I've been experiencing problems with engine knock.
Over a year ago it started as a quiet tapping and has developed into a full on loud knock. I've been running around with it like this but I want to try to fix it now that I have a little extra money.
When I start the car, it is fine and there is no knock. If I move it in the driveway, it is fine as well.
If I rev it or drive it, the knock comes in as the rpms drop usually showing up around 2000-2500 rpm. The knock disappears or at least can't be heard above 2500 rpm.
I don't hear any knocking when I'm accelerating or at any point when I'm on the gas for that matter. It is only audible when the car is idling after a drive or coasting through a gas station etc. So under load, it is fine, but I hear the knocking when it's not under load.
My question is, what do you guys think it is? I've researched and found possibilities ranging from exhaust to lifters to a rod knock.
I doubt it is the exhaust but I'll take another look.
The car drives fine and doesn't seem to have any loss in power. It doesn't use much oil and the oil always comes out clean. Oil pressure is fine as well.
I was looking at rebuilding the motor but I really don't want to go through that right now.
Any ideas?
Hmm mine knocks when the engine is idling at about 800 rpms after a drive. When I first start it up there is no knock. After the drive if I rev the engine to 1,000 rpms the knock goes away and isn't heard all the way to redline. Funny thing is it only knocks in park. If it's idling in drive at 800 rpms no knock :dunno: . I would think that in both our cases that if we had a rod knock the sound would get worse as the car accelerated or when the rpms went up. Then again yours knocks at a higher rpm than mine does so I couldn't say.
sounds almost like a deisel right? valve train....
Yeah, its weird. From what I've read, if it was a rod knock, I'd hear it all the time, accellerating or not/ just starting or not.
I'd like to think valve train since I won't have to pull the motor and rebuild it. Just the heads.
I just couldn't imagine this kind of sound coming from that. It sounds almost like two pieces of particle board slamming into eachother.
It's such a PITA to describe. Maybe I can get a sound clip of it.
You can usually tell a bottom end knock from a top end knock by the frequency - a top end knock will be at 1/2 the engine RPM (because the cam only spins at half the engine speed). Generally if the knock is slow enough to actually hear the individual "knocks" at idle it's valvetrain. If it sounds more like a rattle it's bottom end...
Bingo, individual knocks I can hear. Okay so it's valvetrain then. That makes me feel a bit better. There's no rattle to it what so ever. I would think any rattling would cause metal shavings in the oil (which I don't have), correct?
Anything in particular I should look for or would it just be best to have the heads rebuilt?
Maybe it's time to go aftermarket.
get a long screw driver, or a broom stick or something, and poke around your engine with it running to pin point where the knocking is coming from, on my car it turned out to be the alternator...
Very good point. Also check the serpentine belt and all pulleys. A chunk out of a belt or pulley can cause a knocking sound. You forgot to mention that you should stick the other end of the screwdriver or broomstick in your ear though (use it as a stethoscope) :D
5.0WillGo: The valvetrain knock doesn't necessarily have to be in a head (in fact it's not likely to be there). A worn cam lobe, bent pushrod or sticky lifter is more likely than something in the head. My first guess would be a sticky lifter.
Gotcha, thanks Carm.
My motor mounts are worn out and the safety keeper thingys make a nocking noise when they bang together. The inside of the thing is all shiny where its been rubbing.
5.0willgo...I've been trying to figure out the same sort of noise for many months now as well. I replaecd the tensioner pulley with new, replaced the water pump (started leaking shortly after and thought I had found it), new belt, and many long hours of listening with a stethescope. Problem is, I can only duplicate the noise when driving, or when raising the engine RPM's and noone can keep it constant when we do this. As the RPM's drop, the noise goes away. Everything sounds fine through the stethescope. I get the noise when it's cold, or after it's been running for awhile. It has gotten louder, but hasn't changed tone or anything. Also doesn't feel like any lost power. Gas grade idn't change anything, oil looks good with each change, and I have been TOTALLY FRANTIC trying to figure this out. It's driving me crazy. This is my daily driver, and I've felt like I was racing a clock before it leaves me stranded. I SHARE YOUR FRUSTRATION. I've actually started looking for a motor to rebuild as I can't have my car down for long when the time comes to tear it apart. Sounds like the only difference from what you are explaining is your 5.0 and my 3.8.
