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:: Our early '65 convertible overheats. It has a new thermostat, radiator is ok, water pump ok. The freeze plug was pulled and some sludge was found, not much. Car still overheats. Help!! Any ideas why????
 

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:: Our early '65 convertible overheats. It has a new thermostat, radiator is ok, water pump ok. The freeze plug was pulled and some sludge was found, not much. Car still overheats. Help!! Any ideas why????

You werent very specific about how you know the radiator and water pump are OK.....


First guesses (assuming the info you provided).......loose belt, radiator hoses (check for spongyness when squeezed cold), head gasket (get the system pressure tested), crack in block/head(s)


The hoses could feel OK and have the inner layer delaminating, blocking flow, BTW
 

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Need a bit more info... You say the radiator is okay; but what radiator do you have? If it's the original 2-row, you more than likely need to upgrade to a 3 or 4-row. You also say the thermostat is alright; but what degree is it? You may want to go as low as 160.

Do you have a fan shroud? Probably need one. Stock 4-blade fan? Probably need to upgrade to a 6-blade. How's your radiator cap? Try installing a new one for use with an open system, and add a coolant recovery tank.

As for the sludge – you probably should backflush the system. Get a Prestone Backflush kit from WalMart and follow the instructions.

By the way – how 'bout filling out your bio so we can know a bit more about you? ;) Welcome to the forum!
 

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You need to complete your profile so we can know more about you and your car.

When does it overheat - idling or highway speeds or always?

What kind of engine - 6 or 8? How old is the radiator? Often times an old radiator can't cool well enough, so this could be the problem. Don't over mix with antifreeze, maybe 20-30%, water cools much better.

What temp thermostat did you put in? Any thing more than a 180 degree can cause overheating.

Have you changed the hoses recently? Sludge in the bolck can cause hoses to close up also.
 

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...radiator is ok, water pump ok. The freeze plug was pulled and some sludge was found...
When you say it overheats, are we talking coolant spewing out the overflow and getting really hot, or is the gauge just running a little further over than you would like. It could be that the gauge is just off. Unless it's getting REALLY hot, I would first verify the gauge with a good mechanical one.

If you have any sludge in the block, you can be sure those little thin radiator cores are partially plugged off. I would run a good flush, as someone else already suggested. If that doesn't help, I would either take the radiator to have it rodded out, or just replace it with a 3 core. Be sure to install a Gano filter on the inlet hose, or it will just plug off the clean radiator in short order.

Timing issues can often lead to overheating. I would check it and make sure it is on spec.

Contrary to what you hear a lot, a higher thermostat doesn't cause overheating. If it's indeed running hot, any properly operating thermostat will be open far before the temperature gauge shows a problem. Doesn't that make sense?

Get a read on the plugs to determine if it's running lean, as this can cause overheating. If the plugs are burning white, this is an indication of a lean condition. To richen the mixture, you must replace the jets internal to the carb.

Hope this, along with recommendations from others will help to solve your problem. Keep us posted on how you come out. Good Luck!
 

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Another thing you can try is to reduce your anti freeze ratio down to about 20% and add water wetter. The theory being that water is a much better coolant than anti freeze and the water wetter raises the boiling point.

By the way, if it's just the gauge, mine does the same thing where the gauge indicates very hot but the car really isn't overheating i.e. no coolant spewing out the overflow and no pinging, popping noises after shutdown.So at least in my case, the gage seems to be saying things are hotter than they really are.
 
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