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#1
11-25-2008, 11:55 PM
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Valve Stem Seal replacement procedure?
My '84 380sl has all the signs of valve stem seal failure and I cannot seem to locate a sticky on the procedure for replacement. Help anyone? Thanks!
James 
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#2
11-26-2008, 03:24 AM
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Quote:
1) Removing the spark plugs and valve covers; 2) Placing a 27mm socket on the nut that's deep in the crankshaft hub; 3) Using that nut to rotate the hub's markings from 0 through 90, 180, and 270 degrees, causing the various cylinder pairs to reach top dead center; 4) Inserting rope or a spark plug adapter on an air compressor into each of those cylinders to keep their valves from falling; 5) Removing each cylinder's rockers 6) Compressing each valve spring with an "on engine, over-head cam valve spring compressor", which has a hook to grasp the camshaft; 7) Using a magnet to remove the valve spring's keepers; 8) Removing the springs and their covers; 8) Prying the old seals off; 9) Carefully installing the new seals, so as not to damage them; and 10) Reinstalling the springs and keepers. Although this might sound fairly easy and straight forward, the job can be quite difficult, especially if you don't have the compressor MB specifically designed for the job, as putting the keepers back on can be a real PITA. KD makes a similar compressor, but having used both, I can safely say that the job is far more difficult using it, rather than the MB version. If you've never done anything like this before, considering the cost of having an Indy do it for, say, $400-500, I'd recommend that rather than doing it yourself.
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#3
11-26-2008, 06:37 AM
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The procedure is basically as per mbboy description and you can find further info on this link:
http://www.peachparts.com/Wikka/M103ValveSeals You will need the valve spring compressor referred to as per pic, you can get one on ebay for a few $. 
__________________
 Deltacom ~ Absit Iniuria Verbis ~
Last edited by Deltacom; 11-26-2008 at 07:13 AM.
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#4
11-26-2008, 12:11 PM
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Thanks guys, both procedures are excellent, I did the seals on a MG 30 years ago and that was the last time I did seals! Thanks again!
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#5
11-26-2008, 12:38 PM
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Use the rope .....do not use the air to hold the valves up...
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#6
11-26-2008, 02:05 PM
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thanks, why not air? Rope just easier?
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#7
11-26-2008, 07:25 PM
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Rope safe and foolproof...
1. Air potential for accidental turning of the crank ( computed this way : your piston diameter times 3.1415 times the number of pounds of pressure you apply to the top of the piston ( then at half a rotation multiplied by the length of the crank throw )... if perfectly centered ... fine... if not it turns the crank violently.... 2. Ability of air to hold the valves up depends on PERFECT seal at the valve lip... one SPECK of carbon or burned area on valve and you drop the valve into the bore.... Diesel guys don't have this problem... piston gets so close to head with the 21 to one compression ratio the valve can rest on the piston...
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#8
11-26-2008, 08:12 PM
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I agree rope might be *more* foolproof-few things in this world are foolproof.
I have always used air because it's much quicker. Bringing the cylinder of attention to TDC will prevent the valve from dropping into an abyss and using about 30 psi will not cause the piston to move. There will be no speck of carbon to hold the valve open and if the valve is burnt, changing seals in place is a waste of time-pull the head and fix the valve.
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#9
11-26-2008, 10:26 PM
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Chas H. ... If something unusual happens while not using the rope... will you pay for the damage to his engine or him ?
No you won't... so your bravado with HIS engine and body are recognized by others for what it is... Warmblood58, use the rope, Sleep well at night.
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#10
11-27-2008, 12:27 AM
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Quote:
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#11
11-27-2008, 10:51 AM
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Quote:
Otherwise you are promoting taking unnecessary chances with other people's stuff and safety, not just ' offering your opinion' ....
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#12
11-27-2008, 11:37 AM
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Quote:
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#13
11-27-2008, 04:36 PM
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thanks guys, I am off the opinion that rope sounds both quicker to use and essentially fool proof . . . why use a more complicated procedure when none is needed? All advice has been greatly appreciated! Call off the dogs!
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#14
11-27-2008, 05:50 PM
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He has shown that his dogs have no teeth...So no problem there...
Here are two things which can cause serious consequences using air to pressurize a cylinder in which the piston is NOT at the bottom of the stroke... One... the timing pointer can be damaged .... or the wrong one be on the engine... which causes you to think your piston is exactly at TDC when it is not... I have seen both those things ... not in connection with pressurizing the bore fortunately ... but you can figure out what would happen... it only takes a few degrees off TDC to cause a problem. Two... some cars have the crank timing mark on the balancer which is rubber mounted to the front of the crank... I have seen old ones which had rotated as much as 90 degrees. While that much difference should show up in the position of the valves... less would not... and the amount of pressure ( 4 x pi x 30 ( plus 1/2 ft at 90 degrees ) ( or times 100 when doing a leakdown test)... can thrown a tool attached to the crank bolt, turn the engine backwards, catch a finger in a belt, hit your hand with the fan blade.... just too many things which are easy to avoid completely with the rope. And that is not even mentioning that if it goes far enough to activate the valve mechanism on the exhaust it will take away the pressure and let the intake drop into the bore... I have had some close calls in my 40 years of DIY car work.... but I still have all my fingers and eye sight... we do not know for sure about others who post with lots of bravado when they are not going to get hurt if something unusual happens. I feel we as a group have an obligation to go with the safest advice we can give since we have so many levels of experience potentially reading the information.
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#15
11-28-2008, 03:59 PM
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The only thing stopping me from doing this job is the fear of (a). losing parts and (b). dropping a valve - I have all the tools and parts to do it (even the mandrel for installing the new seals). It seems to me that the "rope" trick is more safe and sane, although I wish I had x-ray vision to see that I had stuffed in was enough to do the job!
The other thing that's stopped me is that a lot of people think that if the valve stem seals are leaking, a valve job looms anyway.
__________________
86 560SL With homebrew first gear start! 85 380SL Daily Driver Project http://juliepalooza.8m.com/sl/mercedes.htm
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