Rattling/Knocking sound in engine

[95 Mustang Convert]

I recently just started getting a nasty noise coming from the engine in my 95 v6. The noise sounds like someone shaking a can of spray paint and is only apparent at idle when the engine is up to full operating temps. It goes away once you rev the engine past 1200 rpm's or put it under any sort of load. It also seems as though it is coming from the passenger side of the car, near the valve cover. The car has made the noise before although it was never this noticable. It became very pronounced after putting my mac CAI back on the car. (I took it off for a while due to the sucking sound bothering me on highway trips) Now it is definately noticable at idle. My dad seems to think that it is a lifter problem, but I was thinking something more like detonation. I was wondering if perhaps someone could point me in the right direction for I am lost on this issue. Any help would be greatly appreciated. :)

[MSP]

I recently just started getting a nasty noise coming from the engine in my 95 v6. The noise sounds like someone shaking a can of spray paint and is only apparent at idle when the engine is up to full operating temps. It goes away once you rev the engine past 1200 rpm's or put it under any sort of load. It also seems as though it is coming from the passenger side of the car, near the valve cover. The car has made the noise before although it was never this noticable. It became very pronounced after putting my mac CAI back on the car. (I took it off for a while due to the sucking sound bothering me on highway trips) Now it is definately noticable at idle. My dad seems to think that it is a lifter problem, but I was thinking something more like detonation. I was wondering if perhaps someone could point me in the right direction for I am lost on this issue. Any help would be greatly appreciated. :)

I know you said its coming from the valve cover.. But have you listened to your CATS? When they go bad, they start to rattle as well.. Just a thought..

Is your car normally aspirated?

[95 Mustang Convert]

I dont think its the cats. I have listened to them and they sound fine. The noise is defiately coming from the engine. The rattle/knock sound seems to sync with the exhaust pulse as if it is occuring with the stroke of one or more of the cylinders, so it is not just some random rattling.

As for mods the car is basicaly stock with the exception of the usual boltons (Flowmaster catback, CAI, and pulley)

[95 Mustang Convert]

Ive listened to it more closely and the sound seems as though it is definately coming from the passenger side bank of cylinders. Anyone else have any thoughts on what could be causing it or what the sound actually is? Please help as I am afraid to drive it like this.:cry:

[michael.konor]

Broken piece of piston rattling around inside cylinder? Broken valve?

How is the engine running?

[95 Mustang Convert]

The engine runs great, no vibrations, plenty of power (well for a 95 v6 anyways), no smoke, all fluids look fine. If it wasnt for the noise at idle I wouldnt think anything is wrong. The noise is not loud enough to be heard while driving, but during idle it is quite apparent from the outside of the car only. It also seems to go away above 1200 rpm although this could just be from the rest of the engine drowning out the noise. I have tried listening around the engine with a screwdriver but have not been able to track the noise down to anything specific other that it is most prevenlent around the left bank of cyliders. I dont have any of my tools with me (im in college) or else I would pull the plugs. Any thoughts?

[NMStang218]

Have you had a chance to do a comp test? Maybe when you get some tools you can try that. I have heard this sound before and know exactly what your talking about. A buddy of mine, also with a 94, had it also coming from the passenger side valve cover, but we havent figured it out yet. It goes away when you rev it but as the RPMs go down from 2000 to 1000 it makes a brief knocking noise. The engine also runs strong. The only difference is that it does not do it during idle. We're thinking about pulling the head and redoing the gaskets as a preventative measure so I guess we can check the valves then. GL though and keep us updated.:word:

Edit: when you shut off the motor, do you you hear any sounds coming from the same area?

