Knock, knock...
Thread Starter
|
Posting Guru
Joined: Apr 2000
Posts: 1,746
Likes: 4
From: PNW
Knock, knock...
Who's there? I don't know, but I'm starting to get worried. The engine ('95 4.0) in my van has developed a knock that is only heard after startup after sitting for some time. It can only be heard at a certain speed (high idle) and goes away when the engine is warm. It's a heavier sounding noise sort of like a rivet gun, not a ticking like valve train noise, so I'm fearing the worst - main or con rod bearing - but I've never heard what a bad bearing sounds like. It's not getting any worse, but I think my days are numbered. I'm having a hard time trying to pinpoint the location. The engine is way too young to have bearing problems, it's only got 106K on the clock (I said the same thing when I had to replace the heads at 70K). Anybody got any other ideas?
Senior User
Joined: Feb 2004
Posts: 467
Likes: 0
From: northwest
i dunno, but id stick my ear in a garden hose, and find outwhere the noise is really coming from on the block or heads.
cut a hose bout 3 feet long and plug one ear, and listen through the hose as you point it around the engine to locate the noise.
my aerostar has never knocked like that, but my truck did, and it was a rod. the truck knocked louder at idle, and the noise died down at hiway speeds. when finally it went bang! and the engine was seriously unbalanced and hella louder, and oil was gushing out the side of the block. no fun.
so, get it figured out before it breaks!
cut a hose bout 3 feet long and plug one ear, and listen through the hose as you point it around the engine to locate the noise.
my aerostar has never knocked like that, but my truck did, and it was a rod. the truck knocked louder at idle, and the noise died down at hiway speeds. when finally it went bang! and the engine was seriously unbalanced and hella louder, and oil was gushing out the side of the block. no fun.
so, get it figured out before it breaks!
Senior User
Joined: Feb 2004
Posts: 195
Likes: 0
i would say that you may have piston slap. i have seen over the years. this happens when the engine gets overheated and collappses a piston. when the engine warms up the piston exspands and the knock goes away. good news is it will not hurt anything and will last a long time like that if ya can live with the knock. i know i did.
Postmaster
Joined: Apr 2001
Posts: 3,818
Likes: 3
Could also be a worn wrist pin - had a fairly new 3.0L engine do that once, just on one piston. Sounded like a heavy knock but was up high on the engine, not low like you would expect with a main bearing. One of those inexpensive sound amplifiers helped to pinpoint the correct piston and location of the noise. This was a battery powered 'wand' with a pair of earphones. Can't remember where I found it - Sears possibly.
New User
Joined: Apr 2004
Posts: 9
Likes: 0
From: Central Texas
Piston slap
Originally Posted by lasher
...good news is it will not hurt anything and will last a long time like that if ya can live with the knock. i know i did.
Senior User
Joined: Mar 2001
Posts: 403
Likes: 0
From: cincinnati hamilton
i always learn alot reading these threads.!my 4.0 is approaching 200 thou. miles. it too has similiar knocks. at start up they seem to be from many sources. after 10 min it seems to be lifters...after 20 or 30 min it purrs except for a low knock...still has power. not burning oil.so i'll just keep driving.. i bought some rislone to add to the oil, not sure if it will help the engine, or just me ,by thinking i'm doing something good for my aging road warrior.so we can continue going on down the road!!! 
rick
rick
Thread
Thread Starter
Forum
Replies
Last Post
RedDevil460
1999 - 2003 7.3L Power Stroke Diesel
53
Mar 29, 2014 08:16 PM
bra$$monkey
1987 - 1996 F150 & Larger F-Series Trucks
5
Nov 18, 2013 05:04 PM
