Cavitation Damage? 3

[RodgerA]

Hi

I have tried to find an answer on automotive forums without success, so I thought I would try here. I hope this is appropriate.

The attached photos show an inlet/outlet pipe to the oil cooler on a Chrysler Voyager 2.8 CRD diesel engine (VM Motori engine).

The oil cooler is a sandwich type heat exchanger mounted underneath the spin on oil filter, there is an inlet and outlet from/to the cooling system. The cooler is in the circuit very close to the waterpump. The engine is standard and unmodified.

The damage looks like small areas of aluminium "scooped" out resulting is oval craters. The photo is of the inlet pipe but the outlet is similarly damaged. The coolant was clean, no sign of corrosion and has been changed as per the service schedule.

To me it looks like cavitation damage, but I would not have thought the pressures would be high enough in a diesel engine cooling system.


I would appreciate your thoughts.

 

[dgallup]

The picture is not large or clear enough for me to pass judgement. However, cavitation is not caused by high pressure but by low pressure allowing bubbles to form. It is the collapse of the bubbles that causes the damage.

Is the cooler on the discharge or suction side of the water pump?

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[EdStainless]

A higher resolution photo would help.
But I will offer a few comments. It could simply be turbulent flow erosion.
AL has poor erosion resistance. If there is a change in flow path direction or size then it could be erosion.
A restriction in flow that would result in a pressure drop is more likely to cause cavitation.
Cavitation in hot water is rather easy because it take a lot of pressure to suppress boiling.

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Plymouth Tube

 

[tbuelna]

RogerA-

Due to the resolution of the photo it is a bit difficult to make an accurate guess. It does look like it could be cavitation damage though. As dgallup & EdStainless pointed out cooling system cavitation commonly occurs in local zones of low pressure. Since there is cavitation damage in both the inlet and outlet pipes, one possibility may be a kink or blockage in the rubber hose connected to the coolant inlet.

The heat transfer within the liquid/liquid oil cooler core is quite efficient. And turbodiesel engines tend to reject quite a bit of heat to the lube oil, which means high oil temps at the cooler inlet. Restricted flow on the coolant side of the heat exchanger would result in a greater local temperature rise in the coolant, which would also increase the possibility of cavitation.

Good luck resolving your problem.
Terry

 

[mrfailure]

This really should be looked at in a metallurgical lab to identify the damage mode. Many times customers have sent in parts they thought had failed by cavitation, but that has never been the actual mechanism after examination.