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valve adjustment

Discussion in '2nd Gen. Tacomas (2005-2015)' started by OCTaco, Mar 25, 2010.

  1. Apr 27, 2010 at 9:30 PM

    davidch New Member

    Apr 27, 2010
    I recently adjusted the valves on my two Toyotas: a 2002 Tacoma with the 2RZ engine and a 2000 4Runner with a 3RZ engine. I have done a lot of Internet searching to see what's out there on this subject. Not much.

    There are lots of misconceptions and false statements about valve adjustment on these engines. I thought this might be a reasonable place to clarify things. The factory shop manuals, which I own for both vehicles, does state how to adjust valves. However, it doesn't always say so in the clearest fashion.

    My Toyotas have 4-cylinder engines. Both are DOHC, shim-and-bucket adjusted. The 6-cylinder 5VZ-FE engine uses an identical system, though of course it's a V engine and drives its camshafts via belts rather than a chain.

    A recent question on this thread concerns where the shim is placed. In the 3 engines named above, the shim is over the bucket. It fits between the bucket and the cam lobe. This means the shim can be replaced without removing the camshafts. A special tool is needed to do this.

    Regarding shim under bucket: This arrangement will be found on high RPM performance engines. Many motorcycles use it. Also, I think, certain exotic Italian cars. The major reason for putting the shim under the bucket is that the shim cannot be spit out at high RPM. It has little to do with being more impervious to wear. (Furthermore, shim-under-bucket aids high RPM by being slightly lighter due to smaller shims than shim-over bucket.) Replacing shims on these engines requires removing the camshafts. No special tools needed, other than standard mechanics tools.

    Your 5500 RPM Toyota truck engine does just fine with the shim on top of the bucket.

    What's the advantage of shim and bucket anyway? What's wrong with rocker arms? Plenty of DOHC engines use rocker arms.

    In the shim-and-bucket system, the camshaft pushes straight down on the valve. Side thrust on the valves, which causes the valve guides to wear, is thus kept to the minimum possible, very near zero. Shim-and-bucket is the kindest system to valve guides.

    In any engine with rocker arms, there is some degree of side thrust on the valve, thus causing valve guide wear. The end of a rocker arm always moves in an arc. Think of a see-saw. When you ride one you're not moving in a straight line, but instead are moving in an arc.

    Now, on with valve adjustment. In my Tacoma, which I bought new, I first checked the valves at 38k. Perfect. No adjustment needed. Again recently at 90k. Again, perfect.

    In my 4Runner, which I bought in '03 with 65k on it, I don't think the valves had ever been adjusted. I checked them at 90k - this may have been the engine's first adjustment - and 15 of the 16 valves were perfect. One exhaust valve was .009 inches (minimum is .010, maximum is .014), so I replaced just one shim.

    That 4Runner now has 143k on it. In a recent check, 6 of the 8 exhaust valves needed adjustment. 2 had shrunk to .009, 3 had shrunk to .006, and one had shrunk to .005.

    All intake valves were still within spec. This is understandable. Exhaust valves have a much tougher life.

    Sadly, one of the valves that needed adjusting was the one closest to the firewall. Access is extremely difficult to that valve with the special tool used to compress the bucket to permit shim access. Primarily, the heater hoses are in the way. I worked at it for a long time, and even got under the vehicle, unbolted the motor mount at the transmission and jacked the engine/transmission assembly up an inch or so to rotate the engine away from the firewall a little bit. Still not enough room. (The 2RZ in my '02 Tacoma would have the same problem.)

    I don't think I'd encounter this problem on a V6 engine. I should state right here that I have never adjusted the valves on a 5VZ engine.

    Anyway, I have the knowledge, tools, and time to remove the exhaust camshaft. So that's what I did, primarily to ease access to that hindmost valve. It turns out that removing the camshaft made changing the shims on the other 5 valves easier as well.

    My rule in the future will be this: if more than 2 valves need adjusting, or if the hindmost valve needs adjustment, forget about using the special tool; just remove the camshaft.

    Here's how you have to use the special too. First, rotate the engine to TDC on the #1 cylinder's compression stroke. Check all 4 valves on #1, the intake valves on #2, and the exhaust valves on #3. For each valve needing adjustment, remove the shim, measure it, make a note, and put it back in. NEVER TURN THE ENGINE WITH A SHIM OUT.

    Okay, next rotate the engine (clockwise only) 360 degrees (the cam rotates 180 degrees). The engine is now at TDC on the #4 cylinder's compression stroke. Check all 4 valves for #4, the exhaust valves for #2, and the intake valves for #3. Remove, measure, note. (Reinstallation isn't necessary if you're now going to replace these shims with correct thickness shims before turning the engine back to TDC on #1 to adjust the first set.)

    Now buy the shims, and repeat the process of removing and reinstalling.

    Consider the process if you remove the cams to replace shims. It's still a 2-stage process to check all 16 valves. However, you never remove - and reinstall - any shims to measure them. Just note the clearances. Now remove the cams as explained in the shop manual. (No special tools needed for the 2RZ and 3RZ engines to do this.)

    All 16 shims are readily accessible. Measure, note and replace. Easy.

    However, if I had just a few accessible valves needing shimming, I'd use the special tool method.

    A word about noise: there are many out there on the Internet who advise only inspecting and adjusting your valves if they are noisy. I don't understand that. Certainly a valve that's too loose will be noisy, but a valve at .002 on its way to zero clearance is not noisier. Though it might get noisier once there's negative clearance and the valve is being held open during engine operation. But clearance below spec makes no extra noise.

