not running a thermostat. I dont do this all the time because i live in Northern illinois and dont drive the vette when its above 85 f outside as it doesnt have a/c.
Stewart Pumps highly recommends you get the balanced type Robertshaw thermostat from them so there isnt any problems. Mine stuck completely closed recently 5 miles away from home (luckily, cause i didnt have tools in the car ) , so i replaced it with a high perf. Stant brand and drilled two 1/8" holes thru the top -- works fine.
The Stewart Pump i got , has a small disk behind it which is supposed to reduce cavitation when operating at very high rpms -- sounded like a good thing, so i opted for it. Its called the 'Stage 3' six impeller pump.

Dave