Rod knock/spun bearing

Adam Vinnicombe · Dec 7, 2019

Hi all I've decided to start a new post on my possible spun bearing issue and my other post was getting messy with other issues the car has, hope this is allowed.
Let's start from the beginning.
I have a 2001 ford mustang GT with only 44,000 miles on the clock, she has never been raced driven hard and has had an oil change every year with 5w30 oil.
Now to my issue, the old girl has developed an engine rattle when at light throttle settings /cruising between 2000 & 2500rpm any thing under or over this and she is fine. She is not burn oil or water, she idle great and accelerates a dream and is not down on power. There is no rattling/knocking sounds on a cold start up. When the engine is cold I can easily get the engine eto rattle by cruise in that rpm range BUT after about 30 minutes of driving its extremely difficult to get the engine to rattle, when it does its very quiet. Now this does not sound like a rod bearing or any other bearing going bad does it, if it is a bearing it should be easier to reproduce the rattling sound and it should be getting louder as the engine warms up?
I will post some links to the engine rattling sound. The ones when I'm at a stand still) in neutral) the engine was stone cold and air temperature was - 3 degrees C
The ones when the car is moving it is hard to hear the rattling sound but it sounds like stones in a metal tin

Adam Vinnicombe · Dec 7, 2019

Adam Vinnicombe · Dec 7, 2019

Could someone please describe to me the topical signs and symptoms of a spun bearing before I go and blow £2,500

ttocs · Dec 7, 2019

it almost reminds me of the sound I had when I had a cat converter go out. I was able to diagnose where it came from when I got under the car.

Adam Vinnicombe · Dec 7, 2019

Hi mate I should of said I don't have any cats fitted and I'm running long tube headers.
So far I have removed all the plugs which were nice and tight and they look spot on. I've also brought evey piston to TDC and slightly pasted so it's just started on the down stroke and with a long rod pushed on top of each piston in turn to see if there was any movement but there isn't.
I will be draining the oil and cutting up the filter in a few days (if weather allows it) and when my cutters turn up so see if there's any metal in it.
The sound is coming from the rear of the engine but I can't tell for sure if it at the top or bottom. The nosie sounds sounds high pitch not what the videos of rod know on YouTube sound like.

D3VST8R96GT · Dec 7, 2019

usually rod knock will get louder as the oil warms up and become less viscous.
rpm window knocking isn't normally associated with rod knock (excluding high RPM stuff). It will knock at idle (low oil pressure), at high RPM (low oil pressure), or eventually all the time until it stops

lol.

I vote chain tensioner usually you will get a code with that one but not always.

RAU03MACH · Dec 7, 2019

That sounds horrible

OLD H2S · Dec 7, 2019

Get a stethoscope or a long screwdriver and start probing around with it up to your ear. I do not think it is a rod knock because they sound off at idle when the oil is hot and the pressure is lowest.
A knock at specific RPM is more often piston wrist pin that has egged out the top of the rod and just a little slop will make big noise, the screw driver will find it higher up on the engine. Lower rod knock will be loud right at the harmonic balancer as the vibration travels down the crank to the front.

Adam Vinnicombe · Dec 7, 2019

There is no rattling sounds at idle either when I'd hot or cold or first start up. If it was a wrist pin nosie would that get quiter as the engine warmed up?

OLD H2S · Dec 7, 2019

Mine got louder as it warmed up???

Adam Vinnicombe · Dec 8, 2019

Stethoscope on order should be here in a few days.
My engine rattle, at the moment, most definitely quietens down after about 30 minutes of driving

07GtS197 · Dec 8, 2019

Out of curiousity how many quarts of oil did you use? And what filter brand are you using?

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Adam Vinnicombe · Dec 8, 2019

I filled it to the max line on the dipstick which was about 5. 5 liters (6 quarts) the filter I got from ebay

07GtS197 · Dec 8, 2019

Motorcraft oil filters have an anti drainback valve, which most others dont have. Ive read that not having that valve can lead to noise on startup.

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RAU03MACH · Dec 8, 2019

Motorcraf oil filters are good that valve holds the oil in all gullies and passages and oil pump
Like oil pressure

Adam Vinnicombe · Dec 9, 2019

OK I will look in to these filters.
But just to make clear I don't have any issues on first start up, there is no banging, rattling or any other bad nosies when I start the car from cold

ForeverDriven · Dec 9, 2019

Adam Vinnicombe said:
Hi all I've decided to start a new post on my possible spun bearing issue and my other post was getting messy with other issues the car has, hope this is allowed.
Let's start from the beginning.
I have a 2001 ford mustang GT with only 44,000 miles on the clock, she has never been raced driven hard and has had an oil change every year with 5w30 oil.
Now to my issue, the old girl has developed an engine rattle when at light throttle settings /cruising between 2000 & 2500rpm any thing under or over this and she is fine. She is not burn oil or water, she idle great and accelerates a dream and is not down on power. There is no rattling/knocking sounds on a cold start up. When the engine is cold I can easily get the engine eto rattle by cruise in that rpm range BUT after about 30 minutes of driving its extremely difficult to get the engine to rattle, when it does its very quiet. Now this does not sound like a rod bearing or any other bearing going bad does it, if it is a bearing it should be easier to reproduce the rattling sound and it should be getting louder as the engine warms up?
I will post some links to the engine rattling sound. The ones when I'm at a stand still) in neutral) the engine was stone cold and air temperature was - 3 degrees C
The ones when the car is moving it is hard to hear the rattling sound but it sounds like stones in a metal tin

Hey man, dont be worrying about it online like this. I just bought a 97 GT with 167K miles on it and it had a very similar rattle. I started looking it up and saw the same possible problems and got worried. Once you think it's something bad all you do is imagine the noise as that bad thing, which isnt good for unbiased diagnostic.

Go get a mechanic to check it out. My "terrible shattered bearing" ended up being a loose exhaust. It was so easy for them to find that they didnt even charge me for the diagnosis.

The noise from your interior sounds exactly like the noise I had from the inside as well, but it sounds different on the outside a bit. Also mine was random at all RPMs, you said yours was consistent around 2000-2500 so that might be a important difference.

First order of business, get someone else to rev it for you while you tap the exhaust (or any other metal components you can reach around the noise) with a long breaker bar. Anything that's held on with bolts can get loose and rattle. If it stops when you push on it with the bar, just tighten it or have a shop redo those bolts. Other than that, just drop it off and have a mechanic check it out. The $0-100 you'll have to pay is well worth the certainty.

I love this community and many other mustang forums like this one, but sadly you cant ever get a 100% accurate diagnosis on any of these sites.

Best of luck man.

Adam Vinnicombe · Dec 9, 2019

It's going into a garage tomorrow morning mate. I will be back with some news good or bad tomorrow, wish me luck

cwgu3 · Dec 9, 2019

If it knocks while your accelerating its usually a rod bearing , If it Knocks when its decelerating its usually a main bearing. If it Knocks when cold but stops a few seconds after starting up its usually piston slap. if it knocks at a particular rpm when warm its usually either the timing chain, or a a lash adjuster.