The Stovebolt Site Forums The Shop Area Engine Shop Radiator Pressure Test

I'll be taking Ol Roy's radiator to my radiator guys this week. Since it's a zero pressure system, I want to let them know but what would be the maximum pressure that that radiator could withstand?

I use a 4 lb pressure cap. So I know that it can at least take 4 lb. I just want to let them know so they don't accidentally blow up the radiator when they test it.

These days I don't take anything for granted, or that professionals actually know how to do their own job.


They're probably aren't many zero pressure systems left these days that the shop works on.

No need to worry.

As soon as I walked in, the guy knew it was a 50s Chevy radiator. He also told me the radiator has been re-cored at some time in the past. The "new" old core can take pressure to around 15psi.

I was shocked to see that the Sim's Radiator location I've been using for years has closed. I should have called first. I had to drive to a farther out location warehouse to drop it off so that it can be taken to their single location even farther away where they now do all of the work.

They used to have four or five locations around the Metro for decades. It's the usual story - they can't get good help. Now all the best people are in one place doing all the work.

He also mentioned, as someone else on this forum pointed out, that half the rad caps he tests brand new out of the box do not match the rating on the cap. 15lbs hold 12 or 13lbs, etc. No industry is safe from incompetence.

Otto,
I know its Common for failure in parts these days but I bought my water pump (216 pump) at Napa a few years ago . Works great, no leaks. I believe it had a "warranty" of sorts. But check into it. I think they are about $150 now.
If not, have it rebuilt by someone who knows what they are doing!
Keep us posted. Stay cool.
Todd

The Frying Dutchman (come for the freak, stay for the food) quoted me $129 for the water pump rebuild plus shipping and whatever the price of a new impeller. That probably means about $200 when I include tax and shipping to him.

I think Rock Auto has one for $100+. I'll consider all my options.

Zero pressure system. I found this.... The liquid travels into the catch-tank. Once the engine is finished pulling a hill and the system cools down a bit again, it will make a slight vacuum at the reservoir and suck the liquid coolant that has built up back into the system. This is why the catch-tank is fed at its bottom, and also why I had to seal off the coolant cap totally. The coolant cap normally will relieve any bit of vacuum, kind of like a check-valve in the system so it had to be blocked. Otherwise the coolant will not get sucked back into the system and just keep building up in the catch-tank.
could that later be the case?

Guitplayer, how did you seal off the coolant cap? I was always under the impression the coolant cap relieved pressure above a set amount. I never realized it works as a vacuum breaker.

If the radiator cap has an "upper seal" the cap doesn't act like a vacuum breaker. Instead, the vacuum is applied to the "overflow bottle", pulling coolant back into the radiator to fill the void. Early radiator caps did not have this second seal.

Just got a call from the radiator shop. They'll have it ready for pickup tomorrow afternoon.

LOTS of hardened crud came out of it. Stuff was solidified so didn't readily come out during flush on the vehicle. Re-soldering leaks and tank seams, etc.

$125.00

Sending off water pump today. 3 week turnaround time on that.

I sort of suspected you might find a dirty radiator core. Once a layer of hardened crud accumulates inside the tubes, it forms a very effective insulator that prevents the proper heat exchange from taking place. Even the acid flush I do can fail at times, if the stuff is thick enough, or the chemical composition of the deposits resists reacting to the acid. Good luck on the pump rebuild!

Even though your radiator recore job is rated for higher pressure, be aware that the heater core probably isn't. Be cautious about using a cap that's compatible with the radiator, not the heater.
Jerry

A question about the radiator repair. Was it:
1) Rodding out the coolant tubes of the old radiator core for re-use.
or
2) Fitting a new radiator core.

I believe the radiator had been recored previously, with a higher pressure rating than the original. This time it was just rodded and some leaks repaired.
Jerry

Jerry is correct.

Radiator dude said the rad had been re-cored sometime in the past with a ~15lb modern core. They're rodding it and fixing leaks, as Jerry said.

Thanks for the clarification, good to know the old core is useable.

Jerry, the heater core is brand new but who knows if it's rated to modern standards.

Most of the replacement heater cores I've seen are also rated for high pressure, but with a clean OEM size radiator, there's no need to build a pressure cooker. The only reason to have a 15# cap is to raise the boiling point of the coolant to 250+ degrees F. That lets today's car manufacturers build radiators half the size they really need to be.
Jerry

Yes, I don't plan to use a 15lb cap. I'll keep using the 4lb cap that worked perfectly fine before this incident.