Knock sounds when cold start.
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More Turbo
Joined: Aug 2019
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From: Norcal
Knock sounds when cold start.
Hey guys, wondering if anyone had any ideas where i could start looking for this knocking sound? i have a 87 idi 6.9 turbo 2wd C6 and when I cold start the truck most of the time for the first 5-10 seconds I hear a knocking sound and it goes away. Its not hella loud but noticeable. It has no other issues unaccompanied with it. If i start it when still warm it doesnt make this sounds. Whats the possibilty it could be a lifter spring or something? Or a loose pully that balances out after a short period? Anybody have any possibilties what it could be or where i can start looking? Oh yeah, i think the truck has low miles under 100k hard to really tell though.
Scope Wizard
Joined: May 2019
Posts: 6,530
Likes: 25
possible oil drain back worn rockers maybe... (valve train Related) .. probably normal wear.
you might read this thread too... https://www.ford-trucks.com/forums/1...-start-up.html
you might read this thread too... https://www.ford-trucks.com/forums/1...-start-up.html
Elder User
Joined: May 2018
Posts: 695
Likes: 22
Worn rockers won't knock, they'll make a light tick that's easy to detect as coming from the upper end. From what you describe, it's impossible to diagnose by looking at a monitor. Could even be a cracked auto trans flex plate.
More Turbo
Joined: Oct 2014
Posts: 697
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From: Alberta Eh
What oil are you running? I’ve cold started mine with 15w40 when it’s been cold out and there’s been a couple knocks until oil gets up top. It also did it once with light oil, but it sat for several months prior. Just two or three quick knocks then it’s normal. Cold heavy oil combined with a higher mile engine. Try running 0w40 or plugging it in for awhile if you can to see if it makes a difference.
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More Turbo
Joined: Aug 2019
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From: Norcal
It may be more of a ticking noise. Im running 15-40 oil. Im in cali so my cold starts aren't really that cold. Just started now and barely heard anything. Its 57 degrees and sunny outside.
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From: Norcal
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Scope Wizard
Joined: May 2019
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exactly I know what ya mean... I'm pretty OCD myself 
.... you get a lot of miles on these IDI engines and they do clatter a bit at start up and it's not a big deal.
They seem to develop their own personalities over time (of course it's a mechanical contraption) maybe a better term is they develop their own "Signatures"
from your explanation it just seems like some parts might be a little slow to oil up.... not being right next to your engine when it happens I can only give you a best guess.
.... you get a lot of miles on these IDI engines and they do clatter a bit at start up and it's not a big deal.They seem to develop their own personalities over time (of course it's a mechanical contraption) maybe a better term is they develop their own "Signatures"
from your explanation it just seems like some parts might be a little slow to oil up.... not being right next to your engine when it happens I can only give you a best guess.
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Mountain Pass
Joined: Aug 2019
Posts: 190
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From: Racine County
I would be willing to bet that it's an injector. I had the exact same issue and I thought the motor was gonna send a rod out the bottom and a piston to become an astronaut. The first thing I though since it didn't cause severe vibration is replace the injectors. Sure enough I put a fresh set in and the knock was gone the second I fired it up and hasn't returned since. I would give that a try first personally before you tear into a motor that could very well be perfectly fine.
More Turbo
Joined: Oct 2014
Posts: 697
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From: Alberta Eh
Ah okay, lol my cold start was about -20C with 15w40. Yep, these IDI trucks sure do have personalities, and many different noises
Fleet Mechanic
Joined: Sep 2016
Posts: 1,519
Likes: 224
From: Nevada
That`s what they do
Welcome to the world of old mechanical injected Diesels. That`s what they do when they are cold. The colder it is
the more they belch smoke of various colors.
I have owned a Diesel vehicle for the past 39years, so don`t give it much thought.
Now if you come from always owning a Gasser and get your first Diesel, yeah every sound is alarming.
Couple days ago i started the 86 after she was sitting for a few days. Nights down in the 20`s and day`s in the high 30`s
low 40`s. Snowing off and on and lots of wind.
Have manual GP`s, glowed for 8sec and she started, and shook to a stop. Glowed once more and she started with
one cylinder hammering real hard. probably one plug not heating enough...IDK
Glowed the plugs a couple time`s
for a few seconds. and let her warm up while complaining, and went in the house.
10 min later we got in to leave and she was running smooth. Hasn`t done that since.
Bought the truck with 192K now up to 297K, how old are the plugs and pump, IDK.
Wait till you change the oil for the first time, and then check the level after starting it, and it is still black.
Charlie
the more they belch smoke of various colors.
I have owned a Diesel vehicle for the past 39years, so don`t give it much thought.
Now if you come from always owning a Gasser and get your first Diesel, yeah every sound is alarming.
Couple days ago i started the 86 after she was sitting for a few days. Nights down in the 20`s and day`s in the high 30`s
low 40`s. Snowing off and on and lots of wind.
Have manual GP`s, glowed for 8sec and she started, and shook to a stop. Glowed once more and she started with
one cylinder hammering real hard. probably one plug not heating enough...IDK
Glowed the plugs a couple time`sfor a few seconds. and let her warm up while complaining, and went in the house.
10 min later we got in to leave and she was running smooth. Hasn`t done that since.
Bought the truck with 192K now up to 297K, how old are the plugs and pump, IDK.
Wait till you change the oil for the first time, and then check the level after starting it, and it is still black.
Charlie
Elder User
Joined: May 2018
Posts: 695
Likes: 22
Welcome to the world of old mechanical injected Diesels. That`s what they do when they are cold. The colder it is
the more they belch smoke of various colors.
the more they belch smoke of various colors.
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