Yes new Stant Cap tested at the counter with the same tester used to condem the cap we were using.

It's always had coolant in it. A touch stronger than 50/50 mix

Have you verified that the temperature indication is correct?  145 idle is low.



Lawrenceville, GA

"tested the brand new radiator cap and found it weak and leaking down."

You replaced it and you are using coolant instead of water?

____________________________

The Studebaker guys found that the brand new  aluminum radiator was beautiful, but the fins on the core were so tightly woven that not enough air could flow through at speed to cool their engines.  Slow speed running was acceptable, but not highway speeds and loads.

John - "The Hoosier Hurricane"

Home is 2500 miles away on the other side of the Rockies!

We went to Lowe's and got some rubber pipe insulation and sealed up the core support to hopefully force more air through at speed. It's fine in town/traffic now.

I could live with 205-210 steady, problem is once it passes 210 it gets into thermal run away, and we have to stop to cool it off.

It does cool off much faster now. Even half way on it's own without water on the radiator. And we can cool it to 145° while idling. Yesterday we could barely get it under 190°

That shroud is blocking a significant amount of airflow.  It may not allow enough to cool under load.

If the temps stabilize at 210 and it does not boil over, then it is ok.  210 is not too hot.  It does seem like something is not right but in this circumstance, I would simply keep my eye on it and get it home for troubleshooting.



Lawrenceville, GA

Stopped at O'Reilly's and tested the brand new radiator cap and found it weak and leaking down. While stopped we did the hydrocarbon test in the radiator and it was negative, so I don't think we have a engine hardware issue.

Open to other suggestions

Spoke too soon. As soon as we got on the highway up to speed the temp climbed to 210.

I'm almost out of ideas. Thinking it might have a head gasket starting to go. Going to to a hydrocarbon test and test the radiator cap.

Just to sum up.

New 4 core aluminum radiator
New 16" Electric Fan 3,000 CFM in good shroud
New GMB stock pump
Smaller Car Pulley
New #304 Robert Shaw thermostat.

It's fine until it gets under load, then the temp starts climbing.

Gentlemen! A heat felt thanks for the ideas and advice.

New car pump installed. Old truck pump had a bad bearing. Installed the new summit pulley and high flow #304 thermostat and 3,000cfm fan and shroud.

Just idled uphill in through Reno and the highest we saw was 187° and it quickly dropped as soon as we started moving. It stays just under 180° pretty constant.

Thank you all so much!

Our current pump is the 3/4" piloted truck pump(engine is all 62-64 truck from what I can tell). No top fan mount.

We are trying to do exactly as you describe. Car pump, and got a car pulley. I'm heading out the hotel parking lot with new parts and jelly donut and will report back if it all works!

I appreciate everyone's ideas and experience. This is a big enough challenge without having you guys to bounce ideas off of!