Hey Scotty! Thanks for all your advice. Perhaps you can shed some light on this please…
The Car:
1998 Honda CRV, 1997cc B20B3 engine, DOHC, 100k miles on the clock. Running fine with good power but with a faint hesitation only when cold between 2000 and 3000 RPM, that clears up when warm.
The problem:
I adjusted the valve lash, setting the clearances at TDC for each cylinder to the factory spec as per the owner’s manual (0.005 Intake and 0.008 Ex).
I noticed at cylinder 1 was pretty much in spec, but 2, 3 and 4 where way too tight on both the intake and exhaust valves. I had to adjust the screws on these to increase the gap to fit the feeler gauges by turning them at least 3 or 4 full turns!! Thinking that there is something wrong with that amount of adjustment being needed, I double checked the gap spec and the feelers and they are correct.
I set the gaps and locked them, afterwards I checked gaps again to be sure and all were good.
I noticed that on cylinder 3 exhaust valve 2, I had to adjust the screw to its full adjustment to get the gap to 0.008. So, there is no more loosening adjustment left on that one, it can only be tightened.
Now the valves are far noisier than they were before, even when warm (sounds like an old diesel) and the car feels like it might have a bit less torque down low in the RPM.
If the car has never had the valves adjusted like it was supposed to during its life, do you think it was a bad idea to put them to spec now? Is it a like an old auto transmission where it’s a bad idea to fully flush the fluid because of wear and tear?
I can live with the noisy valves if that is how it is suppose to be, but I is pretty loud and I’m fairly sure they are not supposed to sound that loud when warm.
What are your thoughts please?
Thanks
Found a clip on youtube with a chap who has the same problem with the exhaust valve adjustment screw being fully out and he chose to grind down the rocker face a bit to get more travel on the screw. (Not sure this is the way I would go, but interesting fix nonetheless.)
At 1:30 he describes the problem and at 2:16 he describes the reason he found on internet for this problem occurring.
https://www.youtube.com/watch?v=keLQI2hebsQ
Would anyone like to comment on his fix? Is it safe, or asking for a that rocker to break with time as it is now thinner than originally designed?
Update:
Yesterday I decided to re-check the valve lash and the gaps were all far too big! This is after I adjusted them the first time, so I must have done something wrong. This time I adjusted them when the pointy part of the cam lobe was on the opposite side to the rocker surface (at 180 degrees from the rocker). I adjusted them to be spec (so not on the larger or smaller side of spec, but exactly what spec says.) I then rotated the engine until the cams were in their corresponding TDC position, and re-checked the lash here, as this is the position the manual says one should set the valves at, (though I believe it is simply to speed the process up as one can set both exhaust and inlet at the same time per cylinder). The clearances checked out fine.
Interestingly, the exhaust valve on cyl 3 no longer had the issue I found the first time - where the lash adjustment was out as far as possible with no more travel left on the screw. When I checked the valve I found that I had in fact adjusted it to its full extent to just get the feeler gauge to slide in the first time I adjusted it. Puzzling, its almost as if something was sticking the first time??? This time the clearance was so large that I had to turn the adjuster screw 3 or 4 full turns to get it back to spec.
I double checked and triple checked the clearances before closing it up. (Spec feeler had drag on it and the next feeler size up would not fit.)
Started the engine up and it was way quieter. Some ticking to be heard with the bonnet open, but nothing in the cabin with doors/windows closed. Test drive showed good torque and after a full tank of gas, the gas mileage was spot on.
The lesson I learned:
1. If it sounds too noisy after adjusting the valves, go with your gut, especially if you know the car, and double check your work, cause in this case, I F it up somehow, despite being careful with what I was doing and using the exact same tools.
2. If you find that a valve is at the end of its adjustability, don't dive into trying methods that others have used immediately, without double and triple checking your work. Only as a last resort should you be thinking about grinding down rockers like in the YouTube vid I posted with this thread. (Thankfully I did not just go straight to this solution.)
Cheers
Only thing I can think of at this point is that some of the valves have worn a great distance into their seats, requiring you to basically unscrew the adjuster. You should never have to file down a rocker to make it work. I think a rebuilt cylinder head is in your future.
Sadly, I'm thinking the same thing.....
Did the manufacturer specify that the valve lash needed to adjusted when the engine was hot or cold? Are you sure you got the firing order right? For most in line 4 cylinder engines it is 1-3-4-2. If you had to screw the adjuster all the way in, something is terribly wrong. On some engines, you only turn the crank 180 degrees to get TDC on the next cylinder. If you went 360 degrees, you were adjusting the valves on the wrong cylinder.
Thanks for your comment. I set them at TDC when dead cold as per the manual and the sticker on inside of hood. (I also took the plugs out and used a long screw driver to check that the piston had stopped coming up was at TDC.) The cam lobes also were in the correct position for each piston at TDC. Set them in the order of 1,3,4,2 - with the markings on the cams as per the manual.
Has the belt ever been changed yet? If that was off & you did an adjustment you'll amplify the issue.
Thanks for your comment. The belt looks reasonably new to me. With 100k miles on the clock, I suspect it was changed once probably. Don't think the belt is off (I think you mean the timing? ) because the car runs really well and makes good smooth power throughout the revs, gas mileage is correct too. Also when I rotated crank to set the pistons to TDC as per the shop manual, the markings on the cams were exactly as per the manual for each cylinder. (I also took the plugs out and used a long screw driver to check that the piston had stopped coming up was at TDC. So I think the belt okay and the timing is correct.) The cam lobes also were in the correct position for each piston at TDC, as per the shop manual. I think there must be another problem, likely some shortening of the valve stems if the valves had never been adjusted in their life.
With parts as critical as a timing belt especially when you hit 100k, unless you have a receipt proving it was changed always assume it wasn't..
The exhaust valves I have found on newer hondas have always gotten "tighter" with mileage. After a proper adjustment to proper gap they were always a little noisier but the car actually ran smoother, especially at idle. Like previously said check your timing belt for slack.
Thanks for your comment. Yes, my research found the same that these B20B engines valves get tighter with time. I think perhaps the no 2 exhaust valve on cylinder 3 might actually be shortened by never having been adjusted, so that might be why no more adjustment is available on the screw to open the gap. The timing belt feels pretty tight to me, a couple of mm play under a strong push between the cam gears, so don't think there's slack there. Out of curiosity, why would slack cause valve clearance issues, is it because the play in the belt would be the cams would not rotate evenly? Thanks
If the valves are to tight it will make it quite, but it could cause you to burn the valve up. Just keep it in spec.
This isnt uncommon. This is why the dealerships damaged 20% of the engine they did this on. After you do the adjustment take it for a drive. Then go back and readjust to factory spec. The heating cooling cycle can cause you to lose adjustments and secondary or third adjustment is needed. Just make sure your doing properly and you fully tighten to spec. Make sure you double check your work before test drive. I've done valve adjustments on b20 engines at least 15 times not including my crv and I had this happen 8 times. If your still having the issue chances are things are just worn out.
Hi, thank. Yes I will recheck the lash as it really sounds like an old diesel and I'm pretty sure that is not right. A bit of ticking is fine, but not clattering like its doing now. I might have done something wrong.
If it's noisy it means to much lash. If it's really quiet to little lash . Just take your times double your work . When you tighten the nut make sure the screw stays still. If it moves Even slightly when tightening everything up, your adjustments will be off.