No, it's not the exhaust manifold rattle. I know that noise by heart and this is definitely not it.

I did a bit of work around the engine head back in February/March (valve lash adjustment, replaced some oil seals on the head, etc). Ever since then I hear this odd rattling sound around 2500-3000 rpm, most notably when shifting as the engine speed falls through that RPM range before engaging the clutch again.

I can hear it when shifting, or when in neutral and revving a bit (again as the RPM falls is when I usually hear it). Or if I just hold the clutch disengaged and rev it, I hear it.

I feel confident it's something to do with the engine, not the transmission. It is not speed-dependent at all. It's engine RPM dependent only.

It's hard to describe what this "rattle" sounds like. When I hear it, I get a picture of something like a spinning shaft with a plastic washer free-wheeling on the shaft and rattling against something, if that makes any sense.

I've checked around the engine bay and really can't find anything loose or any loose washer on a rotating assembly or anything. I replaced the timing belt in May 2008, but as I said I never heard this sound (or never noticed it anyway) before March 2010. So I wouldn't think the timing belt is slapping around or anything. I triple-checked the tension on it back in 2008, and the engine has been running in top shape with zero problems since then.

Any thoughts as to what this sound could possibly be? When driving next to a wall or any large sound-reflective surface, the noise is VERY apparent and kind of annoying.

 

whats the engine? d? just a shot in the dark but..... maybe timing cover vs alternator belt? somewhat comon.

lol also I have all these toys that my mom just gave me and while looking through the box I have this semi and some other toys that go with the group and your avatar just reminded me what they are! i lost the missle that goes in the launcher in the back of the semi. they were the best toys. off to google.....

 

holy crap you have MASK toys?!?! DO WANT!!!!!!!

sorry assumed engine would be clear by user name - B18C1.

As I said I haven't messed with the timing belt in 2.5 years, and I just now noticed this noise earlier this year.

 

Have you tried manually opening the TB "by hand" while the car is parked and on.

 

lol wut? Nobody works on my car but me, been that way the past 9.5 years and 206,000 miles.

 

check and see if your header is touching your oil pan.i had a funky rattel at 2000k dead on.i put the car on a lift a come to find out header was taping oil pan.

 

i would say do a test to see if the bearings are going. have you drained your oil to see if you have any gold? i would rev the engine by hand, then pop a plug wire off to see if the noise goes away.

the reason i think rod bearings is all the honda engines ive done bearing work on started with a rattle noise around 2500-3500 rpms, then progressed into a serious knock

 

Well I just changed my oil 2-3 weeks ago, but I didn't notice anything. Don't plan on draining the oil again for another 6 months, though.

oh lawds I hope it's not the bearings. Sure the engine has 295K original miles and all, but the engine itself has been pretty much trouble free since I bought it more than 200K miles ago. I really don't have the time or money to try to repair such issues.

 

From my experience with a bad rod bearing. It only knocks upon acceleration

 

Well I poked around in the engine bay a bit today with the engine running, revved it a few times. I still can't seem to pinpoint the noise, although it does seem to be coming from the drivebelt-end of the engine, possibly around the alternator.

I noticed a wiring harness had some old hardened electrical tape hanging down in between the alternator and the pulley. I was like whoa that can't be good, and was hoping it was the source of the noise. No dice, that would have been too easy.

So it's still making the noise but I can't seem to locate what exactly is causing it.

 

that would be a slightly damaged bearing. a rod bearing will knock and time the rod moves up and down.

more than likely it can be you timing belt tensioner too. have you pulled the covers to inspect?>

 

have not looked inside the covers since I had the engine out of the car in May 2008.

 

LMAs can make a light rattling sound as they get into higher mileages, but you can kinda tell that the noise they make is under the valvecover, not really the front of the engine...

How old is the waterpump?
Have you tried taking off the accessory belts and seeing if the noise goes away? Whats weird is the noise started right after the valve adjustment, yet the noise is coming from the front of the engine. I assume your 100% on your valve lash settings?

 

check to see if its the bearing in the distributor housing...or something in the distributor

 

Well it could be the LMA's. I put my head down close to the valve cover and thought maybe the sound was coming from under the valve cover. I've been hearing a tick for a long time that I figured was the LMA's.

All belts, t-belt, water pump, cam and crank seals, were all changed just 25K miles ago back in May 2008 at 270K miles (regular 90K interval for timing belt). And yes valve lash is spot-on. I always check it at least once a year.

I wish I would have thought to replace the LMA's when I had the engine out of the car at that time.

 

Not too hard to do LMAs, you certainly don't need to pull the engine.

HOW TO: Install New Lost Motion Assemblies in a Vtec head (LMA)
https://honda-tech.com/forums/showth...&highlight=LMA


At close to 300k I don't know if it is really worth replacing them though.
And who's to says that's the source of the noise anyway? I hate throwing parts at a problem.

 

water pump bearing? place a long pry bar down the back of the motor around the alternator bracket or water pump area and put your ear to the end of the pry bar handle. the sound may travel and you might be able to find it.

 

It would be worth it to me. I currently have no plans in sight for replacing the car. I plan to continue to drive it for as long as possible and could easily see putting another 100K or more on it. These are the original old-style LMA's and I feel pretty certain they are pretty worn.

But I don't know for sure that the LMA's are causing this particular sound in question.

And it better not be anything related to the water pump. I always use genuine Honda parts for the timing belt, water pump, tensioner, etc. and those have all been on for only 25K miles.

 

your lma's are the newer style not the dinky b16a style. so your lmas should be fine, but normally the lmas tap loud when bad mainly when cold.

 

huh? I have the original LMA's at 17 years old now. How could they be the newer style? I'm pretty sure they're the old hydraulic style.

 

That's cool, you must have taken very good care of it to reach 300k. I would probably feel the same way if I were you.

IIRC the new beehive spring style LMAs are about $150-$180 for all 8 of them.

 

Any chance of a sound clip? Theres so many things that can make noise, it would suck to go through the effort and expense to replace the LMA's and it not be the problem..

Im sure there are some honda guys in the area that might be able to recognize the sound, arent there?

 

I could try taking a vid with my iPhone or point and shoot camera. The problem is that the sound itself may not be distinguishable over the other sounds around the engine bay as it revs up.

But I really do think that replacing the LMA's would make my whole valvetrain quieter, even if it didn't fix this particular issue. And if that was the case it might make this issue easier to pinpoint!

 

thats what i meant. the shitty lma's are the dinky b16a ones, you have the fatter itr style

 

This has nothing to do with your rattle, but I had the red M.A.S.K. Camaro when I was a kid. That thing was awesome with the gull-wing doors!