timing chain, oil pump chain and tensioner question - 99 E300
 

Got a customer with a 99 E300 with 305k miles. The head has never been off of the car. I have recommended to him that over the next 50k miles or so we replace the timing chain and guides/tensioner slides, etc..... To do the job correctly, in my opinion, requires the head to come off. I recommended having a head shop go through the head at the same time. Obviously this is a pretty involved job. I hate to see him run it to failure and mentioned to him that it would eventually need a new head gasket during which time would be ideal to change the chains, guides and slides. Oil changes have always been with synthetic oil.

Any thoughts/comments regarding how far anyone has run one out till the oil pump chain tensioner failed? The car starts easily and runs out good.

I am interested in people's experience as to how far one of these can go (assuming regular maintenance and synthetic oil, of course) without needing to address timing chain or head gasket. I suspect that, when something bad happens on one of mine, the cost of repair will exceed the value of the car....perfect excuse to go buy a CDI.

I would recommend to leave everything alone except the timing chain if one is really concerned. To answer your questions.

1) head does NOT need to come off to change the oil pump or timing chain,
2) Engine face plate + head need to come off for tensioner guide or slide.
3) Anything would fail eventually..., including head gasket. The issue is when?

If the customer is concerned and has a deep pocket then change everything.

Preventive overhaul
 

What is the overall condition of the car? If the owner has kept everything in good repair during those 305,000 miles and intends to keep the car "forever," then it might be worth dumping a couple thousand dollars into the engine. Are there any symptoms? External leaks, burning oil, bits of chain guide in the oil change?

As another data point, my '96 E300D has 298,000 miles and neither leaks nor burns any oil (by which I mean none needs to be added between annual 5000 mile oil changes). I measured the timing chain stretch at 275,000 miles and it was 1 degree. Everything on the engine is original and everything in the car works. I'm interested in what you and your customer decide to do. Please keep us informed.

Jeremy

When I opened up my silver 95 E300 the oil pump chain tensioner was the one showing the most wear at 250k. I think I will advise him to leave it alone.

Wow...impressive and encouraging.

Nothing to write home about. Car is like stocks, past performance is not a guide to future results. Past performance of other cars have nothing to to do with your car.:)

I would estimate the one I replaced was half way thru it's useful life.

Is your timing chain replacement based on the miles or the amount of stretch you measured ?

If you take the head off, you should do a valve job. And, that is why you should leave it alone.

Or, as Click and Clack would say... unless you really really need that new boat...

LOL

I recommended to him wait till we needed to pull head.

Good question. I've wondered this often. Asside from transmission , the timing chain, tensioner is the only other thing that worries me on my 250,000 mile cars. What happens when the tensioner goes or the timing chain goes? Does it just trash the head normally ?

This usually comes up for me when someone needs 1000 or 2000 in suspension and tires and such and wants to know if they can get a few more years out of their old benz. I generally say yes but am always wondering about the timing chain tensioner.

Did someone say you have to pull the head to replace that? It sounds like the best option is to just drive it till something breaks and then do a head and chains and all ? I like that answer . I'll keep driving and forget about it.

Please keep in mind that my crude home-made measurement (thread here) was plus/minus 1 degree, so the actual stretch was somewhere between 0 and 2 degrees. This was indeed good news but not unexpected, as Ah-Kay notes. A lightly-stressed diesel engine like the 606NA, provided it has regular oil changes and proper use, should last 300-500,000 miles. YMMV, of course.

Jeremy

You can remove the timing chain cover without removing the head and oil pan but you play heck re-sealing it if the gasket at the oil pan is damaged.

I ran my 300SD to 305K w/o any of that maintenance. Not one engine problem. Subsequently, the next owner I sold it to is still driving it 16-years later - last I heard.

I'd advise the owner to consider trading-up and out of that car, ASAP. The odds of needing to continue to spend out-sized money beyond what you've outlined so far, outweighs even keeping it right now. IMO. BTDT.

If that is the norm then all old MBZ owners will be trading their cars like their underpants everyday.