Tracking Down A Knock
#1
05-10-2011, 10:13 PM
Join Date: Mar 2010
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Tracking Down A Knock
I got a loud knocking that started the past couple days and it doesn't always happen but it does quite a bit. It's intermittent.
It doesn't knock at idle and the knock increases with RPM but again it doesn't always do it and the engine sounds great when it don't.
I'm almost positive it's not a bad rod bearing because it sounds like it's coming from the back of the top of the engine.
I listened underneathe the truck with it revving and it sound like its definitely coming from above the block or at least towards the top of it at the rear, right around where the bell house meets the engine.
Anybody heard something like this before and knows what it might be? Maybe piston slap, bad rocker or something? Hell I don't know!
It doesn't knock at idle and the knock increases with RPM but again it doesn't always do it and the engine sounds great when it don't.
I'm almost positive it's not a bad rod bearing because it sounds like it's coming from the back of the top of the engine.
I listened underneathe the truck with it revving and it sound like its definitely coming from above the block or at least towards the top of it at the rear, right around where the bell house meets the engine.
Anybody heard something like this before and knows what it might be? Maybe piston slap, bad rocker or something? Hell I don't know!
#2
05-10-2011, 10:17 PM
Join Date: Mar 2010
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
#3
05-10-2011, 11:19 PM
Check the sparkplugs. You could have one thats loose and coming out.
Also always give information such as year, engine, mileage. and if you recently performed any work on the engine before the noise started. I am assuming you are talking about the 1998. Thanks
Also always give information such as year, engine, mileage. and if you recently performed any work on the engine before the noise started. I am assuming you are talking about the 1998. Thanks
Last edited by DYNOTECH; 05-10-2011 at 11:24 PM.
#4
05-11-2011, 01:39 AM
Join Date: Mar 2010
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Thanks I'll check them first thing in the morning. Its a 1998 F150 4x4 4.6L 150k miles always maintained it sees a lot of mud and I drove it in almost 3ft of water the other day when the river out here flooded.
The rear transfer case seal was leaking a little oil the other day and I replaced that I think the bearing in there is OK but thats not where the noise is coming from anyways.
It also lost a little motor oil not sure if it burned or what I didn't see any leak.
The rear transfer case seal was leaking a little oil the other day and I replaced that I think the bearing in there is OK but thats not where the noise is coming from anyways.
It also lost a little motor oil not sure if it burned or what I didn't see any leak.
#5
05-11-2011, 12:34 PM
Join Date: Mar 2010
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Did you point it to the block itself, outside each cylinder?
Don't forget there have been incidents where the cam followers fall out. A simple vacuum guage with tell you. Stock (NEW), you should see 22 or more inches of vacuum at idle. In past decades 15 was an average. Anyway, under 20 or less and you are starting to get tired. If it FLUTTERS, you have a valvetrain problem. Here are the charts.
http://www.classictruckshop.com/club...ts/vac/uum.htm
IF you pull the plugs, get a cheap compression tester. Remove all 8 plugs. Take a ball peen to the fuel cutout. Hand tighten the hose to the compression tester. Off the top of my head, 200-220 PSI was normal. Once I blew the ring lands out of one cylinder, it went down to 170 PSI on #4. That number is higher now too.
Don't forget there have been incidents where the cam followers fall out. A simple vacuum guage with tell you. Stock (NEW), you should see 22 or more inches of vacuum at idle. In past decades 15 was an average. Anyway, under 20 or less and you are starting to get tired. If it FLUTTERS, you have a valvetrain problem. Here are the charts.
http://www.classictruckshop.com/club...ts/vac/uum.htm
IF you pull the plugs, get a cheap compression tester. Remove all 8 plugs. Take a ball peen to the fuel cutout. Hand tighten the hose to the compression tester. Off the top of my head, 200-220 PSI was normal. Once I blew the ring lands out of one cylinder, it went down to 170 PSI on #4. That number is higher now too.
http://www.youtube.com/watch?v=68G10LFJ-TI