1987 300SDL

You can email me direct at snipped-for-privacy@comcast.net

Why not rebuild that engine of yours? Any machine shop can do a good job resleeving it for you.

Rebuilding a 603 Mercedes diesel engine is a fine idea. However, there is a excellent chance that you will need to buy a new cylinder head for the engine. The old ones are usually cracked. Don't even think about resleeving a cylinder unless a sleeve has been damaged by corrosion from a cracked and leaking cylinder head.

The replacement cylinder sleeves on Mercedes diesels are prefinished in one dimension. That means that the only part of the replacement sleeve that is finished is the outside of the sleeve. The inside and the top of the sleeve are not finished. The existing sleeve which came with your block can be bored over and fitted with oversized pistons a couple of times before you need to think about replacing sleeves. That is unless you really want to pay a machinist the extra dollars to remove your old sleeves, install new sleeves, bore and hone them and surface the top of the block. The new sleeves are oversized on top too. And don't try resleeving your block and reusing your old pistons. That is a no no with any diesel.

Mmm... the piston thing you mentioned goes against that MB tech who I know worked on MB for over 35 years. Diesel engine piston are tough sucker... not like gas engine which can warp to oblong shape. He is a diesel engine specialist. Alot of his clients clocked in over 400,000 miles in their cars.

A set of new pistons for this engine is retailed $2700... and $1360 wholesale. I don't think any engine rebuilder replace the pistons... it would be too costly That's like 40% of the cost of rebuilt engine... they wouldn't be making that much money.

Why don't you talk to Metric out in California which only rebuilds Mercedes engines. They don't reuse pistons. My machinist who has 30 years of experience, warned me not to reuse the pistons in my 617 engine. So you're recommending reusing pistons in an engine with say 300,000+ miles already on them? I would say that's pretty foolish. The pistons used in Mercedes diesel engines are not forged pistons. They are heavy duty cast pistons and as such they can crack. For more on Mercedes diesel piston construction, go to the Mahle website.

By the way, there are many wholesale sources for Mahle pistons. I paid $80 per piston for the pistons in my 617 engine.

Only $80 per piston? Wow! At that price, I would change it. Where is your source?

No, I didn't say that the engine has 300,000 miles and then rebuild with same piston. All I am saying was not specific to 617 engine. From what I remember he said a long time ago... that the diesel pistons are super heavy duty that he didn't change it ... I believe the engine he was talking about were those of the 5 cylinders diesels of the early 80's.

MAHLE manufactures cast ring carrier pistons for passenger car diesel engines, made of high temperature aluminum alloys with or without cooling gallery.

Mahle said "Cast" and not much info on their website.

Thanks for the input...

Let's say I go for the full rebuild, including pistons, sleeves and whatever else...plus water pump which is leaking...how much should the job run me in the end and what's the chances of the lower end of the motor failing after all of the upper work is completed...oh and yes, she has 305K miles.

Here are the details surrounding this car..

The car had been running great with the exception that it had been running a bit hotter than usual since the beginning of the hot weather. (I had the thermostat changed and the antifreeze flushed last fall so that sort of surprised me). I was coming home one recent Sunday night and the car overheated - got very dangerously hot - The engine turned off on its own and all the antifreeze and half of the oil drained from the car. I had it towed home. I recently worked up enough nerve to look under the hood.

It seems the water pump is shot. Not the end of the world. I checked the oil and it was low but clean - no sign of antifreeze in the oil. There is a sensor up high on the left side of the block (by the fuel injector pump) that blew out. The wire and connector tip need repair and a new sensor. When the sensor blew it must have knocked out a spring on or near the fuel pump on the motor side...can't locate the spring but I have a second 300SDL as a reference point and can see how the spring connects to the linkage assembly... I filled the liquids and tried to start but she won't turn over.(I was conservative in my efforts to not risk further damage).The antifreeze immediately started leaking from the water pump. The transmission fluid looks and smells ok.

My questions: Would a faulty water pump cause the extreme temp problems I experienced? The 300SDL has a sensitive head - what's the chances that It's cooked, warped, etc? How can I check the status of the head and block without ripping it apart? The radiator looks new-how do these radiators respond to high temp shock treatment?

Concerns: I can't start the car. What's the chances that I put all of this work into it and it still won't start? Motor has 305K on it. When I got the car the coolant reservoir was cracked and had it replaced after unsuccessfully repairing it-a possible sign of previous overheating problems? I can manage the water pump install, sensor install, and replacing the thermostat and fluids but have little idea where to begin with the head job. If I go the rebuild route, I'd like to have some level of comfort that I can make the investment and the engine will be corrected without any "major" repairs necessary for a while.

As always, your help and advice is always greatly appreciated.

By the way, I posted to this group back on 5/11 with a Temperature rising message...I guess it's reasonable to assume that the temperature rising symptoms were due to a failing water pump. It took a good 2 months for the water pump to completely die. :{