coolant formulation tech questions
coolant formulation tech questions
(OP)
At my fab shop I deal mostly with the driveline engineering. By default I almost always just dump in a 50/50 mix of green coolant from a bulk 55-gallon barrel and ship off the car, but after recently having purchased a diesel F250 and a diesel Mercedes, things have me curious.
The F250 requires a special anti-cavitation additive to preven water jacket corrosion. Can someone clear me up on that? Why would the diesel be concerned about cavitation corrosion and not a gas engine?
I am currently flushing the Mercedes and I can't get a straight answer on which coolant I can use. Mercedes of course wants you to buy their $25 coolant, so of course they recommend it. Most Mercedes owners (no offense) don't know anything technical about their cars so I haven't found anyone Merc forums that can intelligently advise me either.
So, my second question is a little broader: Can someone give me a quick rundown of some coolant formulations and which ones are best suited for certain metals/plastics? For instance, my Mercedes has an aluminum/plastic radiator, iron block/Al heads, and probably some brass fittings here and there. I'm hoping to reach an understanding of why certain coolants are spec'd for certain applications so I can make wise decisions on my own... instead of listening to a Mercedes dealer's opinion. :)
The F250 requires a special anti-cavitation additive to preven water jacket corrosion. Can someone clear me up on that? Why would the diesel be concerned about cavitation corrosion and not a gas engine?
I am currently flushing the Mercedes and I can't get a straight answer on which coolant I can use. Mercedes of course wants you to buy their $25 coolant, so of course they recommend it. Most Mercedes owners (no offense) don't know anything technical about their cars so I haven't found anyone Merc forums that can intelligently advise me either.
So, my second question is a little broader: Can someone give me a quick rundown of some coolant formulations and which ones are best suited for certain metals/plastics? For instance, my Mercedes has an aluminum/plastic radiator, iron block/Al heads, and probably some brass fittings here and there. I'm hoping to reach an understanding of why certain coolants are spec'd for certain applications so I can make wise decisions on my own... instead of listening to a Mercedes dealer's opinion. :)





RE: coolant formulation tech questions
RE: coolant formulation tech questions
I've been using a special Cat coolant designed for their deisels in the F250. It is supposed to have enough anti-cavitation additive for 300k miles. That is, of course in a large diesel with five times the coolant capacity of mine, but I think I'm safe for a while.
Should I be concerned with that in the Benz?
RE: coolant formulation tech questions
Per another site "the concentration of air bubbles increases when cooling system pressure is low or when the system leaks. Also, increased vibration amplifies the quantity of air bubbles. Vibration multiplies when the engine is run cold, because of increased piston-to-cylinder clearance. Vibration also multiplies when the engine is lugged." You could also add that vibration goes up when the engine power is "enhanced" through chipping or turbo upgrades.
If I remember correctly it is more of a problem on engines that run wet sleeves. It could also be a problem on a parent bore engine with thin cylinders. Basically the more the bores flex the worse the problem will be.
FYI - Some of the old International tractors ran a "coolant filter" which was in reality a time release coolant additive to prevent/limit cavitation.
ISZ
RE: coolant formulation tech questions
it is important to understand that cavitation of cilinderwalls has two components: vibration and the building of "virgin" surfaces that are very prone to corrosive attack. both these items indicate where the solution should be sought. apart from using better linermaterial, giving the liner a surface treatment or using better seals at the bottom to prevent vibration itself, good anticorrosion properties of the coolant and perhaps a "damping influence" of the coolant on the "impact" of the implosions are used. for the latter emulsions of water and oil are used (about 2% of oil in water), in the past even higher concentrations were used in combination with oilcompatible seals at the bottom end of the cilinderwalls.
a good anticorrosion additive in the coolant may prevent the forming of cavitation holes or at least retard it, but basically it is a design problem that the engine builder did not fully solve.
the international tractors mentioned where a nice demonstration of that: the engines in the tractors used simple cast iron cilinders that showed cavitation occasionally that to a certain extend was solved with the extra "filter", the same engines mounted in shovels used cast iron cilinders that where chromed at the outside and had no problems at all...
to prevent cavitation the best you can do is thus use a coolant that has excellent anticorrosion capability for cast iron.
the formulation that is best for cast iron is usually not as good with other materials, especially aluminium.
most us manufactured coolants are geared towards protection of cast iron liners and work not as good with aluminium. that usually is no problem, since us made equipment usually is somewhat "beefier" then european equipment.
the european situation is different. cavitation with cast iron liners is no problem anymore, but aluminium, solder, and copper are a problem, since material thickness usually is quite thin. that has led to quite different formulations, that cater for those specific material combinations. another problem is the waterquality that may vary enormously, and therefore usually "complete" coolants are used: antifreeze, water and anticorrosion additves in one package. therefore it is advisable to use the prescribed type of coolant in those cases, since the standard us type coolant or the prolonged use variety may not necessary give full protection.
RE: coolant formulation tech questions
Any word on the different formulations and how they affect the different metals so I know which ones to choose in the future? Edumacate me :)
RE: coolant formulation tech questions
RE: coolant formulation tech questions
RE: coolant formulation tech questions
RE: coolant formulation tech questions
RE: coolant formulation tech questions
Jim Allen
Keeping the Good Old Days of Four-Wheeling Alive