08 engine knock

[04lariat711]

Hey guys. I bought my 08 6.4 about 2 months ago. I got a great deal, as it was prior salvage. All cosmetic damage from a front end collision. I took it to my diesel mechanic to have everything looked over before I bought it, and he said everything checked out. Well right after the first oil change I did, I got a bad tap or knock sound. I have searched, and I have seen the TSB on the issue, but it seems to be progressively getting worse. Everything I've read has said the tap or knock should not get worse. The same time I did the oil change, I put in a S&B intake. I bought a Spartan tuner, but have not installed as I'm waiting for the relicense stuff to be completed. Do you think the extra airflow could be causing this if it is not tuned for it? I'm also wondering if maybe one of my injectors is cracked or stuck open. How can I check this issue? I've also read about a valve problem that could be the cause, any extra info on that? The truck sounds bad, and as it is prior salvage, I have absolutely no warranty so I'm pretty freaked out. Any suggestions would be great.

[strokemyego]

a knocking noise is never good, especially in an 08. but you have to specify, is this a knocking noise, a tapping noise, or a thumping noise? a tapping noise can be considered normal most of the time. i thumping noise or popping noise is a valvetrain issue usually rockers, lifters, or cams. now a knocking noise i've dealt with alot too. can you isolate which bank it is? is it loudest in the drivers side rear of the engine? that is the hot cylinder. cylinder number 8 and cylinder number for are famous for overfueling injectors causing seized piston rings, burnt pistons, and cylinder wall scoring. i have a piston from an 08 6.4 on my table as we speak kept it as a souvenir after replacing an engine. ha! best one i saw though was an 08 with a dead miss. compression was at 0 in that cylinder 8. pulled the heads and all that was there was the wrist pin and the pod, the piston was in pieces in the pan. which in addition 08's are known for main bearring issue. sorry wish this wasn't so negative sounding... and a bit shorter.

[04lariat711]

Thank u for the reply. I believe it started as the normal "tap", but somewhere down the road turned into what you are describing as a knock. I actually hear it worse under the wheel well of the passenger side, probably more towards the back of the motor. I guess I'm going to have to bite the bullet and bring it to a mechanic to have it diagnosed at least. I'm pretty good at working on an issue, just not diagnosing it. Any other suggestions please let me know.

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[Johnsabine2003]

Take the air filter out and see if it seems to be coming through the airbox. If it is it's valve train related..


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[srjd]

Did they change the berrings or something on 09 and 10??? Why would 08 be worse???

[strokemyego]

no bearrings are the same, the 08 was just the weak link of all the motors. it might be better due to different pcm strategies. when the 08's were first shipped there was a recall that ford issued. you'd type in the vin and they'd send you a message tell you which injectors to replace. some were 1 injector others 5 injectors. the injector is the root cause of most base engine issues on the 08. as for the original issue i'd check codes and see if there are any codes that the truck does have. even better if you can run a compression test on the vehicle, that'd help too. yes but you can check with the airbox and hear it. i'd recommend also removing your valve covers and cranking the engine with the fuel pump fuse removed see if any of the rockers are moving abnormally or catching.

[04lariat711]

Well, I brought it in to the dealership. The head diesel mechanic came and listened to it and he thinks maybe a cam issue. He said it was for sure not the common tap that is in the tsb. He's gonna run some tests, including a compression test, and get back to me tomorrow. I didn't know about the injector issue, I'll have to ask him about it. I'll let y'all know what he says.

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[strokemyego]

if he is suspecting a cam, then he has concluded your truck is making a ticking or popping noise, not a knocking noise. and i'm sure he knows a compression issue will not always show up with a valvetrain issue depending on if the damage is on the intake or the exhaust side.

[04lariat711]

I think that he said cam was the best case scenario. He did conclude, at least from just listening to it, that it was on top of the motor. If I can describe the sound better, it's almost as if the fan is hitting the shroud somewhere. But that is definitely not the case. I wish I could describe it better.

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[Johnsabine2003]

see the following threads
chirping or tapping from back of engine


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