603.691 versus 603.960
 

Does anyone know if the 603.960 engine in the 300D is interchangable with 603.961 in the 300SDL? As it appears I'm facing the typical headgasket/head replacement in my '86 300SDL, I'm wondering if I can locate a good used engine for similar money?

Thanks,

David Jonas

'86 300SDL 139k mi.
'84 300TD 240k mi.

A good used engine will be more than the head job, if you can even find one. Last time I checked with European Connection he didn't have one that was good, all had something serious wrong with them.

I don't know about interchangeability, but I would assume it would fit, don't know of any serious differences.

Peter

I saw that Adsit will rebuild the head on this car for $520. New springs/valves are extra.

Potomac has a 603 engine for $1800 I think. It had 224k on it though. I would just rebuild the one you have, which is what I'm going to do with the one that I have.

And the hole in the block?

The message I sent you with the ad for a 300SDL bounced back so I guess you didn't get it. The ad's gone and I didn't save a copy of it.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Sometimes, if you look off the "beaten path" you can find a wreck with good running gear for cheap money.

Dave Jonas

'86 300SDL
'84 300TD

Trust me, you aren't going to find a complete running condition 603.xxxx for what it costs to have a head gasket replaced! Rebuild of a decent condition engine is $5000 for parts alone, 50 hrs labor, I checked.

Good condition 603 probably would be in the vicinity of $3000. Blown one in rebuildable condition, $1500. They are fairly uncommon, and usually driven to death.

Peter

Peter,

I'm going to rebuild the head and get a replacement block. I've found one for $280, but I don't know if I should grab it. Is that a good price? Maybe it's irrelevant if I can't find another. I can only use blocks from 86-87 OM603's. My choices are very limited.

Grab it!

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

For $280, if it doesn't have a hole in it, and no cracks, grab it!

Sleeves are $35 apiece or so, so if the pistons are OK (don't remember the whole story) you can save the $2500 you will spend on new ones (ouch!).

Bearings, etc are similar to other Benz engines. Rods aren't cheap, but you want the latest ones.

Peter

Michael,

If you go rod shopping, let us know if the .96x rods have been updated like the .97x rods. Maybe gsxr has looked into this.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

I haven't taken the head off yet, so I don't know where that 6th piston is at. Still in the hole I hope. I knew I needed to replace the one rod, but was thinking that I should replace all of them. (and not very happy about it either)

The car is stored at my moms farm and I don't expect to get up to it for a few weeks. I'm heading out to Oshkosh this weekend and I think we're going across the state next weekend.

I had the trans rebuilt last month in Cummins, GA. It looks pretty sweet now, all wrapped in plastic. The engine is so covered in oil and grime, I'd just like to dip the whole darned thing in a big tank of Gunk. This rebuild is going to be extended over a long period of time...

Dave, forget swapping engines and just replace the head. A good used engine will cost you $2-$4k with shipping and then there's no guarantee on the labor if it's a lemon! You want either a new head, OR a used head from a 1990-95 3.5L OM603.97x, since the later heads are stronger and won't crack like the early 3.0L (1986/87) heads. Used 3.5L heads can be found under $1000, and the cheapest source I know of for a new head is www.speed-autoteile.com in Germany, about $1500 total including crappy exchange rates and shipping to the USA. Cheapest source in the USA will be ~$1750+. Dealer wants over $2k. That's a BARE head (with guides) that you swap you valves, etc into. NOBODY sells rebuilt OM60x heads. When they fail, they crack, and are impossible to repair without expensive welding procedures (and VERY few shops are capable of performing this properly).

The only way you'll find a good OM60x head under $500 will be if it is one of the early, crack-prone 1986/87 heads. This is a big enough job that I would NOT put one on my car since you may be pulling the head off a second time! IMO, there are two types of early heads: those that have cracked, and those that will shortly. You can tell from the casting number above the #2 injector, will be something like 603-xxx-yy-zz. If "yy" is 15 or lower, it's the old/weak head. If "yy" is 17 or higher, it's the new, stronger head. My car got a new head in 2002 and it's number "yy" is 22. Here's photos of the head swap:



Good luck,

Thanks to all the senior members for taking the time to reply. As you are all in agreement on the subject, I guess I'll be replacing a head rather than an engine.

Dave M., the "yy" numbers on my head are 14 which confirms my impression the the head is original. I thought I was being smart by purchasing an '86 instead of an '87 but I neglected to take into account that the car came from California where trap oxiders were installed on the '86s.

What started my thinking on an engine swap was the '87 300E on Ebay with 75k ona rebuilt engine. I thought, hmmm.... a good engine and spare parts as a bonus. What's with the yellow valve cover and IP on thids car?


Dave Jonas

'86 300SDL 139K mi.
'84 300TD 240K mi.

New rods come only as sets -- the new ones are heavier so you will need all six.....

Peter

Do you mean that when I saw a price for rod a while back for $175, it would have been for a set? In that case, it isn't so bad.

What is the part number for the con rods that I want?