1968 Overheating Problem Troubleshooting
Thread Starter
3rd Gear
Joined: Jun 2007
Posts: 3
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1968 Overheating Problem Troubleshooting
I could use some help with troubleshooting an overheating problem. My stock '68 overheated rapidly (within about 15 minutes of starting) when I was no more than a block from home. The temperature gauge climbed very quickly over 250 degrees.
The coolant level appeared normal in the expansion tank and the expansion tank (aluminum) was relatively cool to the touch.
The upper radiator hose was hot, the bottom radiator hose was about the same temperature, perhaps a little cooler.
As the car cooled down, the radiator failed with coolant coming out the lower third of the fins.
I have pulled the radiator and the thermostat. The thermostat appeared to be stuck open when I pulled it from the car.
I expected to find the thermostat stuck closed, given the rapidity of the overheating. Any thoughts on what caused this failure?
The coolant level appeared normal in the expansion tank and the expansion tank (aluminum) was relatively cool to the touch.
The upper radiator hose was hot, the bottom radiator hose was about the same temperature, perhaps a little cooler.
As the car cooled down, the radiator failed with coolant coming out the lower third of the fins.
I have pulled the radiator and the thermostat. The thermostat appeared to be stuck open when I pulled it from the car.
I expected to find the thermostat stuck closed, given the rapidity of the overheating. Any thoughts on what caused this failure?
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
Hard to tell really. Could be just blockage in the cooling system itself. If the radiator burst at the seams then the radiator cap failed to do it's job.
That quick of a temp climb would make me think the waterpump might have failed internally (assuming it wasn't a bad seal that was weeping).
When was the last time you drove it and did you make any changes to the car before this event happened?
If that is all original stuff then be happy it lasted so long. Time to upgrade unless you car is of the "stay stock" type.
That quick of a temp climb would make me think the waterpump might have failed internally (assuming it wasn't a bad seal that was weeping).
When was the last time you drove it and did you make any changes to the car before this event happened?
If that is all original stuff then be happy it lasted so long. Time to upgrade unless you car is of the "stay stock" type.
Thread Starter
3rd Gear
Joined: Jun 2007
Posts: 3
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No changes to the car before this event, it has been months since I drove it. The water pump is not weeping so an internal failure is possible. I expect to change that too given its age but am trying to ensure I don't miss any other possible causes.
The radiator cap on this 327/350 is on the expansion tank and it never got hot so radiator failure happened without putting pressure of any magnitude on the cap. It was so cool that I opened it shortly after parking the car with only a small amount of pressure released.
The radiator cap on this 327/350 is on the expansion tank and it never got hot so radiator failure happened without putting pressure of any magnitude on the cap. It was so cool that I opened it shortly after parking the car with only a small amount of pressure released.
Thread Starter
3rd Gear
Joined: Jun 2007
Posts: 3
Likes: 0
I don't have an IR gun, but it was very hot and note that it had only been running for 10-15 minutes. No issue with shroud/seals. Fan clutch appears to be good.
I pulled the pump tonight and the impeller is intact and there is no evidence of failure. I am going to take the radiator into a shop and see if they can tell me anything about it.
I pulled the pump tonight and the impeller is intact and there is no evidence of failure. I am going to take the radiator into a shop and see if they can tell me anything about it.
CF Community Team
Joined: Oct 2004
Posts: 19,354
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From: Cape Cod, Mass.
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If you have coolant coming out of the lower 1/3 of the radiator fins as you stated, it's a pretty safe bet that your radiator is shot.
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