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Old 06-21-2019, 03:40 PM   #1
Bruce_MO
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Default 8BA potential leak- Bubble test

I have a '51 8BA that runs great and stays cool. It has a rebuilt short block I bought from Dennis Carpenter maybe 25 years ago and has about 11k miles on it now. For the last couple years, the car would cause the coolant to foam up and push out a bit of foam after a pretty hard drive. I've changed the coolant and no impact. I have suspected a crack or head gasket issue, so I've been checking lots of posts on FB on this issue. I've researched the "coolant analyzer" as a means of confirming a leak, but people seem to say it's not a dependable test. I recently tried the "bubble test", filling the radiator to the top and looking for bubbles. Results: no bubbles at idle, no bubbles at fast idle and beyond, but several big bubbles after engine slows to idle after higher RPM's. Would you say that would be indication of a block crack or gasket failure?


Never had any other issues or indication of leaks (coolant in oil, on plugs, etc.), and the car never "leaks down", other than the 3" diameter puddle of foam that gets pushed out after a hard drive. I can live with that, but I'm not keen on taking longer drives if I do have an issue.


Thoughts on the test result, and what your next steps would be? Thanks
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Old 06-21-2019, 03:48 PM   #2
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Default Re: 8BA potential leak- Bubble test

I'm thinking the big bubble you describe is just accumulated cavitation bubbles that are allowed to escape at lower RPM. If you had a gasket leak to the coolant, you would see like a iridescent thin oil slick on the surface of the water. That's my story and I'm sticking to it.
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Old 06-21-2019, 03:51 PM   #3
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Default Re: 8BA potential leak- Bubble test

Just a 3 inch puddle?
Try lowering the coolant level.
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Old 06-21-2019, 05:48 PM   #4
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Default Re: 8BA potential leak- Bubble test

What's the difference between a "hard drive" and a "long drive"? Lower the level of coolant in your radiator until it just covers the top of the fins. Is your system pressurized?
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Old 06-21-2019, 07:18 PM   #5
Bruce_MO
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Default Re: 8BA potential leak- Bubble test

The coolant level is sufficiently low. The foaming is the problem. It’s pressurized at 4 psi. I have several other flatheads and they don’t foam up whatsoever. Lots of other postings on FB state that foaming is a possible indication of a crack or a leaking head gasket.

I think a drive around the neighborhood will typically not result in foam. But a longer drive or some time on the highway will give me some foam. Maybe there’s a brand of coolant that’s less prone to foaming?

Thanks for your opinions and ideas. Keep them coming.
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Old 06-21-2019, 07:21 PM   #6
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Default Re: 8BA potential leak- Bubble test

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Have you tried a block/radiator sealant?
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Old 06-21-2019, 09:11 PM   #7
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Default Re: 8BA potential leak- Bubble test

By coolant analyzer are you referring to a block tester? I have found them to be very accurate for indicating any hydrocarbons in the cooling system. Just make sure your coolant level is low enough to not contaminate your test fluid and a hot engine running at idle.
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Old 06-21-2019, 09:35 PM   #8
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Default Re: 8BA potential leak- Bubble test

Did you remove the waterpump drive belts during the bubble test? With the belts removed, fill the radiator to the top. Start the engine and jam the throttle wide open for a few seconds. If combustion pressure is leaking into the coolant it will become obvious.
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Old 06-22-2019, 09:51 AM   #9
Bruce_MO
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Default Re: 8BA potential leak- Bubble test

That’s the analyzer style I watched several YouTube videos on and there were ones about cars with an obvious blown head gasket, and the mechanic said the test was not conclusive. So he said they’re not reliable. But I’m willing to try it if experience says they’ll be worthwhile. I like the idea of taking the water pumps out of the equation and I will give that a try. There’s no oily sheen on the surface of the coolant in my opinion.

I’ve considered a crack sealer and purchased some, but I’m waiting to be better convinced I have a problem before I try it. Thanks for all your feedback.
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Old 06-22-2019, 01:46 PM   #10
1931 flamingo
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Default Re: 8BA potential leak- Bubble test

Are you running the same "coolant" in all 4 cars?? If so, this is the only one that "foams"??
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Old 06-22-2019, 03:08 PM   #11
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Default Re: 8BA potential leak- Bubble test

Is there thermostats in the motor?
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Old 06-22-2019, 03:53 PM   #12
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Default Re: 8BA potential leak- Bubble test

Quote:
Originally Posted by Bruce_MO View Post
I’ve considered a crack sealer and purchased some, but I’m waiting to be better convinced I have a problem before I try it.
It's not going to hurt anything even if there isn't a crack.
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Old 06-22-2019, 05:09 PM   #13
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Default Re: 8BA potential leak- Bubble test

My '36 did the same thing a while back. I was using a 50/50 mix ( I don't remember the brand) and it would foam. I drained out some coolant, added water to about 75/25 and the foaming stopped.You might drain all of the coolant and save it in a large bucket then fill with straight water and see what happens. Just a thought.
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Old 06-23-2019, 05:58 PM   #14
Bruce_MO
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Default Re: 8BA potential leak- Bubble test

Yes it has thermostats. Coolant is the same. I usually buy a couple gallons of Prestone ethylene glycol (green) and mix 50/50 pretty carefully. But I could try the 75% water mix or some ratio that gives adequate freeze protection with a lot lower concentration of ethylene glycol. Never gets below 28-30 degrees in my garage.

Plan is to try a couple things in this order:
1) drain some coolant and replace with water. See what that does
2) remove fan belts and try the bubble test again
3) add crack sealer

Thanks for all your ideas and comments
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Old 06-23-2019, 06:53 PM   #15
flatjack9
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Default Re: 8BA potential leak- Bubble test

I had a foaming problem with my 39 when I had anti-freeze in it. Switched to only water and never had another problem. I don't run in the winter and have a heated garage.
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Old 06-24-2019, 10:32 AM   #16
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Default Re: 8BA potential leak- Bubble test

On my 51, the temp gauge would do alarming things when I ran the correct 4# radiator cap, possibly due to air bubbles. I run an open system now and it works fine, my thinking being that if it's not close to boiling point there is no advantage to pressurizing the system. Ken
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