I have been told there was a way to remove and replace the rubber valve seals with the head still on the car ( a 78 300D). Does anyone know how to do this? Is a special tool necessary? Thanks in advance!! τΏτ

Greetings Gerry,

I assume you got my email describing this procedure? Maybe I went over it in too little detail. You do not need to remove the head to change out the valve seals. Your engine is an overhead valve setup and pulling the valve cover you will see the rocker arms, cam and valve stems. After removing the rocker arm assembly, using your 8mm allen wrench bit socket you can get access to the valve cap nut and spring tension nut. The trick to doing it is making sure, starting at cylinder 1 that the piston is at TDC before loosing the valve spring nut all the way otherwise the valve will drop into the cylinder. Line up your cam to TDC line on front of cam housing to "0" on the damper housing and that will be the no. 1 cyl. TDC loosen the valve cap nut and remove, loosen the valve spring retaining nut until you see no more thread left at the nut. Push down on the valve with a wide screwdriver or suitable item to ensure the valve makes contact with the top of the piston with very little movement. This ensures that you can remove the nut the rest of the way without the valve dropping into the cylinder. After removing the nut and the spring washer as well as the spring, you have access to the seal which is probably the black rubber item snuggly fitted to the head and surrounding the valve stem. Pry up slowly from the base of the seal using a screw driver, just to unseat the seal, then use a pliers with great care not to make contact with the stem, but only the rubber head and twist slowly until the seal releases from the head. Remove old seal, and place a new one in it's place, appling a small amount of pressure with a fitting open end wrench to the base of the new seal to seal it firmly onto the head. Replace the spring and spring washer and the nut, tightening it about the same turns as you used to loosen it, count them, makes life easier upon final assembly before you do the valve adjustment. The rocker arms will go back into place a lot easier without all the cuss words. Now let's move on the the next cylinder. The easiest way to get close to each cyl. TDC is following the firing order stamped into the valve cover, and have all the injector lines off, and watch when the fuel on the injector pump pipe fitting for the next cylinder just starts to spit, you are probably pretty close to the TDC of that cylinder. You can turn the engine over slightly either way to maximize the piston height either using a 27mm socket on the crank housing bolt or I cheat and use the power steering pump bolt, easier to get to and turns the engine over just the same. Follow the above removal procedure for each valve and after all is done replace the rocker arm assembly and you're ready to set the valve clearance for each valve. Trust me, this isn't an after work job to do unless you get off work at noon. It's gonna be frustrating enough with all the piddling you have to do to get max piston height and then after all seems done, you still have the valve clearance to set. Plan on at least three hours to do the job, and if you are extremely careful at least four.
If I can help anymore, let me know. I dreaded doing this one myself, but been there and did it. I did see a reduction of start up oil burn though, but valve adjustment can account for that as well. Seal replacement isn't a cure all. Tell us what are your symptoms are as far as engine performance or oil problems, and let's take a look at other items as well. My largest oil consumption item yet was my vacuum pump diaphragm spitting oil into my intake filter housing and causing a huge consumption problem. $9.00 and about an hour fixed that problem.

Charles