Exhaust flutter or Knock?
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Senior User
Joined: Sep 2008
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From: Penticton BC Canada
Exhaust flutter or Knock?
Ok guys/or girls, what does the dreaded exhaust flutter sound like?
My 99 v10 has what I assumed to be a bottom end knock but its only heard between 2000-2500 rpm. It really does sound like a knock to me but Im confused with it only being in that rpm range.
The previous owner did have the cat removed and the only muffler is a thrush glass pack. Not sure if that will make a difference in "flutter" sound.
I do get the cold start few second rap on start up sometimes, mainly just on mornings below 0deg celsius. Im in Canada Thought i'd throw in the celsius just to be cheeky.
Anyway, the previous owner did the oil change before I bought it last week and it has a motomaster oil filter (made by fram) soon to be changed and he thinks he might have put 10w 30 in it. His thinking was its an old engine with 300k km's on it.
Hoping im hearing flutter but fearing its a knock.
My 99 v10 has what I assumed to be a bottom end knock but its only heard between 2000-2500 rpm. It really does sound like a knock to me but Im confused with it only being in that rpm range.
The previous owner did have the cat removed and the only muffler is a thrush glass pack. Not sure if that will make a difference in "flutter" sound.
I do get the cold start few second rap on start up sometimes, mainly just on mornings below 0deg celsius. Im in Canada Thought i'd throw in the celsius just to be cheeky.
Anyway, the previous owner did the oil change before I bought it last week and it has a motomaster oil filter (made by fram) soon to be changed and he thinks he might have put 10w 30 in it. His thinking was its an old engine with 300k km's on it.
Hoping im hearing flutter but fearing its a knock.
Hotshot
Joined: Mar 2007
Posts: 10,101
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From: Pa
In that rpm range it is most likely exhaust flutter due to the junk exhaust manifolds. Your 99' has the old design y-pipe which does not get rid of the flutter. Around 00' Ford switched to the new design y-pipe to get rid of the flutter. It got rid of the flutter but also hurt power somewhat. Flutter sort of sounds like an exhaust leak, hard to describe.
As to the "rap" during cold start up I would expect that to be piston slap. A long stroke, small bore and short skirted pistons can produce some piston slap. Once the pistons get some heat into them they expand and the "slap" goes away.
I would change the oil filter and oil. Both could be helping to contribute slightly to the engine "knock" you are hearing at startup. Use a Motorcraft 820s filter (has the speced silicone anti drainback valve) and replace the oil with a 5w-30. Ford speced the 5w-30 that year. You should notice better cold startup with the lighter oil. Synthetic oil performs better in the cold however just make sure to check oil level often.
As to the "rap" during cold start up I would expect that to be piston slap. A long stroke, small bore and short skirted pistons can produce some piston slap. Once the pistons get some heat into them they expand and the "slap" goes away.
I would change the oil filter and oil. Both could be helping to contribute slightly to the engine "knock" you are hearing at startup. Use a Motorcraft 820s filter (has the speced silicone anti drainback valve) and replace the oil with a 5w-30. Ford speced the 5w-30 that year. You should notice better cold startup with the lighter oil. Synthetic oil performs better in the cold however just make sure to check oil level often.
Elder User
Joined: Apr 2010
Posts: 619
Likes: 6
From: Steeler Country
Throw a quart of Lukas oil stablizer in there and see if cold start changes. Leaves everything coated when turned off. Knock would be at any speed but usually under moderate to heavy throttle. Flutter is like a leak. Check your manifolds, see if studs are still there or rusted away. Could be there, seals up some once warm, like an exhaust head gasket leak.
http://www.lucasoil.com/products/dis...show&headTitle= - Lucas Heavy Duty Oil Stabilizer
http://www.lucasoil.com/products/dis...show&headTitle= - Lucas Synthetic Oil Stabilizer
http://www.lucasoil.com/products/dis...show&headTitle= - Lucas Heavy Duty Oil Stabilizer
http://www.lucasoil.com/products/dis...show&headTitle= - Lucas Synthetic Oil Stabilizer
Thread Starter
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Senior User
Joined: Sep 2008
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From: Penticton BC Canada
I definitely plan to do an oil change asap.
The noise im hearing sounds more like a knock than an exhaust leak but maybe its just the tone of the exhaust making it sound that way.
One thought I had was if the crank has excessive end play would that cause a knock just in certain rpm ranges?
The noise im hearing sounds more like a knock than an exhaust leak but maybe its just the tone of the exhaust making it sound that way.
One thought I had was if the crank has excessive end play would that cause a knock just in certain rpm ranges?
Moderator
Joined: May 2004
Posts: 6,518
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From: Home Base Nebraska
Exhaust flutter sounds like a bad lifter or exhaust leak in the RPM ranges you are talking about with a stock exhaust system. In late 01 Ford changed the Y pipe to eliminate it, they changed mine to a 01 pipe under warranty and it cured the problem with no lose of power.
Denny
Denny
Elder User
Joined: Apr 2010
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From: Steeler Country
I recommend it for every Harley due to the lifters, cam chains and heat.
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Senior User
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From: Penticton BC Canada
I might try Lucas if the oil change doesnt help. Truck is on jack stands right now due to wheel bearing, stub shaft, and ball joint replacement. All of which according to the previous owner which I just bought the truck from was checked and good.
Ya....... Good and F**ked!!!!!!
Ya....... Good and F**ked!!!!!!
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Lucas oil stablizer
Just my 1.5 cents worth on Lucas products.. Drove a police package crown vic couple of years ago and this product took a 4.6Lt modular motor from burning a quart of oil every 1,000 miles to one quart every 3,000 miles in 2 oil changes.. This motor only had 90,000 on the speedo.. I know I would use this product if it would help in excessive oil consumption...
Last edited by smgcrawford; Feb 26, 2013 at 07:01 PM. Reason: punctuation
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From: Penticton BC Canada
Well after spending the better part of the last two days basically rebuilding my front diff, suspension, and steering components I can hear over my wheel bearings and other rattles and clunks that it doesn't have anymore it sounds much more like a knock, periodically I can hear it higher than 2500 rpm but not much, although the exhaust gets much louder at that point. May just be drowning out the engine noise.
Can the pan be pulled with the engine in the truck?
It has a 4" suspension lift if it helps with diff clearance.
What would need to be removed to get the pan off and clear of the engine, does the engine need to be unbolted and lifted at all?
I'd like to look at the rods and mains to see if the bearings are worn or worse yet any spun. Hopefully if they are worn I can catch it before it damages the crank or rods.
Also its a 5spd if it makes a difference for clearance.
Can the pan be pulled with the engine in the truck?
It has a 4" suspension lift if it helps with diff clearance.
What would need to be removed to get the pan off and clear of the engine, does the engine need to be unbolted and lifted at all?
I'd like to look at the rods and mains to see if the bearings are worn or worse yet any spun. Hopefully if they are worn I can catch it before it damages the crank or rods.
Also its a 5spd if it makes a difference for clearance.
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Senior User
Joined: Sep 2008
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From: Penticton BC Canada
In my case it ended up being bottom end knock. One rod bearing had spun a little, two others were badly pitted, looked like it was running way too thick oil according to the machine shop and was not getting proper lubrication to the bearings.
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