Cavitation - PeachParts Mercedes-Benz Forum

dieselmania · #1 08-20-2004, 12:22 AM

Does anyone know if cavitation of the coolant is a problem with Mercedes diesels, particularly the 603? I know it has caused problems for Powerstroke owners, I am curious about the Mercedes. Maybe the Mercedes coolant has Supplementary Coolant Additives?

BoostnBenz · #2 08-20-2004, 01:23 AM

I don't remember exactly what off hand makes the PowerStroke worse but it seems like it has something to do with liners inside the head. It needs SCAs to reduce cavitation wear. I know cavitation is caused by a pressure difference in a fluid, an air buble forms then implodes. Yes cavitation can be a problem in any vehicle but as long as a respectable coolant is used I don't think it is a problem in the Mercedes at least. If you go to a waterless coolant, ie one that has a very high boil temperature this should no longer be a concern. Those have had my interest for a little while, maybe someday I'll swap mine to waterless.

dieseldiehard · #3 08-20-2004, 01:16 PM

Ford has had cavitation problems, my brother researched the subject once and I was amazed at the number of failures that were discussed on another group. Ford refused warranty if people failed to show receipts for factory maintenance, particularly the use of some special Ford coolant additive that is necessary to prevent cavitation.
I haven't heard of cavitation problems in MB automotive diesels, I believe the liners are much different than the Ford and the large commercial diesel truck engines. Here is some info on diesel cavitation: http://www.penray.com/coolingtechfacts/cavitation.htm

OTOH, corrosion can be a problem in MB engines especially the aluminum heads, when coolant breaks down over time. That is why the local dealership had a stack of heads removed from customer car, like cord wood. My friend's brother is a mechanic there and told me about it, they hid it because it got so large it was embarrassing and I wonder how many were #14 serial heads off OM603 engines? (knock on wood, my '87 300DT has the original #14 still strong at 257K miles!)
I believe many also were from gas engines because people stopped having factory maintenance done at specified intervals, you know after 50K miles or something, or use aftermarket anti-freeze that isn't specified.
DDH

BoostnBenz · #4 08-20-2004, 01:28 PM

Pherds are pretty stringent on their SCA levels. It seems like the Cummins just prefers low silicate, nothing special. I don't think the MB diesels really require anything special either. However when I was doing my timing chain I became a strong believer in using a flush additive prior to adding the new coolant. It was nasty inside the head, the hoses had crud in them and what not. I put the flush in with clean water and out came this appauling, nasty fluid. A month or two later I looked inside the head's coolant passageway again and it looked like new.

Since you brought up gas engines and lack of maintenance that reminds me how the big three are all trying to get 100k miles or more out of their coolant. What they don't tell you, at least for GM dextron, is that by time it hits 80k it starts coating everything with gunk. If you push it to 120k you may need a new radiator, heater core, ... I guess that was a real common problem on the Jimmys and S10s, they needed a whole new coolant system.

bullwinkle · #5 08-20-2004, 05:31 PM

Powerstroke problems are due to the steel cylinder liners (pre 1997 I believe)-Cummins engines (at least the smaller ones like my 6BT ISB) are "parent bore" engines with no liners-are the benzes the same way? I can't imagine getting a million miles out of a diesel with liners!

dieseldiehard · #6 08-20-2004, 06:09 PM

MB's uses sleeves, I suppose they are similar to the liners you speak of, but yes they do last about 300K miles before they are typically getting oval shaped and the rings are worn such that oil loss is unacceptable (depending on the driver, as to how they put up with exhaust smoke).

psfred · #7 08-20-2004, 08:29 PM

Cavitation is caused by the flexing of the cylinder wall under the stress of direct injection and thin cylinders.

Benz engines have a LOT more beef to them, and the indirect injection produces considerably less instantaneous overpressure.

The ealier, smaller displacment block didn't have anywhere near as much problem, but cavitation corrosion (usually displays as a row of tiny holes in the casting, all nearly lined up) is a common problem on diesels.

Peter