I'm under the process of changing the valve stems in my '89 300E. I just have one question(for now) about the procedure. In the repair manual that I need to bring each piston to TDC in order to remove the vavle springs. I understand that this is to preasurize the cylinder but what if I presurize it with an air compressor? At this point the cam bearing is already off and the vavles are already closed. So why do I need to bring the cylyider to TDC?

Thanks.

 

If for any reason the cylinder is not holding enough compressed air or your air supply is interrupted, the valve may fall into the cylinder. If your piston is at the top of its stroke, you can retrieve the valve. If it is not, you will likely need to REMOVE the head to retieve the valve, as it will disapear into the cylinder.

-D

 

Just one question...How do you intend to change the valve stems(valves?) without removing the head?

I can only assume that you mean the valve stem seals???

 

Replacing valve stem seals on the 2 valve per cylinder inline 6 mercedes is easy.

Dlafever is right in what the purpose of putting the engine to TDC on the cylinder you are removing the keepers from. When I did the valve stem seals I did not do that, I just made sure I was careful in removing the keepers and springs. I also did the job rather quick as soon as I remove the old valve stem seal I have the new one oiled and ready to go. It shouldnt take more then 2-3 hours to do them all. Trust me its a lot easier than doing valve stem seals on a DOHC engine.

Sp!ke you do not have to remove the head to do valve stem seals, we use compressed air that is pumped into the cylinder to keep the valves from falling down.

Dan

 

Thanks guys.

Your right I'm replacing the Seals not just the stems.

 

I replaced them with the compressed air and rotating the pistons method but I've heard of people just sticking something in the spark plug hole in case you lost grip of the valve. It helps to have extra hands in this operation. This replacement is one of the most beneficial things you can do at such a small cost. Dealer price for the seals was ~ $20. It can be done under an hour if you don't compress and rotate.

 

You don´t need any compressed air to replace the seals. Turning the engine to TDC brings piston 1 and 6 to top. The valves won´t drop but some 5-10 mm down before stopping on the piston head, so you are in no danger of dropping them down. Then when nr 1 and 6 are done, rotate the crankase until nr. 2 and 5 are at TDC( 1/3 out of 360°). You see when either 2 or 5 cam followers are opening/closing( pistons at TDC). Then repeat the procedure for nr 3 and 4. Done it many times myself.

Regards

 

Thank you so much w124-fan!!

Saved me a great length of time and saved me around $100 as i didnt need to get the compressor!

Excellent guidance that was spot on for any of you out there who need to do this job on your m103

 

Nice to hear

Drink up mate.. !
Cheers,

 

how easy was this for you guys? and can you use household tools or do you need special stuff? i kinda wanna do it, but i dont think i have the experience or tools for it.

 

It's not too difficult, you just need a valve spring compressor

 

very easy as long as you do it carefully. Take your time as there are a number of small parts that need to be taken off and put back in their place again. I DEFINATELY recommend getting a strong MAGNETIC tool with a small precise tip. Because the small parts could drop somewhere and you wont find them! We did use valve stem seal pliers to pull off the seals because the stem is really oily and you dont want to be slipping and sliding trying to pull it out. Very cheap. Pliers were 16 pounds and valve compressor was 15 pounds. Although my compressor was the hand operated one, not like the one pictured. I think the one pictured would have made my life easier as it appears to require less effort.
As we did it just a couple of days ago its still fresh in my mind. So if you need help just ask