Knocking noise at idle

[eric17mx]

Hey guys ive noticed over the Past few weeks a slight knocking noise i thought it was a lifter but it sounds nothing like my other 4.0 and its lifters are shot, anyway i dont notice it until i put it in gear and hold on the brake when the rpms come down a bit motor runs the same as it always has only thing i noticed was this noise awhile back could it possibly be an exhaust leak? Just changer my oil last week oil was fine no metal or anything. Thanks for any and all help

 

[Toms01PSD]

What year and how many miles? Look in the tech library and read through the 4.0 article. This could be your issue.
http://www.therangerstation.com/tech_library/4_0_Page.html

However, one major design fault was not completely eliminated: Valve rockers and upper pushrod tips still received poor oil supply, resulting in eventual wear to these areas, and consequential valvetrain noise as a result of the increased clearance. Required replacement of these parts is common in older engines.

 

[eric17mx]

Its a 93 with 233k on it i was reading else were about maybe a intake mani leak or a idler pully it sounds like a rod knock but i can only hear it at low idle or just barley touching the pedal changing maybe 200 rpms after about 1200 i dont hear a thing no smoke and doesnt burn or leak anything after work im going to look for any exhaust leaks like the manifolds? Maybe crackd i hope could happen when i was washing it or something i duno but it doesnt really sound like lifters like my other 93 4.0, anyone know if i can swap in a sohc and trans i can get both for 600 with 73k on them

 

[Downey]

i have always been told wth motors unless its really broke dont fix it. my truck has 270k on the original motor and top end i want to rebuild it but was told if it runs good dont worrie about it.

 

[eric17mx]

Well its not supposed to make the noise beside the motor runs good i highly doubt its a rod knock because it doesnt change or get any louder im hoping for a bad exhaust leak or idle pully but im guessing an exhaust leak ill get a video later and post it on here i should be able to with my phone. Ive called a couple local yards and they have a few ohv around 150k for 350.00$ i just dont want to waste a weekend puttin it in but its really a quick fix anyway. I thunk i may just buy one for a spare and see if i cant find whats up with this one, o one thing i forgot i drive about 75 miles a day and for the past few weeks it hasnt made it any louder or run any different id think it would get worse and worse if it were a bearing?

 

[eric17mx]

Well i got a couple vids it seems alot louder on my cell you can hear it real good then i hold the brake and put it in gear when its just ilding its hard to hear anything it sounds horrible though on this vid if someone could post the vid for me i can email them to you im on my phone right now so just let me know thanks

 

[Mosinman76254]

It very well could be carbon build up in the combustion chambers. I had the same noise as you're describing. Basically the carbon can build up so much that the piston, (because of the carbon build up), will be hitting the cylinder head. You can try using Top Engine Cleaner or, much cheaper, Sea Foam. Slowly... very slowly suck it into the intake through either the brake booster hose or the PCV port using about half the can and shut it down. Wait 20 minutes and drive it. Make sure you're not too close to people as in with open windows in their home cuz it's gonna smoke like hell! Don't beat it but you've gotta get on it some when you take it for a drive. You may have to do this a few times. Otherwise it's... off with the Head!s!!