Well, here it is the day after the BIG JOB, and I can’t believe I DID IT, and it's a smashing success! For a bit of background, I’d been getting the blue smoke on start-up for the 2 years I’ve owned the car, and figured (correctly) that it was valve stem seals. I paid little attention until this year, when the oil started fouling the plugs and affecting the idle, badly. So, I bit the bullet and took 2 days off work, finishing last night.

The project was a success in large part due to the search on this forum and the many posts/tips learned herein. It was also a success because of careful planning, the right tools, and that old standby, luck. So I thought I’d share a few tips that didn’t show up in the searches, and certainly weren’t in the MB shop manual.

To begin, the valve spring compressor I used is home-built from a copy of the real MB tool that my friend made up when he left Mercedes to go on his own. I found the geometry of my version a bit off, so that made pushing straight down on the spring retainer (to get slack to remove the %$^&*$# retainers/keepers) difficult. If I had it to do over, I’d probably get a buddy to do the pushing down while I used both hands to get the retainer halves out.

To hold the valves up when the springs are out, I followed procedure and used about 100lbs air pressure. I made up a fitting by smashing out the ceramic and all internals of a used plug, then brazed an air line fitting to the plug casing. Unfortunately, the female air coupling won’t quite fit the plug recess, so I added a 4” length of hose and another fitting to get it out beyond the exhaust manifold. Turning the hose by hand works fine, no wrench is needed to seal the air connection at the spark plug hole.

Tip no 1 is about getting the air pressure inside the cylinder without moving the crank and carefully positioned cam lobes (now in TDC. I chose to do each valve completely, 1 by 1). First, turn off the air and connect the fitting, then reduce pressure to about 40lbs. Turn on air, then slowly increase to 100 lbs. I mashed a finger when the socket wrench jumped as I connected at 100lbs, so that was when I changed my method. Plus, if it moves the cam too far, you've got to start all over to get back to TDC.

Tip 2 is all about my previous post about watching the crank damper markings and finding TDC. It is MUCH easier to go 1 cylinder at a time, 1 – 8, doing each valve completely before moving on. By sticking a 12” piece of wire, bent at about 8” or so, into the spark plug hole, I put a bit of white tape lined up with the edge of the valve cover seat on the head where the TDC position of the piston is. This is about the same for each one, so I just turned the crank until it was there, removed the 2 rockers and shims, then did each valve in turn completely for each piston. (springs off, old seal out, new seal in, springs back in, return rocker arms before moving to next cylinder).

I used tweezers to pluck the keepers out of the retainers, but found that magnetized ones work best to get them out, but are a pain to put them in because they aren’t easy to release with one hand (other hand is holding the spring compressor. Be ready for mighty sore muscles next day!).

Use rags, lots of them, to cover as much of the exhaust area and especially oil holes, as possible, for when one of those little cone halve keepers bounces out of your tweezers, or hemostat, which I also found useful for returning them to the spring retainer. But, Tip 3, watch that you don’t get the rag caught in the cam gear when turning the crank over to get to TDC! (You can’t turn the engine backwards either). This is easy to do when your attention is on the rear cylinders.

Tip 4 is from another post, but a small magnet sitting between the valves will catch the wayward keepers some of the time. I was very lucky, and only ‘lost’ 1. It ended up on the floor, just waiting to be picked up!

I’ll end this with a question for those who’ve been there. One of the hardest steps was actually detaching the old seal from the guide groove. I used a flat blade screwdriver levered on the head for most of them, but every one was a ***** to pry loose because there’s no room to work. Especially on nos. 4 and 8. Those I used a trianglular scraper on, levering the point with the handle.

But is there a special tool or trick to getting these off? Pliers don’t grip at all.

All told, it took 8.5 hours to fabricate the air fitting, remove and mark all vacuum lines, fuel lines, plugs and wires, valve covers, and complete the seal change on numbers 1 - 4 . The keepers on no. 1 took me ¾ hour alone! The change on cylinders 5 – 8 took only 3 hours. Add another 3 hours to put everything back, including new plugs and an oil/filter change, and you have the DIY amateur verson of an $800.00 job. But, my engine purrrrrs now..... ....and my wallet is only out $80.00 for seals.

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1986 560SL
2002 Toyota Camry
1993 Lexus