[95 Mustang Convert]

Its hard to tell if the engine makes the noise when shut off. I have listened to it and it seems as though it makes one last rattle as the engine quickly slows down and stops spinning. How many miles does your friends car have? Mines turning 115k. Also, does it only do it when the engines warm and up to full operating temps? If you could keep me posted on anything you find on the car it would be greatly appreciated.;)

Also, ive heard that there is a problem with the pcv valve on these cars that lets oil into the cylinders and thus causes detonation/pinging on the passenger side bank. Do you think that this could be causing the problem? I have never heard detonation first hand so im not sure what it sounds like. Ive heard its like pennies rattling in a soda can. Could the noise i described (shaking a spray can) be evidence of detonation? Thank you guys so much for all your help. I really appreciate it.

[NMStang218]

Its hard to tell if the engine makes the noise when shut off. I have listened to it and it seems as though it makes one last rattle as the engine quickly slows down and stops spinning. How many miles does your friends car have? Mines turning 115k. Also, does it only do it when the engines warm and up to full operating temps? If you could keep me posted on anything you find on the car it would be greatly appreciated.;)

Also, ive heard that there is a problem with the pcv valve on these cars that lets oil into the cylinders and thus causes detonation/pinging on the passenger side bank. Do you think that this could be causing the problem? I have never heard detonation first hand so im not sure what it sounds like. Ive heard its like pennies rattling in a soda can. Could the noise i described (shaking a spray can) be evidence of detonation? Thank you guys so much for all your help. I really appreciate it.

OMG that is so erie. He has the same "rattle" sound on shut down. He has over 120,000 miles on the motor as well so it could be a high mileage issue. I think I know for a fact now that you and my friend are having the same problem. As far as the knocking sound, it seems present all the time during those RPMs described earlier regardless of engine temp so Im not sure about that. Like I said we'll be pulling the heads off soon when we both have time and we can visually see what the problem is (hopefully). In the mean time does anyone else have some insight into this???
-matt

[94stang3.8]

I have a very similar problem, except mine usually kicks in in higher RPM's, 1800+ then goes away at higher RPM's, 3200 up, or when i floor it (but it could just be that it's drowned out). It's also coming from the passenger side, what we believe to be the middle cylinder. I've been told by a couple people that it's a lifter knocking but never pulled the heads to check. I've had this problem for the last 2.5 years or so, and my engine has 176K+ miles on it. Oh also it doesn't "knock" when it's freezing out. Keep us posted

[95 Mustang Convert]

It sounds like all three of us have the same issue just under different conditions. I have listened to the engine furthur and have narrowed it down to what seems to be the middle cylinder (just like 94stang) I did this by listening to each exhaust manifold flange, and the sound is only audible in the middle one.

I think I have had the sound for quite a while as well. I remember hearing it a few months back but thought nothing of it because it would come and go (probably with temperature changes). Still, do you think it is okay to drive it like this? I know you said you have had the problem for the last 2.5 years, but i want to make sure im not doing any damage to the engine.

NMStang218 keep us posted on anything you might find, as I would really like to know what this is. In the mean time, does anyone else have any input on what it might be?

[moparvin426]

I think it could be a broken piece of piston rattling around inside your cylinder. The piece of metal might be too small to hear at first, but when your motor heats it up the metal expands, then makes a more substantial amount of noise.

[NMStang218]

I think it could be a broken piece of piston rattling around inside your cylinder. The piece of metal might be too small to hear at first, but when your motor heats it up the metal expands, then makes a more substantial amount of noise. This is a possibility, BUT...

For my friend, here is the info: It occurs regarless of temp, warm or cold motor, the sound does not get louder or softer depending of amount of driving. There is ZERO performance loss. Also woulnt a broken piston exhibit a loss of compression at least? And if it was a something floating around, woulnt you hear it more as RPMs went up? We did a comp test and have found nothing out of the ordinary ( 165 avg and all cylinders were within 20% of each other)

To the other person exhibiting the same problems, do you hear a sound when you shut off the motor that resembles what we heard? (as the motor stops turning there is a small subtle rattle that lasts maybe 1-1.5 secs)

Im begining to believe that this might be a valve issue but we wont know until we pull off the head and inspect for ourselves. Im still considering the possibility of a spun bearing, however, ive heard many sound clips of this an in NO way does it sound as awful as that. And the fact that it is RPM influenced but NOT proportional( does not get louder as RPMS get high at like 2-4.5 thousand) this also makes me lean another direction. Ill keep you guys updated but thanks to everyone as ALL input is welcome:chrisb:

[95 Mustang Convert]

Any updates thus far NMStang?

