Tiny bubbles..... in the cooling tank......

[wormshoe]

Wormshoe here.....

My initial thought was that there might be a problem with the coolant flow through the castings....passages narrowed or sand/debris stuck to the inside wall of the casting somewhere in the coolant circuit that is not easily seen (high in the cylinder or in the head casting). Even if a passage is not blocked, but the coolant is kept from making adequate contact with the casting, localized overheating can occur and bubbles will be generated as a result.  If my guess is correct, than this problem will intensify over time because of the constant buildup from the evaporating coolant when under a heavy load.

You folks have looked at everything else...all of the normal things....all of the possibilities that sharp mechanics would explore.  That's what brings me to making this suggestion.  Pull the head and using a bore scope (or something similar) snake the sucker into the castings and throughly check the places that can't readily be seen. Look for white colored areas of buildup. An internal void in a defective casting could also cause this to occur.

I normally only follow the interesting conversations that appear on this site.  Because I don't own a Lister, I have very little to add. What makes this different is all the stuff that I have read about casting sand being found in your engines....and it is the possible presence of this sand or associated crap (on an interior coolant passage wall) that makes me think it might be causing this problem.

Hey, just my two cents.  Good luck to all of you that are actively chasing this problem down.

[oliver90owner]

what is composition of limewater?

It's a solution of lime in water of course.

Calcium hydroxide,  pretty well saturated (it isn't that soluble) in water.  Insoluble calcium carbonate formed when it absorbs carcon dioxide.

An alternative for us old chemists might be an Orsat for analysing gases.  Time consuming, reasonably acurate if done properly but years out of date.......Used to use one regularly for combustion gas analysis.

Regards, RAB

[Petersbpus]

Coolant passages have been poked prodded and cleared, there is a captive pocket between the intake and exhaust gas passages maybe a tablespoon or so. But passages in the area are opened and clear, I increased the antifreeze ratio to increase boiling point to check the hot spot Idea, didn't seem to matter, I do have inline coolant pump I could hook up to see if that changes someting, but seems alot of lister heads  out there in the world are running water and thermo siphon without bubbles.


I have not pumped coolant, just a well raised 5 gallon bucket with nipple top and bottom for 1” hose. Heat exchanger assembly not yet complete.
Have run it without the 195 degree thermostat and it bubbles just the same,

I have used a new head gasket each time the head is off,
The original was a composite fiber and metal ring, the “spares” are double copper sheet with fiber core, I have been placing the rolled over ring side up towards the flat of the head so that the liner compresses solid copper sheet,
Today I took the head back off and was able  to look down into the block, and the ring that the cylinder sleeve O rings slip into has an even coating of sediment and oxides, does not appear, visually to have been letting crankcase pressure (if any) past the O rings.
Just for kicks I flipped th used gasket over, applied a thin film of high temp copper RTV and reinstalled, If the top edge of liner was leaking  that ought to stop it.
Drying overnight and we will see in the morning before work.

The possibilities are dwindling, I hope
Down here when you say limewater we would think  Tahitian Lime or Key Lime?
so that is lime like you might use in the garden??