M116 guide rail failure!

[260ebenz]

Just reading the MBCNSW Facebook page.

I wish Mat all the best with the repairs and hope to The Gov back on the road very soon!

https://www.facebook.com/mercedes.nswclub

 

[Helmet]

Sorry to see this Mat, it does happen often unfortunately

 

[260ebenz]

Spoken to Mat the guide rails are on there way to Sydney to be repaired.

Mat's 420SEL has travelled 400,000kms and I can tell you it is a superb car.

So to The Gov get well soon and see you back on the open road again soon.

 

[Helmet]

Spoken to Mat the guide rails are on there way to Sydney to be repaired

Lmao

 

[260ebenz]

What causes guide rails to fail?

Does the M103 6cyl engine have guide rails if they do when should the guide rails be replaced?

Perhaps this post is very useful for M116 8cyl and M103 6cyl Mercedes out their.

 

[Styria]

That's an absolute disaster. Even with Matt doing most of the work himself, it will still be an expensive exercise. Matt sort of indicated that it happened at start-up with the consequence of minimal damage to pistons when they touched the valves. It's my understanding that this problem normally arises on start up, as there is no provision to keep the chain tight after the engine has been turned off. Maybe Helmet, could you confirm this.

It is also my understanding that the M100 engine, as in 6.9, is not prone to the sort of problem particular to the M116/M117 engine. Furthermore, the 6.9 chain tensioner is ratcheted in both directions - in other words, it remains under tension and tight at all times. It is the initial slash of the chain in the M116 engine that causes the guides to break, which in turn jams the plastics in between chain wheel and rocker cover which, in turn, causes the chain to jump a tooth (or perhaps two, not sure) and that in turn results in valves touching the pistons. 'orrible 'n nasty ! Regards Styria

 

[Helmet]

That's an absolute disaster. Even with Matt doing most of the work himself, it will still be an expensive exercise. Matt sort of indicated that it happened at start-up with the consequence of minimal damage to pistons when they touched the valves. It's my understanding that this problem normally arises on start up, as there is no provision to keep the chain tight after the engine has been turned off. Maybe Helmet, could you confirm this.

It is also my understanding that the M100 engine, as in 6.9, is not prone to the sort of problem particular to the M116/M117 engine. Furthermore, the 6.9 chain tensioner is ratcheted in both directions - in other words, it remains under tension and tight at all times. It is the initial slash of the chain in the M116 engine that causes the guides to break, which in turn jams the plastics in between chain wheel and rocker cover which, in turn, causes the chain to jump a tooth (or perhaps two, not sure) and that in turn results in valves touching the pistons. 'orrible 'n nasty ! Regards Styria

That's a very accurate description of what happens.
My apologies at laughing at Tim's comment.
Cheers

 

[260ebenz]

No need to apologise Helmet.

 

[mathew]

Yes indeed it was a moment of what the (*&^*&%^*%*&%*&%*&% just before hooking up the boat to go on holidays, in hind sight I'm grateful it did it in my driveway and not on the boat ramp 500km from home.

Anyway having rebuilt the transmission and aircon two years ago and given the car wins every show it enters, my head said ditch it, my heart said how could you let him go.

I read through some forums and it appears it is not a job for the feint hearted, luckily I appear to have had a pretty good run without a single bolt getting stripped broken or jammed. Although I did break my guide pin removal tool, so it's holding back the lifting off, of the second head but all head bolts have been removed so it's only a five minute job when the tool rocks up.

The previous owner did indeed change the tensor and chain but sadly, was unaware of the need to do the rails so here's an eye opener for you all, the original rails have done just shy of 400,000km!!!!!!! Given 15 years or 100,000km is their life it speaks volumes as to why regular oil changes can extend the life of the whole engine.

I read alot to discover this job can cost about 6-7K initially I laughed and now I am half way through doing it myself I can see why the labour is huge!!!!! When you add in new valves etc the bill racks up pretty quickly, luckily I'm not paying for the labour otherwise it would have written the car off I guess.

In pic five you may notice the rotor not at TDC don't panic I put cylinder one at TDC before dismantling.

