Engine knock
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New User
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Engine knock
I have a 94 4.0 with 130K. It's always been garaged and except for the floormats it looks almost new. I have had it since 30k and have only replaced the alternator so I've been fortunate (so far).
Recently, on a cold start I will get a loud knock that gets quieter within 5 seconds but the knock sound remains and sounds like a diesel. I can't seem to pinpoint the exact area where the noise is emminating. Not ever having this problem before I have decided it won't leave the driveway until I get a better understanding of the problem. Therefore, I don't know what it currently sounds like under a load. I did notice a slight knocking sound under load earlier before I decided to park it but not the loud knock on start-up.
I have not done the Seafoam thing or any additives yet. My concern is that I have crossed over into something much more invloved (and expensive).
Any thoughts or suggestions would be appreciated.
Pesobill
Recently, on a cold start I will get a loud knock that gets quieter within 5 seconds but the knock sound remains and sounds like a diesel. I can't seem to pinpoint the exact area where the noise is emminating. Not ever having this problem before I have decided it won't leave the driveway until I get a better understanding of the problem. Therefore, I don't know what it currently sounds like under a load. I did notice a slight knocking sound under load earlier before I decided to park it but not the loud knock on start-up.
I have not done the Seafoam thing or any additives yet. My concern is that I have crossed over into something much more invloved (and expensive).
Any thoughts or suggestions would be appreciated.
Pesobill
Post Fiend
Joined: Apr 2005
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From: Washington state
first, change the oil hot drain and look for any metal flakes in bottom of drained old oil
cut the oil filter open and examine pleats for any metal flakes
put a real oil pressure gauge on it and measure hot idle and hot 2k rpm oil pressure
don't waste time and money with the Seafoam or additives now...you have a more serious problem
use a section of garden hose or low cost engine stethascope avail from low end auto parts stores and the Chinese Mac (Harbor Freight) tool store in your area to listen to and locate the source point for the knock
just guesses at this point with no testing but prime possiblities are rod bearing, push rod-lifter or rocker arm, timing chain/gears
cut the oil filter open and examine pleats for any metal flakes
put a real oil pressure gauge on it and measure hot idle and hot 2k rpm oil pressure
don't waste time and money with the Seafoam or additives now...you have a more serious problem
use a section of garden hose or low cost engine stethascope avail from low end auto parts stores and the Chinese Mac (Harbor Freight) tool store in your area to listen to and locate the source point for the knock
just guesses at this point with no testing but prime possiblities are rod bearing, push rod-lifter or rocker arm, timing chain/gears
Postmaster
Joined: Sep 2003
Posts: 4,452
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From: Southern California
Peso:
Also check your transmission modulator. If the diaphragm broke, transmission fluid will be sucked into your engine and that will cause it to knock.
If that does not pan out, try listening near the valve cover. I'd suspect it's one of the rocker arms. The 4.0L gets very poor oil supply between the pushrod & the rocker arm. None in fact, and all they could rely on is the oil splash every now and then.
Also check your transmission modulator. If the diaphragm broke, transmission fluid will be sucked into your engine and that will cause it to knock.
If that does not pan out, try listening near the valve cover. I'd suspect it's one of the rocker arms. The 4.0L gets very poor oil supply between the pushrod & the rocker arm. None in fact, and all they could rely on is the oil splash every now and then.
Elder User
Joined: Apr 2005
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From: Wichita
5 second sounds like a lifter to me. One or more might have a weak internal spring and bleeds down when at rest. It's annoying but not critical. Lower end sounds usually take longer time for the engine to heat up to go away. What pitch is the sound? A knock, clack or tick?
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Justin-
Actually, when starting cold it's definitely a knock but after 5-10 seconds it settles into a clacking sound, not unlike a diesel at idle. I'm sure it would be more helpful if I could pinpoint the sound's origin.
Actually, when starting cold it's definitely a knock but after 5-10 seconds it settles into a clacking sound, not unlike a diesel at idle. I'm sure it would be more helpful if I could pinpoint the sound's origin.
Posting Guru
Joined: Aug 2002
Posts: 1,041
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From: Orland USA
Pesobill:
What grade of oil are you using. If too thin it can cause a knock.
My son had a car that sounded like all the tappets were rattling like in a diesel. Read the manual and said use only a certain weight oil. We were using 10-40. Changed the oil and the clacking went away.
A weak lifter can cause a tappit knock. If you have had the van sitting for any length of time can cause sounds until everything gets re-oiled.
JaY
What grade of oil are you using. If too thin it can cause a knock.
My son had a car that sounded like all the tappets were rattling like in a diesel. Read the manual and said use only a certain weight oil. We were using 10-40. Changed the oil and the clacking went away.
A weak lifter can cause a tappit knock. If you have had the van sitting for any length of time can cause sounds until everything gets re-oiled.
JaY
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Mountain Pass
Joined: Oct 2002
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From: Jaqcksonville
My 97 aerostar started at 80k with a diesel like tapping. I seafomed it etc. The noise comes and goes. sometimes it is a hard metallic rap.If I turn the air on and off It changes in intensity level, so it is a load related noise. The van has 220k now and Ive learned to live with it. I was worried when it started but after a while ..... well you know you live with it, 100k 120k 160k 200k etc. Leave well enough alone.
Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
Well.... but how can I be sure, that this nock will not cause more serious problem.... Look, I draw to kiev from Lugansk today (500 miles), and nocking sound gone after first 50 miles, but it appeares every morning... and someimes dissapeares in 10 miles, sometimes in 50 miles... sometimes when I drive somewere far it may appeare after 300 miles and dissapeare next 20 minutes later.
The road is really difficult, snow and mud.... I had to stop near Poltava to have get sleep, next morning this sound dissapeared in 10 miles.
The road is really difficult, snow and mud.... I had to stop near Poltava to have get sleep, next morning this sound dissapeared in 10 miles.
Elder User
Joined: Apr 2005
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From: Wichita
Originally Posted by pesobill
Actually, when starting cold it's definitely a knock but after 5-10 seconds it settles into a clacking sound, not unlike a diesel at idle. I'm sure it would be more helpful if I could pinpoint the sound's origin.
Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
__________________________________________________ __________
did the knock start appear when you put in the Mahle Mercedes pistons?
__________________________________________________ __________
no, much laterr... 4 years later... And I'm not sure, that this is piston nock....
did the knock start appear when you put in the Mahle Mercedes pistons?
__________________________________________________ __________
no, much laterr... 4 years later... And I'm not sure, that this is piston nock....
Junior User
Joined: Nov 2006
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i have a 92 4.0 that knocked after siting all winter..... i started it up for the first time after siting for almost a year.... i will not try to start it again untel the weather warms up... i think i will try a synthetic oil change before i fire it up... maybe it will lube enough in this cold weather so i wont damage the crank..... hummmmm???? what is the best all weather synthetic oil on the market today??? it has quakerstate 20-40 in it right now!! i don`t dare hit the starter... i know it will knock like hell in this cold weather.... but i do want to get it running SOON
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Quaker State oil is terrible stuff. So bad in fact, that adding Slick 50 is apparently considered and improvement (Yup Quaker State now has Slick 50 already in it). Go with Mobil1, Redline, Amsoil, or Royal Purple. Those are excellent synthetic oils that are worth the extra money. Everything else is either made from cheap base stock, or blended.