    And frankly, diminished clearance is likely what you'll get on shim-and-bucket engines. The cam and the shim itself - the rubbing surfaces - are nearly impervious to wear given proper oil changes. The diminished clearance is due to the very gradual but inevitable eroding of the valve's contact face and the valve seat. The valves - and in particular the exhaust valves - are very slowly eating their way into the cylinder head.

    The word out there on the Internet is that the exhaust valves on the 2RZ and 3RZ engines need regular checking when you've got over 100k. Lots of reports of 3RZs with 120+k and tight exhaust valves. As I discovered, my 3RZ tighened not at all in the first 90k, and then considerably in the next 50k.

    If a valve runs with near zero or negative clearance it's only a matter of time before it burns and the engine will need the head removed and a valve job. Big bucks.

    Proper clearance gives the exhaust valve the most time to sit on its seat and dissipate heat. That's key to longest life.

    I think it behooves any owner with one of these 3 engines (2RZ, 3RZ, and 5VZ) to have the valves checked when the engine hits 90k and then every 30k thereafter.

    Even non-mechanics can learn to check valve clearances and then leave adjusting - shim replacement - to someone else. A few wrenches and a set of feeler gauges suffice to check clearances.
  2. Apr 27, 2010 at 11:37 PM

    Peru Well-Known Member

    Aug 8, 2009
    First Name:
    Redmond WA
    SR5 -- V6 -- 2005 -- 4X4
    X2 what he said. If left out of spec the ensuing damage will cost a whole lot more than a couple of hrs and the price of shims.

    Don't ask me how I know.
  3. Apr 7, 2011 at 1:50 AM

    bwill808 Active Member

    Nov 27, 2010
    First Name:
    00 extra cab 5lug trd supercharged
    trd supercharger the grey version , k&n intake , trd headers , 2 1/2 inch catback
    so whats better loose .014 , or tighter , smart guy i dont know, read a forum stating .015 for v6 is ideal , but , the spec is .011 .014 i have asked wrote like 100 forums with no straight answer ffrom any one, i dont want to be the guuiny pig but i will if i have to , . the new v6 1gr tacoma etc. changed there spec to include .015 , i am debating . what do u think about burnt shims hot spots , same for my cams r they ruseable
  4. Apr 7, 2011 at 7:35 AM

    chris4x4 With sufficient thrust, pigs fly just fine. Moderator

    May 8, 2008
    First Name:
    Tenoe, AZ
    2013 Rubicon Unlimited,
    4.10 gears, sliders, and lots of buttons.
    Loose (a little) is better than too tight. Thats why the specs dont go lower than .011.
  5. Jan 9, 2016 at 11:37 PM

    EJPHI Well-Known Member

    Jan 9, 2016
    N CALI
    2003 2.4l 5sp 5 lug
    pt474 cruise control Alpine head unit
    I'll echo a lot of what Davidch said 5 years ago.

    I just did this on my new to me 2003 2.4l with 110k miles. The service records did not indicate that the valves clearances were ever checked.

    My #2 exhaust valves were both at 9 mils (spec is 10-14 mils) and both my #4 intake valves were at 6 mils (spec is 6-10 mils). So I replaced the shims on these 4 valves to get 11 mils on the exhaust and 9 mils on the intake valves. All the other valves were in the middle of the specified clearance range.

    I thought I would pass on what I learned along the way:

    The service manual for my truck says that the valves should be checked every 60k.

    Most of the factory installed shims have a 0.01 mm (0.4 mil) thickness increment. Check the valve adjustment charts in the FSM.

    The replacement shims are only sold in 0.05 mm (2.0 mil) thickness increments. So save those original shims in case you need to get in range with a thickness that is no longer available.

    Dealers charge about $7 per shim with the on-line 30% discount. The bend over counter price can be double that if you are lucky. Most local to me dealers did not have the shims in stock, so plan ahead for truck down time.

    These guys sell the shims for $5 each, but you have to buy 4 at a time:


    They also sell a tool you can use to lap your existing shims down to size.

    My machinist friends don't have a problem with lapping shims because the case hardening is much thicker than a couple of mils. But they say that lapping a mil of hardened steel will require a lot of elbow grease. If you go this way, they recommended placing the lapped side down so the un-lapped side interfaces with the cam lobe.

    I did not remove the cams and would not do so even if I had to replace all 16 shims! I found a great tool on You Tube that makes it very easy to push the valve bucket down even for the cylinders near the fire wall:

    Motion Pro 08-0018

    I still used the wedge from the Schley Products 88250 valve adjusting tool kit, but the pliers were too big and didn’t press the bucket down far enough without a struggle. To each his own.

    This is a precision operation so use good quality measuring instruments and make sure they are accurate.

    My Starrett dial calipers were not good enough because they only have 0.5 mil resolution. My Mitutoyo micrometer has 0.05 mil accuracy and resolution so it is good enough. My feeler gauge set agrees perfectly with my Mitutoyo micrometer, but would not agree with my Starrett calipers.

    So check your feeler gauges against your micrometer. I found the Toyota shims were dead nuts so your micrometer should agree with them too.

    Really if you cannot get the micrometer, feeler gauges and shims all on the same page, please buy better tools before attempting this project.

  6. Jan 11, 2016 at 10:56 AM
    Lester Lugnut

    Lester Lugnut Well-Known Member

    Mar 3, 2010
    '15 Tacoma PreRunner V6 SR5 Auto
    Would be curious to know how many here have adjusted the valves on a 2nd Gen Tacoma V6 1GR-FE engine and at what mileage this took place?

    Attached Files:

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