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For 98+: Valve Clearance

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I have a 98 626 with solid lifters for my valves. It is now quite a while ago the valve clearance was checked, so I'm planning on doing it rather soon. However, I (off course) don't have the mazda tool for valve clearance adjustment. Has someone on this forum experience in changing the shims without this tool (by for example pressing the lifter and getting the shim out by something magnetic)?

A second question out of curiosity: does the valve adjustment of most 98+ 626's here only need to be checked or do you also have to adjust them (and by how much)? (I expect a bit more wear in my cylinder head because of running LPG which has a higher burning temp)

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I usually check my shims the weekend before I do a timing belt change(due to the fact that your gonna be in there anyway). The standard for the clearance is .026mm(.010in), but the allowable range is .225-.295mm(.009-.011in).

If you're doing a timing belt change, measure the clearance right after you take the valve cover off but before you do anything else. The equation is basically: new shim=removed shim thickness+measured clearance-standard valve clearance. If you need to replace them, you can see if any of the ones you have to replace can be switched around with others to save you some money.

To replace them, remove the timing belt, then remove the camshafts. Remove the shims(you can get the measurement for the shim thickness now), replace the shims, reinstall the camshafts and bearing caps, then continue on with the timing belt change.

Hope this helps.

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Thanks for the reply!

It is not yet necessary for me to replace the timing belt. However, because I run LPG, I wanted to check the valve clearance in between two timing belt changes....but this weekend I noticed my belt is now 50,000miles old, in stead of 35,000miles (which was in my memory). So I'll probably postpone the valve clearance checking to the end of the year to do it together with the timing belt change...Especially because this will make the shim adjustments probably a lot easier. Also, I don't have any sign of valve clearance problems (I recently timed accelaration, top speed and determined average fuel consumption and intake vacuum, and all parameters are still the same as when I bought the car)

Only I should not forget to get some camshaft oil seals from the dealership in that case I suppose...(dealership is a long way from home, and it is easy to forget things like that ;) )

Just out of curiosity, do you have to do (major) adjustments to valve clearance, or are it only minor adjustments. I ask this because the range of shims is very small (less than 1mm) which means that the cylinder head will need to be reworked if major adjustments have to be made regularly....

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No, they shouldn't be too major, unless you haven't done it for like 200,000 or so miles, and even then it shouldn't be too bad.

If you want to check between timing belt changes, you can. The only thing you'll be able to check is to see if any of them is outside the clearance range. That will let you know which ones are out and which aren't. To check them you have to manually turn the crank till cyl 1 is at TDC, check certain ones, then turn it one full revolution and check the rest. Don't remember right off hand which ones to check on which turn of the crank, but it's in the Haynes manual.

If you do check between changes you might want to replace the valve cover gasket depending on it's condition.

Check is basically: Remove valve cover, set TDC, measure, turn crank, measure, record measurements, reinstall V.C.

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Thanks again! I have the Haynes manual, so that won't be too much of a problem :smile: I was just hoping someone had already tried to get the shims out with the camshafts installed....

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  • 4 months later...

Just to answer my own question ;)

It is possible to adjust valve clearance with the camshaft in place. Not very easy, but doable for the experienced DIY'er:


>>Check valve clearance

-Wrench with 10mm socket & 16mm spark plug socket

-RTV sealant

-Depending on its state: valve cover gasket

>>Adjust valve clearance

-2 large (10mm wide tip) screwdrivers; as long as possible

-1 medium (6mm tip) screwdriver also not too short

-very tiny screwdriver

-magnetic pencil/bar


-Measure valve clearance (e.g. Haynes does explain this very well, or see this: http://www.mazda626.net/index.php?s=&s...t&p=229085)

-If one or more valve clearances are out of tolerances remove the shim using the procedure below:

*Have the cam above the shim pointing upwards for maximum clearance

*Press the tappet down as far as possible with the first large screwdriver

*Put the tip of the second large screwdriver between the tappet and the camshaft to block the tappet in the lowered position

*Remove the first big screwdriver

*With the tiny screwdriver, loosen the shim from the tappet (there's some suction of oil between the shim and the tappet), then pull it further out with the magnet pencil/bar

*You can't completely remove the shim, because the second large screwdriver is blocking the way

*Now, with the medium screwdriver, press the tappet down from the other side

*Remove the second large screwdriver which was between the camshaft and the tappet

*Now completely remove the shim with the magnet pencil/bar

*Calculate the new shims size and buy the correct size at the dealership (probably the only place to get it)

*Press the tappet down again on the back side using the medium screwdriver

*Insert the new valve shim and push it into the tappet as far as possible (possibly 80-90%)

*Now remove the medium screwdriver and press the shim in totally

-Do this for every valve which is out of tolerance

-Put the valve cover back on, and you're done!

The procedure will be a pain in the ass the first time you do it. It took me 30 minutes before I found out this procedure myself and was able to remove the shim. Next shims were much more easy to remove!

Because the insertion of the shim is so much easier than the removal, you don't have to be too afraid of removing the shim, withour being able to put it back in....

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With a bit of practising, you can do it in 5 min per shim (and normally you'll only have to do a few), so it is even faster than removing the cams.

Only when all valves are out of tolerance I would remove the cam shafts, because my procedure is not that fun if you have to do it 16 times (and it also makes swapping shims between tappets easier with the cams off). But that is not something I would expect to happen...(except maybe if some does his first check after 200+k miles)

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