Was not sure where to list this....

[67 GT350]

In Knoxville today it was sunny and 80 plus degrees. Took my 3 cars out for a ride.

66 GT350, guage shows hot but that might be The Normal? no signs of overheating, I did top it off so it did spew a little, but not much, upper hose was hot and tire to squeeze.
67 GT350, guage almost midway, not really overheating, but it did spew more, upper hose same as the 66. I did top it off.
70 Boss 302, guage shows nice, but it spewed, upper hose same as above, topped it off also.

Is it because I topped them off? I have done that before and once they are done spewing, they seem fine however level seems very low. Are any factory gauges to be trusted? All radiators have been cleaned and serviced. Not sure on the caps but the 66 has a 14 on it, the other two have a 13 with the 67 being the loosest and the 66 being super tight.

Do I have issues? I would like to take one to cars and coffee Sunday?

[shelbydoug]

You most likely need to pressure test the caps. The caps should be able to hold the 12 or 14 psi they are rated at.

It is very common for the caps not to be holding pressure. I can say that because I have invested in a pressure tester and has become part of a regular maintenance routeen to test all of my caps annually.

The Stant kit is about $110.



The fluid level cold on any of those cars should not be more then about 1/2" over the tops of the fins.

[67 GT350]

Good info! The 66 has a super tight cap, and maybe the others need that also...I will look into a tester.

[98SVT - was 06GT]

Water expands when it gets hot. Topping them off will mean some gets expelled when they come up to temp. About 1/2 below the neck is normal fill.

[FL SAAC]

What they said and :

Look at the lower hose it may be soft  or collapsing causing to heat up.

But more than likely you topped it off and it's just belching the excess

Buena suerte  !

[TA Coupe]

If your hose is collapsing then get one of these:
https://www.npdlink.com/product/spring-lower-radiator-hose/143875

         Roy

[J_Speegle]

Water expands when it gets hot. Topping them off will mean some gets expelled when they come up to temp. About 1/2 below the neck is normal fill.

+1  You can keep filling them all the way to the top and they will just keep spitting it out. Easy to forget though