603 valve seals
 

I see from the manual that the cam has to come off to replace OM603 valve stem seals. Duh, since it has bucket tappets.

Questions:

- is it possible to rig a tool to compress the valve springs? gsxr, do you have this tool I can rent from you?

- in the manual, is the sequence or shading accurate for loosening the camshaft towers? It says remove the cam towers 1, 5, 6 with dark arrow in the diagram, but cam towers 1, 5, 6 have light arrows in the diagram.

- what's the purpose of the retaining gear in place of the cam sprocket?

- do the valves pretty much rest on the piston at TDC? The manual says nothing about using compressed air to keep the valves up.

- What is SAE 10 engine oil as used in the tensioner?

Thanks,
Sixto
91 300SE
87 300SDL
81 300SD

I am glad I am not the only one that has been confused by the dark/white arrows. They are reversed. I pondered on this until I had the valve cover off and was able to inspect. I think you can rig a tool pretty easy to compress the springs. THe problem would be to keep the valves from dropping int ot he piston. You can easily do the no. 1 and 6 with no problem. I am confused by you comment about the retaining gear. WHere do they have you put it.

Henry

Hi Sixto,

I'm only replying to your post so I get e-mailed when you get answers because I am also interested the answers.

The only answer I know is that the valves will rest on the piston when it is at TDC and you won't have to worry about the valves droping into the cylinder. But you have to rotate the engine to bring other pistons to TDC. This might screw up the timing if you do it with the cam off the engine and the timing chain loose.

P E H

Ah! I think that answers the retaining gear question -- it takes the place of the cam sprocket so you can rotate the engine without the camshaft in place. I can't imagine what it looks like.

Sixto
91 300SE
87 300SDL
81 300SD

Sixto:

I don't know, but I suspect the retaining gear has a short shaft so it sits in the front tower and allows the engine to rotate.

Don't drop the chain on this engine, the IP is a HUGE pain to retime -- it is keyed to the injection timer, not like the old ones with just a splined shaft you could put in at any position. You also have to lock the pump in at the correct position with a special tool, or you cannot set the timing.

That said, all you have to do is rotate the engine to place the cylinder you are working on at TDC for valve seal replacement.

If you have any noisy tappets, this is the time to replace them, too!

Peter

I would guess it is a part similar to one cam tower with a gear similar to the cam gear attached to it and it would bolt on the head where the cam tower does. That way you can turn the engine without losing the timing. JUst a guess though.

I haven't had the valve cover off my 300SDL so I don't know what its looks like under there and since I don't have to adjust the valves I hope I don't have to take the cover off. But I just can't figure how they fit hydraulic valve lifters in there. The new valve cover looks smaller than the one on the 5 cylinder engines.

P E H

PEH

The tappets sit on top of the valves under the cam. Pretty slick, except when you have to replace them!

I'm sure the head is deeper than the cast iron one to hold the tappets.

Peter

Sixto,

You should be able to work on 2 cylinders at once on a 6 cylinder engine. 1st and 4th, 2nd and 5th, and 3rd and 6th numbers of the firing order should respectfully be at TDC at the same time. Note these are the numbers in the firing order not the cylinder numbers. So if the 4th number in the firing order is 5, #1 and #5 cylinder will be at TDC at the same time and so forth.

Psfred,

You and I are thinking on the same plane on the retaining gear. How do they get th oil to the valve lifters?

P E H

Before you go to all the problems of replacing the valve stem seals, what do you think the problem is?

Henry

Henry,

I'm not addressing a specific problem. I removed the valve cover so I could get more leverage on the lower #5 cylinder intake manifold bolt. With the valve cover off, I got to thinking of how to replace the valve stem seals. The procedure in the manual made it seem a lot more complicated than the same procedure in the M103 (that I'll be doing soon).

The limiting factor is compressing the valve springs, but maybe a tool rental place has a generic form of compressor that'll work.

Sixto
91 300SE
87 300SDL
81 300SD

Spring tool?
 

Here's a picture of a similar tool if that would help.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1822672538

I think samstagsales.com sells a generic tool like this $70? you would have to rig up some type of bar across the length of the engine block to place the tool's hook under. Looks like you could fabricate a tool also maybe use an appropriately sized cheap socket and grind away most of it leaving only a portion neded to bear upon the spring. I anticipate some 603 headwork and I plan on fabricating this tool the hardest part would seem to be the bearing surface that contacts the spring it will need to be strong because much of the supporting area needs to be removed to allow access to the top of the valve stem. I'm considering use a screw and beam arrangement bolted to the head rather than a hand lever also, it might be easier to just screw the tool down on the spring let it be held in place and remove the clips than trying to remove the clips while at the same time exerting pressure with a hand lever style tool. Just a couple thoughts along this line. I'll probably scare up a used camshaft timing chain sprocket to attach to the #1 cam tower as a retainer also, should be pretty simple, the sprocket mounted onto a shaft and both mounted on a tensioning base mountable to the cam tower or even the head itself attacthed to the valve cover bolt threads from in front a simple device could maintain the needed tension.

The "retaining" tool is just what sixto said. It's not needed though, and besides it's expensive. It's very hard to "drop" the chain. I did the whole head replacement without keeping tension on the chain, it drops down there, you pull it back up with a wire hook. It pretty much can't fall off the I/P timer gear or crank gear. Peter is right, this engine is a PITA to time. If you are pulling the cam AND turning the crank, you'll have to at least check the timing. So you'll need the I/P lock tool (~$25 at the dealer or your favorite e-vendor).

The valve lifters sit in pockets above the valve springs. There is an oil gallery on the intake side of the head that feeds the lifters through a hole in their body.