omg! wits end...

[AGH Sasquatch]

01 d2 82k

last motor was loosing water and had questionable knock under load. I rebuilt another block that was tested good and had no signs of slipping liners or anything. new block has all new parts inside it and were put together right.

new motor fired up and has same knock as old motor.

it only does it under load. sounds like a rapping like metal to metal knock. lous enough to be heard at highway speeds. light load is fine but moderate load makes it knock. i can get it to do it by power breaking the engine in driveway also so it doesn't have anything to do with driving. doesnt have anything to do with rpms either. wont do it unless in gear and under load reverse or foreward. gets a little better when warmed up/takes more load to make it do it.

I figured it had to be a crack in exhaust that was opening up when the engine twists in its mounts. so i replaced the ypipe and manifolds=same friggin noise.

obviously i have been under there looking and looking for loose stuff. i cant isolate it to either side of engine bay. just sounds like its coming from middle of enigine down low.

The only things that came over from old motor are the ancillaries.

any ideas?

 

[TOM R]

Running super for gas? If not could be pinging/detonation

 

[KyleT]

Immediate? Or when hot?

What all was reused?

 

[AGH Sasquatch]

This would have to be some pretty loud pinging.

Kyle. The only things reused were the ancillaries: power steering, ac, alt, pulleys...the bolt ons. all new internal parts (not that it matters because its a completely diff engine) new mounts. same oil and trans lines, same trans and torque converter.

The more i drive it the more it sounds like something is just loose and tapping against something but i cant find anything loose.

 

[KyleT]

Thermostat?

 

[jims95]

"just sounds like its coming from middle of enigine down low."


The exhaust manifold outlets, and the mating 'Y" pipe flange surfaces need to be flat. Use a new gasket between them, and make sure the studs, and nuts are completely tight. If not,you probably have an exhaust leak. The leak is heard under load, or when revving the engine. It gets louder as the engine warms up, too.

You can take a short piece of tubing, or pipe to use as a stethoscope. Have someone rev the engine. Put one end of the pipe, or tubing to your ear, and move the other end on the side of the engine. This is the easiest way to locate an exhaust leak. You can also check for leaks where the "y" pipe bolts to the muffler, weld joints on the "y" pipe, weld joints on the catalytic converters, and weld joints on the oxygen sensor fittings.

I had a manifold stud break, the gasket burned out, and the "Y" pipe flange warped. I had to rework the flange. I put in new gaskets, studs and nuts. The noise was gone.

 

[capri_auto]

I have had the same issue since day one owning my truck. Got it with 104k it's has 135k now. I used a mechanics stethoscope and couldn't isolate the sound. When I take off the oil cap it goes away sometimes, not sure why. I just keep the thing well maintained and hope for the best.

 

[roverMc]

Sure it's not the transmission? You changed motors and not the transmission or tcase. Did you check the universal joints? The front ones are close to the lower part of the motor. Just throwing it out there.

 

[sedat]

Remove the belt to verify its not an ancillary. I've found a few P/S pumps that knock when ran low on fluid for a while.


also: You'll get a light off-throttle rattle if you cam the shit out of the engine/port the heads/intake/trumpets and retain the pot-metal manifolds.
The above had me chasing my tail for almost a week.

Do you have any way of getting live data from the engine? if so, what are your base ignition advance during the knocking?

 

[Jay B]

I like the direction Jims95 was heading; taking the belt off for a minute is also a good idea. My first thought is a cracked torque converter flex plate, or something in the converter itself.

 

[crown14]

i like the direction jims95 was heading; taking the belt off for a minute is also a good idea. My first thought is a cracked torque converter flex plate, or something in the converter itself.

x2

 

[Roving Beetle]

X3