Curing noisy Mazda hydraulic lifters

Everything on this page relates to a 1987 Mazda Capella (aka 626, aka Ford Telstar). It probably applies to many other vehicles - the parts shop told me they sell the same lifters to Subaru owners - but treat with due caution.

This page reflects my recent laboriously acquired experience with hydraulic tappets (lifters). If your engine sounds like a giant knitting machine, workshop manuals are not much help - they typically say things like "Remove the lifters and check their condition". Check them how? What did they ought to feel like?
That's why I wrote this page. And, because in all my Googling around, I couldn't find anything useful on the subject.

How they work, sorta

First, a brief description of how the things are supposed to work. You can skip the next few paragraphs if you like.

The Mazda has a single overhead cam with twin rockershafts - quite a tidy arrangement. The lifters sit in cylindrical chambers in the end of the rockers. They're fed with oil via the hollow rockershaft and through a drilling in the rocker. This drilling feeds the chamber above the lifter; just before the drilling reaches the chamber it steps down a size to restrict the oil feed. The fine drilling continues out of the top of the chamber to fresh air, so the chamber stays full of oil but not under pressure.

Mazda rocker with lifter in place Rocker with lifter removed.
The start of the oil feed drilling can be seen
in the bore for the rockershaft.
Seen from above. The tiny hole for the oil bleed
can just be seen on the flat top of the lifter chamber.

The lifter is hollow, it has a light internal spring to keep it extended, and a little non-return ball valve in its base to let oil in but not out. When compressed, the lifter will very slowly leak down - this doesn't happen when the motor is running because each time the valve shuts and the load comes off the lifter, it can suck in oil through the ball valve to replace the tiny amount that's leaked out. If the oil supply fails (through blockage) then the lifter will end up sucking in air instead - and will clatter.

Hydraulic lifter Showing the hole in the base
for the ball valve

How should it feel?

If the lifter is OK, then it should feel 'solid', with no springiness. If it's springy, then it very likely just has no oil in it - it's full of air instead. I found most replacement lifters I bought were pre-loaded with oil and 'solid', but a few felt 'springy'. If you can feel any springiness at all (by hand), the lifter will be noisy if installed in that condition. That doesn't mean it's a dud, it's just oil-starved.

This one feels 'solid' And this one's 'springy' - probably full of air

If your lifters are clattering

It doesn't necessarily mean they're duds. It may just mean there's some dirt or sludge in the oil which is clogging the feed drillings in the rocker. If that's the case, fitting new lifters is a waste of money, it will silence the noise for all of a quarter mile till the oil leaks out of them. You need to do things like change the oil, fit a new filter, clean out the drillings in the rockers, and make sure that any lifters which are full of air are pre-filled with oil.

To check lifters in situ

To check which lifters are noisy, remove the rocker cover and see which rockers have too much play. Check each rocker when its valve is fully closed, that is when the cam load is off it. If you can feel a lot of 'rock', say an eighth of an inch (2 or 3mm), then the lifter will be noisy. Most likely the rocker has a clogged oil feed and the lifter has filled with air.

An easy way to make sure you're checking each lifter with the valve closed is to check no 1 cylinder's exhaust when no 4 is fully open, and vice versa; and no 2 when no 3 is fully open, and vice versa. Ditto for the inlet valves (in pairs of course).

You can just see from the angle of the rocker that the third exhaust valve back is fully open...
(the inlet rockershaft on the left has already been removed)

... so we check the second rocker by waggling it. Then turn the motor over a bit
and repeat for the other rockers in turn.
(Where'd the water come from? A torrential rainstorm in the middle of it all)

To fix noisy lifters

First, establish which ones are 'springy' as in the above paragraph. Remove the rocker shafts, and disassemble.

Pull each noisy lifter out of its rocker. It may be stiff, you may need to grip it tightly with pliers and turn it round in its bore to free it.
Refill the lifter with oil by submerging it in a tray of oil, squeezing it (by hand) and prodding the little ball valve with a piece of stiff wire (e.g. a paper clip) to let the air out, then releasing the pressure so it extends and sucks oil in. It should now feel absolutely 'solid' when squeezed.

Thoroughly clean the oil feed in the rocker. You'll need a fine piece of wire to poke through from the outer end - the wire should enter the fine drilling above the lifter chamber and continue all the way to the rockershaft bore in the middle of the rocker.

Then, push the lifter back into its chamber in the rocker. If you can pre-fill the chamber with a little oil before fitting the lifter, so much the better.

Next, clean up the engine's oil system as much as possible. That is, change the oil and fit a new oil filter. If the underside of the cam cover is covered in gritty sludge, clean it (the 12-valve Mazda has a steel plate inside the cover, held in by screws, which can be removed to make cleaning easier).

Then, reassemble and reinstall the rocker shafts. This is a bit of a fiddly job, to get all the rockers and the plastic spacers in the right places and not jamming or binding. I found I had to screw down the bolts little by little, constantly waggling the rockers and pushing the plastic spacers against the spacer springs to make sure they weren't stuck.

And that's it, or should be. Do check your workshop manual for the right torque settings, of course.

Rocker shaft, partly reassembled. It pays to keep all the bits in the right order...
(This is, of course, the inlet shaft - it has more rockers on it.)

Does it work?

Well, I had incurably noisy lifters. Over the space of a couple of years, I fitted sixteen new lifters (in a 12-valve motor!) without any lasting improvement. I had tried changing the oil (but without cleaning the rockershaft drillings, so it didn't do any good). Eventually I followed the procedure above - took the rocker gear all apart, carefully cleaned the rocker oil drillings, checked the lifters, removed the steel plate from the inside of the cam cover and scrubbed and waterblasted it all clean before reassembling it, changed the oil and fitted a new oil filter. It took all morning, but that was six months ago and I haven't heard a sound from the valve gear since.

Footnote - Oil Filter

The oil filter seems to be quite critical in all this. My motor is now fairly old, probably a lot of blow-by past the rings to make sludge, and when cornering hard it seems to get stirred up into the oil. I let the oil get a bit low and yesterday the motor started clattering like a knitting machine factory. I changed the oil, did the full lifter clean as above, but I didn't fit a new filter as I didn't have one. The motor started out quiet but within five miles was clattering as badly as before.

So I bought a new filter and fitted it (as I'd intended to do anyway), I didn't dismantle the rocker shafts again, just probed with a fine piece of wire through the bleed holes and checked by turning the motor on the starter, (spark plug leads disconnected), that oil was coming out of all bleed holes. (N.B. Don't let the engine start up when doing this unless you want oil squirted everywhere, guess how I know). At least four of the lifters had air in them, by feel. The motor was, naturally, clattery when started up but gradually got quieter and within ten miles all noise had disappeared. Which is what I hoped might happen.

So, as a first step, I'd say change the oil filter first, before doing any of the stuff up top. (And, like, new oil is probably indicated). If that doesn't silence the lifters within a few miles, then you'll have to do the full works above.

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Any comments or questions, email: cr at orcon dot net dot nz

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