3.5 engine: changing valve stem seals- need help - PeachParts Mercedes-Benz Forum

werminghausen · #1 01-05-2012, 07:35 AM

Here is where I am stuck changing valve seals:
I took the pair of rockers off at cylinder 1 and put the engine into TDC of the cylinder and now I can push the springs of the cylinder down with the spring compressor...
until the valve hits the piston but then I can't get it further down to release the cone halves. No matter how hard I push with the compressor I can't get the cone halves out. Is there a trick?
Maybe these cones were never removed since 41 years. I don't want to use too much force and brake something.
Any help?

werminghausen · #2 01-05-2012, 07:37 AM

I tried with a helper who pushed the retainer down with the spring compressor to rap the retainer form above with a punch in order to free the cone halves....but without success. I feared that I might damage something.
Instead I decided to move on to cylinder 8 and try my best here. Cylinder 8 was leaking oil from the plug hole and when I looked at the plug this one was entirely full of oily soot. All the other plugs are actually fine. Cylinder 8 also had only 120psi compression versus the other ones were better.

Here at cylinder 8 I was able to push the retainer further down, took the cone halves off and tried to get the old valve stem seal out. The old seal is whitish plastic with a spring coil around (while the new is black rubber with a metal ring).
However when I pulled the seal the entire valve guide came out (see pitcure). It came out relatively easily, so I guess it is going back the same way.
However the valve guide didn't slip all the way out but is stuck now at the end of the valve stem. Maybe the end of the stem is a bit deformed?
What shall I do now?
1) Would you try and push the guide back and move on (I didn't measure the radial play yet)?
2) Or is there a chance to install a new valve guide with the head installed?

Here are a few pics from cylinder 8 intake.
There is another detail. There was a very thin washer below the rotating plate at the bottom. This washer was broken- see picture

Best, Martin

wbain5280 · #3 01-05-2012, 07:50 AM

You are supposed to pressurize the cylinder with compressed air to keep the valve in place. Then compress the valve retainer, take out the conical retainers and take the springs out. Then you can remove and install the seals.

Get a compressor and a spark plug adapter and have at it. Don't drop a valve.

werminghausen · #4 01-05-2012, 08:19 AM

Hi Warren,
thanks. To be honest, the way I pushed with the compressor I kind of doubt that the pressurized cylinder will hold the valve? Anyhow I can probably pressurize with some gymnastics and see what happens.

Quote:

Originally Posted by wbain5280

You are supposed to pressurize the cylinder with compressed air to keep the valve in place. Then compress the valve retainer, take out the conical retainers and take the springs out. Then you can remove and install the seals.

Get a compressor and a spark plug adapter and have at it. Don't drop a valve.

wbain5280 · #5 01-05-2012, 09:05 AM

What do you mean by 'pushed with the compressor'?

Mike D · #6 01-05-2012, 09:11 AM

I'm guessing he is using a lever style spring compressor.

werminghausen · #7 01-05-2012, 09:48 AM

Yes, spring compressor.

werminghausen · #8 01-05-2012, 09:50 AM

Why is this guide coming off when I am puling the valve seal? What am I doing with this thing?

wbain5280 · #9 01-05-2012, 02:44 PM

Someone must have replaced the guide with the wrong size. They are an interference fit and need to be shrunk by liquid CO2, or something close, and hammered in.

You would be better off replacing them all with the correct ones. Use a micrometer on the guides to find the bad ones. They should not come out. Also, replace the valve rotators with spacers, check with the Classic Center to see if they have them.

werminghausen · #10 01-05-2012, 09:34 PM

Thanks Warren,

Do you think I can change the guide that came off with the head installed or do I really take the head off?
I think you are right that someone was replacing or was doing something with the guide at cylinder 8. The guide has marks on the outside which were not from my work.
Problem is that I am in Oman and I don't know anyone whom I trust to rebuild the heads, also I can't drive now any more.
Martin

Quote:

Originally Posted by wbain5280

Someone must have replaced the guide with the wrong size. They are an interference fit and need to be shrunk by liquid CO2, or something close, and hammered in.

You would be better off replacing them all with the correct ones. Use a micrometer on the guides to find the bad ones. They should not come out. Also, replace the valve rotators with spacers, check with the Classic Center to see if they have them.