valve lifters/valve clearance adjustment

The "inspection" really consists of listening for excess valve noise, which implies that if the valve clearance is going to move out of spec, it is going to move in the direction of larger clearances.

If you don't hear unusual noise from your engine then I think you are OK leaving well enough alone.

 

I believe all current BMW engines (since about 1992) use hydraulic lifters on their high performance, high-revving, OHC engines.

 

Personally, I wouldn't worry about valve clearance on these engines - or any Toyota engine with solid lifters until you hit the 200K mark with proper maintenance. I did a valve adjustment on a Lexus V8 and while it was a PITA, it was a doable job and only 8 out of 32 valves were out of adjustment, I was able to shuffle shims around and I pulled the exhaust cams to facilitate access to the lifter buckets. There's a formula used that calculates the new shim/bucket needed, which IIRC is the thickness of the old shim+(measured clearance-specified clearance).

The only engines I would worry about REGULAR valve adjustments on are Honda engines, due to the fact they use screw and jamnut adjustments and they should be checked every major service.

 

I totally agree, Honda recommends valve adjustment every 15K miles. That's ridiculous. The tappets are made of aluminum to reduce weight so to allow 8000 rpm red line without floating. But the AL tappet wears out fast on the cast iron camshaft and requiring frequent valve clearance adjustments. This is one of the reason I don't buy Hondas, the other is the interfering valve clearance engine design.

The valve clearance on my 87 Camry is still within specs after 300K miles.

 

I'm hearing so many newer Accords and Civics with noisy valves recently. Heck, I worked at a Honda dealer for a while and the service manager's Accord with the K24 engine had bad valve clatter!

 

Great post by galaxee! On my 2010 Prius, there is scant room for working in the valve area since the hood when opened doesn't even expose the entire head. The reason for this solid lifter design has to be cost. I don't see any disadvantage to hydraulic lifters except cost. My 20 valve Volvo and 30 valve Audi both have hydraulic lifters and both redline to 6000 rpm with no problem. And I haven't had any of these 50 lifters fail in the combined 350K mile that these two engines have accumulated. BMW is all hydraulic, too. I have to conclude that Toyota is not giving its engine designers the budget to do everything they might wish.

 

At 160K my valves are still noisy till the engine warms up, if they don't get better at 250K I am going to think about looking into it.

 

My engine at 250k runs fine, a little valve noise under acceleration when cold, which has always been the case since purchased with around 110k, runs fine when warm. Repair info.
| Repair Guides | Engine Mechanical Components | Valve Lash (clearance) Adjustment | AutoZone.com
I was curious about valve clearances so I took off the valve cover and checked the clearances. I took notes on getting No. 1 cylinder top center, turned the crankshaft , but looking at the valves, I must have misread the camshaft markings, some of the cam lobes were engaging that shouldn't be for that reading. I then just read each valve clearance with the lobes in the upright position. Had I actually changed the valve buckets, I would have redone this part. Readings:
Intake valve clearance. (0.007 to 0.009) reference-- all inch readings.
1- 0.004 & 0.005 2- 0.004 & 0.004.
3- 0.005 & 0.005 4- 0.004 & 0.004.
Exhaust valve clearance (0.011 to 0.013) reference
1- 0.012 & 0.012 2- 0.012 & 0.013
3- 0.012 & 0.015 4- 0.013 & 0.015
The valve gasket was not leaking, but was fairly stiff and I replaced it. The job wasn't too difficult, mainly because I didn't change any actual buckets. So my questions is, how far can I push it before I really should do a valve adjustment, or am I already at that point? Since the exhaust valves have plenty of clearance, and the car is running well, including the idling, I'm planning toward leaving it alone for another ???k miles.
The above repair guide misses the gasket replacement need for sealant at the front of the engine at two spots, another guide should be referenced for this. Also interested in what others find, not much recorded in actual readings.

 

Since the Prius engine is like a typical gasoline engine with a 4-stroke cycle, my guess is that you needed to rotate the crankshaft 360 degrees to get the valves positioned as they should with cyl 1 at TDC.

It is interesting to see that you find intake valve clearance is less than spec. I would not have expected that. If that continues then you'll need to adjust that clearance soon - or else the engine will have big problems if the intake valves do not fully close and hot exhaust gases get into the intake manifold.

It definitely made sense to replace the valve cover gasket. Did you use the Toyota black FIPG sealant on the seams between the valve cover, cylinder head and oil pump casting?

