So about 3 or 4 months ago I had a 9000rpm over rev with my car and right after I had a loud tapping sound. It sounds like it is coming from the back cylinder head. I have done a valve adjustment already examined both heads as best as possible with valve covers removed and dont see any problems. I have checked my loss of motion assembly on both heads also and they are still good. Furthermore I dont think im burning any oil. The noise also is only there once the car gets warmed up. The noise has not got any louder since the day it first started happening either so I don't think I spun a rod bearing. The Car runs great besides this loud tapping . Finally I have done a compression test and all are within 10 psi of one another. Anyone have any ideas of what could be going on?

 

Jeez, how'd you rev that high? Must have been an interesting story.


It really sounds like you just bent a valve. Even a difference by a few millimeters can cause issues. Interference engines ftl.

Still, if it passed all the tests you ran, I'm at a loss.

 

you could have trashed a bearing on one of the rocker arm rollers .

 

X2 look at the bearings on the rocker arm.

Sounds like an accidental down shift into 2nd instead of 4th

 

Ohhhh, he has a 6 speed.

I'm so scared of doing that.

 

Checked all the bearings on the rocker arms already and they are all fine.

 

gone thru it with a mechanics stethascope? great way to find noises, pinpoint tip accuracy
harbor freight has them on sale for 3 bucks! again

otherwise get a cylinder leak-down test done
It injects air into cylinder and measures for pressure loss- will see things compression guage wont..like bent lip on exhaust valve
If an exhaust valve was on the loose end of spec, its more exposed to the piston=danger
- valve float occurs in overrev situation- valve springs can be damaged

also send a sample of engine oil to a lab like blackstone- if there is any metal that doesnt belong or in higher than normal amounts- they can tell you whats up

 

how are you testing all these bearings?

 

well im stumped, maybe you spun a rod bearing or damaged a valve spring. I think someone on hear had an over rev and had to replace a few rocker arms and bearing, i think a few shattered on him. forget who it was....

 

I checked the bearings by spinning them with the rocker arms removed. I have listened to the engine with a stethoscope and I cant exactly pinpoint the noise but it seems to be from the back cylinder head. I guess I will get a leak down done next. Im thinking maybe its a slightly bent valve or something but would a compression test show this. Also wouldn't the motor not be running right if it was a bent valve? If I spun a rod bearing It would have more of a knock sound. This seems more like valves tapping very loud.

 

Check your pullys

 

Tough one without being there.
The only thing I can think of other than all the other responses is a bad lost motion assembly. If the over-rev cracked or distorted the assemblies internal spring it would allow for the tap. At ambient temps the part may feel ok but at a couple hundred degerees at even idle rpm it could account for the tap.
Reopen up the back valve cover and check all the motion assemblies again and if you see any scuff or chatter marks on the v-tec cam lobes check the assemblies and replace as per the factory manual.

 

Could it be the purge control solenoid? I know that is a common problem on the cl. It makes a clicking/ticking noise and replacing it can get rid of it.

 

thats located on driver side near the firewall--always worth checking--good call brian

 

I wish this is were the noise was coming from but its defiantly not .

 

Does anybody know if you have a slightly bent valve could the engine still run good ? Also since i have done a compression test with the engine cold and everything seemed good could I try it with the engine warm since the tapping noise does not happen until the engine is hot.

 

yes a slightly bent valve could cause it. Unfortunately, You may need to take the head off to find out what the problem is so you can inspect every thing close up.

 

Yea it will still run fun with a bent valve, but like above said you wont' know til the head comes off

 

If it was your car would you pull the head just to inspect, even though it runs great. Also if it was bent valve wouldnt 4 months of hard abuse would have caused it to break by now?

 

Nope. A friend of mine has been running with a Ben valve for about 2 years in his crx. Shooting nitrous and all. His idle was even lopey. Car runs good tho. Lol

 

Yes, i would. I would pull it and all the valves to inspect. If its just a slight bend thats all it would take for it to make noise. I know people who have run vehicles with bent valves for years. You have done most of the things that one should look at first. The next step is to take the head off and throw it on the bench and inspect everything.

 

yikes.
When i first got my car, Was very unfamiliar. Mis-shifted into 2nd but caught it before I let up on the clutch fully.
I have a tapping sound as well.

I'm afraid I've bent a valve.
I have no noticeable performance loss.
but on cold start ups, very loud tapping. it goes away slightly when warm, but I still hear tapping when I gas it.

yikes. Looks like I'm gonna have to pull it apart to inspect.

 

 

If I do pull the heads do I have to replace all the head bolts and change the head gaskets? Also would it be necessary to change the timing belt tensioner ?

 

sounds expensive....
dammnit, Why'd I have to mis-shift!!!! FAAWK.

 

Have you done a valve adjustment? Pull you valve covers and check it out.

 

will do this weekend.

 

justn- are you gen2 in hiding,, or really a gen3 posting in gen2?

while some gen2 have done a 6speed mod,,the rest of us wonder `what is this talk of overrev`??? auto trans wont allow it!!

 

Gen3 and have similar tapping noise that was attributed to my incompetence when I first got the vehicle.

I "over-revv'ed" for sure. caught my mistake, but I AM SURE that the tapping noise is from a bent valve or something not in tolerance.

 

fuck all this talk. lets get some vids up!

 

^you got it.....as soon as I make it home to the garage queen at 7pm.

 

Before you go tearing your heads off make sure the valves are all adjusted properly. You may just have one that is out spec.

 

Dont need to replace the head bolts but its cheap insurance, Head gaskets i would, and timing belt tensioner No.

 

Can a bent valve produce a hissing noise?

I mean an ever so slightly disturbance, letting air out kinda bend.
I believe I caught my mistake in time, Butt it COULD have hit the piston hard enough to bend it.

 

^never mind my theory.

if it was letting air out, I wouldnt be able to hear it. unless I took the covers off.

the only reason why I asked, was because my neighbor ALWAYS comments about an exhaust leak when I take off.

 

I just dont understand that if I do have bent valves why does it not tap when the engine is cold? It only taps when its hot especially when i shut it off for a few minutes then turn it back on this is when it taps the loudest. Heck sometimes you barly hear it tap when it running at normal operating temps then other times like if I drive for a while or beat on it it taps.

 

because metal expands when its hot therefore the clearances change.

 

i dont understand why you havent posted a video yet.

these engines are noisy period

 

ya i figured that it expands when its hot but than my thoughts are if its bent even slightly it should tap cold or hot. I know these engines are kinda noisey but trust me this is far beyond that. Also ill make a vid a little later today.

 

Rod bearings always get worse as the engine heats up.

Rod bearings get worse with load on the engine.

Valvetrain doesn't care about load but rpm can make changes in the noise.

Temperature sometimes does affect valvetrain noise and sometimes not depending on what the cause is.

A bent exhaust can make a sucking sound at the tail pipe or a small backfire. Bent intake can pop back through the intake.

Too much valve clearance will be noisier when cold. Too little valve clearance will get noiser when hot.

Before you tear into your engine, a leakdown should be performed even if compression results look good. If it passes the leakdown it nearly eliminates a bent valve.

There's always a chance you have a hurt piston which *usually* is worse when cold and gets louder under load but not always.