My car has always been prone to overheating in hot weather. Done the Coolkat fan thing. Not sure if the centrifugal advance is working correctly. Anyone know how I can check this?

I have the 1" diameter bypass line from radiator hot side back to the header tank. I suppose this was designed to prevent deadheading the waterpump and overpressurizing the radiator, but it seems large for the job when compared to cross-sectional area of fully open thermostat. Appears to have been eliminated on later cars.

Curious if anyone has tried introducing a restriction (orifice) in the line to reduce the recirc flow somewhat and if so, what was the result?

Jay Boyce
JANE member
Lincoln, MA

Submitted by jboyce@foster-… on Thu, 11/12/2009 - 09:57

Patrick,

I had the brass radiator checked by a local shop and they told me it was in good shape.
Overheating seems to occur after hard driving at speed. On shutdown, I can hear coolant boil in the block. Haven't had any hot weather since I replaced the fan. Maybe that will correct, but also wondered if I might be getting too much advance at full rpm. Also maybe I need to modify fan switch so that it runs for a bit after shutdown?

Jay

Submitted by SC38-21185J on Wed, 11/11/2009 - 15:30

Don't the springs in the distributor only come into play at higher RPMs? If your car is overheating just sitting on the driveway at idle, I don't think distributor springs is the problem. Is this the original '66 radiator? And if so, has it ever been serviced? That would be the first thing I'd suspect.

P

Submitted by jboyce@foster-… on Wed, 11/11/2009 - 15:13

Advance mechanism moves but springs don't seem to offer much resistance. Wonder- do they tire from old age? I'll check it with a timing light.

Just bought thermostat from a major jag house supposed to be proper, but missing top bypass hole. Old one tests OK, but opening is smaller than the bypass, so more water is flowing around the radiator than thru it. Doesn't make sense to me.

Thanks for the advice,

Jay Boyce

Submitted by rcmaury@bellso… on Wed, 11/11/2009 - 10:28

The original system will work fine when it is in proper running order. With the CoolCat fan, you should not have any issues. The only reason to add a restriction in the bypass system is if you are not running the proper thermostat. As they are available, there is no reason to modify the system, just get the proper parts.

Submitted by pharmon@jcna.com on Wed, 11/11/2009 - 10:21

A quick way to check the centrifugal advance is to remove the distributor cap and turn the rotor with your hand. It should rotate under spring pressure and then snap back when released. Failure to lubricate one of these is one of the most common maintenance mistakes. If it is frozen then you'll need to remove the points plate to access the springs and weights. With some oil they should free right up. The other way to check the advance is with a timing light.