I did valve clearance measurements on my 2001 a few years ago and posted the results at that time. I found that clearances generally were either at or greater than spec. Like you, I did not try to actually remove the camshafts to replace any of the "bucket" spacers.

 

I've adjusted screw type valve adjusters on quite a few hondas we've had over the years, but don't think I'd deal with buckets. I believe third gen Prius doesn't need adjustment, is hydraulic?

Anyway, in my experience any gaps that were beyond spec. were always on the loose side:

Could it be you didn't have the engine rotate quite right, the intake gap was starting to close up?

 

From reading in other sites I usually found the caution was on the exhaust valves, but I see your point.
Googling 'tight intake valves' I found mostly motorcycle references, and that tight is worse that loose. Something not to ignore. Some work for me to consider doing , on some long weekend. I do want to put this off.
I did measure the first intake valve with the lobe 'sideways', and the clearance was less than 0.004 in, actually very little at all. My method of measuring with the lobes 'up' gave me a sure method for the next time I check, but acknowledge I should follow the book. I'll also check the valve clearance when the engine is still hot, to see if that makes a difference.

I used Permatex ultra grey sealant, which I had on hand, other forums suggested its suitable when doing Honda's valve adjustments.
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Edit. I remeasured the valves last weekend , go the No. 1 cylinder top center, and got the same basic measurements as before. I also measured with a warm engine , temp around 140 degrees, with no real difference. I did plan on removing some of the valves, but had trouble with the little access plug on the timing cover.
There is little access to the little plug that gets to the chain tensioner, and that plug is locktite tight, I managed to 'round' the allen head hole. The next step-removing the timing cover- is a lot of work, I gave an attempt to remove the main pulley nut, but didn't have the right tool to keep the pulley from moving. So I've have decided to just leave it for a while.

 

Yes, it would be good to follow the procedures per the repair manual, but if you are checking the clearance with the cam lobe pointed 180 degrees away from the bucket spacer and valve stem, that should give you a reasonable result.

Regarding your Permatex sealant, if the valve cover is not leaking then you are good.

 

Thanks for sharing. You'll be okay. The main worry for you is your traction battery getting too dirty from those dusty Kansas roads. It might be worth taking the cover off the battery and using compressed air to blow out the air passages between the modules.

If your valve cover doesn't leak, then there is no compelling reason to ever take it off again.

 

Well knock me over with a feather, the G2 Prius uses various sized buckets, no shims.

Here is a link to a how to check and adjust valves.
http://techno-fandom.org/~hobbit/cars/TIS/ileaf/04toyrm/04toypdf/04rmsour/2004/04priusf/14/21bkbc1u/a040001.pdf

Guess mine is going to hammer it's way to the grave. The "tapping" has increased with 173K now showing....
Local dealer said they have never set Prius valves. Alluded to deposits (on the piston crown?) causing some interference that causes tapping. I have gone up and down on engine oil viscosity with no noticeable difference in the tapping. Oil consumption is now about a quart in 3-4000 miles. Used Prius motors are so cheap it's probably about as easy and cheap to swap motors as adjust the valves.
Someone asked about rear brake life. I have drilled several 1/4" holes through the drums to let the dust out, that has both gotten rid of the "very touchy when cold" issue and increased shoe life. I think I am over 35,000 on the latest set and they have some more miles in them yet.

 

My dealer said the same thing - wanted $200 to "clean" the valves. I said "if it doesn't help, I don't pay?" They decided it probably wouldn't help! No offer to check the valve clearance, though. Do dealership mechanics not know how to maintain and service engines?

 

It's really too bad they don't use adjusting screws. They are very easy to deal with. Well, relatively. My biggest issue with our last car, that had screw adjusters, was just getting at the valves: had to pull the lower windshield trim off. Once you do it once though, it's not that hard.

 

I've had vehicles with bucket lifters and several with screw adjusted lifters. The bucket lifter types have always required fewer valve adjustments. Usually none.

 

Maintain, yes; service, to an extent. Valve adjustment jobs are extremely rare. Given that the car runs fine already, and there is always the risk of boogering something else, a good tech would be reluctant to do anything. And the service adviser that you talked to probably didn't even know adjustment was possible.

Don't ever worry about the valves.

Do stay on top of oil consumption. I tore down a couple of motors and found worn main bearings. Every time oil runs low, those bearings wear a little more and the consumption problem gets worse.