[tweeaks]

Well this is my first post here. I bought a 2000 Mustang with 62K miles a little over two weeks ago and after about a week of driving the engine started knocking. When the engine is cold the noise isn't apparent, only after the car has been fully warmed up. I'm not a first-timer when it comes to automotive mechanics and this sounds like a rod knock. Listening to the engine and after having a couple other mechanics look at it it was concluded that the rod bearings were going. Specifically the number 4 cylinder because if the spark plug is pulled from that cylinder the knock goes away.

I ordered a set of rod bearings and pulled the oil pan. To my surprise all of the rod bearings look perfect, no sign of wear at all. There is also no up and down play in any of the bearings, just side to side.

Someone please help me! What can be causing this problem?
I am replacing the rod bearings anyway just to rule them out, and they are a cheap replacement anyway. Maybe there is a common problem that imitates a rod knock in these cars?

Well, any information is greatly appreciated.
Thanks,
Jeremy

[El_Cangri]

welcome to M.M well rigth now idk anything about these but wait a little more and maybe some1 can help u out....

[Onemanzu]

check the exhaust manifold ... that sounds like a small exhaust leak... does it get faster as you rev... and or does it sound lie a certain side of the car is louder then the other

[GreenFaleen]

does it have that weird timing of a rod click, or is it kinda airy

[tweeaks]

It sound's exactly like a rod knock. It's not like a lifter tap/tick or nothing like that, it's a deeper thumping sound. And yes it has that timing, like it does it every revolution. As the RPM's get higher it gets faster at a parallel rate. I'm not sure what you mean by is it kinda airy.

Something else I forgot to add is that it doesn't do it in neutral. The only time it does it is under a load while in drive or reverse.

Originally Posted by GreenFaleen does it have that weird timing of a rod click, or is it kinda airy

Onemanzu No I don't think that the noise is generated from an exhaust leak, granted the car does have an exhaust leak further down, the noises aren't similar. Also there are no signs of an exhaust leak from either exhaust manifolds.

[Onemanzu]

really?

im still sayin exhaust leak... but uhh... idk i can't think of anything

[GreenFaleen]

well exhaust leaks are common, but airy is like it has a bubbley sound to it.

[tweeaks]

Defanetly no bubbley sound to it. It is a deeper thump/knock sound......sounds like rod bearings going out that I've heard before. I have never pulled rod bearings out that were knocking that looked brand new though. That is what is stumping me. These bearings look like they haven't even been broken in yet.

[97stanger]

Originally Posted by tweeaks Defanetly no bubbley sound to it. It is a deeper thump/knock sound......sounds like rod bearings going out that I've heard before. I have never pulled rod bearings out that were knocking that looked brand new though. That is what is stumping me. These bearings look like they haven't even been broken in yet.

if it gives a "low rumble" it would be your mains. if its a deep knock, its the rod bearings/rods. if it gives a higher pitch knock it would be the lifters. if it gives that "double knock" it would be wrist pins. if none of those, i would say it is a busted ring. its gotta be one of these.

[crashnebula]

does your spark plug look like its being hit? maybe its just hitting your spark plug under the pressure (long shot but worth a try)

[stephen]

Loose flex plate or torque converter bolts perhaps.

Just a guess.

[stephen]

You might check the oil pressure. Bearing problems should reduce it.

[tweeaks]

Originally Posted by 97stanger if it gives a "low rumble" it would be your mains. if its a deep knock, its the rod bearings/rods. if it gives a higher pitch knock it would be the lifters. if it gives that "double knock" it would be wrist pins. if none of those, i would say it is a busted ring. its gotta be one of these.

Well from that description it would be the rod bearings. If it were rings the cylinder walls would at least be scarred, and they look good. Like I said I'm replacing the rod bearings just to eliminate them. They will be here tomorrow. I will keep everyone informed of how it goes. If it's still giving me the problem I'll try and post a sound clip.

[tweeaks]

I am also going to run a compression check if the noise doesn't go away. I'm thinking that if enough carbon or something got built up on the top of the chamber and it is causing it to pre-detonate extremely. I'm not really sure what else to do besides run it to failure then replace it with a fresh stroker.

[GreenFaleen]

post pics of the bearings when you get them as well, (the old ones)

[stephen]

Specifically the number 4 cylinder because if the spark plug is pulled from that cylinder the knock goes away.

I think this piece of information is very important, since it localizes it to a cylinder.

These engines tend to build up carbon and cause pinging which in turn can cause engine damage, but usually it's worse on cylinders 3 and 6.

One option since you have the oil pan out is to also pull the left head and remove that piston and rod assembly. Perhaps it's a piston pin or damaged
piston or ring.

Is the plug on that cylinder damaged? We had a problem with excess carbon buildup/preignition and #3 plug had damage to the porcelain portion which had also made a little ding in the piston.

[Juggalo_X]

Originally Posted by 97stanger Originally Posted by tweeaks Defanetly no bubbley sound to it. It is a deeper thump/knock sound......sounds like rod bearings going out that I've heard before. I have never pulled rod bearings out that were knocking that looked brand new though. That is what is stumping me. These bearings look like they haven't even been broken in yet. if it gives a "low rumble" it would be your mains. if its a deep knock, its the rod bearings/rods. if it gives a higher pitch knock it would be the lifters. if it gives that "double knock" it would be wrist pins. if none of those, i would say it is a busted ring. its gotta be one of these.

dude get outta my head lol +1 to 97stanger he knows his shit i know this cuz he says what i think lol

[stephen]

One more suggestion for diagnostics is to use plastigage to check the rod bearing clearances.

[Juggalo_X]

Originally Posted by stephen One more suggestion for diagnostics is to use plastigage to check the rod bearing clearances.

is he using the correct grade of oil and how is the oil pressure? usually if the rod bearings are going your pressure will drop cuz the pump is putting all the the pressure through the sloppy rod bearing clearance.