Strange internal noise

[Nathan]

Well, I've developed a strange noise. Its intermittent, rev dependent, and halfway between a knock and a tap or tick. It's decently loud when present, my friend could hear it over the phone. However, it sometimes goes away and it'll take a few throttle blips to bring it back. It didn't appear until after I got my new tires and subsequently drove the car hard for a while. During that time, it saw several 7k revs and one that according to the tach was 7200 (which I dont believe, as I've bounced of the limiter at 7 before). I've done the old screwdriver in the ear trick to track it down (yeah, I'm about to buy a stethoscope as the screwdriver isn't ideal) and verified that it is NOT coming from the bottom end (listened intently to all parts of the oil pan and sides of crankcase) nor from the timing chain cover. It is loudest when I listen to either the valve cover, or the intake manifold...both of them seem to transmit the sound very well. I'm going to do more testing tonight and eliminate any of the accessories as possibilities...but does anyone have an idea as to what this could be? One of my theories was that I floated a valve with those high revs (still have stock valve springs) and there is now too much clearance between the cams and bucket shims, causing a cam lobe to kinda slap the shim on whatever valve got floated. I was thinking that could be caused by the spring being softened up and not returning the valve fully. However, this wouldn't explain it going away at higher rpms unless I just cant hear it. The sound DOES disappear at anything over 1500-2k rpms. Its a noisy motor though, so I dont know if it is just that I cant hear it, or if its actually gone. The other thing I thought of was wrist pin knock, but thats highly unlikely with the high quality pistons and rods in there. Not impossible I'm sure, but unlikely that the machining would be off enough to cause that this early. Currently I'm not too worried since its not coming from the precious bottom end...but I am a bit annoyed. I welcome any suggestions, as it'll help when I go digging into the engine this week to track the little gremlin down

[C-Kwik]

I hate trying to diagnose based on sounds over the internet. It is never easy. I will comment that if a valve floats, it's not going to suddenly start knocking, unless something broke as a result. Usually, this is when the valve hits the piston and bends. But if it did not hit the piston, there shouldn't be any damage. At worse, if there is no valve damage, a shim may have popped out of the bucket, but realistically, the valvetrain should be fine up to the RPM's you hit. I'd remove the valve cover and take a look though.

[Nathan]

Hmmm, yeah...the only way I could see it was if the spring was so shot it had lost its ability to return the valve to its fully closed position. However, that probably would have skewed the compression test I did after hearing the noise (just as a matter of routine, I wanted to make certain it wasn't something that had seriously damaged a piston etc.) The test came out perfect though, so I doubt its a bent valve or my theory of a totally shot to hell spring. Shoot, who knows...maybe there's a loose bolt rattling around in there or something I know there's a nut behind the wheel...Seriously though, if a shim had popped out, I dont think it'd be an intermittent sound, I'd think it would be continous...what do you think?

[bruinbear714]

Hmmm, yeah...the only way I could see it was if the spring was so shot it had lost its ability to return the valve to its fully closed position. However, that probably would have skewed the compression test I did after hearing the noise (just as a matter of routine, I wanted to make certain it wasn't something that had seriously damaged a piston etc.) The test came out perfect though, so I doubt its a bent valve or my theory of a totally shot to hell spring. Shoot, who knows...maybe there's a loose bolt rattling around in there or something I know there's a nut behind the wheel...Seriously though, if a shim had popped out, I dont think it'd be an intermittent sound, I'd think it would be continous...what do you think?

Is this the single cam engine or dual? If single, it can be a dead rocker.

Or the infamous timing chain rattle?

[Nathan]

New timing chain, tensioners, and guides, and its a dohc so it cant be a rocker. I didn't make it out to the garage tonight either...I'm kinda tired Hopefully I'll get around to working on it tomorrow if I get more sleep tonight.

[huguetpj]

New timing chain, tensioners, and guides, and its a dohc so it cant be a rocker. I didn't make it out to the garage tonight either...I'm kinda tired Hopefully I'll get around to working on it tomorrow if I get more sleep tonight.

I used a new timing chain kit from Courtesy when I rebuilt my engine last year. And it started making noises again... but that was after like 4-5k miles. But as C-kwik said, it's kinda hard to diagnose over the internet .

[Nathan]

Well I'm really stumped now...I got under the car and found that the clutch slave was so loose the bolts were about to fall out. I thought that was probably where the noise was coming from but after tightening it up the noise was still present. I'm starting to wonder if its piston slap (I DO have forged pistons in there) but I'm not sure. It seems loudest from under the oil pan, and I cant tell jack **** with the ol' screwdriver in the ear. I think I'm going to have to buy a stethoscope. My new plan is to take it out tomorrow evening and get it nice and warm, then see if its still making the noise. If not, I'll chalk it up to piston slap. If it does, I'll worry more and go from there.

[TrunkMonkey]

piston slap should dissappear once the engine is warm.

-demetrius

[Nathan]

Yeah I know...and thats why its my new leading theory. The noise SEEMED to get quieter once the engine was warm, and I cant remember ever hearing it after some driving. Actually, as of last night we decided my car sounds like a really quiet diesel. We were going to a Ranger game when I asked my friend "hey, whats the truck sound like?" to which he replied..."a quiet version of your car". It seems it makes a similar noise as a diesel at low rpms, but much quieter.

[mikesloud]

Hey, same thing here ,that noise!!! I just got my motor rebuilt 1400 miles ago , complete ross pistons, pauter rods,jim wolf cams, new valves, stiffer valve springs ,etc and I have had the same damn noise , It kinda sounds like a knock sort of, and goes away some times. I have had three different mechanics look at it they said it wasnt a knock. I first thought it was valve lash but it was all in spec. I have hell trying to figure out the noise. It seems to drive fine and the noise gets a little quieter as it warms up. I hate it , The car has great power but still worries me. What causes piston slap and is that common with forged pistons? what can fix it or what causes it? Could that be it ? No one is very helpful or even cares about hi performance imports here. I spent all this money and it worries me. I wish some one could help us !! thanks mike

[Nathan]

Yep, sounds like an identical build minus the headwork...and the same noise. How frieking weird is that? I have 600 miles on mine. Did it do it right from the get go or did it start after about 500? Mine seemed to wait for a little while before making the noise, but now its there. Let me dig up a few links on piston slap for you, I'll edit them in in a minute It'll be easier than me explaining it and probably more accurate too...

Edit: here's a guy with a similarly built but different 4 cylinder who also has cold start noise and still some when its warm. This one is particularly interesting to me because he's running the same piston to wall clearances I am. http://www.linkline.com/person....html

Here's an excerpt from another site, this guy seems to have the same sound I do as well: "I had a 86 Aries with "piston slap". When my ear was close to the oil pan you could hear it loud and clear. The noise wasn't too loud otherwise. I thought my bearings/lower engine was just going to seize up on me at some point. I just changed the oil, kept driving, put on over 130,000 miles while I owned it, junked it at 230,000 miles because of an accident. I only found out that this symptom is common with the engine from this website"

Yet another: "it may be piston slap or a going piston. This is what I noticed. It makes a "clack" noise every time the engine rotates, It's sounds as if it were a little diesel engine. I can't figure it out. It isn't as audible if the RPM is above 2000"

I'll find more later.

[klattr1]

make sure all your bolts on your manifold and turbo are tight. I had a similar noise before but some of the bolts that hold the C-clamps on the compressor and turbine were backing off. Just an idea.

[brage]

yeah I get a similar noise occasionally. running ross pistons + pauter rods. I'm 99% positive it is piston slap. It goes away after the car is warm and the pistons expand. I'm at 749 miles...

VERY common when using forged slugs!!! nothing to worry about.

-jeff

[Nathan]

Yeah, but mine doesn't really go away...gets quieter it seems, but NEVER goes away. I took it out and made certain it was warmed up, still slightly there. I'm going to check the turbo, exhaust mani, and intake mani bolts. Then I'm going to pull all the accessory belts. If its still there, I'll be a bit pissed and have to pull the rod caps just to make myself feel better.

[brage]

hmmm ... what are your skirt clearances, and oil pressure?

[Nathan]

They were between .004 or .006, I just know the guy said he followed the instructions that came with the pistons and thats what the specified. I'd have to call them to ask probably. Chances are he set them at .005 or .006 though.

[Nathan]

Oh, and oil pressure is 75 at idle cold, and about 30 or 40 once it warms up and the idle speed drops. in normal driving its around 60-70 depending.

[brage]

obviously that isn't your problem then... thats all the input I have, sorry.

[Nathan]

Yeah, oil pressure is great...the skirt clearances ARE pretty open though, so its entirely possible it has some slap. It just annoys me, I'm not convinced its piston slap yet, and if its not piston slap then I'm a bit worried. I'll get it figured out when I have some more time I'm sure.

[EstoMax]

did you guys have any results on this? because i think my 'new' old motor has the same problem. i just dropped it in, it has 91k miles supposedly (91 s13 motor) and it has a rattle over 1800 rpms with no load on engine, if theres load on the engine (20-60% throttle) then theres no rattle, if i floor it it seems to come back at about 3000 and then my car gets too loud to hear it after that. Otherwise if i cruise and let go of gas even if it stays in gear and 2k or so rpms the noise goes away.

So i pulled the motor out and put my s14 timing chain tensioners there, the s13 guides were in much better condition so i left those, except for the right side lower guide, (my s14 motor never had chain rattle, both upper chain guides are removed btw)

anddd that didnt change anything.. so im kinda lost now on where this blasted noise could be coming from, seems similar to what you guys are experiencing