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Old 06-01-2011, 12:56 AM   #1
KenCoupe
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Default Radiator bubbling over

I have a 31 coupe with a motometer. The car also has an alternator. It runs cool (no red in the motometer). However, occasionally the radiator will bubble out from the bottom of the motometer where it meets the radiator neck. I use straight water with some water wetter to help prevent rust. There is no antifreeze. It is kind of a foam that bubbles out. It is a relatively new Brassworks radiator and I have flushed it out. I also took some of the tension off the belt around the water pump and alternator. That helped a little, but it still bubbles out.

Does anybody have any suggestions on what is causing the foaming and bubbling out, and how to prevent/stop it?

Thanks.

Ken V.
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Old 06-01-2011, 01:20 AM   #2
Kurt in NJ
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Default Re: Radiator bubbling over

Perhaps when you tighten the belt it distorts the shaft and seal of the waterpump enough that it sucks air in.

On my 31 coupe if I can see the coolant above the baffle it is too high and it will puke it out ---my belt is quite loose because I use a generator, I do use a thermostat, and antifreeze.

Perhaps the motometer base was tightened too much and the radiator neck is distorted enough that it can't seal totally.

I don't look to see if I have any foaming--actually I don't look inside the radiator more than a couple times a year unless it seems to be running warmer or someone abandoned a water bottle in the car with a little in it.

try lowering the coolant level to the baffle, and inspect the radiator neck/seal on the cap
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Old 06-01-2011, 05:32 AM   #3
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Default Re: Radiator bubbling over

Excess water or expanded water should overflow through the overflow pipe. Check that's clear. But if expanding quickly ( or as you indicate posssibly over-agitated by w/pump ) it is rising to the level of the top of the rad neck. Maybe unscrew the cap and smear a bit of sealant such as Hermatite ( or whatever equivalent you have in the US) but check the overflow pipe first as othwise the system is going to be pressurized. ( Weeping head gasket I guess could also cause rapid agitation but assume the easiest things first!)
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Old 06-01-2011, 08:44 AM   #4
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Default Re: Radiator bubbling over

Typical symptom of a head gasket that leaks combustion gasses into the water jacket. Try re-torquing the head. Check the radiator for the presence of CO. You can do this two ways: With an electronic 'sniffer' or with pH paper. Exhaust will make the water acidic.
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Old 06-01-2011, 08:59 AM   #5
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Default Re: Radiator bubbling over

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Originally Posted by MikeK View Post
Typical symptom of a head gasket that leaks combustion gasses into the water jacket. Try re-torquing the head. Check the radiator for the presence of CO. You can do this two ways: With an electronic 'sniffer' or with pH paper. Exhaust will make the water acidic.
I agree with Mike, except I think he means CO2. In my experience, the sudden, almost explosive, appearance of bubbles or foam is due to combustion gases.

Another check you can do is to disconnect the fan belt and watch (safety glasses or goggles) for foam to appear in the radiator opening when you or a friend revs the engine. If the bubbles require the fan belt, then it's the water pump sucking air in. Water pump sucking should be worse at high rpms; combustion gas leakage should be most severe under load, i.e., open throttle at low rpms.

Also, NAPA stores sell a block tester kit that draws "headspace" air from the rad. tank thru a liquid that changes color if combustion gases are present. I believe that the color change relies on a pH indicator; you can regenerate the original color by drawing fresh air thru it. If you go this route, you will need the "large radiator" adapter usually sold for use with trucks. Hopefully, retorquing will fix, although some of us are driven crazy by warped heads--but them's fighting words.

