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Cavitation
What is it and why should I care?
Cavitation, or cylinder liner pitting, is one of the most talked about articles on any diesel board.
About 99% of light truck diesel owners don't know what it is, but they are scared of it.
Cavitation is essentially, the erosion or pitting of the cylinder liner. Small vapor bubbles actually drill through the liner from the coolant into the combustion chamber. This causes rapid coolant loss, and oil/coolant mixing. This is by all means, not a good thing. Damage such as this requires either new sleeves pressed into the block, or engine block replacement. So let's back up the truck,(beep-beep) and look at what's happening.
Gas engines don't have this problem, right?
The big difference between gas and diesel engines is the fuel. Diesel requires a much higher compression to detonate(explode). This higher detonation means much higher pressures on the engine. That's what makes a diesel so loud. In all engines (gas or diesel),The piston hammers against the side of the cylinder wall while transferring up and down motion to the rotating crankshaft. In a diesel it has a much harder impact. Imagine hitting a bucket of water with a hammer. What this does is cause the cylinder wall to first move towards the coolant, and then away from it, at a very high frequency. This rapid movement causes very small vapor bubbles to form. These tiny bubbles (not the ones in your wine!) then implode or collapse as the wall comes back again. This creates very high pressures in very tiny areas. This is what causes small horizontal holes to form. These holes will eventually drill right thru into the combustion chamber. This will allow coolant into the oil when the engine is off, and oil into the coolant when running. This can happen in as little as 500 hours of operation when using just water as a coolant.
Several things can also contribute to this erosion. Such as a cooling system that can't hold pressure, air in the coolant, miss-routed hoses, or overheating.
But have no fear, SCAs are here.
SCA stands for Supplemental coolant additive. What SCAs do is to form a very hard microscopic film on the coolant side of the wall. Most SCAs do this by transforming the soft ferrous oxides (rust) on the liner into Fe3O5, a very hard substance. No I don't know what it is either. If there is any chemists out there, please inform me. This protective layer suffers from damaging bubbles too,but as long as the SCA concentration is high enough, it will heal itself.
This is the reason that all coolant leaks must be repaired. As you add more coolant to top off the radiator, you need more SCA too.
What can be done to prevent this you ask?
By following simple maintenance schedules this whole problem can be avoided. At the shop, we test truck's coolant at least every six months. If coolant is removed for any reason, it should be checked. This can be done with a simple coolant test kit. They contain paper dipsticks much like a home pregnancy kit.Fleetgaurd makes a very good one that tests SCA concentration, freezing point, and the level of corrosive elements.
Be sure to read the manufactures instructions with any SCA or test kit. they usually vary. Another option is to use Diesel specific coolant. These already have SCA in them.
So be sure to keep up on the coolant maintenance, and you should never have a problem with Cavatation.
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