Timing chain + oil pump chains breaking - PeachParts Mercedes-Benz Forum

jbach36 · #1 07-20-2010, 10:17 AM

I read a post a while back, that a guy was cruising down the highway when his oil pump chain broke. Ouch. That's gotta hurt. How/when do they need to be checked? I reeeealy don't want that to happen to me.

Then today I saw a 1995 Mercedes 300d for sale, the guy said the timing chain broke, which ruined the engine. Ouch again. I thought the chain only had to be checked at 200k, and if/when it was bad, it'd simply be harder to start the car to let you know it's about time to change it, not break on you while you're driving.

What are your thoughts? Do you guys replace your chains to prevent such problems. Toasting your engine like this is pretty final. Might be good for me to replace these while all is well. What are your thoughts?

jeff 1991 300d 148k

vstech · #2 07-20-2010, 10:22 AM

I paid 200.00 for a 93 300D that broke a chain...
if you don't want yours to break, change your oil at proper intervals, and inspect the chain every 50K for stretch.

scottmcphee · #3 07-20-2010, 11:46 AM

Not only check it for stretch, but visually check it. Rotate the crank slowly and examine the whole length of the chain as it comes around on the camshaft sprocket.

I just took my valve cover off one day, was going to check stretch. Staring back in my face was a chain with a missing link segment. I posted on hear a while back about this.

The chain was not terribly stretched and original. If I hadn't seen the missing link, I would have put everything back together and thought nothing of it.

Needless to say... I towed the vehicle to the shop and had a new chain rolled on that day. They would not warranty the work unless it was a MB chain, which I had bought months earlier, on spec, for doing the chain "one day". Hologram intact on the box, so they took it and did the job. Mechanic figured it had been broken for about a month. Chain would have snapped in another month.

Other things you look at are the teeth on the cam sprocket, check every tooth. And check the face of the gear for side/side tracking error or chain slap rubbing itself the wrong way on the sprocket. My broken link produced a strange wear pattern on every other tooth so it got replaced too. Sadly, the sprocket on the IP and oil pump down below probably also show the same funny wear pattern, but I did not change them. I will if I go into those areas on some other related service.

funola · #4 07-20-2010, 12:01 PM

Did you retrieve the missing link in the sump?

Jeremy5848 · #5 07-20-2010, 12:41 PM

If the oil pump fails due to a broken chain or any other reason, you will have only a second to notice that the oil pressure gauge has dropped to zero and shut off the engine. One thing that might help is an alarm like the one in this link.

Jeremy

scottmcphee · #6 07-20-2010, 03:10 PM

A few shards of metal were found in the sump using a magnet, but not enough to add up to the missing piece. What was found was small. Some of it may have ended up in the filter, did not split that to find out.

Diesel911 · #7 07-20-2010, 03:34 PM

When the Drive Arm on the Vacuum Pump Fails the parts can drop into the Timing Chan or Gears and cause a Timing Chain Failure.

From what I have read on this forum I can remember one or 2 members had the Oil Pump Gear come loose and I believe one believe had the Oil Pump Shaft failed.
I believe they were all on 6 Cylinder Diesels.

The 617s with a Turbo seem to have their faliures caused by the Vacuum Pump; due to a Bearing Failure or secondary to the Timer Drive Shaft Bushings being worn.

The non-Turboed Engines have some issues with the Oil Pressure Valve in the Oil Pumps where the Valve or Valve Spring breaks. I guess they can also suffer from a Vacuum Pump Failure and the parts falling into the Timing Gears/Chain.

compress ignite · #8 07-20-2010, 04:16 PM

Scott has the program,for the Timing Chain.[AND every 50K is not Paranoid]

'Same should apply to your Oil Pump Chain System.
(Howeveah,as we all know access to the Oil Pump Sprockets and Chain are
usually [If EVER] a once in a lifetime chance.)

