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#1
10-11-2006, 11:25 PM
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3.5 bent rod?
I pulled the head of the SD. Pics show findings -
First pic is cylinder 1 cross hatch. Looks good but there's a band below the ridge with little to no hatch. Is this the result of a bent rod? Second pic is cylinder 2 cross hatch. The hatch is clear to the ridge. Third pic is the crown of cylinder 1 at TDC. More carbon than the others. What's the white ash? WVO? Fourth pic is the crown of cylinder 6 at TDC. Fifth pic is the valves of cylinders 1 (right) and 2. The other cylinders look like cylinder 2. What's with the crud on the exhaust valve of cylinder 1? More to follow... Sixto 93 300SD 
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#2
10-11-2006, 11:33 PM
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but there's also a leak
There's a bunch of goop outside cylinder 1 exhaust runner. I thought it was from the runner itself but it looks to be leaking from the block/head surface.
First pic is a general view of the leak. Curious that it creeps up the head. Second pic is a closer view of the head surface. Is there an oil journal in the area. Third pic is a view of a dry exhaust runner. Or is it? Fourth pic is a view of the block surface. Is it leaking from a journal or the cylinder? Kind of a lot of oil to be blowing from the cylinder. Sixto 93 300SD
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#3
10-11-2006, 11:35 PM
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Then finally the gasket.
First pic is the top/head surface of the gasket. Second pic is the bottom/block surface of the gasket. Doesn't look like it's leaking from the oil galley between cylinder 1 and the timing chain cavity. Sixto 93 300SD
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#4
10-11-2006, 11:44 PM
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Then the indication of a bent rod -
I eyeballed protrusion between pistons 1 and 2. On the intake side there's about the same amount of protrusion. On the exhaust side piston 2 has about as much protrusion as on the intake side whereas piston 1 is about flush with the deck. That suggests that piston 1 is rolled about the wrist pin axis. But the piston is free to roll. Why would it assume the stance because the rod is bent like a letter C? I'm kicking myself for not doing a compression test before pulling the head. Sixto 93 300SD
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#5
10-12-2006, 01:21 AM
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Interesting, great pictures. Looks like that cylinder was pushing oil out past the gasket.
A compression test after it's all good again might be interesting to know.
__________________
1982 MBZ 300SD Turbo Diesel- just turned 200,000- just breaking her in 
Last edited by rocketman93116; 10-12-2006 at 01:34 AM.
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#6
10-12-2006, 08:12 AM
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Piston protrusion is the only real way to measure for a bent rod..
__________________
MERCEDES Benz Master Guild Technician (6 TIMES) ASE Master Technician Mercedes Benz Star Technician (2 times) 44 years foreign automotive repair 27 Years M.B. Shop foreman (dealer) MB technical information Specialist (15 years) 190E 2.3 16V ITS SCCA race car (sold) 1986 190E 2.3 16V 2.5 (sold) Retired Moderator
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#7
10-12-2006, 08:50 AM
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Not too bad.....
Nicely blown head-gasget... Remove pre-chambers and valves machine head, check piston heights and if OK stick the lid back on, with correct thickness gasget.... Doubt if the rods are bent, the 'carbon deposits' above the ring-travel look to be the same on all pots in the pics... Rod bending would affect the piston travel in the bore and make for differing/no carbon at the top in places, say, at one side, where the other pots show carbon.... Use Dial Guage to test for the piston height on each pot, Measure at the same place on each piston, preferably in the centre. The X hatch on Nos 2 is only Just visible, not that much different to nos 1 May have leaky valve-seals on the pot burning some oil, but I have seen much worse... Hows your EGR? maybe a little leaky...Disable where possible... Head re-face, Valve-re-cut and grind, new valve seals, run engine, check cylinder leak/compressions away to go....
__________________
http://i190.photobucket.com/albums/z...0TDnoplate.jpg Alastair AKA H.C.II South Wales, U.K. based member W123, 1985 300TD Wagon, 256K, -Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.  W114, 1975 280E Custard Yellow, -Great above decks needs chassis welding--Really will do it this year....
Last edited by Alastair; 10-12-2006 at 09:00 AM.
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#8
10-12-2006, 03:12 PM
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Sounds to me like #1 is bent, not protruding correctly, and the cause of the lack of crosshatch. The white residue has to be something burning that doesn't belong there, either coolant or oil - but I'm not sure.
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#9
10-12-2006, 04:45 PM
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A big thanks to M.B.DOC for the protrusion check instructions (in the Tech forum).
I don't have a dial gauge but I have the 603.971 beside a 603.961 and the protrusion of the 603.961 leaves no doubt. Consequently it's clear that the #1 rod of the 603.971 is bent forward. Now to see if fitting a 603.961 block in a W140 is as straightforward as we figure. Dang! That's some sweet torque I'll be giving up Thanks, Sixto 93 300SD
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#10
10-12-2006, 07:17 PM
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Sixto,
I feel your pain buddy. I was considering doing what you are doing if I found the "right car", bought that W140 S350, that I wanted and see how Lucky, I would be.  Put a good rebuilt engine in it and go on from there. I wish I could give you a hand, maybe learn from the experience. I still haven't given up that dream, but I am unlikely to do it now. Good Luck, 
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#11
10-13-2006, 11:16 AM
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Sixto, so you have decided that you have a bent rod at #1?
And you based it on the amount of protrusion or the piston's crown above the block's deck? I have an open 603.961 and went to check the protrusion at TDC. I found that there is protrusion of about 1 mm, guessing, but there is protrusion at both #1 and #6, which makes me ask the question; would a bent rod at #1 make #6 protrusion be exactly as the protrusion at #1? Also, I was under the impression that a bent rod would cause the rod to LESSEN in length and become shorter, not elongate and cause the rod to stretch and cause the piston to protrude.
I'm in the process of making the decision that you are currently already in the middle of. Thanks for posting the pictures! Also, I was ecstatic to see that the head gasket was blown at #1 in your pictures, which could be the source of your problem, "IF" the protrusion of the piston at TDC doesn't indicate a bent rod and is just normal protrusion of the piston above the deck. I was thinking of just having the head valve job done and replacing the head gasket on my car. And if that didn't work, THEN I was going to work on the bottom of the car, next year and ponder putting in a 3.0 liter block, as you are pondering doing. Anyway, it would be great that all is wrong is that it needs a head gasket. BenzDiesel
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#12
10-13-2006, 12:52 PM
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Quote:
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#13
10-13-2006, 03:15 PM
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BenzD, not sure if I understand your comment. There is supposed to be ~0.8mm of protrusion. The bent rod in the 3.5 manifests as reduced protrusion.
The protrusion spec calls for a measurement of the piston crown above the deck at the very front and very back of the piston (along the pin axis). In the 3.0 block there is almost 1mm front and back. In the 3.5 block there is about 1mm in the back and no protrusion in front. That suggests that the rod is bent forward. I wish it was a half inch low so it's very obvious. As it is I'm still trying to internalize that a 0.7mm difference is significant I will make a better assessment of the block when it's out of the car. A proper measurement of the bore requires removal of the piston. If I can reuse the 3.5 block, you bet I will! Sixto 93 300SD
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#15
10-13-2006, 04:19 PM
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Quote:
 I am sure they are even more for the OM 603.971. Of course the two ultimate tests will be actually examining and measuring the rods and checking diameter and out of roundness on the cylinders.
__________________
Doug 1987 300TD x 3 2005 E320CDI
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