Do you have to pull the head - PeachParts Mercedes-Benz Forum

Diesel240D · #1 08-16-2007, 08:43 PM

Do you have to pull the head to do the valve stems seals? On gas motors I done it without pulling the head.

bgkast · #2 08-16-2007, 08:54 PM

No.

blindwolf · #3 08-16-2007, 09:01 PM

According to the FSM, no.

aklim · #4 08-17-2007, 01:42 AM

I'd get the firing order and make each piston at TDC BEFORE do that cylinder. I dropped a valve once. Not a nice thing. However, since the piston was at TDC, it never went far and I could retrieve it without yanking the head.

Diesel240D · #5 08-17-2007, 02:13 PM

Quote:

Originally Posted by aklim

I'd get the firing order and make each piston at TDC BEFORE do that cylinder. I dropped a valve once. Not a nice thing. However, since the piston was at TDC, it never went far and I could retrieve it without yanking the head.

Thanks I will keep that in mind, I really don't want to pull the head,good info

aklim · #6 08-17-2007, 02:19 PM

Quote:

Originally Posted by Diesel240D

Thanks I will keep that in mind, I really don't want to pull the head,good info

I think you can guess how I learnt that one so hopefully you can "freeload" on my dime.

GRIESL · #7 08-18-2007, 08:44 PM

I would highly recommend getting the valve stem kit from **************.com or Dieselgiant, because they send you a pretty good photo manual with the parts. But here's a littel tip no matter where you get the parts. Try to position the cylinder at TDC for each hole you're working on. But as a safeguard, hold the valve stem with some needlenose pliers that fit through the valve spring. Hold the valve while you unscrew the nut at the top, then remove the nut and cap while holding the valve with the needlenoses and put the nut back on top. Voila, let go the valve, because it doesn't matter if it hits the piston or not since the nut will prevent it from going anywhere. Good luck!

sailor15015 · #8 08-18-2007, 10:36 PM

I did it with the head off and everything out of the way and it was cake. I had the head off anyway though so it was a no-brainer. I believe there's a cylinder firing roughly every 70* of crankshaft rotation, or about one fifth of a turn. You can fine tdc for cylinder 1 and, following the firing order, replace the seals.

If you ever take the head off, you'll see that the top of the cylinders are only a millimeter or so from the head, if that. You can use this to check that the cylinder you're working on is indeed at tdc. If it is the valve won't drop more than a couple of millimeters.

aklim · #9 08-18-2007, 11:52 PM

Quote:

Originally Posted by GRIESL

But here's a littel tip no matter where you get the parts. Try to position the cylinder at TDC for each hole you're working on.

Beat you to it. See post 4.

Did you learn that the hard way like I did?

Diesel240D · #10 08-19-2007, 12:23 AM

I have been a barn yard mech for years and these diesel engines are new to me. I love to drive my old 1975 Mercedes , it handle the dirt roads very smoothly .I sure appreciate all the great info as I am learning alot from you guys.

Thanks

Cervan · #11 08-19-2007, 01:05 AM

if your really worried about dropping a valve you can do the gasser trick and put compressed air into the cylinder through the glowplug hole.

bgkast · #12 08-19-2007, 02:34 AM

Quote:

Originally Posted by Cervan

if your really worried about dropping a valve you can do the gasser trick and put compressed air into the cylinder through the glowplug hole.

TDC is safer. When the compressed air leaks away you valve can go bye-bye.

GRIESL · #13 08-27-2007, 09:42 PM

Quote:

Originally Posted by aklim

Beat you to it. See post 4.

Did you learn that the hard way like I did?

Sorry, did not mean to be repititious. Did just about the same thing you did, except my needlenoses slipped off and the valve luckily just sat there for a second. I paused for a moment in complete awe that I had not done something catastrophic. Then the valve guide started to let go her hold and the valve began to creep ever so slowly down the guide. I caught it in time, but since I was close enough on the compression stroke it would have hit the piston anyway.

kerry · #14 08-27-2007, 09:58 PM

On a gasser, I once fed some 1/4 inch rope through the spark plug hole and then pushed it up against the valves. Worked fine.