How do you find a spun rod bearing?

v8ranger · Post by **v8ranger** » Mon Jan 19, 2009 4:29 am

I would make sure you pull ALL the rods and mains. That noise sounds kind of tinny to me, it doesnt sound like a hard enough or dence enough knock to be a rod or main, but its very hard to tell over a puter. I would look at the flywheel, see if there is any play in it. If its an automatic you should be able to see the crank bolts. I had an automatic in another car I use to own that cracked around the crank bolts and it sounded like a rod knock. I did what your doing then found out it was the flywheel. Check the torque coverter bolts also. Check and make sure your main bearings anrt spun on the side. I think its the center main that centers the crank, make sure thats not wore out on the side and letting the crank have play movement from front to back.

plowboy34 · Post by **plowboy34** » Mon Jan 19, 2009 7:59 pm

When I listened to this when you first put it on here I was thinking wrist pin, but I don't have the best puter or speakers and antique phone lines here in the middle of nowhere. A wrist pin will knock like a rod but usually will get quieter when engine gets warm if you ever had a chance to run it that long. They will also cause scoring as you said the one cyliner was. Most times I had a bad pin it was a tight pin, when I pulled piston you could put piston face down on table and position rod at any angle and it would just stay there instead of falling on over. I know you don't have engine that tore down. I wonder if you could undo that rod get crank positioned where you could move rod and see if it has a tight spot. Just a thought, I have never been in one of those modular engines so I may be just blowing smoke.

MalcolmV8 · Post by **MalcolmV8** » Mon Jan 19, 2009 8:33 pm

Thanks for all the info so far guys. Right now I'm thinking a wrist pin closely followed by pressure plate or clutch (stick shift). That's really where the sound seemed like it was coming from initially and I probably should have stuck with it and pulled the tranny first.

It could still be a rod bearing (I only pulled 4 of 8 caps - one in each pair) but they all looked great and no metal shavings anywhere. I've never heard what a spun main bearing on the crank sounds like but it doesn't seem like it would be a knocking sound like that?

I'll try and pull the bearing caps off and move the con rod and piston around and see if I can find anything.

As for super charger bearing mentioned above. I don't think so because top of engine was so quiet. I've seen a few vids of other people who managed to damage their blowers and you could hear the bearings and noise from up top the car.

I wish I had started up the vehicle without the super charger belt on before pulling the pan as someone mentioned.

plowboy34 · Post by **plowboy34** » Mon Jan 19, 2009 9:02 pm

Main bearings are usually a deeper thud and they are alot slower than a rod or pin knock.

MalcolmV8 · Post by **MalcolmV8** » Mon Jan 19, 2009 9:31 pm

Thanks.

Another bit of info - The night the knocking noise started it was pretty faint at first and I didn't pay attention to it. On the way home I heard it pretty decent but I still got on the vehicle real hard possibly heating it up good. When I got home the noise was almost 100% gone. I even got out the car and listened and I heard nothing. I figured oh wow what ever that was I heard earlier is gone.

Next day I fired it up to go to work and it was LOUD. Like you heard in the video. I drove to work and it was loud the whole way and never went away. I drove it real easy though and it probably never got hot enough for the noise to go away. I then drove it home and parked it and it's sat ever since.

Warpig Racing · Post by **Warpig Racing** » Mon Jan 19, 2009 9:57 pm

Have you pulled your valve covers and checked your rockers?

MalcolmV8 · Post by **MalcolmV8** » Mon Jan 19, 2009 10:06 pm

I have not. They look like a bear to remove. Maybe not the passenger's side so much but the drivers looks horrible. I need to research what's involved in removing them on this car. Can that be a rocker sound? Does it make sense though with the sound being really loud under the car and quiet up top?

v8ranger · Post by **v8ranger** » Tue Jan 20, 2009 6:01 am

I wouldnt think it would be a rocker. I would think if one was broke or "out of adj" it would clatter up top and if it was broke off the engine would be missing. Didnt think about the wrist pin, very possible. I still think it may be in the flywheel or flex plate. I would think you should be able to take the cap off and rotate the engine enough the see if the rod is binding. Is this a 4.6 or a 5.0?

MalcolmV8 · Post by **MalcolmV8** » Tue Jan 20, 2009 10:31 am

It's a 4.6 DOHC

v8ranger · Post by **v8ranger** » Tue Jan 20, 2009 11:03 am

Did you pull all the rod bearing off and look at both halfs? After listening to it again I think its a rod bearing not a wrist pin. Or the flywheel bolt holes are cracked or broken. I hate looking for noises. It always seems like what you think it is, its not lol.

MalcolmV8 · Post by **MalcolmV8** » Tue Jan 20, 2009 12:11 pm

I did not pull the top of the rod bearings out. Only the bottom half. They all looked brand new though, none were spun around, no slop or play in rods at all. No shavings.

I'm very tempted to put the oil pan back, put the kmember back and pull the exhaust, tranny, and clutch and see what that fly wheel looks like. So much work and if nothing I have to put tranny back, pull kmember again and reopen engine. The joys

v8ranger · Post by **v8ranger** » Tue Jan 20, 2009 1:49 pm

I would look at the other half of the bearing. I have seen where only one half of a bearing is bad. You have it apart, better to be sure than sorry later. Like a said before, I hate tracking down noises. I just had a squealing noise on my wife's 5.0L Mountaineer and thought for sure it was the idler pully, wrong, then thought, well it must be the water pump, wrong. Glad I didnt rip it all apart and put in the water pump. I thought, I better start it up first after I took the belt off and just make sure the noise is gone, it want, it was still there. It ended up being the cam position sensor, I think thats what its called. Its in the same hole the distributor whould have been in.

MalcolmV8 · Post by **MalcolmV8** » Tue Jan 20, 2009 2:33 pm

Yeah it makes sense to go through it all better while I have it open down there. I will pull each and every single rod bearing cap and check top and bottom and while I have it off move piston and rod assembly up to free from crank and see if I wiggle around and tell anything on the wrist pin end.

I've never seen crank mains in person that have bolts coming through the side of the block into them to secure. Kind of interesting.

v8ranger · Post by **v8ranger** » Tue Jan 20, 2009 7:29 pm

Ya I remember the first time one of them came into the dealer. A guy ran his car ( Lincoln Town Car ) into the ditch and put a hole in his oil pan. I dont think the car was 6 months old. The mechanic that was working on the car had to change the oil pan and check and make sure he didnt ruin any bearings. He couldnt get the mains off. Then he noticed they where bolted through the side of the block also. I guess if you think about it, it probably add strenght to the block and mains. I guess you can says its a wierd way of making a 4 bolt main lol.

usmcrp1044 · Post by **usmcrp1044** » Wed Jan 21, 2009 6:46 am

I've never seen one inside before. I know how a standard 2 bolt or 4 bolt main is, and I've seen splayed caps. But the caps, I'm assuming, have bolts coming through the block into them?