I should get a video of this, but basically this is what's going on:

96 si - h23
rattling sound at just above idle and higher, it sounds like it's coming from somewhere around the bottom end/header, but on the back side of the engine from underneath it is loudest
compression is fine
idles fine, no really noticeable miss
disconnected the cat to make sure it wasn't that
it's nothing in the trans or clutch/fw, that's all fine

My inclination is to say that it's a bottom end knock, but it isn't fully regular, it's more of a random rattle. We have more to still check on, I've listened around with a screwdriver and the damn thing is just too loud to pinpoint.

As far as how loud it is, you can hear it over the open header. Could it be detonation from bad gas? Would it be that loud?

Thanks for the help guys

 

This isn't an automatic is it?

If so, ot's possibile it could be a broken or cracked flexplate/flywheel

 

Nah, it's a 5spd.

We just had the trans off to do the clutch, replaced the throwout bearing, cut the fw, they're all fine. It isn't any of that stuff....

Good to see you're still around chris, it's been a while.

Thanks

 

Good to hear from u2 gagz

 

Bump

Come on prelude forum, somebody has to have some advice here....

Tell me this, presuming that it is a bottom end knock, if we were to pull the oil pan off, you think we'd be able to find it by jiggling rod caps? I guess that is assuming that it's a rod bearing, but really who knows.

 

You're sure no part of the header/exhaust is loose?

 

How's the oil look? any pretty pearlessence? Is it not as bad when the engine is cold (thicker oil)?

Does it go away at any rpm other than idle or does it just get worse and worse with more RPM?

Does the noise go away with the clutch depressed or no?

If you're willing to get a little messy pulle the oil filter and cut it apart. Is there any metal in the pleats?

Does the gearbox have oil?

What's the valve lash?

Pirate

 

We're in the process of checking the rest of the header just to be sure, but we disconnected the cat to eliminate that.

I listened with a screwdriver and it sounds internal...

Pirate, will check on the oil. I've only observed it cold, and let it run for maybe 5 minutes, so not too hot, but he said it was doing it on the freeway too so I don't think that makes a difference.

It won't do it at idle, but just slightly above, and it stays about the same magnitude/pattern with rpm, but increasing in frequency with rpm.

I've already eliminated the clutch and gearbox as possiblilites. It will do it in neutral with the clutch out, or in gear with the clutch in.

Marcus set the valve lash after he first heard the sound, I didn't work with him, so I'm not *sure* that it's perfect, but he's not usually careless with stuff like that so it should be correct

We'll take a look at the oil and get back to you.

Thanks for the help guys

 

I had a similar problem which turned out to be the header hanger bracket. The bracket plate literally snapped off and was banging up against the header.

 

Worse case scenario, drop the pan and have a look at the bearings.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SKDRCR &raquo;</TD></TR><TR><TD CLASS="quote">Worse case scenario, drop the pan and have a look at the bearings.</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">Tell me this, presuming that it is a bottom end knock, if we were to pull the oil pan off, you think we'd be able to find it by jiggling rod caps? I guess that is assuming that it's a rod bearing, but really who knows.</TD></TR></TABLE>

Any insight on that?

 

I don't know how definitive wiggling the rods with the pan off will be. If it's a really badly spun rod bearing then it will probably be obvious but without a side-by side comparison for a qualitative comparison it can be hard to guage.

IMO if you pull the pan you can pull the entire main girdle and look at all the bearings.

 

we might as well.

I'll update sometime next week on it, no time for wrenching right now.

thanks

 

Possibly a problem with the rear balance shaft? I've heard of them siezing up and breaking before, maybe pull the balancer belt and see if it stops? Kinda labor intensive but just a thought

 

I have a similar problem, except my car accelerates really slow. It also tops at like 3-4k. Anyone have any ideas?

 

OP is this noise RPM dependent?

 

hey matt, you can't get a sound clip can you? or would that not help? I've been doing lots of work on other preludes (can you guess that sound) and I'm getting pretty good at it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by viper_boy403 &raquo;</TD></TR><TR><TD CLASS="quote">Possibly a problem with the rear balance shaft? I've heard of them siezing up and breaking before, maybe pull the balancer belt and see if it stops? Kinda labor intensive but just a thought</TD></TR></TABLE>

That is an interesting thought, if we get down to that, I'll give it a shot. Thanks.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by teg_95 &raquo;</TD></TR><TR><TD CLASS="quote">OP is this noise RPM dependent?</TD></TR></TABLE>

Yes, like it says above, it stays at about the same magnitude, but gets more frequent.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mattsnooz &raquo;</TD></TR><TR><TD CLASS="quote">hey matt, you can't get a sound clip can you? or would that not help? I've been doing lots of work on other preludes (can you guess that sound) and I'm getting pretty good at it.</TD></TR></TABLE>

I'll see about getting one sometime next week.

Thanks guys

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bboixtc &raquo;</TD></TR><TR><TD CLASS="quote">I have a similar problem, except my car accelerates really slow. It also tops at like 3-4k. Anyone have any ideas?</TD></TR></TABLE>

That *could* be a combination of 2+ problems not sure yet. Don't think this car has loss of power, but marcus said he felt that once.

 

that hanger that gets bolted to the block is a piece of usesless shiet. I cut mine off last week. Your motor torques too much, that things gonna break anyway. Theres more than enough support anyhow so its not necessary. Also, its located after the flex so its almost redundent. It being bolted to the block after reduces the use of even having a flex pipe.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mattsnooz &raquo;</TD></TR><TR><TD CLASS="quote">that hanger that gets bolted to the block is a piece of usesless shiet. I cut mine off last week. Your motor torques too much, that things gonna break anyway. Theres more than enough support anyhow so its not necessary. Also, its located after the flex so its almost redundent. It being bolted to the block after reduces the use of even having a flex pipe.</TD></TR></TABLE>

Yeah I know that man, we'll take a look at that next time just to be sure, but after listening around, I'm 90% sure the noise is internal.

As far as I can tell, the original reason that bracket is there is to keep the header off the oil pan under torque, but that is beside the point. We're gonna pull the 2-1 section and see if that doesn't change anything, it's gonna run rough w/o that thing, but at least we'll be able to eliminate that as a potential cause, plus it will only be on for about 20 sec.

 

yeah, thats a good idea. Isolation is the key.

I didn't think the bracket was your particular issue. I accidently sent the response to your post rather than no1knows908.

I'm sure almost everybody knows what that sounds like LOL (hanger off the twin pipe banging off your block) as it literally happens to almost everybody eventually

Yeah, thats a good point about the oil pan. That would make sense. I would assume that would only be an issue if you have bad motor mounts though or perhaps a shiet load of torque .

We should start a "whats the sound" sound clip archives lol. It will have sounds that you can compaire to with a list of possible causes. It would be more like a game I guess, but who knows!

 

Yeah, good idea, I just gotta see about borrowing my friend's HD camcorder, bc my digital camera's movie function sucks bigtime.

 

mhm that rear balance shaft sounds like a good thing to check. but i reread everything and and it does sound the that shaft. and have you checked for all exhaust leaks.

 

not a honda motor but does it sound anything like this?
http://www.youtube.com/watch?v=GulE6_SWXIk

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by viper_boy403 &raquo;</TD></TR><TR><TD CLASS="quote">not a honda motor but does it sound anything like this?
http://www.youtube.com/watch?v=GulE6_SWXIk</TD></TR></TABLE>

not quite but close

we'll see sometime in the next few days