I'm back on the road after CAT fixed the broken clamp on the exhaust manifold. The truck pulls like crazy (475 hp legal; tuned to 500 hp at 1,600 rpm) but the ticking/tapping/clanking in the engine compartment persists. Believe it or not I'm wearing ear plugs! Can't stand this noise...

Bob, thanks for the suggestions: so it can be a damper, another clamp or bearings ... Can I check the damper myself somehow? Or can it only be done at the dealer?

The noise I'm hearing is the strongest when the engine is under load (going uphill, for example) and it dies down when I cruise down the hill. If I put the engine on high idle (1,000 rpm) and squat near the exhaust under the right side of the sleeper (I have only one stack) I can clearly hear this metalling "ringing" on top of the regular engine noise. I'm sure that's the sound that becomes much louder when I'm driving at 1,350 rpm on the highway. Checked the clamps on the manifold - they seem okay. What else the heck can it be? I recently received the oil sampel results - everything is "normal", no metal found.[/quote]

 

Thanks, Fredog. I'm compiling a list of possible culprits. Just added "engine break crossover" to it.

 

Hi Tracer Here is a shade tree idea. Find a place that is very dark and bump your idle up and have all the lights off and look around the exhaust manifold for a little fire. And take a small flash light and if any exhaust is leaking out you should be able to see (little bit of smoke) it and find where it is coming from. Truck should probably be at operating temp for this.

I am "not" a mechanic at all but I have been reading your posts and my brain just keeps saying exhaust manifold problems.

You say it is quite now at idle but when you pour the coal to it it gets real loud. When the motor is under load it is burning more fuel and the exhaust manifold gets hotter. Maybe there is a crack in it somewhere that you can't see or hear when it's at idle but when it hot it opens up and starts making noise.

Or maybe the exhaust manifold is warped and it is letting the exhaust leak out between the head and manifold even if you have new gaskets.

The exhaust manifold is in two or three pieces and it is made to slip inside it's self to compinsate for the growth from the heating and cooling. Is there allot of black soot around any of the joints?

Cats like to break exhaust manifold studs, are all yours still there?

Like I said just a few shade tree ideas.

Mike

 

mike, i think now it's an exhaust too ... thanks for the great tip. i'll check the manifold out. i've been doing some thinking of my own and i have this stethoscope... i found that the sound becomes different when i touch the exhaust on both sides of one clamp. left of the clamp the sound is very shrill metallic in quality; while when i touch the pipe to the right of this clamp - the sound is much quiter. the clamp itself looks ok and i couldn't move it with my hand. so, it's not loose. but i'm going to take it off and see what's underneath. i'll try the trick with the light too. thanks again.

 

I'm still living on the road with my tapping/ticking/clanking noise too. I now discovered that the noise is tied to ENGINE SPEED and is not effected by the road speed. I tried idling at 1,200 rpm and heard nothing. However when I start moving - especially with a trailer, better yet, a loaded trailer - the noise becomes very clear. As I accelerate through the gears the clanking starts at 1,200 RPM every time ... When I change gears and the RPM drop, the noise disappears. As soon as I reach 1,200 RPM in this higher hear, the noise comes back. I hear it all the time when cruising in top gear... If I push "brakes" to cancel the cruise control and the truck starts slowing down, the clanking noise stops as the engine speed touches 1,200 rpm. If I depress the clutch and move the shifter to Neutral while cruising, the noise dissappears (the engine rpm falls to 550).

I checked the exhaust itself but couldn't find any holes or leaks. It cannot be the valves or injectors because I have already done the "top set" twice since April 2007. Also, my oil analysis in January 2008 came back clean - "no metals". The truck seems to perform okay (I just came back from New Jersey with a 41,000 lb load on a 20,000 lb dry van trailer); but the engine sounds a bit rough when I accelerate.

Does anyone have any more ideas? Vibration damper? Loose/missing fasteners on the fly-wheel? Bad bearings inside the turbo?

 

You are describing, perfectly, a single cylinder exhaust leak.

 

When your engine is cold and the hood is up start check for the leak by looking for the smoke and also look for soot on the block. Also check for the leak by putting your hand on each spot of the exhaust manifold were the gases come into it. The one that is leaking will be COLDER than the rest since it is leaking at first then warm up or use a infared gun if you do not feel like risking a burn. Sorry that is how we had to fgure out which ones were missing on the old manuals was see which one was colder.

 

I tried this at night and didn't see any smoke or sparks.

Ironeagle, are you referring to the part of the manifold that goes INSIDE the cylinder block? What I understand by 'exhaust manifold' is the pipe that goes parallel to the cylinder block on the passenger side of the engine. It has a couple of slip joints and 3 or 4 'forks' that branch out into the cylinder block. That's what I should be touching?

 

If I find which cylinder is the culprit, any idea how it gets fixed? I mean is it expensive to repair or is it just a matter of replacing a gasket or something - you know the usual routine of 10 hours labour plus 40 bucks for the gasket

 

Has anyone thats worked on the noise problem actually heard it first hand?