Regular diesel and turbo diesel cranks are very different.

The turbo diesel crank shafts are nitride hardened.

Where can I get one for $100? The dealer sells a crank for 3k, and most junk yards sell them for 1k, I would rather buy a running car and part it out.

If anyone has a line on a turbo diesel crank for 200 dollars, Id like to get it.

Id prefer not to grind on the crank for the fear of loss of oil pressure. I have heard that even with the correct new rod bearings to match the ground down crank, they loose oil pressure.

Supposedly, there are a few places in the US that can regrind and re nitride harden mercedes cranks. Anyone know?

Thanks,

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

YOU are aware of REPAIR SIZE BEARINGS ? ? ?

Must be a new invention...

Oh, I most certainly am. I have heard from some mercedes mechanics, that every time they had a crank ground down, and they used undersized rod bearings with correct tollerances, and they still had low oil pressure.

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

RE-BUILT Diesel engines that I've purchased from a re-builder here in So. Calif. have crankshafts machined to 1st repair size .25mm (.010") on the Mains and Journals that maintain a PROPER OIL CLEARANCE of .050-.075mm. (.002-.003") with NEVER an OIL PRESSURE problem . . . EVER ! ! !

ps: and I know his Crank Grinder PERSONALLY . . . so I know with NO DOUBT ! ! !

I just purchased a 300Sd motor off of ebay for $550.00, turned out to have a bad piston, I'll sell the crank in a heatbeat.

__________________
Jerry LaBant
1982 300 SD
1959 MGA Roadster
1985 380SE
1991 Volvo 740 Turbo Wagon
2003 Mini Cooper "S"
1973 Triumph "Stag"
1998 Chev Surburban
1985 Volvo 240DL Wagon

Omegabenz, with regards to your statement:

" I have heard from some mercedes mechanics, that every time they had a crank ground down, and they used undersized rod bearings with correct tollerances, and they still had low oil pressure."

Since millions of other engines have had this process done when they needed the crank journals trued... that is.. taking them down to the next size bearings available... and functioned with no problems afterwards....

What do you think/suggest/ suspect is different about the Mercedes cranks these mechanics who relayed that information to you dealt with which would cause oil pressure problems even when they followed normal mechanical procedures ?

wow! this is almost as much fun as the oil arguments!!!

__________________
rayroyw
_______
'85 380SE (238,300) my "new" old car!
'84 300D (303,000+)
'72 250/8 (mercy heaven)

Roy, wasn't there a song that said " let me entertain you " ? That is our goal... LOL

I am not looking for entertainment, but if that is what it comes to, thats ok.

I just want some first hand advice about turning cranks, and who can do them and reharden them to factory specs.

Is it good to do a rebuild yourself or just buy one from a place that does mercedes engines all the time?

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

Omegabenz,
I do not have any 'first' hand experience with regrinding and hardening cranks...
I do know a guy that spent a couple of years grinding cranks, including Mercedes. However, he is a little crazy and I am not going to have anything else to do with him.
You did not address the question I asked in the post above...
Since those mechanics stated their experience concerning the cranks and low oil pressure... Did you ask them the reason for that ?
Or is it implied that it is the removal of the nitrided surface which wears out (fast?) and causes the excess clearance and thus loss of oil pressure ?
Does that mean that when the engine is put back together the oil pressure is ok for a certain amount of use ?
What I do believe on grinding cranks is that you want someone who does it all the time... and has a good reputation.
Most fine grinding on hardened metals is done under coolant. Therefore I doubt that the crank needs to be rehardened. If the surface needs to be nitrided or peened that is a different question. There is a lot of difference between affecting the overall strength of the crank and just dealing with the crank journal surface.
Why don't you ask those mechanics more questions about their experience.... for instance, was this one regrinder they were dealing with ?

It is possible that the mechanics had the engine cranks ground locally. And they cut to the low side of the tollerances instead of the high side.

Metric motors grinds to exact mercedes specs. I talked to a guy there and they have been regrinding cranks forever and they dont have problems, they even offer warantees.

I suppose it would be ok to grind it to mercedes specs, then reharden it to mercedes specs, then use the correct bearings.

