Timing Chain - PeachParts Mercedes-Benz Forum

777funk · #1 10-29-2007, 10:58 PM

So from everything I gather on this forum it seems useless to change a timing chain if the other parts touching the chain are not also changed. Is it something that can be done in an afternoon without too much chance of messing something up or should I just forget about the timing chain and hope my 300d makes it to 300k miles before it breaks?

I'm assuming if I do change the chain I should change also:
the cam sprocket
The tensioner
all guide rails for the chain

I've already updated the vacuum pump of course.

I guess I could just drive it till it breaks and when it does, consider it time to replace my #14 head. But... it's always easier to do Preventative Maintenence. That's why I ask if it's possible/worth doing. Any words of wisdom here?

pawoSD · #2 10-29-2007, 11:01 PM

A bad chain break can also destroy the connecting rods and pistons....so the entire engine can end up junk.....

Stevo · #3 10-30-2007, 12:44 AM

Have you checked for chain stretch? That would give you an indication of its condition.

Alberta Luthier · #4 10-30-2007, 12:52 AM

you need to do a search here and get a dial guage to do the valve adjustments and measure the chain stretch. that in itself is an easy DIY. then you know how streched your chain is and can search what you want to do from there.
when I was new to my 300CD I had planned on replacing my chain. After setting my valves and measuring the chain strech I realised that in my case the chain is almost like new:+)
Good luck

777funk · #5 10-30-2007, 09:01 AM

It seems like that's the fatal flaw of the Mercedes Diesel engine. I had a w116 style 300sd with over 300k on it and my compression measurements were STILL in the low 400psi range! Amazing! And it'd start with the GP's unplugged.

But it doesn't matter much when most people are realizing a broken chain before 350k-400k. Compression doesn't mean too much at that point! So... in order for the MB diesel to be worth anything more than a toyota (or VW) gasoline engine, I think there's got to be a solution to the timing chain problem. I have no complaints with 300 or 400k miles. I think that's amazing. BUT this is a much better engine I think than a toyota or honda gas. It's a bummer that the chain has given it the doom it usually has. Everything wears out I guess.

Maxbumpo · #6 10-30-2007, 09:20 AM

Quote:

Originally Posted by 777funk

It seems like that's the fatal flaw of the Mercedes Diesel engine.

Rubbish! Changing the chain and tensioner (and cam sprocket when required) is not difficult at all and can easily be done by a good DIYer in a few hours. Measuring chain wear (aka stretch) is easy; although measuring valve lift is far more accurate, simply lining up the marks on cam tower and gear and then reading the harmonic balancer pointer position is more than close enough. Replacing the chain guides is more involved but usually is not necessary before 500k miles.

#7 10-30-2007, 09:32 AM

I personally would prefer a gear train and pushrods than an OHC chain.

Still, at least MB refuses to use a timing belt on their diesels!

75Sv1 · #8 10-30-2007, 10:33 AM

I did as the PDF Max attached says to do. I had about 10 degrees of chain streach. I replaced the timing chain and the guides and the tensioner. My OD shows 250K, the PO said it probably has 300K. The bottom two guides are hard to get to. I took out the vacum pump to get to them. Actually one of the replacement ones didn't fit, so I used the old one. The tensioner guide was the only one with wear on it. About 1/16 inch deap. I had to remove the cam sprocket and place the chain on the right side of the engine to get it out. The top one is easy. I used new locator pins. The pin for the tensioner was worn a bit. The sprocket didn't look worn.
As far as gas motors, their timing chains streach and need replaced. I have a '75 Brickling with a Ford 351W. I had to replace the timing chain at 30K. They used nylon teeth on the sprocket and it wore. I have heard a lot of problems with 70's car that had 'plastic' timing gears. The emmisions stuff made the engine run hotter, so the plastic didn't stand up.
I have replace the timing chain in my Jeep Comanches 4.0L. I can't say it needed or not.
I've had two timing belts break on me. Fortunately, they were no interferece motors. Or at least I got lucky on my '96 Ford Contour 2.0L. I only had about 45K on that belt. It should have lasted 60K. I ran 126K on the factory belt.
Tom

777funk · #9 10-30-2007, 10:38 AM

Quote:

Originally Posted by ForcedInduction

Still, at least MB refuses to use a timing belt on their diesels!

NO joke! That and IP's failing frequently at 100-150k is the main reason I'd not buy a TDI anything.

pawoSD · #10 10-30-2007, 10:44 AM

MB originally used a gear driven system on their diesels, and I think they still do on their large semi engines.

The Volkswagen V10 tdi has an entirely gear driven system, no chains at all.

#11 10-30-2007, 10:51 AM

Quote:

Originally Posted by pawoSD

The Volkswagen V10 tdi has an entirely gear driven system, no chains at all.

I'll take one of these please.

777funk · #12 10-30-2007, 10:59 AM

Quote:

Originally Posted by pawoSD

MB originally used a gear driven system on their diesels, and I think they still do on their large semi engines.

Which MB diesels???

777funk · #13 10-30-2007, 10:59 AM

Quote:

Originally Posted by pawoSD

MB originally used a gear driven system on their diesels, and I think they still do on their large semi engines.

Which old MB diesels???

#14 10-30-2007, 11:10 AM

Quote:

Originally Posted by 777funk

Which old MB diesels???

The OM636/621 in the 1953-1962 180D.

Stevo · #15 10-30-2007, 11:16 AM

A neighbor and I rebuilt his three cylinder, diesel excavator engine in my shop, timing was easy, the body of the IP is part of the block casting and the little pistons and crank (in the IP

) just lift right out. What a sweet little engine, Izusu as I remember. It was a fairly low millage engine that had got "dusted", which I found out meant, "operated with no air filter (backet broke off) in a dusty environment". #2 piston could be "wobbled" in the cylinder.
It was interesting to compare the 616, which of course is the better engine