Steve

Last edited by steve s; 06-01-2011 at 09:06 AM.
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Old 06-01-2011, 12:28 PM   #6
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Default Re: Radiator bubbling over

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KenCoupe ......................
No matter, what the cause, you need a better seal on your radiator cap. It should not bubble out at the neck, especially on a non-pressurized system. You need a new gasket.
MIKE
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Old 06-01-2011, 02:40 PM   #7
Barry B./ Ma.
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Default Re: Radiator bubbling over

I agree with Mike (Fla/WV). I had to smear some silicone under the rubber gasket to build up the thickness and make a good seal otherwise it would leak under the cap of he Motormeter.
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Old 06-01-2011, 03:48 PM   #8
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Default Re: Radiator bubbling over

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Originally Posted by Barry B./ Ma. View Post
I agree with Mike (Fla/WV). I had to smear some silicone under the rubber gasket to build up the thickness and make a good seal otherwise it would leak under the cap of he Motormeter.
I use 'neverseize' all over the inside of the cap/gasket! Side benefit too...makes cap easier to on/off! Does a great job of controlling/preventing rusty cap inside also!
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Old 06-01-2011, 03:56 PM   #9
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Default Re: Radiator bubbling over

Motometer leaks are a continuing issue. I've replaced the gaskets and re-tightened the screws that secure the base in the radiator neck. Still leaks some. Have not gone the silicone route yet as I may need to flush or re-rod the radiator and prefer to not have to wrestle with the goop. It'd be really nice if the repro motometers attached in a manner similar to the regular radiator cap.... From what I read in the JS, the original motos (1930-1931) used an approach like the repros. I'd like to think that it worked better in 1930 than today's version!
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Old 06-01-2011, 04:36 PM   #10
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Wink Re: Radiator bubbling over

Pilotdave,

Yes, the original locking caps with MotoMeters do indeed fit better. I just replaced the original to the car Stanco locking cap on my '31 roadster. The cap still closed and locked O'K, but was starting to deteriorate because of age. I took the original MotoMeter off of it and used a repop locking cap. I finally got it to fit on the radiator neck after using 2 thick rubber gaskets and 2 new longer locking "tabs" I made out of aluminum. Somewhat of a PIA to do, but a crappy repop is better then no repop.

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Old 06-01-2011, 06:20 PM   #11
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Default Re: Radiator bubbling over

I had that on my '31 A until I replaced the head gasket.

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Old 06-01-2011, 06:49 PM   #12
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Default Re: Radiator bubbling over

Use the block test kit from NAPA first to see if it is a head gasket or cracked head or block. Blue fluid turns yellow very quickly if you have any combustion gasses at all in those bubbles. Easy test to do and definitive.

I have done the "disconnect fan belt" thing and still had bubbles.

I put some Hot Tub and Spa antifoam additive (just a small amount) in my radiator last year when running only water and anti-rust additive, and the foam ended right away. (The bubbles did not end, but the foam stopped.) I had the additive here in the shop for my hot tub at the house and I figured I would give it a shot. It is made for hot water, so what the heck...

I believe my bubbles are being formed by hot spots in the cooling jacket in the engine. Difficult to prove, but I ruled out combustion gases and air leaking at the water pump shaft. I was at a loss for any other explanation.

Unless the engine has been rebuilt recently and the cooling jackets were cleaned well, there is no telling what sort of rust, scale and crud has built up in there that will interfere with cooling. If steam bubbles form in the block, get stirred up by the water pump on their way out, and bubble up into the upper tank, you have foam.

Regardless if the foam is air or steam, the Spa foam breaker additive stopped them.
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Old 06-01-2011, 07:50 PM   #13
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Default Re: Radiator bubbling over

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Originally Posted by Jim/TX View Post
Use the block test kit from NAPA first to see if it is a head gasket or cracked head or block. Blue fluid turns yellow very quickly if you have any combustion gasses at all in those bubbles. Easy test to do and definitive.

I have done the "disconnect fan belt" thing and still had bubbles.

I put some Hot Tub and Spa antifoam additive (just a small amount) in my radiator last year when running only water and anti-rust additive, and the foam ended right away. (The bubbles did not end, but the foam stopped.) I had the additive here in the shop for my hot tub at the house and I figured I would give it a shot. It is made for hot water, so what the heck...

