6.5td knock noise. High miles

[Bittle Auto Transport]

This is my first post here so sorry if this issue is already posted. My 96 6.5 developed a knock noise last week while towing a heavy load in mountains. My first though was injector so I replaced all injectors. Balancer and pulley are new. The truck runs just as well with the noise but while pulling a load mpg went from 7.5 to 6, this led me to injectors . No miss or hesitation. It started while I was in Georgia. I drove home to jersey and noise stayed the same. Give it a little Fuel and you can't here it. When I first start it it's quiet for about 3 mins. Then the knock starts. Thanks for any help

 

[WarWagon]

Drop the torque converter rock guard and check the bolts. Inspect the flex plate and check for noise there.

Check the exhaust for hitting on something and check the down pipe for the flange breaking off.

 

[NVW]

Are the pulley and balancer OEM or Dorman? Some members have reported Dormans can be bad. With the drop in mpg it isn't likely though.

Could be a valve train problem.

 

[bk95td]

X2 on the torque converter to flexplate bolts. I've had that happen after a heavy pull. It doesn't explain the mpg drop though. A scan tool can disable cylinders to check if it is a certain cylinder making the knock.

 

[Bittle Auto Transport]

Going to check the flexplate now, balancer and pulley are oem. I was thinking of pulling the valve covers to check the plastic retainers, I guess il look into other things before removing the intake and fuel lines.

 

[3500GMC]

Did the oil pressure drop?

 

[Bittle Auto Transport]

Flexplate is good, oil pressure never dropped, im leaning towards the plastic retainers under the valve covers but if they broke and the rocker has some play would that cause any roughnes to the engine when running.

 

[buddy]

Flexplate is good, oil pressure never dropped, im leaning towards the plastic retainers under the valve covers but if they broke and the rocker has some play would that cause any roughnes to the engine when running.

It will when the rocker moves off the valve and the valve doesnt open. Although the engines have run still with valves chewed up by pistons and otherwise not functioning correctly.

The flexplate could be cracked and may not see it just with the inspection cover off.

 

[Bittle Auto Transport]

do you recomend removing the flexplate for a more thorough inspection.

 

[buddy]

do you recomend removing the flexplate for a more thorough inspection.

It just sounds a lot like the flexplate, but could be something engine related. If nothing else comes up I guess I would recommend taking it off for inspection.

Can a stethescope or stick from your ear to the block better place the noise. Like if its coming from top, bottom, front or back?

 

[Bittle Auto Transport]

All i can find with stethascope is that it seems louder on passanger side, cant pinpoint top,bottom or cylinder #