For an engine that's travelled 400,000km I am amazed at how good a condition it was in, no corrosion or wear and remarkably clean given it's age.

Please find attached photos of which i'll post more up as the job progresses, anyone with any helpful tips by all means let me know.

Cheers Mat.

 

[260ebenz]

Looks to be a BIG project Mat.

Good luck with the project and keep us all posted.

Good to see you posting on the Forum again.

See you at the All German Day in a couple of weeks?

Cheers.

 

[Michel]

Commiserations on your predicament, yet heartfelt congratulations for taking on a huge job like that and NOT ditching the Governor!

And most importantly...A great thanks for posting the progress on the Forum for all to see.

Good luck...

 

[Helmet]

Great you are tackling this job. Make sure that you use genuine guides and not Febi. Everything else you need you can buy good quality aftermarket. Do you have someone to rebuild the heads?

 

[Styria]

Great you are tackling this job. Make sure that you use genuine guides and not Febi. Everything else you need you can buy good quality aftermarket. Do you have someone to rebuild the heads?

Helmet, after market - would you include head gaskets, inlet and exhaust manifold gaskets, the eight seals between upper and lower inlet manifolds, as well as new valves ?

I am not sure if you are aware of this (and I am deviating from Matt's thread a little), but the M100 6.9 engine has a very large and long chain guide on the right side of the cylinder block - do you know of anyone that could reline that guide ? Genuine, and I am not sure if still available, will cost an arm (or two) plus the whole leg - not just from the knee down. I went to see an Engineering shop at Thornleigh to try and have them get two units relined, but they couldn't wait to get rid of me - I must remember that for next time I want something done by them - and there was the office girl (maybe wife or daughter) complaining that business was very slow. Wonder why......Regards Styria Regards Styria

 

[Helmet]

Helmet, after market - would you include head gaskets, inlet and exhaust manifold gaskets, the eight seals between upper and lower inlet manifolds, as well as new valves ?

I am not sure if you are aware of this (and I am deviating from Matt's thread a little), but the M100 6.9 engine has a very large and long chain guide on the right side of the cylinder block - do you know of anyone that could reline that guide ? Genuine, and I am not sure if still available, will cost an arm (or two) plus the whole leg - not just from the knee down. I went to see an Engineering shop at Thornleigh to try and have them get two units relined, but they couldn't wait to get rid of me - I must remember that for next time I want something done by them - and there was the office girl (maybe wife or daughter) complaining that business was very slow. Wonder why......Regards Styria Regards Styria

6.9 is a hole different kettle of fish , very few aftermarket parts available

 

[260ebenz]

Is that green coolant I can see in the engine bay?

I have heard not to use the 'green stuff' when it comes to Mercedes engines.

Would have the green coolant had any part to play with the guide rail failure Mat?

300SE has the blue Mercedes spec coolant my Mercedes Mechanic would not use anything else.

 

[BenzBoy]

The short answer to your question Tim is no.
The attached PDF will go part of the way in explaining the coolant issue for you.
Regards,
Brian

 

[260ebenz]

Brian thanks for the Penrite coolant document.

So what causes guide rail failure?

Besides the M116 engine can other MB engines suffer from guide rail failure?

One safe way to change the oil at regular intervals.

 

[BenzBoy]

Usually they fail through old age Tim and they are items to be replaced when a camshaft chain is replaced.
That is, they simply wear out regardless of how frequently the oil is changed. The same will apply to any engine with a chain driven cam. I guess you asking if it could happen to your car? The answer is yes.
Regards,
Brian

 

[260ebenz]

Okay Brian thank you for that information.

300SE has done 197,000kms since 1989.

I wonder when the chain guide rails should be looked at in the 300SE every 100,000kms is that right?

200,000kms might be the ideal time to have guide rails inspected.

Only travelled 17,000kms in the 300SE since buying the car and have of course had the oil changed.

Check the oil dipstick regularly which has never required a top up of oil between oil changes which is a very good sign.

 

[abl567]

Tim, an email to John Green at MB Spares where you bought the car or a look at any service history you have to reveal when the chain and guides was last checked/replaced may put your mind at ease. The V8's are known to be a problem, I'm not sure if the lesser 6cyl engines are as problematic.