knocking noise while accelerating

[KY-B3000]

Ive got a 04 B3000 work/glass truck with about 158K miles on it. It has a huge glass rack on the bed that catches alot of wind on the highway and is always loaded up with glass. Its literally all the truck can do to run 70 mph and has been worked like this its whole life.....

Last year (about 40,000 miles ago) it started knocking/ticking from what sounds like the passenger side head, only under a load. Whenever you got up to speed it stopped and didnt make noise anymore, but now its louder and does it more. Now itll do it sometimes when the truck downshifts for a hill or if you just accelerate to pass someone. There has also been an exhaust leak on the manifold (same side) for about 3 years, but its totally different sound. My guess is a lifter but why would it stop after the load on the engine levels off?

The truck has always had the best of everything maintence wise, $50 full synthetic oil changes every 4K its whole life, its driven every day.

Any ideas?

 

[Big Jim M]

MAnifold leaks are really BAD news! What we hear is the exhaust coming OUT the leak. What most of us don't understand is that leak allowa clean unburnt air to ENTER the leak and get burnt in the pipes.. Under certain conditions this new air enters the exhaust valve and makes the misture too hot.. The result of this extra hot mixture can and does result in burnt valves..
So what i'm saying here is to laways repair exhaust manifold leaks promply.

On another note please give the guys here a better description of the noise. Is it a thud/knock or is a click/clack? Does it occur while coasting, or only under load? Does it change or go away when downshifting to lower gear?
Big JIm

 

[KY-B3000]

Thanks for the info big jim. Ill get right on the manifold leak, but its been doing it for quite some time hopefully nothing is burnt already.

As for the noise, its hard to explain. It definatly isnt a rod, but thats the sound it makes under a load. As soon as you take your foot off the gas the noise stops,,,,it only does it under a heavy load like taking off from a red light, downshifting for a hill on the x-way, or just plain accelerating kind of hard. Whenever your up to speed the sound stops, it does it in every gear to.

I think it may be a collapsed lifter. Does anyone know if a bad lifter would only make noise under a load?

 

[B3000SE]

+ 1 On Big JIm's comment an exhaust manifold leak is NOT GOOD and will cause the particular cylinder to have a lean condition due to the "added" air entering the engine bypassing the mass air flow sensor so basically the computer cant compensate extra fuel for extra air because It doesn't know its sneaking in.The sound your describing does sound like a possible "stuck" or "collapsed" Lifter Id would investigate if the noise is coming from where the exhaust leak is,It will make a knock or tapping noise as long as your in the throttle and be faint at idle and possibly or eventually bend a push rod ..... V6 engines aren't meant to be revved,they do all of their Business down low with torque,part of the reason you see so many with valve train problems And Blown Head Gaskets,Have you checked the Gap On The Spark Plugs Lately?

 

[96Greenster]

Could it be spark knock aka detonation?? My 4.0 does a similar "rattle" or "pinging" noise

 

[bcost882]

my truck has the clatter clack when i try to accelerate to hard at too low of an rpm. supposedly this happens alot with 3.0l cause of the head design. since it is n/a it can deal with it alot. some people have adjusted their rockers and it goes away for a couple thousand and then comes back

 

[kimcrwbr1]

You can use a long screwdriver or metal rod put one end up to your ear and touch different parts of the engine (a stethescope) and have someone put it gear and hold the brakes and goose it for you. you can isolate the noise that way also. Just take it and touch different parts of the valve covers and you can hear individual rockers alternator and power steering berings just be careful of the fan and plug wires you dont need to get bit. the noise will get louder the closer you get to it. Old school trick for lifters try and get it down on the intake manifold as far as you can the closest to the lifters.