My '89 Mark is knocking as well.. has to be around 1/2 throttle or higher, and under load. Set timing, didn't go away. Doesn't go away with 89 or 93 octane. I'll change the plugs again in case I gapped the last ones wrong or the SeaFoam REALLY fouled them up, but the one I pulled was pretty clean. Friend of mine rode with me and said he thought it sounded like it came from the exhaust, but I think it sounds like it's coming from the engine.
Thinking about trying that Auto-RX stuff to flush the engine, if my problem ends up being similar to what's being discussed here. (lifters, etc.) *shrug*
I'm still debating the pre-cats in the Y-pipe. I had a new cat converter put on about a year ago (wouldn't pass the da?!#$ emissions test), and the mechanic tells me they will rattle when they are bad, but I'm not sure what they would actually sound like. Guess I'm going orward with the plans to pick up a spare 3.8 to rebuild in the garage and drop in.
piston slap or wristpin.
Ugh, looks like I'll have to tear the motor down regardless.
Oh well, it will be a learning experience.
Thanks for the input guys.
I just better triple check the exhaust to rule that out first.
Have fun with that. I'm going to let mine alone till I build and drop in a 5.0 HO. It still runs real good so as the old adage goes if it ain't broke don't fix it.
I kind of agree, but feel like it's broke enough, if you know what I mean. I'm having a little trouble letting it go...it's driving me crazy. Nothing like pulling up next to someone wanting to punch it a bit, and all I can hear is NOISE that doesn't belong. :nono: :yuck:
Well, I've already got the HO.
I may drive it until it blows and then build something better. I'm not too worried.
The sound is incredibly annoying though.
I'm actually still wondering if this could be exhaust related. Just haven't had the chance to check.
annother thing that was causing a knocking sound on my motor was a broken pipe going to the smog pump... it was like snapped right off and exhost was coming from it, and just in the rythem it sounded like from 1 or 2 cyl... freaked me the hell out...
Woot. I think you just solved the problem I was having... I have the same knocking in my engine, only under load, and from the frequency sounds pretty much like a single cylinder doing odd shiznit.
Took a little gander at it just now with a flashlight (gotta love them Eureka experiences) and there we go, broken pipes to the smog pump. Not that my smog pump works, mind you...
But I do think that's the cause of my problem right there; crimping that pipe shut oughta solve that right?
Okay, so I used the listen with a stick technique.
I put it on the valve cover and could hear the knocking. It is at its loudest at the #3 cylinder. Interestingly enough, this is the same cylinder where my headgasket blew. So, I'm thinking sticky lifter at #3 cylinder. What do you all think?
That would be my guess. *Maybe* a bad valve but I doubt it. Do you knwo if it's louder at the top or bottom of the engine? IE: is it louder in the area of the head or the block. If it's louder closer to the block then it might be a wrist pin problem............
It's louder in the area of the head.
I doubt a bad valve since the heads are different than the ones that were on the motor when the gasket blew. I had the heads checked out and they were fine at the time I put them on. Not saying that they couldn't go bad, but I don't think it's likely.
Ok then I'd gues sticky lifter, bad rocker, or possibly bent push rod. Any way you slice it it's time to take off the intake and poke around to see what's going on, which should be great fun, or not:yuck:
Yeah, I just wish I had this problem when I put the Cobra intake on. It would have been easier to fix since I had everything apart to begin with.
Oh well, I've had the intake off enough, I have it down to a science. :D
Good luck. I hope it's just a lifter. If you're going to change one though might as well change 'em all (it's a roller cam after all).
Thanks. I'm looking at the lifter sets. 150 and up. Might be a while before I do it. Wait a tic, I haven't gotten my tax return back yet. hmmmmm
$104 for a set of Ford Racing hyd roller lifters at Summit :D
http://store.summitracing.com/partdetail.asp?part=FMS%2DM%2D6500%2DR302&N=4294925232+4294892901+4294892863+400070+4294840126+115&autoview=sku
Sweetness!! Thanks man! missed those :banana:
So what do I get for my good deed? :giggle:
(http://www.biola.edu/parent/products/images/cookies.jpg)
a picture of a plate of cookies :D
Mmmm cookies :giggle: