Mercedes OM636 1959

[davpet]

Hi.
I just bought my first boat… it has this engine. Went for a little 15 minute trip today, and the cooling block(it’s green) is still hot after 5hours. Should I be concerned or is this standard? Thanks for any help!

Read more at: Mercedes marine diesel OM636 1959 - Tech corner - Forum - Mercedes Benz club

 

[38mess]

I think it's ok, my Perkins stays hot for hours after I get back.

 

[davpet]

Thanks for that, feeling better already!

 

[38mess]

Thanks for that, feeling better already!

That block is the heat exchanger, should be coolant visible when you take the cap off. Might be worth checking it out and the oil while you are at it. Good engines those, last forever with regular service.

 

[davpet]

Thank you! I can see coolant when I remove the cap. Is that sufficient or is there a measure I should be using?
Oil is checked and at a good level.
Thanks again much appreciated!
Pd

 

[38mess]

Thank you! I can see coolant when I remove the cap. Is that sufficient or is there a measure I should be using?
Oil is checked and at a good level.
Thanks again much appreciated!
Pd

Yes as long as you can put your finger in when cold of course and feel wet. it's also an expansion chamber so don't overfill otherwise it will just gush out of the overflow when hot.
On my Perkins I can see the level mark inside the heat exchanger.

 

[davpet]

That’s super helpful thank you!
Pd

 

[Boater Sam]

After a bad experience with a Merc OM636 years ago, I would advise AGAINT putting any oil additives in, like Molyslip and STP.
We sold a boat that was fine engine wise, the owner put additive in and the engine deteriorated rapidly. We suspect it either blocked something or released sludge form the sump.

 

[davpet]

After a bad experience with a Merc OM636 years ago, I would advise AGAINT putting any oil additives in, like Molyslip and STP.
We sold a boat that was fine engine wise, the owner put additive in and the engine deteriorated rapidly. We suspect it either blocked something or released sludge form the sump.

Thanks for this, great to be able to learn from your experience. When you say additives do you mean to the fuel or the oil? Please excuse my ignorance!
Thanks
Pd