M119 - No Valve Cover Leaks or Timing Guide Issues at 175k Miles? Normal?

[geekhou05]

Long-time lurker here with a 1998 S500 (W140, late M119) at 175k miles, owned since 2012 (~100k miles). It's a highway-only car for occasional medium/long trips, never a daily driver. Oil changed every 5k miles with full synthetic.

Powertrain Maintenance:

• Engine: Spark plugs, coil packs, MAF, MAF boot, air temp sensor, crankcase vent hoses, vacuum joints, all coolant/oil hoses, radiator
• Drivetrain/Fluids: Conductor plate, 2x for all other fluids - trans, rear diff, SLS fluid, coolant, power steering, flex disks, and engine/trans mounts.
• Leaks Fixed: Lower pan gasket, oil filter housing, oil level sensor, cam magnets, rear main, crank seal, steering gear box

No Issues: Zero oil consumption, ever. No valve cover or spark plug gasket leaks. No timing chain rattles. When I replaced the lower pan gasket, I expected some chain guide material, but found none—pan was clean! I figured valve cover leaks would prompt checking chain stretch and guides, but at 27 years and 175k miles, the valve covers have not leaked.

Questions:

• Is this typical for a well-maintained M119? Or any M119 at this age/mileage?
• Should I pull the valve covers to check guides and chain stretch anyway? What about the tensioner? I see this recommended for M117 engines on purchases.

I also own a 1992 600SEL (M120) and 2000 SL500 (M113), and I’m considering an M117 car.

Is this normal or is something going on?! I plan to keep this car for quite some time, but just expected to do more by now.

 

[emerydc8]

There is a good chance the valve cover gaskets were changed before you got the car. If original I would change the upper chain guides between the cam sprockets and install new gaskets at that time. Remember to shove shop towels under the chain to prevent broken pieces of the tensioner from winding up in the oil pan. No special tool is required but the shop manual does describe a removal tool. I don’t know if any one of us owns one. It is really unnecessary if you intend to install new guides.

It is my understanding that the M119 engines are less prone to jumping a tooth than the earlier M117 engines but others will be able to chime in on this. According to a master tech I once spoke to about it, the only time he had seen an M119 jump a tooth is when an upper chain tensioner disintegrated and left room for a worn chain to slap the underside of the valve cover and jump a tooth in the process. I think he mentioned that with the upper guides in place there isn’t enough room for the chain to jump a tooth.

As for the chain tensioner, although there is an internal spring, it is powered primarily by oil pressure so not normally something that requires changing. Replacing the timing chain isn’t usually required at only 175,000 miles but some like to do it. It’s a lot of work and requires at least one special tool. N.B.: This job almost always leads to mission creep (while your’re in there stuff).

The valve cover gaskets can go a long time without leaking. On one of my M119 engines it has been well over ten years since renewing the gaskets and still no leaks. In the event I had to remove the valve cover I would absolutely replace the gaskets because they are very likely to be hardened and wouldn’t make a good seal once removed.

 

[R129 UK]

No Issues: Zero oil consumption, ever. No valve cover or spark plug gasket leaks. No timing chain rattles. When I replaced the lower pan gasket, I expected some chain guide material, but found none—pan was clean! I figured valve cover leaks would prompt checking chain stretch and guides, but at 27 years and 175k miles, the valve covers have not leaked.

You can see through the oil filler if your engine has metal oiler tubes. If so, they have been replaced by a previous owner and likely some top end work e.g. gaskets, guides etc. was done at the same time.

 

[gsxr]

I agree with Jon. It's likely a previous owner may have already replaced the valve cover gaskets and/or some chain rails. It would be almost unheard of for them to be original at 175kmi with zero rail debris in the pan. You can also have larger chunks of broken rail stuck in the timing cover, which do not fall into the pan, and cannot be seen until the valve covers are removed.

THe M119 rarely has timing chain issues beyond the worn guide rails. As described above, the tensioner is from oil pressure and does not "wear out" and need replacement. The chain rarely stretches, any measured "stretch" is almost always from worn/broken guide rails. Need to replace broken rails first, THEN measure chain stretch. FSM indicates ~2° is normal on a used chain.

Near zero oil consumption is pretty normal for an M119 in good condition. If consuming 1 quart or less in 5kmi, that's excellent.

M117's are a very, very different animal. For starters it requires high-ZDDP oil if you want the camshafts to survive. Brad Penn 20W-50 is recommended. If you buy one, make sure the PO was using high ZDDP oil or it may have camshafts that are on the verge of death. YMMV. I'm not a fan of any CIS engine, btw... I prefer the EFI stuff from the early 90's and newer. CIS requires a degree form Hogwarts to diagnose, maintain, and tune... not my thing.

 

[geekhou05]

Thanks everyone for chiming in.

I got the car in 2012 and I highly doubt that the previous owner did any engine work. From 0-60k the car was dealer maintated and the original owner was a known figure in town and this would have been too early for any engine work. After this ownership cycle (from 60k-100k) I don't have much information but you could tell that the car wasn't looked after well. Also I doubt anyone would have done engine work this yearly in the mileage cycle.

I went in head first because I got the car for a really good deal and could see its potential. This was the first of my car maintenance level "restorations."

All these years after understanding the M119 more I simply expected that I would:

a) some day hear the chain slap upon start up or some other surprise
b) take a look when the VCG were changed, but they refuse to leak!

 

[gsxr]

It would not be unlikely that the valve covers were removed at some point by 60k. It's more unlikely the valve cover gaskets and rails are all original from 1998. Could be, just unlikely.

You would also NOT hear any chain slap on startup. There's no audible warning of broken chain rails. This is why it's a good idea to pull the valve covers proactively and do a visual inspection. At a minimum, the rails are probably very brittle, and the "fingered" clips between the sprockets are almost guaranteed to break when you try to remove them.

 

[geekhou05]

It would not be unlikely that the valve covers were removed at some point by 60k. It's more unlikely the valve cover gaskets and rails are all original from 1998. Could be, just unlikely.

You would also NOT hear any chain slap on startup. There's no audible warning of broken chain rails. This is why it's a good idea to pull the valve covers proactively and do a visual inspection. At a minimum, the rails are probably very brittle, and the "fingered" clips between the sprockets are almost guaranteed to break when you try to remove them.

Ah this explains it! Thanks for explaining what the scenario likely is.