Top rad hose collapses

[Rich G.]

66 327/350. Runs fine, no cooling issues. But....a few hours after shut down the top radiator hose is collapsed. Opening the cap on the expansion tank allows air to go in which I can hear and then the hose gets round again.

Is it just that the hose is old and the vacuum is normal, or is the creation of the vacuum an indication of another problem? It has done this for a long time. The cooling system has been drained and refilled at least once in that time period.

Rich

[John F.]

Re: Top rad hose collapses

Sounds like an air pocket in the coolant system. You can burp the system in many ways. Some fill the block thru the thermostat opening, some drill a small 1/8" hole in the thermostat, others just keep filling the system and eventually the air gets out and water is flowing freely.

[Robert S.]

Re: Top rad hose collapses

Check the radiator cap. It should have a small aluminum disc that allows air to pass into the cooling system under vacuum conditions.

[Rich G.]

Re: Top rad hose collapses

Thanks guys. I will check those things. The cap is not judging correct but I thought it was the correct one for operation but I didn't know about the disc.

I assume if it is air I can run it with the cap off until it stops burping out coolant... Yes?

Rich

[John H.]

Re: Top rad hose collapses

Rich -

The proper radiator cap has two valves in it - pressure and vacuum; if the vacuum valve isn't working, exactly what you describe will happen. As the cooling system cools down, a vacuum is created, and if that valve is stuck (or isn't there at all), the upper hose will collapse until you remove the cap. You need a new (and correct) radiator cap.

[Rich G.]

Re: Top rad hose collapses

Thanks John

The cap I have looks to be close but not exact to the JG&TM. On the 9 o'clock position it has AC in a circle. On the three oclock position it has 15# and RC -15 in a circle with the 15# over the RC mark. At the 12 o'clock position it says turn tight and at the six position it says remove slowly.

I will definitely try another and will also be sure the system has no air in it.

Rich

[Larry M.]

Re: Top rad hose collapses

Rich:

Agree with the others, the cap is not functioning correctly.

The 1965-67 327/350 HP engine is essentially self venting and does not have air pocket issues if the correct 326 water pump with the bypass hose is installed ,and the hoses to the heater are open (valve is open for the AC cars). Any air in the system will be vented through the expansion tank without issue(s).

Larry

[John H.]

Re: Top rad hose collapses

Thanks John

The cap I have looks to be close but not exact to the JG&TM. On the 9 o'clock position it has AC in a circle. On the three oclock position it has 15# and RC -15 in a circle with the 15# over the RC mark. At the 12 o'clock position it says turn tight and at the six position it says remove slowly.

Rich -

That cap is for use with a conventional copper/brass radiator with the cap on the side tank (like big-blocks use); the cap you want for your aluminum radiator and separate expansion tank is an RC-26 with an aluminum center rivet.

[Rich G.]

Re: Top rad hose collapses

Thanks John.

That explains a lot. I now have a spare cap for my 68 L71!

Rich