MTU 4000 thermostats fail position

Not sure, but a dirty bottom/running gear will increase load at the same rpm point and increase oil temps as well.

You folks are levels way over me, but If the coolant is running at normal levels, why would high oil temps indicate a thermostat problem. Particularly since its both engines - simultaneous failure are rare? The fluid that's being effected is the oil. I would go back to the coolers. We are assuming the oil coolers were serviced and reinstalled properly. Is there sufficient incoming water, is it exiting, impellar pieces, zing slugs, low oil level, dirty filters? If it is effecting both engines, is the problem non mechanical as Capt J suggests?

Pascal

Even if the oil coolers are using raw water, doesn't this fact pattern seem to eliminate the thermostats? It's reported that only the oil temps are elevated. The compounding fact is that the elevated temps are occurring in both engines - coincidental failures?

So that's great that they hit the solution dead on. Did they explain why that solution works, and why extra heat was evident in both engines? I always like to learn.

Capt

What makes you say it's closed coolant system rather than raw seawater - that the thermostats were changed and oil temp dropped? Maybe, but I'd like to confirm that is true. This is screwy set of facts, to me. I don't think we have all the info. Recall that the claim is that both sides had the same symptoms. That means that several thermostats failed at the same time? (How many does each engine have? My Mans have 2 or 3 a piece) I'm a skeptic of the fact pattern - something is missing for me. Both engines is the trouble fact. One engine, I go away.

They want to keep the clutches at a higher temperature to keep moisture out of them.

The new C12.9's, the aftercoolers have their own thermostat, this is to meet emissions.

Do the clutches use the same oil reservoir as the engines - it was engine oil temp that was elevated on both sides not gear oil, yes? So how many thermostats does each engine have?? We are now in that theoretical discussion area where we have flown by the OP. His problem is solved....

It keeps out sources of the coolers leaking saltwater into things such as the oil cooler, or the oil cooler developing a leak and blowing it out the seawater. Only the heat exchanger cooled by sea water, and that's the only item. It keeps temperatures of everything more stable, versus dealing with raw water of varying temperatures and hotter to meet tier III emissions. If the oil is a constant temperature, less expansion/contraction of metals.

On Cat C12.9's the aftercoolers have their own thermostat. To keep them hotter and a certain temperature. They're fiat's what more do you want, retarded engineering.

on the 4000's I have no idea, I know very little about them.

On the C12.9 cats (1000hp), each motor has 2 thermostats and I had at least one of each fail on each motor in under 50 hours along with numerous other issues with those motors. A c18, THEY ARE NOT.