Rod Knock

[boom boom]

When it rains it pours. Driving home from work yesterday I started hearing a small tick which quickly became a louder knock. Shut it down and got it home. Started it back up and tick, tick, tick with rpm. It gets worse with a little throttle and then really bad when I let off throttle around 1800 rpm. Above 2500 it smooths out again. I think my worst fears are confirmed- rod knock. The reason I bought this car was the 50,000 mile longblock put in by Ford under warranty but it appears the previous owner may not have treated it well either


So my next step is to drop the oil pan and see how bad it is. This is my first experience inside the DOHC engine so I have a few questions.


Can I get the pan off without pulling the engine?


Has anyone done a single bearing?


Depending on the amount of metal in the oil, can these engines survive a spun bearing or should I plan on a complete rebuild?

[crouse]

Would a spun rod bearing show really high oil pressure?

[8UWITH6]

Pull it. Not worth trying to get the pan off in the car.

[Themarauderguy]

A rod knock would be a consistent knock through the whole rpm. you either have a bad valve guide seat or timing chain guides are bad. I would take off the front timing cover before I start pulling the oil pan off. If those are good then. you can hook up an oil pressure gauge to where the oil pressure sensor is. start the car let it idle and see if the oil pressure looks good. if it's low and not getting any ol pressure it's a spun rod bearing. or main bearing. You mentioned it was a rebuilt engine could be a rod cap bolt came loose as well. Those are things I would check anyway.

[boom boom]

This noise really sounds like it is coming from the bottom end, but I haven't had the timing cover off. Engine still has full power and it hasn't given any lights or codes and of course the gauge never moved. I'm pretty annoyed with the dummy oil gauge, what's the point. I'll check the oil pressure when I get back to it.


Would a timing issue get louder and irregular as you came off the throttle? That's the part that gets me, unloading the throttle around 2000RPM gets very loud and then settles again as the RPM drop. Dead steady knock at idle, really bad around 1800-2000 RPM and then starts to quiet as you approach and pass 3000 RPM. On the highway it actually sounded better at speed before I shut her down.

[Invective]

This noise really sounds like it is coming from the bottom end, but I haven't had the timing cover off.

Hoping you don't start it again until you correctly diagnose/fix the issue. Really don't want you to trash it unnecessarily and then unload it on someone else who also has no clue.

[RubberCtyRauder]

Number 8 cylinder known to overheat and bend valve due to poor coolant passage in head.

[boom boom]

Maybe I wasn't clear about "shut it down and got it home?" I towed it home. This happened last night on the way home from work so this is about getting together a game plan.


Thanks 8UWITH6 when it comes time I'll pull the engine rather than try to get the pan off.


TheMarauderGuy - Ford put Engine Assembly 3W3Z-6006-ABRM in it October 2007 - 60K miles ago.


I think that is a long block which means it should have been a new timing set with the new block and improved heads?

[boom boom]

Number 8 cylinder known to overheat and bend valve due to poor coolant passage in head.

I have no discernable power loss associated with the noise. Would that rule out a bent valve?

[RubberCtyRauder]

I have no discernable power loss associated with the noise. Would that rule out a bent valve?

I'm not sure, just adding to possible areas to look into. A few people have had the number 8 cylinder bend valve so hopefully they'll reply with better info as to their diagnosis. But it is a known issue even with the cobra mustangs, Mach 1 of those years.

[mustangeddie]

If you can, cut open the oil filter and inspect the element it will have chunks of bearing material in it if it's a rod knock.

[decipha]

do you run only motorcraft oil filters and 5w20 oil ?

[crouse]

You could post a video with sound if you dare run the engine for a few minutes.

[decipha]

nothing good can come from running it

[MyBlackBeasts]

Put your ear down by the starter.


It has happened where the starter starts going bad and the drive stays partially engaged fooling people they had internal engine issues.


Worth checking out.