i have a 69 396. having a problem with loosing coolant when driving, doesn't run hot around 180. intalled a new thermostat and radiator cap and still loosing coolant. i drove about 35 miles and lost about half of the coolant.

i thought about changing to a new alum. radiator with electric fan, and maybe changing the water pump.

If you cannot isolate any leaks, you'd better hope it's not going out through the exhaust, could be a cracked head/block. Does it leak any while not driving it?

i beleive that it is coming out of overflow

does not leak while not driving

I can't believe it is coming out of the overflow with losing half in 35 miles....

You have a serious problem is you loose 1/2 coolent 2-3 gals in a short period.

If you dont see any leaks you need to get your car/motor to someone that has a good rep as a motor mechanic.


I suggest this becasue i get te imptression from your posts & answers you failry new to this motor stuff which is ok,we al have to start somewhwre.

But it may be a craked head or intake,bad head or intake gasket both of which can leak into the crankcase . This can wipe out your complete bottom end & cam bearings along with the cam & lifters too so dont run the motor any more than you need to until you get it to a pro to find out whats going on.

Scott

But it may be a craked head or intake,bad head or intake gasket both of which can leak into the crankcase . This can wipe out your complete bottom end & cam bearings along with the cam & lifters too so dont run the motor any more than you need to until you get it to a pro to find out whats going on.

Scott[/QUOTE]
I agree
the longer you run the moter the bigger bucks it will cots to fix

What lb cap did you put on it? It should be 16lb, if it is coming out of overflow cap is too weak.

What lb cap did you put on it? It should be 16lb, if it is coming out of overflow cap is too weak.
I agree with that statement..... If your just guessing at where its coming from you could be in trouble. There is no way you could miss seeing coolant from the overflow. Also another bad area of lost coolant is from the guides, they are in the water jacket on the BB heads. But with that much coolant lost, your oil pan would be brim full with oil/coolant.

I would put a pressure tester on the radiator and pump it up to what the psi on the cap indicates and then watch for the leaks. If you don'thave one, some of your local parts stores may let you use one. You will also be able to check the radiator cap with the same tool to see if is leaking down.
Hopefully, It's just something simple.
Good Luck!

Normal overflow would not account for that much loss.

You have other problems that need to be addressed, most of them already mentioned. Possible cracked head, Gaskets, loose hose clamps, cracked heater core, etc.