Author Topic: M116/117 V8 engine - whos changed their valve stem seals?  (Read 5554 times)

13B

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Just a quick one, I'll expand on it later...

Who has changed their valve stem seals to cure smoking engine and was it successful / how long was the problem solved before returning again?

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

13B

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #1 on: 13 March 2008, 02:08 AM »
My local european car guy, not a MB specialist but all expensive european car dude (does the work on my car I can't do myself) (well anyway he drives a W140 and thinks the 116s are great, so he can't be too bad)...

I said I wanted to change the valve stem seals on the M117 in the race car, and his opinion was that it was wasted time and money without doing the valve guides at the same time, or else it'll start smoking again soon.

This comes from the M117 VSSs being a harder plasticy type material which is easily damaged/worn/cracked etc. if the valves are wiggling around loosely in their guides.  This is in constrast to, say, a Mistubishi engine which has a relatively soft rubbery VSS which will effectively stop smoking in a Magna even if the valve guides are fairly worn out.

The other concern is how quickly the VSSs start to fail again if the valve guides are worn... if it does it in 500km then there's a problem... bu if it takes 20,000-30,000km then I consider that acceptable since the Team116 car will cover only about 1000km/year* tops and be running high-quality engine oil to boot.

* Granted that this 1000km/yr will be covered at high revs under racing conditions I would expect VSSs, as well as everything else in there, to have a pretty difficult and short life..

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

jmperkins

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #2 on: 13 March 2008, 10:01 AM »
To GUARANTEE that you do not have this problem for I would say as long as for 200K miles, I would recommend valve seals AND valve guides!

I have had heads rebuilt out of vehicle for both my 110 and 100 engines by a machine shop. They replace ALL the valve seals but only replace the BAD or worn valve guides.

I know people who have replaced the seals  with head in car but you must be careful to keep the valve from falling into the combustion chamber after removing the valve springs and valve spring keepers!

Good luck,
Joe Perkins
Berkeley, CA

13B

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #3 on: 13 March 2008, 02:36 PM »
Thanks Joe.

Not exactly what I was asking by I appreciate your input.  Yes I know the best is to get the guides done at the same time... 

What I'm after is anyone's real-world experience of changing the VSSs without doing the valve guides.

I've changed VSSs without removing the heads on other non-MB cars, you just run compressed air into the spark plug holes to stop the valves falling in...

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

oscar

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #4 on: 13 March 2008, 04:40 PM »
I was thinking along the same lines as Joe, however, I only got stem seals.

My 350 used to smoke on start up as oil leaked past the VSS.  A quick puff of blue.  Depended on how long the car stood.  If not used for a long time (couple of weeks) it would be ok as if the oild would seep past rings back into the sump.  Stand for a an hour or so and the oil would leak into the cylinders. 

Most noticeable was going down a hill and throwing the car into a low gear.  A second or so later an embarassing blue plume would develop.  When cruising and putting the foot down, i wouldn't notice any smoke unless it was fuel related, timing etc ie hints of black smoke.

So, March 06 I had VSS replaced, guides left in.  I wished I had both done but anyway, the difference was great. ie no smoke.  Fast forward a couple years later and about 11,000km.  It has not returned to being smokey like before.   I've only noticed oil smoke under two conditions recently.

1. Full accelerator, cold engine.  (I know I shouldn't)  The smoke is part fuel part oil related but not thick
2. On a forced overrun when engine is hot.  ie down hill and shoving A/T into L.  Slight bluish smoke especially when engine is warm.

Another thing to keep in mind. I'm experimenting with oils and am running thin synth that has diluted too.  Due to be changed any moment I get my arse into gear.  I have noticed though that new oil reduced any chance of smoke.  No doubt whatsoever.  Stands to reason as it's thicker.  No idea what you'd use in the raceing version but generally, Ive noticed that thick new oil will cut down the smoke.



« Last Edit: 13 March 2008, 05:32 PM by oscar »
1973 350SE, my first & fave

jmperkins

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #5 on: 14 March 2008, 02:57 PM »
I apologize, Oscar, for not directly answer your concern/question.

I know a gent i, Jim Hoffmann, the m100 (Mercedes 6.9 discussion group) that I believe just changed his valve seals only. Granted it is a 6.9 liter v-8 but very similar technology and his feedback might give you some guidance. His story (and results) are as follows:

http://www.m-100.cc/forum/topic.asp?TOPIC_ID=2889

I hope this helps!
Regards,
Joe Perkins

koan

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #6 on: 14 March 2008, 05:16 PM »

I've done the valve stem seals on my 6.9 but I can't comment on the longevity of only doing seals as I've not dome enough kms, probably only 2 or 3 thousand total.

The seals are a hard, not very flexible material and need to heated in hot water for some minutes to have any hope of getting them  over the valve stems.


koan
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torana68

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #7 on: 14 March 2008, 07:48 PM »
it really depends, seals are dead cheap to do yourself, change them and see but if you have an engine that has 200000 miles on it and the heads have not been done the guides are stuffed. How many miles on the engine?
Roger

13B

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #8 on: 14 March 2008, 08:13 PM »
226,000km - assuming the clock hasn't been wound back.

Been reading many past threads on this and other sites and the conclusion that I've come to is that in the wost case there will be no difference, and in the best case the problem will be solved.  Most likely however will be that it will be improved to acceptable (to me) limits.

Next week I'm putting the car in for a full engine health checkout to determine how much I want to spend on the engine.  I'm going to ask if they can check:

compression test
leak down test
timing chain stretch
valve guides if possible to test with cam cover off??
modulator control valve is not leaking.

Can you think of anything else?  Bearing in mind that I can diagnose and solve EFI and ignition problems myself.

Hoping to find that compression and leak down are within reasonable limits, that the chain is probably stretched and needs replacing, as does the chain guides etc., and that the valve guides are Ok but not brilliant. 

Fingers crossed.

I.
450SEL 6.9 #5440 = V MB 690 , 450SE # 43094 = 02010 H , 190E/turbo # 31548 = AOH 68K

oscar

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Re: M116/117 V8 engine - whos changed their valve stem seals?
« Reply #9 on: 14 March 2008, 10:02 PM »
I apologize, Oscar, for not directly answer your concern/question.

No worries, but it was 13B's question ;)  Thanks for the m100 link too BTW.

Good luck 13B, I can't think of anything else apart from EFI and tuning afterwards. 
1973 350SE, my first & fave