Tuning the C20LET - Hydraulic Lifters

These engines suffer from noisy hydraulic tappets. Various remedies have been suggested, from oil flushes to using thicker oil, all the way to replacing them with new ones.

While any of these solutions might sometimes work, most likely the noise will still be there after the herbal remedy. The root of the problem is inadequate lubrication - these are all engines in old cars, in the hands of the 2nd, 3rd or 10th owner, so oil changes have been neglected. If fully synthetic oil had been used from day one and it had been changed every 3-4K miles, I doubt that any of these engines would be suffering.

The tappets use engine oil under moderate pressure to 'pump up'. The idea is that the valve clearance is always zero, irrespective of engine temp, because the tappet adjusts itself by squirting out oil it doesn't need. This leads to more accurate timing (compared to solid lifters) and zero maintenance (no need to adjust the valves)

'Sticky' tappets don't only make the car sound like a diesel, but also allow increased wear on the valvetrain and fudge the valve timing as well.

The main reason the tappets 'stick' is that carbon and crud are obstructing the tiny oil passages. This means that the oil cannot move in or out through the holes - strange how 'thicker oil' is passed on as a remedy. In severe cases, all the flushes in the world won't clear up the holes, the tappets have to come out, be dismantled and cleaned properly.

At the very least they need to be dipped in degreaser overnight, then squeezed clean and finally dipped in hot engine oil.

The following procedure was first described by Dave Andrews, the well-respected tuner, and Yunus from ClubCalibra once wrote a guide. (local copy here). Here's how a tappet is dismantled and cleaned up:

View of a tappet sitting upside down - awaiting it's fate...

It gets banged on a wooden surface, so that the piston assembly loosens up and pops out.

A couple of bangs later, the piston is out:

Now using thin pliers or something similar, we squeeze the little ball at the bottom of the piston. It's got a spring behind it. If we can't feel the spring action, maybe the tappet is dead meat. They are only sold in sets of 16, so let's hope it's OK:

Both tappet and piston spend some quality time in a degreaser bath, to loosen up and dissolve the carbon deposits. Note how small the oil holes are.

When we decide they've soaked enough, we squeeze again to get rid of the degreaser:

We repeat if we feel that they need more. Use your judgement. If the balls spring freely and the degreaser doesn't get dirty, they're done. Take a photo of the tiny holes and show it to anyone who recommends 'thicker oil' to quieten them up. Yours will be quiet now though, don't worry...

Finally we immerse them in a bath of hot engine oil (fresh oil, of course, that we've heated in the kitchen) Careful - it smells bad and it's dangerous if dropped. (Hint: in the middle ages they poured boiling oil from the castles to deter intruders.)

One last thing: the tappets, their pistons and their cylinder head locations are NOT interchangeable. Keep them in family units using 16 small kitchen containers (labelled properly) or egg cartons:

To recoup: mix'n'match is a bad idea, these are not sweeties, they are precisely machined parts that have paired together.

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