Nasty nock at startup

[TWeatherford]

Anyone know what could be causing this noise?

http://youtu.be/OV3_2LbiOzA?sc

The first time I heard it was about 3 months ago. I have heard it a handful of times since then, and it only happens at startup. I have been videoing almost every startup for about a month now and finally got it so I could post. It always clears up quickly (like a few seconds at most) seems if I blip the throttle it goes away.

 

[stumiister]

Its either a rod knock but as it clears up and only happenes some of the time its possible that its an injector.
How many miles in the injectors and IP?

 

[chris142]

Worn bearing that knocks until it gets oil pressure. Id pull the engine and roll bearings in It last month.

 

[riotwarrior]

Rod bearing...or perhaps main...but I suspect a rod...

And rolling bearings in well...I'd be cautious I'd rather like to see that journal and mike it before just rolling in a bearing..

Just sayin

Al

 

[Hydro-idi]

That.....to me....sounds like a worn lifter that has bled down temporarily and pumps back up when the oil pressure gets to it. I have heard this same noise once before with my truck (it does have worn lifters) and other gas/diesel engines I have operated in the past. The chuffing noise will come from either the air intake or exhaust, depending on which lifter it is.

 

[BigRigTech]

An intake valve that is sticking and not 100% seated can make a similar sound by letting it pop back into the intake. It could be an Injector/coolant leak causing some degree of hydro lock until it blows it out and that is why it clears out so fast.

 

[Black dawg]

are you sure this noise isnt coming out of the intake?

 

[77f250diesel]

That sounds just like the knock I had in mine on cold startup a couple of weeks back and mine stopped.
I agree, injector or lifter.

Dennis

 

[jrad235]

I'm on the Lifter bandwagon. Sometimes mine gets a little bit of "Chuff" going on from the intake on startup, never when cold though. I had a gasser that sounded pretty bad, like a dead hole, but it had solid lifters, and half of one was missing.

 

[TWeatherford]

The IP is less than a thousand miles old (and the first time it made this noise was on the previous IP, which had 20,000 on it when it died) and the injectors are about 15,000 old. I certainly wouldn't say its not a fuel system issue, but I doubt it.

I don't understand why a rod would make this sort of noise. If it made it on every startup, sure. But its very intermittent. Sometimes it'll sit for a week and no noise, another time it'll have sat for an hour after running and make the noise.

So, if it is a lifter, what would be the consequence of just running it? I kind of think the noise is coming out the intake, but have no experience to really know what sounds like what. It has always sounded like it was coming from the top driver side of the engine to me.

 

[OLDBULL8]

I would SWAG it's a lifter. If the engine stops with valve pressure on it, it would bleed down rather quickly, with no valve pressure, it might not bleed down at all, making the difference of noise or no noise on different start times.

Just bought a 2004 Ford Freestar SEL with a 4.2 engine. I'm getting a knock just like you, but after running a couple of minutes the noise goes away. I'ts got a 118700 miles on it. Got it cheap on account of the noise, damn that thing is loaded.

 

[Hydro-idi]

The IP is less than a thousand miles old (and the first time it made this noise was on the previous IP, which had 20,000 on it when it died) and the injectors are about 15,000 old. I certainly wouldn't say its not a fuel system issue, but I doubt it.

I don't understand why a rod would make this sort of noise. If it made it on every startup, sure. But its very intermittent. Sometimes it'll sit for a week and no noise, another time it'll have sat for an hour after running and make the noise.

So, if it is a lifter, what would be the consequence of just running it? I kind of think the noise is coming out the intake, but have no experience to really know what sounds like what. It has always sounded like it was coming from the top driver side of the engine to me.

You can continue to run it and it shouldn't damage anything. If you plan on pulling the valley pan off or do head gaskets, I would replace the lifters. If not, no worries. I plan on putting new lifters in when I pull the heads off my rig. I got that irritating ticking noise at idle when the engine is hot so they are beyond worn out