I believe my bubbles are being formed by hot spots in the cooling jacket in the engine. Difficult to prove, but I ruled out combustion gases and air leaking at the water pump shaft. I was at a loss for any other explanation.

Unless the engine has been rebuilt recently and the cooling jackets were cleaned well, there is no telling what sort of rust, scale and crud has built up in there that will interfere with cooling. If steam bubbles form in the block, get stirred up by the water pump on their way out, and bubble up into the upper tank, you have foam.

Regardless if the foam is air or steam, the Spa foam breaker additive stopped them.
Jim,

That's very interesting about your anti-foam agent--clever idea!

What bothers me is that you still had the bubbles. I'm surprised that steam bubbles would persist long enough to get to the radiator, unless the coolant was also at the boiling point, which I doubt was the case idling in the driveway.

I'm wondering if you might still have a combustion leak. Most of the times I've used mine it's taken several pumps on the suction bulb to get the color change. Also, it's important to have a good seal around the filler neck, so you're not drawing in fresh outside air.

Steve
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Old 06-01-2011, 10:06 PM   #14
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Default Re: Radiator bubbling over

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Jim,

That's very interesting about your anti-foam agent--clever idea!

What bothers me is that you still had the bubbles. I'm surprised that steam bubbles would persist long enough to get to the radiator, unless the coolant was also at the boiling point, which I doubt was the case idling in the driveway.

I'm wondering if you might still have a combustion leak. Most of the times I've used mine it's taken several pumps on the suction bulb to get the color change. Also, it's important to have a good seal around the filler neck, so you're not drawing in fresh outside air.

Steve
I know. That's where I started. I expected any steam formed to condense back to water before it got to the upper tank.

I used the block tester on this engine 10 times now over 6 months, convinced those bubbles mean a bad head gasket. Never once did it turn yellow. (The head gasket is 6 months old, put on after a valve job.)

I made a rubber adapter ring to get a tight seal on the radiator filler neck and I capped off the overflow tube to keep fresh air out. I use a hand vacuum pump to draw the vapor up through the blue fluid for a full 2 minutes.

I do the test with the engine at 1400 RPM, full spark advance, coolant temp 165* (after a long run to get everything good and hot), and a new radiator. You can see the bubbles coming up a steady stream. But the fluid stays blue.

That is how I finally decided that it is steam from some hot spot in the block. As long as it does not foam, I can live with it. The steam just goes out the overflow tube and you have to top up the radiator to replace the water that boils off.
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Old 06-02-2011, 08:14 AM   #15
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Default Re: Radiator bubbling over

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Originally Posted by Jim/TX View Post
I know. That's where I started. I expected any steam formed to condense back to water before it got to the upper tank.

I used the block tester on this engine 10 times now over 6 months, convinced those bubbles mean a bad head gasket. Never once did it turn yellow. (The head gasket is 6 months old, put on after a valve job.)

I made a rubber adapter ring to get a tight seal on the radiator filler neck and I capped off the overflow tube to keep fresh air out. I use a hand vacuum pump to draw the vapor up through the blue fluid for a full 2 minutes.

I do the test with the engine at 1400 RPM, full spark advance, coolant temp 165* (after a long run to get everything good and hot), and a new radiator. You can see the bubbles coming up a steady stream. But the fluid stays blue.

That is how I finally decided that it is steam from some hot spot in the block. As long as it does not foam, I can live with it. The steam just goes out the overflow tube and you have to top up the radiator to replace the water that boils off.
I wonder if it would be any different with antifreeze?
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Old 06-02-2011, 09:40 PM   #16
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Default Re: Radiator bubbling over

Thanks for your replies. I will check to see whether the overflow tube is clogged. I'll also re-torque the head and seal/reseal the cap with Hermatite, silicone, neversieze, or new/additional gasket. The disconnect the belt and observe is a good idea also since loosening it helped some. I'll also take a trip to NAPA and get the block test kit. I have a spa and have the anti-foaming additive, so I'll try that too.

I'll get to it this weekend and post what I find.

Thanks for the help.

Ken
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