63 327/300 Overheating

[David F.]

I had the thermostat and antifreeze changed at local garage I use for my late model vehicles (easier to recycle antifreeze) but I am having problem of overheating after driving for 25 minutes. I heard that this may be caused by air trapped in the cooling system. How do I test for this? How do I get the air out of system? I have a non-contact temperature gun with laser to look at various points but not sure what it will tell me. Any suggestions will be helpful.

[Domenic T.]

Re: 63 327/300 Overheating

David,
Wait till it cools down and check the levels. The trapped air should work it's way to the upper part of the cooling system. Most thermostats have a small hole to let the air bleed and escape.

Dom

[Bob R.]

Re: 63 327/300 Overheating

When I remove and replace antifreeze on my 63 I run the engine for a while with the radiator cap off. When the car reaches operating temperature of 180 the thermostat will open and you will notice the coolant level drop in the surge tank. Add coolant to the proper level and you should be all set.

[Frank D.]

Re: 63 327/300 Overheating

Is it hot via the dash gauge or just puking coolant out of the expansion tank ?

If the latter, your mechanic may have just overfilled it and it will eventually reach its 'happy place' which should
have the tank 1/2 full on a cold engine...

[Duke W.]

Re: 63 327/300 Overheating

I had the thermostat and antifreeze changed at local garage I use for my late model vehicles (easier to recycle antifreeze) but I am having problem of overheating after driving for 25 minutes. I heard that this may be caused by air trapped in the cooling system. How do I test for this? How do I get the air out of system? I have a non-contact temperature gun with laser to look at various points but not sure what it will tell me. Any suggestions will be helpful.

You need to give us some hard data.

Why was the thermostat changed?

What kind of temperature readings (dash gage) were you seeing prior the change?

What is the driving type during the 25 minutes is takes to "overheat"? Idling? Stop and go? Highway?

What is the ambient temperature range?

Same questions after the thermostat change.

Have you checked coolant level? The expansion tank should be about half full with the engine COLD.

Point the IR gun laser at the thermostat housing, radiator hose, and radiator inlet nipple. Hold it as close to those surfaces as you can, and report temperature. Make sure the F/C choice is set to F, then just point as above, pull the trigger and read the screen.

Did the shop remove the block drain plugs? If not, you got gypped. I hope they used Zerex G-05 mixed 50/50 with distilled water.

The system should self bleed in a few minutes after the thermostat opens, even with the cap on, but letting the engine run with the cap off for a few minutes at 1500-2000 after the thermostat opens should fully bleed it, but then coolant will have to be added if there is much air that escapes.

Duke

[David F.]

Re: 63 327/300 Overheating

This afternoon I am look at my problem of overheating:
The ambient temp is 85F
Coolant looks good at half tank level when cold.
Using IR laser gun to measure temperatures.
At idle the dash temperature gage reads 190F
Thermostat housing 208F
Top radiator hose 197F
bottom Radiator hose 170F
Heater hose below expansion tank 198F
At 2400 RPM temperature gage goes up to 225F and rising.
Thermostat housing forgot to measure
Top radiator hose 225F
Bottom radiator hose 195F
Heater hose below expansion tank 230F
These measurements takin in driveway.
When I drive on highway 55mph I will hit close to 240F on temperature gage with coolant spitting out at traffic light.

Where do I look now for problem?

[Frank D.]

Re: 63 327/300 Overheating

Sounds like a true case of overheating (not an inaccurate gauge).
All of Duke's questions are spot on as always.
Proper belt tension, fan clutch operating correctly, radiator properly shrouded, all come to mind.
And I've seen newly replaced T-stats screw up...its just two bolts to pop it out and run without for a bit and see if that was the issue...
Make sure the bottom radiator hose has the spring in it and is not collapsing when hot...
I think any air in the system would be long gone by now.

[Duke W.]

Re: 63 327/300 Overheating

You still need to give us more information. Most important is stating whether this problem existed before the thermostat was changed, and why it was changed.

While you're at it tell us about the radiator.

Duke

[David F.]

Re: 63 327/300 Overheating

Yes This problem existed before the the thermostat and coolant were changed. That is the reason I had the change made. I bought this vette in April 2013 from a guy who had it in storage for 10+ years to finish rebuild but did nothing and did not have the history of anything done prior.

It ran great in test drive with no problem, but the first summer (one very hot day) at highway speeds it overheated. The following summers it got progressive worse to where I had the coolant and thermostat (no history of how old) changed May 2015, hoping that would correct the problem. Seemed to work good summer 2015, but problem returned this year really bad.

This morning I checked the fan belt tension (OK), lower hose (has internal spring), fan clutch (no difference in resistance cold or hot), fan clearance to radiator shroud about 1".

No history of radiator. The problem is most evident at higher RPMs (like highway), but can star a local street driving in very hot ambient.

David

[Joe C.]

Re: 63 327/300 Overheating

Yes This problem existed before the the thermostat and coolant were changed. That is the reason I had the change made. I bought this vette in April 2013 from a guy who had it in storage for 10+ years to finish rebuild but did nothing and did not have the history of anything done prior.

It ran great in test drive with no problem, but the first summer (one very hot day) at highway speeds it overheated. The following summers it got progressive worse to where I had the coolant and thermostat (no history of how old) changed May 2015, hoping that would correct the problem. Seemed to work good summer 2015, but problem returned this year really bad.

