4.9 lower end knock
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From: galesburg michigan
4.9 lower end knock
i have a 1990 4.9 with 150k . there is a knock that sounds like lower end. either rod or main. it is worse when engine is cold but can still be heard when warm. most noticable during acceleration. am i looking at pulling the motor to replace rod and piston, or should i be looking elsewhere???
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I bet its your timing gears......I have a 88 and with what sounds like the bigining of a rod knock. Its most pronouced at idle when its cold. It changed when I put my new crane cam in, so I think its the timing gears. Some diiesels run gears aswell and timing gear clack is normal, but when the gears wear it can get noisey. Its mentioned in the factory ford service manual..
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From: Remsen, NY
How's the oil pressure? Your '90 does not show true pressure on the gauge, hook up a real gauge. If you have good pressure I'm guessing it's not rod or main bearing knock.
You can locate OK 4.9's for really cheap out of a junkyard or parts truck. They're everywhere. I just bought an entire truck without the body for 300, with just over 100k miles.
You can locate OK 4.9's for really cheap out of a junkyard or parts truck. They're everywhere. I just bought an entire truck without the body for 300, with just over 100k miles.
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From: galesburg michigan
the truck is a f150 xlt lariat 2whl dr, oil pressure seems to be ok, in normal range center of gage. upper end was rebuilt 50k ago and main bearings the same time. the knock started around august of this year and has gotten worse since.the previous owner was told it was an exhaust leak but this is not the case. i just recently aquired the truck and would like to repair the knock until i have the funds to replace the motor
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From: galesburg michigan
well im going to pull the motor this week and let you all know what i find... i just want the noise to go away
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From: Remsen, NY
Yeah, but that gauge is not really a gauge. It's either all the way down or just up past the middle. It runs off of a switch that triggers at 6-8 psi. When it triggers at over 8 psi the gauge goes up to where you would guess would be about 45psi.
Put a real gauge on there, even just temporarily, to get the real picture.
Put a real gauge on there, even just temporarily, to get the real picture.
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4.9 with a thump
4.9 litr,
I am reading your post with dismay!
My '90 F150 2WD with 4.9 has what appears to be a main bearing thump to it, similar to what you describe!
Just returned from a 600 mile trip towing a car trailer with a Falcon on it.
I get home and two days later start the truck and hear this godawful loud knock.
Not a con rod knock more like a main.
From the sound showever your description is making me believe you think yours is more of a rod type knock.
Am I correct in this?
I've even gone so far as to buy another engine(87) and getting ready to do a swap as soon as a friend gets his garage finished.
I'd be very interested in what you find out in yours.
I hope you do return witht he verdict.
Thanks.
DaveP
I am reading your post with dismay!
My '90 F150 2WD with 4.9 has what appears to be a main bearing thump to it, similar to what you describe!
Just returned from a 600 mile trip towing a car trailer with a Falcon on it.
I get home and two days later start the truck and hear this godawful loud knock.
Not a con rod knock more like a main.
From the sound showever your description is making me believe you think yours is more of a rod type knock.
Am I correct in this?
I've even gone so far as to buy another engine(87) and getting ready to do a swap as soon as a friend gets his garage finished.
I'd be very interested in what you find out in yours.
I hope you do return witht he verdict.
Thanks.
DaveP
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From: galesburg michigan
thanks dave. i just dont know if it is worth pulling the motor right now. its getting cold here in mi. . im going to try an oil change and some lucas oil treatment first. if i can get it through the winter then i might pull it if the noise stays the same ill drive it till it blows!!! if it blows before that ill find another 4.9. the noise could be a main but im just not quite sure. i use a hollow tube, a peice of 3/4 in. copper water pipe to listen to the noise . it seems to be coming from the top side of #1 #2 or#3 cylinders. it sems to be loudest around #2 at the top of the block.if you replace yours first please leave a message on this thread if you tear your old one apart...
thanks... john
thanks... john
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I'm gonna guess you have a little piston knock. Ford had a TSB on this. Ford claims its not harmful as long as the knock isn't too loud.
It's worse when cold but the noise will diminish as the pistons expand while the motor warms up.
It's worse when cold but the noise will diminish as the pistons expand while the motor warms up.
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From: Remsen, NY
I had something really scary loud and deep sounding from around there right after an oil change. I put a cup of marvel mystery oil in it and it cleared right up, so it had to be a lifter. Amazing how loud and deep that sounded for a lifter. Might be something to try...
I'd be interested to see that TSB, where can I get it?
I'd be interested to see that TSB, where can I get it?
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Joined: Aug 2003
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Usually I get the valve tapping sound after an oil change. It only last a couple of seconds . The piston knock is a much deeper sound. You may want to try a thicker oil just for testing. Note any change in the knock.