There seem to be multiple scenarios, BESIDES Debris/Swarf from deceased Vacuum Pumps, causing Oil Pump Chain Drive System Failures.
1.Oil Pump Driven Sprocket Bolt "Backs Out" of the Oil Pump Shaft.
2.Oil Pump Driven Sprocket Bolt Breaks OFF.
3.Failures of the Chain Tensioner.

If the opportunity arises to Loctite the Oil Pump Oil Pressure Relief BOLT,Take It! A 606 owner found his hanging by a thread.

funola · #9 07-20-2010, 04:32 PM

Now you are making me worried (again) about eventual failure of my vacuum pump. At near 300K now and afaik the original vac pump. I am going to try out a 12V vac pump and a small resevoir tank that are common in RV's and see how well that works. If it works well, I'd like to eliminate the OEM vac pump. Has anyone done that? I'll have to get a spare Mercedes vac pump and disassemble it and see what's involved.

jbach36 · #10 07-20-2010, 04:32 PM

Oooooh. More work.

How hard is it to check the timing chain and oil pump chain? I'm not a mechanic, so I might even miss things as I check, since I don't know what I'm looking for.

Also, when checking the timing chain, is this a good time to try to get the timing perfect? My car is not as smooth at idle as it could be. I was once in a 1992 300d with 150k miles on it, and you'd never know the car had been started, it was THAT smooth.

jeff

funola · #11 07-20-2010, 04:34 PM

Quote:

Originally Posted by scottmcphee

A few shards of metal were found in the sump using a magnet, but not enough to add up to the missing piece. What was found was small. Some of it may have ended up in the filter, did not split that to find out.

If you have not found a complete missing link, then it went through the shredder and got chewed into tiny pieces? If that's true you should see telltale marks along the chain and gears wouldn't you?

jbach36 · #12 07-20-2010, 04:42 PM

Also, I heard the timing chain needs to be checked for stretch at 200k, and that mileage, not being nearly 20 years old, is the issue with chains.

My car has 148k on it now, maybe I should not check at this time? Sounds difficult to check, at least for me.

jeff

rkpatt · #13 07-21-2010, 03:23 PM

I am about to change the timing chain in my 1990 300D ( OM 602 ) wiht 250k miles. I want to chain the oil pump chain and all the sprockets as needed too . I posted this on another MB form and the replies weren't too encouraging about doing this with the engine in the car . Also , the vacuum pump is the "new" style but I have no idea when it was installed . I the electric pump idea sounds interesting to me too . Any advice is appreciated .

babymog · #14 07-21-2010, 07:59 PM

Quote:

Originally Posted by jbach36

<>today I saw a 1995 Mercedes 300d for sale, the guy said the timing chain broke, which ruined the engine.

Where? How much?

Diesel911 · #15 07-21-2010, 11:58 PM

Quote:

Originally Posted by funola

Now you are making me worried (again) about eventual failure of my vacuum pump. At near 300K now and afaik the original vac pump. I am going to try out a 12V vac pump and a small resevoir tank that are common in RV's and see how well that works. If it works well, I'd like to eliminate the OEM vac pump. Has anyone done that? I'll have to get a spare Mercedes vac pump and disassemble it and see what's involved.

If you want info on what Electric Vacuum Pumps to use look in the Electric Vehicle threads where they have converted a regular car to an Electric.

The most available one that does the Job (since it is made to operate to supply Vacuum for the Brake Booster) is the Comp Cam Vacuum pump that is sold by a lot of racing sites and eBay. The issue is that it cost as much as a stock Replacement Vacuum Pump and the Electric Vehicle sites say the pump us noisy.
The other new Vacuum pump alternataives mentioned at the Electric Vehicle sites are also expensive.

I bought a Thomas 12 Volt Vacuum Pump to try your idea but have never gotten around to it.

Anoter issue might be that the stock Alternator my not put out enough amps if all the electrical stuff in your car is runing.