[94stang3.8]

mine is definetly valvetrain problem with at least 4 people coming to the same conclusion. I'm just too poor and not that mechanically inclined to crack open the head. I've been doing regular oil changes and not overreving (shifting at around 2500 tops) and it's been fine for the last 20K miles

Keep us updated

[NMStang218]

Hey guys..wont be able do a tear down until May 12 ( about a month away) between my going to school full time and my friend working full time we found that this is the earliest that we'll be able to tackle this down. Hopefully it is valvetrain related (such as a loose or damaged valve) and nothing internal as bearing, which I doubt for some reason. Ill def keep you guys updated with pics when the time comes around:chrisb:

[95 Mustang Convert]

Thanks man, Id appreciated it and good luck.

[NMStang218]

Thanks man, Id appreciated it and good luck.
as a side note..what kinda transmission do you guys have? Also are you mostly highway drivers or city/street?

[94stang3.8]

i got a 5speed, most of the mileage is highway on mine

[NMStang218]

Hey guys, been doing a little thinking. Let me know what you think.

First of all this is happening to high mileage motors, with mostly highway miles. The rattling is being experienced around the same rpm (my buddy-1200 to 1500rpm, 94stang-2300 rpm, 95convertstang- idle to 1200)
Now im not 100% sure but I think our oil pumps work linearly, meaning the more oil they pump with the more RPMS present.
Anyway during thr RPMS described there is relatively little oil being pumped around the motor that could cause this knocking, but im thinking more along the lines of a clogged oil pickup screen.

I would hope it would be in the valvetrain so it could be fixed just with another head, but I was thinking about this today. What do you guys think??

[232Bird]

Out of curiosity, have your head gaskets been replaced? A good shop will have the heads milled, checked, and possibly tear down the valvetrain. The exhaust valves have a rotator that spins the valve every time it opens. If this rotator is not installed correctly (or not at all) then the valve will develop a hot spot and a "V" shaped portion will break away. Not sure what will happen after that, as all the ones I've done were always put back together right. Also, I would be very surprised if you have any detonation at idle. Detonation usually occures at medium or high load. I don't have any specific info on this problem, though, as my engine has 160k and NEVER made a noise like that.

[NMStang218]

Out of curiosity, have your head gaskets been replaced? A good shop will have the heads milled, checked, and possibly tear down the valvetrain. The exhaust valves have a rotator that spins the valve every time it opens. If this rotator is not installed correctly (or not at all) then the valve will develop a hot spot and a "V" shaped portion will break away. Not sure what will happen after that, as all the ones I've done were always put back together right. Also, I would be very surprised if you have any detonation at idle. Detonation usually occures at medium or high load. I don't have any specific info on this problem, though, as my engine has 160k and NEVER made a noise like that.

Never replaced the head gaskets, but this is the first time ive heard of a rotator that opens the exhaust valve. Ive heard of the cam pushing the lifter that pushes the push rod to the rocker arm and then opens the valve. I was however also thinking of the possiblity that maybe a lifter was damaged to that extent, but just thoughts of course. At this point were 100% sure its not detonation so thats not really a factor. As a test, I flashed my vehicle back to stock got a program for his car and used the xcal to retard the timing 4 degrees(from 1K to 2k rpm) and the knocking was till present so this has been ruled off the list. Any input on the oil pickup?

[232Bird]

Well, what kind oil pressure do you have? It should be a little past midway on the guage on fresh oil, and a little below midway by the time it is ready to be changed. That is assuming you use conventional oil, 5/10w-30. That will tell you how well the oil is moving through the system. A clogged pickup will restrict oil movement, cause oil starvation and rattling as the internal parts are slapping together. BTW, the rotators don't open the valve, they only spin it while it is moving.

