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BMW M51 vs MB OM603/6


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Hi all,

Now, with a baby at home, I'm looking for a bigger daily drive. 3 door Corsa is simply too small...

I want a big estate with a good diesel engine, so I could in a future make an engine swap to the 88" and share engine and (automatic) gearbox with it.

Today I have phoned to the owner of a W124 MB300 (OM603) in mint condition for a good price. Unfortunatelly vehicle was already sold...

Looking now for more candidates...and the Opel/Vauxhall Omega Caravan is the other car that suits me.

Uses BMW M51 engine, as does the P38 rangie, making it easier to adapt to the 88 with a 4hp22 from rangie and lt230, and is much lighter than de 606, but it's slso less powerfull and not that reliable (head gasket).

Any experience with both this engines so I could make a pro/cons chart and make the decission?


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I've got a BMW 525tds which has this engine in it and I have to say it's pretty good. I've not heard of head gasket problems in the BMW or Omega's but the extra weight of a p38 may well push it to limits not seem on the car version.

Mine has done 168K miles and I've chipped mine and it's pretty good. It's a higher revving engine than the 200Tdi that I'm used to in my 110, but it seems to pull well at lower speeds regardless.

The only issues I'm aware of is timing chain chatter from worn tensioner and guides, the injector pump leaking (mine is doing this, and it's a recon pump I believe) but it's easy enough to change the pump gaskets without removing it from the car. There is a breather filter on the later version of the engine which clogs up, but mine hasn't got one of those.

I'd certainly be interested in knowing how it goes if you do fit one of these. I was thinking about the time when I have to scrap the BMW and I thought about keeping the engine and fitting it into my 110.

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IMO the M51 is a hopeless engine, with a timebomb of an injection pump. Wouldnt touch one with someone elses stick.

If your going BMW, get something with the M57.

My daily has an M57N2 and its really quite excellent.

If your looking for something cheap, an E39 530d Touring would fit the bill nicely.

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agree with Aragorn M57 much better buy , 530d or 330d good source pre 2002 easiest to run in other vehicle .

putting this engine with auto box or r380 and lt230 into an 88 might be a bit problematical due overall length of powertrain :(

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Thanks for your thoughts.

After some serearch ( mainly superturbodiesel.com) I have discovered that the M51 will do easily 170hp, 250 easy, 300 achievable and it's said that one was built in Finland with 400hp.

Electronic pump can be swapped for the mechsnical one from M21 engine, and there is even a OM603 pump conversion.

All in all, merc engine will do more HP with same effort and will be more reliable.

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  • 2 weeks later...

A high mileage but vvv good condition E39 530d Touring appeared a few miles from home. I could´t visit the owner, and a few days later, when I could, was sold.

Poor Corsa died one week ago, so I have bought the first car I have found that suits me.

My new daily driver is going to be an Opel Omega (not Caravan as I wanted). 1998, 150.000km, vvv condition and powered by M51 derived Opel X25TD engine.

Low end torque is not as low as expected, and it is super smoooooth to drive.

Car is at workshop (fitting a tow hitch) and I will take deliver of it next week.




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why are you looking to fit something like this to a series? Seems like a V8 into a 2CV sort of project. You'll replace the entire drive train, have to fit anti tramp bars on the rear axle, so lose articulation. It will handle like a back of spanners, so you'll need to run wider axles, longer wheel base etc etc

Maybe I'm missing something here

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:rofl: :rofl: :rofl:

Not that vapour! Opel engine is slightly detuned compared to the BMW units. 130HP is not that much. OK, is more than twice the power of the original engine, but same as a carb 3.5 V8. A "power box" second ECU will raise to 160HP, as EFI 3.5 V8.

V8 conversions have been made thousands of times over the years, some even using Rover 4spd boxes.

Another advantage of the Opel engine is that it´s half price of a similar RR or BMW unit. 300 Eur. is enough for a breaker sourced engine, and a six months warraty will be included.

Opel engine + P38 4HP22 is something that I see affordable for me, both in money and mechanical knowledge.

I have decided to take the 88" to the in-laws farm and ask a temporal "written-off" certificate. I will use it as a farm toy and will make the conversion slowly (5 years?). Once completed I will ask engineer´s report and make it road legal.

Wider axles and suspension upgrades, torque bars included, were already in the agenda :glare:

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Good suggestion Mike

I've driven a fair few series motors over the years. Most have had engine conversions - from a Chevy 350 to a 1.6 VW diesel turbo. I know form experience that a standard, second hand carb'd V8 can destroy the drive train on an 88 unless driven carefully. It's got sod all to do with the bhp - its the torque, and a 2.5 M51 in the 96kw/130bhp format puts out 184ft/lb at 2,200 rpm; not excessive but more than enough to simply destroy your drive train

The first lesson of a reliable 4x4 is make sure it has enough strength in the drive train to get you out of a difficult situation

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I would disagree. If you drive any Land Rover product with mechanical sympathy, recommended tyres and within the recommended load, you have to really badly maintain it to get it to fail, yet it will do the job it was designed to do for 10's of 10'000's of miles. The biggest killer of Land Rover's is the driver, either because he/she has no mechanical sympathy or because he/she modifies the vehicle without thought...

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After five days with the meggie I can only say good things about both the car and engine.

Engine roars like a happy cat at tickover. 130BHP and 1600kg (as a regular 88" quite more less) gives it better performance than expected. Spanish Opel forum also suggested Omega B2 (2.5 M57 based), but I really love M51. Enough power for me.

Parting with an old 88 makes things esasier for making it road legal. The older, the better. And I already have the 88 and no money for a 90.





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