Well nucleate boiling is part of the normal heat transfer process between
metal and coolant.

Paul Lamar


Tim Andres wrote:

This is getting of topic, but this liner pitting you refer to is caused
by cavitation of the liner, not acidity. As the liner vibrates away from
the coolant a (local)low pressure area forms and allows the coolant to
boil. The subsequent reversal of liner travel results in increase
pressure locally and the explosive collapse of the bubbles which eats
into the liner material.
                                        FWIW, Tim Andres

John Gibbons wrote:

A more common problem caused by the acidity is the pitting of the

cylinder

liners. I can't remember which side pits more but one side does and it

is a

result of the direction of flow of the coolant through the block. You

wake

up one day and find your coolant is low and your oil is high. The cure

is to

use a coolant additive which balances the ph and change your coolant

every

two years. It is also a good time to change out your hoses too or go

to the

silicone ones which should easily last ten years. You definately do

want the

best hoses and fittings you can get as a catastrophic hose failure is

just

that, with regular replacement of your coolant the acidity should not

be

much of an issue.

John

I ran into an engineer at OSH that works for Cummins I think.
He did not have a card on him but hopefully he will join
up as I gave him my card.

He told me the life limiting factor on a diesel engine is the

cooling

system. When the antifreeze gets old it turns acidic.
When that happens black low cost automotive hose becomes part of

a

battery

because of the conductive carbon in it. You can actually measure
the voltage with a digital voltmeter by putting one probe
on the hose and the other on the hose barb. The black hose
loses carbon to the mixture. This causes a reduction in strength
of the hose. The answer is silicone rubber hose and changing

your

coolant once a year. This could be a factor in the two crashes
we have had due to cooling hose joint failures. In both cases

the

people had been flying their rotary powered airplanes for

several

years.

Paul Lamar

 
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