[P-feif]

O.k. you guys are getting carried away with all this quessing.

You don't have a piece of anything floating around in the combustion chamber. If you did, even the smallest piece of anything would cause major damage, the clearances are too tight and if nothing elese a valve would probably close on it and bend the valve. From what you are saying it's just simply running too good for this to be the case.

You don't have an oil starvation problem. There would be alot more knocking pinging then just this one little spot.

It's not detonation. There is no way in hell that any engine would detonate at idle. NO WAY!

It's not a valve rotator, I can't even think of a year that the 3.8L ever had a valve rotator. I know for sure that the 95 didn't.

You have a mechanicle problem. The best thing that you can do for it is remove that valve cover, and inspect things. Look for foreign matierial floating around inside of the valve cover, such as a broken piece of a spring, or a valve keeper, or even the pintal from the PCV valve (it could be bounceing around under the oil bafel). Checking the lifters is simple, just push on the rocker arm (the side the push rod is on) or lift on the side the valve is at. If you can move the rocker arm without unbolting it, chances are the lifter for that rocker is bad (you can compress the vavle spring if you push hard enough, and that's NOT the motion that I'm talking about).. You can also crank the engine (don't start it, it just makes a big mess) and watch to see if there is oil squirting from the rockers. If one isn't squirting or is even weeker then the others, that's a sign that the lifter is bad. You can even compaire the valve spring heights with each other, if one looks differant then investigate it further, a broken valve spring or missing keeper can cause some strange problems. Look to make sure that all of the push rods are in place and not disslodged, if so then investigate it find out why so that you can fix it.

Heck you can even have nothing more then just a noisey fuel injector. Put a mechanic stethiscope on them and listen to them one at a time.

[Phil]

I agree with P-feif. With the high mileage motor, I would suspect the hydraulic roller lifters as the problem. They are not hard to replace and are not very expensive either. A whole set of lifters, an upper intake gasket, and a lower intake gasket will cost you about $200 new and will take 3-4 hours if you do it yourself. If you pull the valve covers, then pull the lifters, you can do a visual inspection of the underside of the lifter and pushrod ends.

[232Bird]

I agree with P-feif and Phil

[NMStang218]

O.k. you guys are getting carried away with all this quessing.

You don't have a piece of anything floating around in the combustion chamber. If you did, even the smallest piece of anything would cause major damage, the clearances are too tight and if nothing elese a valve would probably close on it and bend the valve. From what you are saying it's just simply running too good for this to be the case.

Already Established

You don't have an oil starvation problem. There would be alot more knocking pinging then just this one little spot.

No pinging, just knocking but beside the point..:p

It's not detonation. There is no way in hell that any engine would detonate at idle. NO WAY!

Already Established

It's not a valve rotator, I can't even think of a year that the 3.8L ever had a valve rotator. I know for sure that the 95 didn't.

This confirms my suspicions

You have a mechanicle problem. The best thing that you can do for it is remove that valve cover, and inspect things. Look for foreign matierial floating around inside of the valve cover, such as a broken piece of a spring, or a valve keeper, or even the pintal from the PCV valve (it could be bounceing around under the oil bafel). Checking the lifters is simple, just push on the rocker arm (the side the push rod is on) or lift on the side the valve is at. If you can move the rocker arm without unbolting it, chances are the lifter for that rocker is bad (you can compress the vavle spring if you push hard enough, and that's NOT the motion that I'm talking about).. You can also crank the engine (don't start it, it just makes a big mess) and watch to see if there is oil squirting from the rockers. If one isn't squirting or is even weeker then the others, that's a sign that the lifter is bad. You can even compaire the valve spring heights with each other, if one looks differant then investigate it further, a broken valve spring or missing keeper can cause some strange problems. Look to make sure that all of the push rods are in place and not disslodged, if so then investigate it find out why so that you can fix it.
Have taken the valved covers off already and inspected valves/springs and replaced rocker arms with RR's. Sound was present before AND after RR replacement and sound level is still the same magnitude. Putting new heads on May so the lifters are the next "culprit" to be inspected. Just didnt want to have to take the timing cover off if we didnt have to.