This morning I checked the fan belt tension (OK), lower hose (has internal spring), fan clutch (no difference in resistance cold or hot), fan clearance to radiator shroud about 1".

No history of radiator. The problem is most evident at higher RPMs (like highway), but can star a local street driving in very hot ambient.

David

Insufficient radiator capacity and/or massive gaps between fan and shroud. Also, does your fan shroud have its lower rubber seal in place?

Thermostat will not prevent an overtemp situation if your radiator is inadequate. The only time a thermostat will cause the engine to run too hot is if it gets stuck CLOSED. In a situation where the cooling system has sufficient heat rejection capacity to handle any situation, the thermostat's stated temperature will set THE LOWER LIMIT of the coolant's temperature when the engine is at op temp. With an overdesigned cooling system, the coolant temp should NOT rise above the thermostat's design temp. Unfortunately, Corvettes of the 50's and 60's were designed with almost NO excess capacity. In other words, EVERYTHING must be PERFECT, and even if it is, there is always some temp rise either when the engine is loaded, ambient temps are above 90, or when the engine idles for long periods on a hot day.

As an example: I added an oil cooler to my engine, which takes quite a lot of the load off of the radiator. My engine acts like a modern engine and because I have excess capacity, I installed a 165 thermostat to keep the upper part of the engine cool. The coolant temp NEVER climbs above the thermostat regulated temperature of 165 degrees, on 100+ degree days, idling for long periods or drag racing at WOT.

[Patrick H.]

Re: 63 327/300 Overheating

What radiator cap? I've seen several reproduction radiator caps fail even though they looked just fine.

How is the timing set up? I fought with an overheating 1972 for a long time before I found out it was a timing issue - even though everything was to spec.

[Joe R.]

Re: 63 327/300 Overheating

Would you please send us a picture of the radiator top and fan shroud?

JR

[Duke W.]

Re: 63 327/300 Overheating

Two items: If the fan clutch doesn't tighten up when the temp gage needle is at about the 3/4 point of the range, it is non-functional. Likely the silicone fluid has leaked out. It can be rebuilt, if original.

Ten years of storage and God only knows when the coolant was last changed. There's a good chance that the radiator tubes are clogged up, and as has been requested multiple times you need to ID the radiator. Snapping a photo of each side of the top plate will likely tell us what we need to know.

While you're at it check the condition of the brake fluid. Is it the color of week old coffee? Wash your hands and dig your finger into the bottom of the M/C reservoir. Does is have black sludge. If so, if you do a thorough flush of the brake fluid including cleaning out all the gunk at the bottom of the reservoir the brakes might not fail at some point when you're driving.

You bought a 50-plus year old car that was likely not properly prepped for long term storage, and it was probably several decades beyond the last time that any time related maintenance was done like coolant and brake fluid changes.

No doubt the distributor upper bushing grease well dried out over 30 years ago. You might be able to save the upper bushing if you overhaul it now.

Your work is likely just beginning. Welcome to the club. If you're not a member of your local chapter, join, and maybe you can find an experienced hand nearby to guide you through the process. Relying on "professional" mechanics is both expensive and often fruitless as few understand proper maintenance and component overhaul of these cars.

If you're lucky there might be a local vintage Corvette mechanic nearby, but even some that hold them out as such aren't very good. The best way to do it right is do it yourself. At least these cars are very simple and most needed maintenance, repair, and component overhaul can be done with common hand tools, but if helps if you've had a little experience as a DIYer over the years.

If you don't have a 1963 Corvette Shop manual and AIM, order them, today.

Duke

[David F.]

Re: 63 327/300 Overheating



Pictures of radiator top and fan/shroud (fan clearance 3/4" on sides and 1-1/8" on top). I do have lower seal shield stapled to lower shroud and a foam gasket at top between shroud and radiator top to minimize air leaking around (self installed).

The fan tension is tight.

The lower return hose does have internal spring. Radiator/reservoir cap is original. Coolant is nice green and filled properly in reservoir.

Brake fluid looks almost clear and found no sediment in bottom of reservoir.

I do enjoy doing some of my own work. I have 1963 Corvette Shop Manual (NCRS), 1963 Corvette Assembly Manual, and The Complete Corvette Restoration and Technical Guide Vol 2 by Noland Adams to help me.

Fan clutch-I am able to spin equally easily when cold or hot (with engine off for safety). Would a bad fan clutch be enough to cause the high rpm (highway) and 25 minute local driving to cause overheating?

I just had the carburetor rebuilt and installed new points with setting the timing just this spring.

When I purchased the vette in 2013 most of the rubber parts were dry cracked aged or leaking so I had:
Brakes - new shoes- pistons - fluid
New shock absorbers (gas)
New tires
New steering column coupler
New PVC and hose
Alignment with stainless steel shims
New windshield arms and blades
New fuel hose to pump

I'm just not sure where to turn now.

David

[Joe R.]

Re: 63 327/300 Overheating

David,

Your radiator is a Brass/Copper Replacement radiator and has no chance of cooling your 63 like it should. Either find you a NOS radiator or a replacement radiator from one of the Corvette Warehouses. You may be able to get a discount being an NCRS member. Buying direct from Dewitt's radiator is not what you want to do. Look for a discount.

JR