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

I think that is a very real possibility... the overwhelming number of times this has been done and turned out fine would sure make me look at the place or procedures which those mechanics experienced, rather than the metal in the MB cranks...
Crank grinding is regularly held to less than one half of one thousandth.... .0005 ..... I don't know how .. but they do...

You would only need to reharden the crank surfaces if they were worn to the point where reestablishing a good surface would have removed the hardened case. In that situation, the crank would not be able to be brought into specifications for dimensions if all you did was remove material.

I believe the process would be to assess the damage, and if the final dimensions were going to fall out of a known acceptable tolerance, you would machine a little more material off and re-nitride, and then go into a controlled machining/grinding operation sequence.

Nitriding swells the surface material, and you have to remove the extreme outer surface, called the "white layer" as it is overly rich in Nitrogen/nitrides and becomes very brittle. Below this layer is the stuff you want. Successfully restoring the final surfaces is a tricky process, as you have to know a lot about the characteristics of the materials and processes.

For example, you need to know exactly how much the surface is going to swell, and how much white layer you will have to remove. As a result, once a process is proven, it is often followed regardless of the detailed condition assessment of the individual crank. You put it into the process and it gets converted in step one to a known configuration, both in terms of dimensions and surface chemistry/hardness. Then you do the exact same thing to every one of the same crank designs, and you should get repeatable, "warranty-able" results.

So, fixing one of these would consist of an inspection, assessment of whether or not it was good enough to just be re-ground, or required more intensive work. The process would not be to invent a custom solution for each crank, but a known process of either grinding journals in a known set-up with known tooling, or, a fixed, but more involved approach of making damaged areas equal to some common, starting condition, and then moving on through more, known, controlled steps of nitriding, heat treating, machining and grinding.

Grinding would always be one of the last steps as nearly all the other steps involve heating and cooling, which are known for changing dimensions, or the potential to change dimensions. These operations involving heat are without any specific dimensional controls that would come close to achieving the necessary tolerances. As a repeatable process this all gets worked out, but on a one time basis, I think it is significantly less likely to be successful. Like leathermang said, go to a guy who does it for a living. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

MB cranks have at least two repair stages. That means, unless really chewed up, they can be ground undersized TWICE before they are shot.

If the engine locked up at low speed, inspect the crank -- if you can polish off the bearing material, and it is still within the size limits for journal diameter and taper, shows no signs of overheating (blue spots), and isn't scratched, put new standard bearings in, reassemble, and drive off.

Since a rod broke, I'd expect some crank damage, so you will need to have a GOOD shop grind to the next METRIC size (DO NOT USE A SHOP THAT DOESN"T HAVE METRIC TOOLS!!!!!!). Have it polished (we use a racing/pulling tractor shop, they do a fantastic job, and on size, too!).

MEASURE the crank when you get it back -- use metric mics, please, don't try to "extrapolate" SAE units, you won't get close enough. Take it back if not perfect, as the bearings won't fit. Scrub all the passages out with soap and water until the scrub brush comes out clean -- no shop EVER gets the cranks clean enough, ditto for cyinder bores and oil passages on blocks.....

Get the correct undersize bearings for the size the crank was ground to. Set up and measure EACH bearing with plastigage -- fight with the guy at the parts store until he sells you the 1-3/1000 inch stuff (green, I think) as you want about 1-1.5/1000 inch clearance. This is tighter than factory, but if you use a GOOD shop, the crank will be straight enough. Ditto on the rod journals, aim for small rather than large within the clearance.

Wether or not you do liners or a bore and hone with oversized pistons is up to you, but if you re-use the old pistons, put new rings on even if you don't touch the cylinders.

These are a failry easy rebuild, although the parts aren't exactly cheap. DO NOT use orange silicone sealant!!!!! Black RTV on the upper pan to block surface, Permatex on the slide rail bolt-pins, and NOTHING on the oil filter to block gasket, its already sticky, a VERY small amount of aircraft (red) permatex, but that nasty orange stuff ruined my brothers 300D -- a glob from the oil filter housing broke off and plugged the oil passage to #2 main......

A new turbo crank is $3K, an used one at least $750....

Finally, verify that none of the bearings spun in the block while welded to the crank-- usually ruins the block, and there is no reason to try to fix THAT!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!