Heck you can even have nothing more then just a noisey fuel injector. Put a mechanic stethiscope on them and listen to them one at a time.
LoL, its def NOT a fuel injector:laugh2:


Thanks again for the input.:chrisb:

[NMStang218]

well guys just wanted to keep you updated. On Friday Im taking her apart and looking deep within:D

Just to be on the safe side I got some used lifters from RPM-mustang.com so Ill be replacing those. Im doing a split port swap so that will eliminate the valves/heads as being part of the problem so if it still makes the sound after the swap ill know it wasnt the head. Ill also be looking at pushrods..etc.

[taylor0987]

Putting new heads on May so the lifters are the next "culprit" to be inspected. Just didnt want to have to take the timing cover off if we didnt have to.
you don't have to take the timing cover off to change the lifters.

[NMStang218]

LOL...I know...

Thats why I wanted to make sure it was NOT a timing issue so I DIDNT have to take off the timing cover, because I dont have to....:laugh2:


Edit, just read what it you quoted but it was taken out of context...but thanks:word:

[95 Mustang Convert]

Definately keep us updated and good luck. Hope everything goes well and no nasty suprises. :)

[NMStang218]

Well I was a little delayed at first but right now im around 50% done with the split port swap. As far as the heads go, I didnt notice anything out of the ordinary. All lifters semmed ok so im hoping it was a poopy valve but I wont know till I get it running with the new heads. Also my 98 had MLS gaskets on there which kinda suprised me. Here are some pics for you:

[95 Mustang Convert]

Thanks for the update. Let us know if the sound goes away after putting the new heads back on. ;)

[NMStang218]

ok guys, heres the deal. Sorry it took so long. I found out one of the heads I got had 2 bent valves (badly) and got those fixed and now the split port swap is complete.

Anyway, That rattle sound that was present when Id shut the car off is now gone. However, the knocking sound is still there, but I have a MAJOR exhaust leak at the pass side due to the egr pipe still being present. Im going to get her to an exhaust shop and cap off that bad boy and see if the" knocking' i still present. Ill keep you guys up to date.

Any new news from you guys?

[95 Mustang Convert]

So far nothing real new here. I have noticed that the knocking sound has gotten quite a bit quieter since we started approaching triple digit temperatures hear in phoenix. If fact if I run the AC the sound pretty much dissapears which is puzzling to me. Unless it is just completely being drowned out by the fan constantly running. Other than that the car still runs great, even with the noise.

Glad to hear you got your car running. :) Ive been wanting to do a split port swap for some time now just never had the money. Let us know how it is once you get it all settled. :chrisb:

[97stangGT]

Well, i ran across the right forum for a change :chrisb: ok i just had the whole top end of my motor redone and i have this damn clicking nosie coming from the right side of the motor right at the valve cover... new heads and they came put to geather so i'm thinking it's a lifter or something any feed back would be nice

oh and i'm just now at the 120,--- mile mark, i'm going to try new fuel injectors maybe 30lb and a new fuel pump.. 50 lph and i have a miss in cylinder 5 and 6

[P-feif]

Check for an exhaust leak, a piece of heater hose works good. Hold one end to your ear and move the other end around by the exh components (like the manifold) and you will hear it when the hose passes the leak. You could pull that one rocker cover and make sure everything looks good. Make sure all of the rockers are on correctly (what kind of rockers do you have?), the springs are not broken and installed correctly (same thing goes for the spring retainers and keepers). Oh and make sure that the spark plugs are in snug, I've seen a ticking sound similar to an exhaust leak from a loose plug before. How about a bad plug wire, when they arc it makes a ticking noise, not a very loud tick, but it's a tick, and since I'm not there to hear it myself then I would say it's worth looking at.