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Hugh Morrow
New User
Username: iconic

Post Number: 2
Registered: 6-2003
Posted on Wednesday, 08 September, 2004 - 20:53:   Edit PostDelete PostView Post/Check IP

The engine of the 20HP consists of a number of different metals, presumably leading to corrosion problems in the far reaches of the cooling system that one has no chance of inspecting.

Is this correct and if so what corrosion inhibitors should be used in the cooling system?
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Graeme Söderlund
Prolific User
Username: graemeaus

Post Number: 40
Registered: 6-2003
Posted on Tuesday, 19 October, 2004 - 10:05:   Edit PostDelete PostView Post/Check IP


speaking as an owner of a 20hp for a goodly number of years, I can advise that I used to reverse flush the system at least every other month.

After a complete flush, I refilled the system and added approx. 1/2 cup of soluble oil (common garden variety white oil) to the system.

This acted as a corrosion inhibitor and at no time did the system on the car show any signs of corrosion etc. The car in particular is now David & Dianna Jones 20hp, Chassis number GKM60.

At the time, (1960's to 1970's) there was a large group of dedicated 20hp owners, and all used white oil in the cars. It is a very old fashioned idea but seemed to do the job for us.


Graeme Soderlund
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David Gore
Username: david_gore

Post Number: 322
Registered: 4-2003
Posted on Tuesday, 19 October, 2004 - 11:48:   Edit PostDelete PostView Post/Check IP

Hi Graeme,

Just a gentle word of warning about using soluble/white oil emulsions for everyone - this mixture is extremely prone to causing dermatitis/bacterial skin infections especially if it comes in contact with cuts/abrasions.

It is also prone to bacterial contamination in use if the mixture does not get hot enough to kill the bacteria hence the importance of regular flushing and replacement - monthly would be the longest I would be prepared to go between changes.
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Jim Bettison
Yet to post message
Username: jim_b

Post Number: 1
Registered: 9-2004
Posted on Tuesday, 19 October, 2004 - 12:51:   Edit PostDelete PostView Post/Check IP

I am searching through my archives for a copy of a paper given in or about about 1947 by a senior engineer with R-R in the aero engine division dealing with the subject of corrosion in those engines - particularly the Merlin and derivitants.
To the best of my recollection several coolant mixtures were examined. They included water (unadulterated distilled); water with borate/nitrite additives; inhibited ethylene glycol (in various concentations); and soluble oil in various concentrations. The prime desired attribute was action in heat transfer.
Water alone didn't rate at all well.
Borate/nitrite solutions were poor conductors of heat but were good at seeking minute leaks, denoted by white "flowers" at joints exposed to air - sunsequently thought useful in locating leaks.
Inhibited ethylene glycol in a 50:50 water/glycol mix was best both as a heat transfer medium and as an inhibitor of corrosion. It did need to be flushed out and the engine well cleared of old coolant on a strict routine; with age the glycol tended to break down, and a byproduct was glycollic acid - and we all know what any acid tends to do to light metals and alloys; the Merlin is full of them. To denote that this was the coolant used, fluorosceine was added purely as an indicator, being inert in this application.
The use of soluble oil was examined and dismissed; its use dramatically reduced engine under-load life. This was attributed to the soluble oil emulsion breaking down at the high temperatures encountered at cylinder walls, forming a heat transfer barrier which caused the cylinder liners to fail.
Consequently, R-R settled on the present coolant, I presume.
I suspect that R-R motor vehicle engines which tolerate soluble oil are no nearly as stressed as aero engines and can tolerate less efficient heat transfer.
I have not used soluble oil for years. I went away from it because of a tendency to accelerate the failure of interfaces between coolant and lubricant if the gap is sugnificant.

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