Why are my exhaust valves so loose?

2016 EX-L
105k miles

I've never done a valve adjustment before so I went through all the cylinders to get a feel for it, and then through all the cylinders again to make sure I'm not imagining things.

Intake should be .009, usually looser before adjusting
Exhaust should be .012, usually tighter before adjusting

Cylinder 1
Intake: .012 & .011
Exhaust: .016 & .016

Cylinder 2
Intake: .013 & .011
Exhaust: .015 & .016

Cylinder 3
Intake: .013 & .011
Exhaust: .015 & .015

Cylinder 4
Intake: .009 & .010
Exhaust: .016 & .015

Cylinder 5
Intake: .008 & .008
Exhaust: .014 & .014

Cylinder 6
Intake: .009 & .008
Exhaust: .012 & .015

I thought exhaust valves were supposed to tighten with time. Am I missing something? Is there something wrong with my feeler gauge? Something wrong with my engine? Only code we've ever had was an oil pressure switch at 40k miles. The engine seemed to rattle a bit to me but nothing to draw attention in a parking lot.

Well if your valves are loose then a little rattle makes sense.

Sometimes loose exhaust valves do happen, although if someone else has done an adjustment on it before it's possible they could be responsible.

Wear of the valve train components makes them looser. Carbon build-up makes exhaust valves tighter. You apparently don't have much carbon build-up, which is good. Adjust them to spec and drive another 105k miles without worry.

WiiMaster said:

Well if your valves are loose then a little rattle makes sense.

Sometimes loose exhaust valves do happen, although if someone else has done an adjustment on it before it's possible they could be responsible.

Click to expand...

We bought it new and plan to have it until it dies so no one else has been in there yet.

I just posted in another Valve Adjustment thread on this yesterday, pointing to an older post of mine with my own results:

Maintenance Schedule - valve clearance | Page 2 | Honda Odyssey Forum (odyclub.com)

Would like to purchase a NEW Denso Alternator for 2011 Honda Odyssey, only find RMD | Page 3 | Honda Odyssey Forum (odyclub.com)

Although I report in metric vs. inches, I think your results are very similar to mine, which is reassuring and helpful to see. I commend your measuring twice before adjusting. Even measuring and logging once seems to be more work than 99% of people who ever do this.

As with many things, there are theories for why something will happen one way, will happen the other way, and the designers surely knew all that and more, and may have tried to optimize offsetting factors, etc. In common situations like this, I usually believe in the careful measurements vs. the competing theories.

As mentioned in my referenced posts, I took that info and used it to decide to aim for the tight end of the specified range during adjustment, since things seemed to loosen up, overall.

I doubt there is something wrong with your engine, and probably not with your feeler gauges either. When I did mine, I used a micrometer to measure the actual feeler gauge thickness, and found some variation with the cheaper set I used, so it is possible. Re-marked with the measured thickness of course. I also separated the few needed ones from the set, bent as needed, marked with tape, etc. for convenience in doing the job.

Another quick tip I did on doing the adjustments (it is a step up beyond measurement in difficulty) - I did the 4-5-6 cylinder intake valves first since those are by far the easiest. Then the 4-5-6 exhaust, a little tougher. Then get ready for working blind, I did 1-2-3 intake and 1-2-3 exhaust. Then checked them all again. There are some tool and procedural adjustments you can make at each step as things get tougher, so starting with the easiest helps - and the learning required depends on the exact tools you are using. Of course the tradeoff in doing this order vs. the shortest distance path is that you need to do more engine rotations. But I think the benefit outweighs the effort of extra rotations.

To give an idea of the precision of adjustment,
M6-1.0 threads, so 36* of screw turn is 0.1mm. 3.6* is 0.01mm. The 0.04 mm range in spec is 14.4*.
Of course adjustment is done based on feeler gauge feel rather than calculating angles, but I found it helpful to know how much turn would be needed.

Here's a pic or my notes and some of the tools where I also noted some of the angles of the adjusting screws prior to adjustment. When I'm back in there at 210k, I will probably do a quick check to make sure things still make sense regarding angle.


Some other pics. First one is the set of tools I ended up using.


I marked the front cam pulley sprocket with whiteout to make it easy to be sure I was on the right cylinder.


Front bank, with engine openings closed. A little extra work to move all wiring out of the way was worth the effort.


Rear bank is much tougher to access. I ended up laying some 2x2' square foam flooring pads on top of the engine, laying on top of those, resting my head on the cowl and doing it all by feel, at least when doing the 1-2-3 exhaust valves.


I did this at the same time as the full TB service, and some other maintenance things. I knew it all succeeded since after all that work, it ran exactly like it did beforehand.

highvoltage said:

Wear of the valve train components makes them looser. Carbon build-up makes exhaust valves tighter....

Click to expand...

Carbon buildup (which would happen on the valve seats) would also make valve clearances increase (looser). It pushes the valve away from the rocker arm and closer to the piston making the lash greater.

It's typically valve seat wear that causes lash to decrease (tighten). If the seats wear the valve sinks into the head which makes it closer to the rocker arm. If it sinks too much, the lack of adequate lash stops it from sealing and begins causing misfires (and even burnt valves since they can't cool properly).

HeatherK said:

I thought exhaust valves were supposed to tighten with time. Am I missing something?

Click to expand...

As others have said, you are all good.

Wear at the 'bottom' of the valve (cylinder side), the clearance tightens. Wear at the 'top' of the valve (valvetrain side) will loosen clearance. If the wear is balanced, the clearance will remain the same. Otherwise, it will tighten or loosen depending on which type of wear 'wins'

You are on the 'happy' side of things - it is better for the valves to get noisy and loose instead of quiet and tight...

-Charlie