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'91 560SEC, '98 SL500
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Discussion Starter #1
Prompted by Ian's thread related to aging valve seals, I thought it would be prudent to start a new thread to visually walk through this maintenance procedure.

On our cars this is a "when" and not "if", all valve seals will fail over time. They live a crappy life, bathed in oil, heat and of course get old.
If you pay an Indy, this can be pricey, so why no tackle it at home, learn something new and help keep the cars maintained for another few decades.

Here are a few pictures of when I replaced the valve seals on my '91 560SEC a few years ago. The car had 155,000 miles on it when I did this and my car was smoking quite significantly, to the point where it was almost embarrassing to drive.

Not terribly hard, you just need the valve spring compressor, another pair of hands AND (most crucial) I recommend you rotate the crank so that when you are working on that particular cylinder it is at the top of its stroke, that way the valve will not fall into the combustion chamber and be lost. If the valve does slip, it will touch the top of the cylinder but there will be sufficient stem still poking out that you can grab it with your fingers or a needle nose pliers.

It took me 10 hours to do this.

Special Tools: You need the Valve spring compressor (available on eBay) and a good 1/2" breaker and 1/2" socket to rotate the crank pulley

Hope this helps.
Best of luck!
Yasin

Pictures:














 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
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4,468 Posts
Aaargh. Why aren't the pictures loading for me? Reboot didn't fix it.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
·
4,468 Posts
That didn't do it. Darn. Maybe I'll see them when you post this to the DIY.
 

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Registered
1989 300SE 232k miles
Joined
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1,221 Posts
Thank you!! This is something I’ll need to do at some point. And I’ve been wondering on how to do it.
 

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Premium Member
1999 500SL, 1988 SEC
Joined
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1,272 Posts
Don’t forget to number the pucks and put them back where they came from
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
·
4,468 Posts
Prompted by Ian's thread related to aging valve seals, I thought it would be prudent to start a new thread to visually walk through this maintenance procedure.

On our cars this is a "when" and not "if", all valve seals will fail over time. They live a crappy life, bathed in oil, heat and of course get old.
If you pay an Indy, this can be pricey, so why no tackle it at home, learn something new and help keep the cars maintained for another few decades.

Here are a few pictures of when I replaced the valve seals on my '91 560SEC a few years ago. The car had 155,000 miles on it when I did this and my car was smoking quite significantly, to the point where it was almost embarrassing to drive.

Not terribly hard, you just need the valve spring compressor, another pair of hands AND (most crucial) I recommend you rotate the crank so that when you are working on that particular cylinder it is at the top of its stroke, that way the valve will not fall into the combustion chamber and be lost. If the valve does slip, it will touch the top of the cylinder but there will be sufficient stem still poking out that you can grab it with your fingers or a needle nose pliers.

It took me 10 hours to do this.

Special Tools: You need the Valve spring compressor (available on eBay) and a good 1/2" breaker and 1/2" socket to rotate the crank pulley

Hope this helps.
Best of luck!
Yasin

Pictures:














Yasin,

What method did you use to keep the valve raised while compressing the springs?
 

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Registered
'91 560SEC, '98 SL500
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Discussion Starter #12
Once the valve spring is compressed, use a pair of long need nose plyers with rubber hose on the ends (to not marr the valve stem and gently hold the valve in place, this will keep the valve from slipping down in the combustion chamber and you can proceed to remove the top retaining 1/2 moon shaped locks or keepers (2 per valve). Again make sure that the cylinder your're working on, that the piston is at the top of its stroke (very important), so if the valve does slip down, its not lost in the cylinder bore.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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4,468 Posts
Once the valve spring is compressed, use a pair of long need nose plyers with rubber hose on the ends (to not marr the valve stem and gently hold the valve in place, this will keep the valve from slipping down in the combustion chamber and you can proceed to remove the top retaining 1/2 moon shaped locks or keepers (2 per valve). Again make sure that the cylinder your're working on, that the piston is at the top of its stroke (very important), so if the valve does slip down, its not lost in the cylinder bore.
Okay I don't get this and really want to. When I pushed my 'hat' down with the compressor, the valve wanted to move down with it. Are you saying you can reach between the valve spring coils with the needle nose pliers?
 

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'91 560SEC, '98 SL500
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Discussion Starter #14
I did not have that issue, once I compressed the valve spring, there was enough of the end of the valve sticking up that I could grab it with the needle nose or my fingers. Are you compressing the spring past the keepers , so you can remove both of them?
 

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Premium Member
1999 500SL, 1988 SEC
Joined
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1,272 Posts
Well ,here are two of my suggestions. Get a pair of valve seal pliars. It makes removing the old ones much easier. Same with putting the new ones on. I also used the air method to keep the valves in but the piston must be at the bottom of the stroke or it can get away on you and rotate with a lot of force, I also would have on haned a pencil magnet to remove the spring locks. A second set of hands is very helpful. Doind it by yourself is not much fun but possible
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
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4,468 Posts
I did not have that issue, once I compressed the valve spring, there was enough of the end of the valve sticking up that I could grab it with the needle nose or my fingers. Are you compressing the spring past the keepers , so you can remove both of them?
I compressed the spring enough to grab one keeper with my magnet then the other. I just can't picture at what point you grabbed the valve with the pliers.

Are you saying you compressed the spring to a point where you could place the pliers on the stem below the keepers? I found that without resistance, either by the air or the rope method, the stem would basically follow the 'hat' down as I compressed.
 

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Registered
1990 420 SEC
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337 Posts
What if one pressurized two cylinders at the same time? One at TDC and one at bottom? Rockers would have to be removed on both. That way engine would not turn so easy accidentally and piston would secure the valves from falling. Maybe even higher pressure at the cylinder with piston down.
 

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'91 560SEC, '98 SL500
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Discussion Starter #18
Luckymike you need another pair of hand to assist It makes a massive difference in this procedure.
 

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Premium Member
1999 500SL, 1988 SEC
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1,272 Posts
Really,. putting air into the cylinders is really easy, even if you have a cheap HF compressor. Doing this alleviates and worries. I tried the rope trick but it was a pain and it did not thread well. The hardest part for me since I was alone was getting the valve keepers in place all the while I was compressing the spring. A second set of hands are angelic. Also the pliars would have made taking the old ones off very easy. Good luck
 
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