Om651

[Liam7755]

Hey group! I’m a newbie to this forum and a newbie to merc engines in general .. have owned a couple but not many. My latest purchase was a jeep patriot (yes it’s strictly not a Mercedes but it still runs the Mercedes om651 engine)

Couple of questions I have as I don’t really know these engines .. do they suffer any serious problems in large quantities? I’ve heard of the odd timing chain tensioner issue but Is there anything else major with them? Bottom end defects or heads cracking .. bad head gaskets etc etc .. them kind of things?

 

[mersum1es]

Yes, main bearings, oil pump pressure control, chain tensioner, fuel filter housing, crank case breather... all true but how common... difficult say. Not more than competitors I would say.

 

[Liam7755]

Yes, main bearings, oil pump pressure control, chain tensioner, fuel filter housing, crank case breather... all true but how common... difficult say. Not more than competitors I would say.

Ahh really? I’ve never come across that one! Main bearings .. fuel filter housing and crank case breather yes I’ve been told to keep on top of those but did not think main bearing was a weak point on this engine at all! Factory defect?

 

[mersum1es]

Bearing failure is probably due to mentioned lubrication pressure control valve issue, which cause bearing immediately starting to wear and then possibly slip...

 

[91dm]

We have a OM651 with nearly 200k miles, no major engine issue so far. Just normal servicing with good oil etc.

 

[Liam7755]

We have a OM651 with nearly 200k miles, no major engine issue so far. Just normal servicing with good oil etc.1

Mine is on 146k miles .. but its unusual because my engine is transverse not longitude as its in my jeep patriot. So my timing chain set up is actually to the gearbox not at the back. I'm tying not to let the usual internet horror stories put me off it, as its a lovely motor.

 

[JHS]

I have a 2017 on 75k miles with no issues so far. Some say that OM651 is a boat anchor but that is b0llocks.

 

[Tonygw]

The OM651 is a very good engine if... its well maintained and looked after.

Regular oil changes and decent fuel will see very high mileages. My Local specialist services a C class with 400K miles on it..

Like anything, you neglect it and it will break.

There are thousands that run into high mileages without issue. The three main issues.. Timing chains can wear, not the end of the world and not a huge job to replace. Excessive use of the Mercedes stop start system is usually blamed for this. Water pumps usually fail around 100K and the fuel filter housing can leak coolant as it has a coolant pipe attached to the head running through it.


Really not much else.. Enjoy, there are far far worse engines out there..

 

[GeorgeR]

Timing chain.
I have just learned that there is a tool to check the wear of the chain>
Chain tester 651589116300

Do you know any workshop that has that kind of tool and checks the chain before replacing in the Surrey / Berks / Bucks region?

 

[Smiley]

The OM651 is a very good engine if... its well maintained and looked after.

Regular oil changes and decent fuel will see very high mileages. My Local specialist services a C class with 400K miles on it..

Like anything, you neglect it and it will break.

There are thousands that run into high mileages without issue. The three main issues.. Timing chains can wear, not the end of the world and not a huge job to replace. Excessive use of the Mercedes stop start system is usually blamed for this. Water pumps usually fail around 100K and the fuel filter housing can leak coolant as it has a coolant pipe attached to the head running through it.


Really not much else.. Enjoy, there are far far worse engines out there..

I would agree. There are some that go for ever; yet there are plenty of serious problems with seized engines and chain problems. With the om 646/7/8 engines they would survive a bit of neglect and not let go - not so with the 651. So if you're buying one buy a good one and then change the oil and filter regularly.