Clacking head? Hydraulic lifters? MUST READ - PeachParts Mercedes-Benz Forum

winmutt · #1 09-26-2012, 03:28 PM

OM60x hydraulic lifter "reset" procedure | Mercedes-Benz Club of America

Quote:

Learned something new. Over the past year and a half, I've replaced the head on my '87 wagon (300TD). Old original head, #14 casting, cracked and started mixing coolant in the oil. "While I was there" I also replaced all the chain guides and installed a new front crank seal. Ended up replacing the injection pump o-ring between pump and block as well.

I found a suitable replacement head, #20 casting, and had the valve guides replaced by a local shop, and new valve guide seals installed. I used an updated cam shaft that came with the head, and the best looking hydraulic lifters taken from the original head and the new head. Installed the head this spring, and upon the first start there was a terrible knocking noise from the head. RATS!!!

Very dejected, I let it sit until a couple weekends ago.

Rotated the engine by hand several times, and all felt normal. I removed the intake manifold, and started the engine again. Same knock, but with the intake manifold removed I could see that the #2 intake valve was the culprit. It was not sealing, but it was allowing the compression charge to escape. Sounded like a terrible knock, but no metal was touching metal, a GOOD thing!!

A key noise that I could not diagnose at first: while cranking the engine it made a wheezing sound for one cylinder. That wheeze turned into a knock once the engine was running.

Called the shop that rebuilt the head to get their advice. First test was remove the keepers and spring, and verify that the valve was not sticking in the guide. It was not. Next call to the shop, they recommended that I bleed down all the hydraulic lifters to "reset" them to zero lift.

Here's how I did it: Hold the valve with the little oil feed hole down, insert thumb(s) into the bottom, and work the element in-out while watching the oil drip out. Once you have no more oil dripping out, the hydraulic lifter is "reset". Install with confidence.

The shop recommended using a vice to squeeze the oil out. Put the lifter under pressure, let the oil drip out, then more pressure, more drip, repeat until no more dripping. I tried a big clamp, but that method did not work for me. Maybe if I had a big shop vice, that would work, but I found the manual pumping method to work just fine.

Once I had bled down that lifter and the rest, and put it all back together, she ran like a champ.

Moral of the story: If you re-use an old lifter, and it is not going back into exactly the same hole _OR_ if any valve work is done by a shop and the valve stem height may have changed, reset the lifter. In a case like mine, where all the valves were touched and a mix of lifters from two different heads was used, best course of action would be to reset all the lifters prior to installation.