Air Bubbles in the Coolant Line

[BigGreen]

Somebody stated that he was getting golfball size bubbles in his coolant exaust. I do not get them that large or that often but I do see the following:
Nominal during warm-up, about 10 minutes
After warm-up I will see an occational 'quarter size' blurp of air come out of the engine. Sometimes as often as every thirty seconds or so. I wrote this off as the water reaching 212 deg and it's boiling a bit.
Am I wrong?
Does anyone else see this?
Is this a concern?

Thanks
BigGreen - 25hp/15kw

[ronmar]

Well how hot is the head getting?  IE, is it actually getting the coolant to 212F?  If so, the early bubbles could be ones from the last run working their way out.  If you lower the load and the temp definitely below 212F do they go away eventually?

[MacGyver]

I seriously doubt that steam bubbles will survive the trip all the way up the coolant hose and to the top of the tank before they cool enough to collapse.

Sounds more like air/combustion gas bubbles to me. It was on mine...

Are you using tank cooling and not a radiator?
If so, try this experiment.  With the engine running and making bubbles, take a tall clear glass or plastic container and submerge it under water so it's completely filled. turn it bottom up and raise it slightly out of the water so that
the opening is down and the solid bottom is raised out of the water an inch or 3. The glass should be full of water with no air in it.

Now hold it over the coolant outlet and let the bottle catch the bubbles. If these are steam bubbles from boiling, they will condense and go away as they cool. If the glass fills up with air that *doesn't* go away then you've got a combustion leak.

Don't burn yourself with hot coolant... use tongs or whatever to maneuver the container around in the hot water.

[BigGreen]

Thanks for the replys.
I do not know how hot it actually get's. I have no way to measure the water temp at ths time. I originally had a clear tygon tubing connecting the coolant exhaust to a 50 gal water heater tank. That's when I noticed this taking place. It has done this from day one... The tygon has been replaced with a hydraulic hose better suited for the heat so now I can't see what's going on in there but I'm sure it still bubbles.

I like your approach MacGyver but my coolant tank, as stated, is a water heater tank and I just couldn't pull that off.
You said something that leads me to believe it is combustion gas. The bubble would sit right at the manifold/hose connection for several seconds before starting up the hose. I agree that a steam bubble would cool there and basically disappear.
Is this small leak a big concern considering I have an open tank coolant system? I would hate to replace sleaves and o-rings at this time if I can aviod it. This is a 25/2 Ashwamegh I bought from Joel two years ago and it has less than two hours of run time on it. She only get's attention during hurricane season and Gustav is getting close   
I still have a brass idler gear to replace. George sent me one two years ago and it's still in the original FedEx box. Embarrassing, I know 

[MacGyver]

You said something that leads me to believe it is combustion gas. The bubble would sit right at the manifold/hose connection for several seconds before starting up the hose.

Yeah, that doesn't sound like a steam bubble does it? You got air/combustion gas coming from somewhere....

Is this small leak a big concern considering I have an open tank coolant system?

Maybe. Maybe not. Small leaks tend to get bigger as combustion gases erode a channel. And there's always the possibility of water leaking into the combustion chamber and causing rust or polluting your oil while the unit sits idle.

I'd fix it. But I'd wait until after Gustav has passed. ...

[oliver90owner]

I do not know how hot it actually get's.

Water vapour bubbles will not remain in water less than 100^OC at normal tmperature and pressure.  It(steam) cannot co-exist with at lower tempeatures.  The laws of science preclude this state of affairs.  The energy of the 'steam' would be absorbed by the water and the steam would condense back to water.

Yes, liquids will evaporate (losing molecules from the surface) at lower temperatures but boiling only ocurs at one temperature, fixed by that substance and the pressure prevailing at the time.  IF, and it is) your water in that pipe is less than 100^o it is not boiling and those bubbles are not steam

If you have a pump in the system there is always the possibility of air entering the system.  In a thermosyphon system, water will always leak from a tiny hole to atmosphere, not air entering.  That leaves you with very little choice, In fact no choice, as to where thatose bubbles are coming from.

Loss of gases at high pressure past a head gasket can either be remedied by re-torquing the head, or by changing the gasket and removal of the cause.  Cause could be:  bad gasket, liner protrusion, flaw in one of the sufaces, cracked (or porous) item.

That should have covered about all you need.  In your case, re-torque and hope it lasts for the duration of the potential hurricane outage.

Regards, RAB

[rleonard]

Replace the head gasket.  If that solves it great.  If not, get a head on order.  You have a crack in it.  With the storm headed your way, maybe order the  head and gaskets  now.

Bob