Hi all, I have the strangest problem that I have not been able to find any similar post on.

I have a 2008 F150 5.4 Triton with about 130k miles on it. The exhaust manifold does have a crack in it, but I've been told by Ford and my primary mechanic that won't cause any issues. It's a little loud and embarrassing but it doesn't seem like it effects the power. I have recently started to tow a 28' camper 6200 lbs dry weight, well under the weight its capable of towing. Note, prior to towing I checked my oil and the levels was good, transmission oil was also good. After about 30 minutes of towing last weekend when I reached my destination and came to a stop the engine sounded a LOT like a rod knocking. I was pretty scared for a moment, but then I turned the engine off, back on and it went away completely. The engine wasn't even off but for maybe 1 minute. So then I pulled the camper back into the campground, got to my site, and as I was coming to a stop and it did it again - very loud. It sounded very much like a rod knocking. No leaks under the truck or sprays under the hood that I could see. I again turned the engine off, back on again and the sound went away, so I proceeded to back my camper into the site and parked my truck. The next morning I started my truck up and drove it about 25 miles (not towing) and beat on it pretty good and it never made the sound. After the weekend I towed the camper back home and it never made the sound again, even when I got home and stopped. Looking for any thoughts you might have from your experience? One guy thought it might be a flywheel, but surely if it was a flywheel it would be making that sound consistently I'd think. Any chance that it was my exhaust manifold issue?

 

Could be a rod knock...I've seen them come and go until eventually it goes kablammo. Needs to be gone through because it might be on borrowed time.

 

I used to have an '07 Nissan Titan. They were notorious for developing cracked manifolds. General consensus was that the crack threw off the computer and caused it to run rich which then destroyed the catalytic converter which disintegrated and could be sucked back into cylinder number 8, thereby destroying the engine. Mine never got to that point because I proactively replaced the exhaust manifolds with long tube headers.

Otherwise, I don't know how to diagnose your issue.

 

Is it throwing any codes? I would guess you have a cam phaser going out.

 

That was my first thought. Cam phasers are a known issue with the 5.4 in F series trucks. And they can certainly sound similar to a rod knock.

A rod knock could come and go depending on conditions but the cam phaser is more likely. Get a mechanic's stethiscope and listen at the cam sprocket area of the timing covers. Then compare to the oil pan.

 

I am definitely considering replacing the cracked manifolds. I took it to our local reputable Ford dealer, as well as my primary mechanic and they both said that the cracked manifold wouldn't cause any permanent/long term damage so I was kind of holding out. But, it sure would seem like it would cause some issues after a while. Good thoughts, thank you

 

No, that's the strange thing I never saw a code, engine light or anything. When I drove it the next day and one the way home, and even right now it runs like a top - other than the exhaust manifold crack.

 

I looked up multiple cam phaser issues for the F150 and my truck doesn't display any of those issues. I have it at my mechanic now, but of course they say it is hard to tell without the truck making the sound. If they don't find anything I guess I'll have to tow the camper again to see if I can reproduce it! I hate mystery's!

 

I'm not familiar with exhaust manifolds on anything but the Titan. On that truck the OEM exhaust manifolds are very expensive because NIssan makes the exhaust manifold and upstream catalytic converter a single assembly all welded together. Outside of warranty, most guys go with headers, but aftermarket exhaust manifolds are available at an affordable price. However, the aftermarket exhaust manifolds follow pretty much the exact same design as the OEM manifolds. So they are probably just as likely to fail as OEM.

I would check in with the F-150 guys and find what they're doing.

 

Thanks, yea they are very expensive for F-150s as well. Unfortunately, it is a common problem with my year of F150 for the passenger side exhaust manifold to get cracks. Because the bolts also get rusted out it adds quite a bit of labor to the job so it ends up being between $900-1k just to replace the passenger side manifold. But, with this new mystery knocking sound, that went away I don't want to spend the money on fixing the manifold issue until I know what the mystery is. It would be great if the mystery knock sound that went away is somehow related to the manifold because even thought it's expensive it's a no brainier to fix it. Thanks so much for your time to read this and reply.

 

Do a UOA and looked for increased wear metals, and cut open all the used oil filters you have for the truck. If you're eating a bearing you might get lucky and catch it before you lose the whole engine.

 

 

That's a really great question, Superdave71. I use the recommended 5W-20 Synthetic oil. Like I mentioned, it was strange because both times it did it was when I came to a stopped. What's even more strange is that I have towed the same 25' travel trailer again this past weekend and further this time but did not experience the same issue once. Once in a while when I come to a stop I can kind of hear the same noise, just not as loud but it sounds like its coming from the exhaust manifold. I am really beginning to wonder if even though Ford and my mechanic tell me I don't need to replace that if I really should, I just don't like how it sounds. Other than that, when I get on it and put the pedal to the floor the engine feels and sounds healthy. I am so baffled!

 

Does the manual have a category for severe duty? I would think that 5w-20 wouldn't be acceptable for severe duty.

 

No, I just double checked the 2008 F150 manual and it has SAE 5W-20 in bold. In fact I just downloaded the 2018 F150 manual and it also says 5w-20 Synthetic