Someone here mentioned to me that I ought to measure the valve clearances on my early 90’s Corolla (to see if that is the reason I’m seeing higher than normal HC’s in the state emission test.) Not an emegency sitution, the next emissions test isn’t until next year, but there was a thread here the other day on this subject of valve clearance and it got me to thinking …
This car of mine has hydraulic lifters. Isn’t the idea of a hydraulic lifter is that it fills with oil when the valve is closed, and in doing so pops up every time right against the low side of the cam, and staying that way as the cam comes 'round and pushes it down, opening the valve, while maintaining zero clearance. As parts wear, which would increase valve clearance otherwise and might make noise or fail to fully open the valve, the oil filled hydraulic lifter keeps it right where it is supposed to be, up against the cam, with zero clearance. With hydraulic lifters the valve clearance seems like self adjusting in other words. So there would be no reason to check valve clearance on an engine with hydraulic lifters.
There’s no recommendation for routine valve clearance measurement and adjustment in the owner’s manual. But the shop manual for the car gives a procedure, basically the same procedure I used to use on my 70’s VW Rabbit (which may or may not have had hydraulic lifters, I don’t know, but the valve clearance never changed in all the times I checked it.)
So what gives? What do you think? Is it a waste of my time to check the valve clearance?
Ok, maybe the recommendation to check valve clearance is to verify that the lifters are working correctly.
When you check valve clearance on a hydraulic lifter equipped engine, how do you know if the lifter is filled w/oil or not? Wouldn’t have to know that? I expect if you checked the clearance in the morning before turning the engine on, the oil would have drained out, and you’d measure a bigger clearance than if you’d started the engine first and filled the lifters.
@keith, according to some quick googling, I think you are right. At least the 4afe engine doesn’t appear to use hydraulic lifters. I’ll look in the shop manual again. Maybe I misinterpreted the wording. I thought it referenced the part at the top of the valve stem that the shim sits on as a “hydraulic lifter”.
It seems there are some Toyota engines that do use hydraulic lifters, but most don’t, from my Googling at least.
I think that you’re overthinking the hydraulic lifter issue. If a hydraulic lifter bleeds down it will usually tick or rattle for a few seconds after startup and may do this even with zero lash until it pumps up.
Lash is usually less than zero on a hydraulic as the hydraulic lash adjuster, pushrod fitted lifter, etc is compressed a bit during assembly.
The old VWs used the bucket and shim method and if yours never needed to be adjusted then you’re the exception to the rule because most of the ones I’ve checked needed adjustments. Usually the dealer kept an assortment of different sizes in a case and these were changed out as needed with no charge for the shims and with the removed shims going into the pot for use elsewhere; assuming they were not damaged.
The bucket and shim is superior to the screw and locknut method but with the former it usually means more complexity, special tools, and more time involved in adjustments.
@db4690, you’re correct again. What I honestly don’t get is whether this bogus lash info is generated by the marketing department or whether there are really that many mechanically inept engineers working for the car manufacturers because that lash info is repeated by most of them.
It’s also amazing how many shops and mechanics buy into that mantra and repeat it. Surely any half decent mechanic who knows anything about valve trains and cylinder heads should understand valve stem stretch, valve seat recession, stem mushrooming, and so on.
It’s kind of odd that Honda for instance (and they’re not alone) used to state that lash must be checked and adjusted very 15k miles. Now they say it can go forever even though the same adjustment method with the same screws and locknuts are used.
At a Subaru service school one time the instructor made a comment along these lines about valve lash and at the end of his little speech asked if there were any questions; which there were none. Deciding to poke I bit, I put on a puzzled face and asked how we were to determine if a valve was too tight or not because it would not be heard during an audible inspection.
Silence, eyes wandering, a few minutes of blather without answering the question, and a quick brush-off while announcing it was time for a break…
A couple of other guys there snickered a bit so I figured they were in the know.
I have owned 90’s era Corollas and they have mechanical lifters with screw adjusters. I know this because of many profanity laced Saturdays adjusting valve clearances with screw drivers and box wrenches. Toyota went to the shims in the mid to late 90’s, depending on the model, so it is possible that this Corolla may have shims instead of screw type adjusters.
Either way, valve lash should be checked and, if out of spec, adjusted. As for the critics of such a system, all I can say is “scoreboard”. All of my “annoying” Toyota engines have gone well over 200,000 miles and none of them were the cause of my cars’ demise. In the same time period I have had plenty of friends with those “wonderful” engines with hydraulic lifters experience various engine failures. This is anecdotal proof (the worst kind in my book) but I will take my chances.
On the 1zz-fe engine (late '90s to 2007 Corolla/Matrix) the cam has to come off to change the shims.
So while I actually enjoyed adjusting the valves on my four Hondas ('75-'88) every 15K miles I hope that everything is still in spec when I check the clearance on my '06 Matrix at 40K (60K in the Maint. Schedule).
On my 1995 Corolla 1.8 7A-FE the factory service manual (which I have) stated that the cams did have to come off to change out some of the shims.
Naturally, I didn’t remove the cams. And even though I did have the correct tool for depressing the buckets and holding them in place to replace the shims, I found it MUCH easier to just depress the bucket with a flat tipped screwdriver.
And wouldn’t you know it?
The local Toyota dealer didn’t have ANY SHIMS FOR ANY CARS in stock. They initially looked at me like I was a speed freak. But when I showed them what I needed, they ordered the parts.
They made their unnecessary and stupid remark that “no one ever checks the valves unless they’re noisey”
This thread got me curious about the conditions which lead to noisy valves (with excessive play), vs those that lead to valves with insufficient gap.
My thinking is that any wear in the valve opening/closing mechanism, including the cam lobe, pushrod, adjusting shim, rocker arm (or whatever it’s equipped with) will lead to noisy valves.
Yet, any wear in the valve seating area (either in the valve or the head) will lead to over-tight valves.
Is that a fair summary for where the wear occurs to trigger which event?
It’s a fair summary with a couple of additions.
Valve stem stretch due (usually the exhaust valves due to the heat factor) will cause tight valves also and severe engine overheating can contribute to this.
With excessively loose valves, the constant pounding can also mushroom the valve stems and cause the lash to gradually increase even more.
Thanks for all the great comments. I looked at the shop manual for the car again, and I was misinterpreting what it said. The early 90’s Corolla’s 4afe Toyota engine , configured w/DOHC 16 valves total, 2 intake & 2 exhaust/cyl, uses mechanical “bucket and shim” lifters, not hydraulic. The suggested valve lash adjustment routine service interval is 60K miles. Shims – if you have the proper tools – can be changed w/out removing the camshaft.
One more question on this topic: What is the derivation of the term valve “lifter”? On an overhead cam like the 4afe, the lifter is pushed down, not lifted. As far as I can tell, the lifter never lifts anything on the 4afe engine. It’s just there for something the cam can push on.
Does “lifter” come from the engine arrangement used on older cars and maybe on new cars too still, where the cam is configured below the valves, and the cam motion is tranferred to the top of valve using pushrods and rocker arms? I can see in that case the term “lifter” would make sense; the cam motion is “lifted” up to the valve, or the rocker arm is like a teeter totter, push down on one side, and the other side “lifts” up.
The ones on overhead cam engines are often called lifters but technically a bucket and shim would be called a cam follower.
Hydraulic versions with rocker arms would use what is called a lash adjuster even though there is no adjustment to be done to it.
