Smokepedal
Member
I have an '03 ALH with 90k miles and have noticed a subtle metallic-like tapping sound. It is easier to hear just off idle when taking off on a steep uphill incline, but can be heard at other engine speeds at light to moderate loads as well. However, typical engine sounds at high revs/loads make it impossible for me to detect. It might be there, but between normal diesel sounds and hearing loss, I can't be certain. Its speed is tied to engine speed and I believe it stops completely when coasting off-throttle, leading to me to believe it's injection-related.
Using a wooden rod as a stethoscope, I have noticed that #3 injector sounds louder and seems to almost make a snapping sound that is sharper than the other injectors. Is this normal for that injector since it has the needle lift sensor, or could this be the source of the noise?
Strangely enough, it is often easier to hear the tapping with hood closed. I guess it masks some of other typical diesel engine sounds. Open the hood and it seems to get lost in the clatter.
I have run several loads of Diesel Purge (It's an annual ritual for me) through the injectors without any effect. It has had CAT 2 micron filtration on it for the last 40k miles and I always run diesel fuel additives with every tank. MPG continues to average 51mpg, no CELs, no other strange behavior, no smoky or hard starts, no discernible oil usage, etc.
Valve cover, N75 valve, injection pump all sound smooth and comparatively quiet.
What could it be? Should I pop for a new #3 injector, or could it be something I've overlooked? I'm going on a cross-country trip next month and want this addressed before setting off.
Thanks for your help.
Using a wooden rod as a stethoscope, I have noticed that #3 injector sounds louder and seems to almost make a snapping sound that is sharper than the other injectors. Is this normal for that injector since it has the needle lift sensor, or could this be the source of the noise?
Strangely enough, it is often easier to hear the tapping with hood closed. I guess it masks some of other typical diesel engine sounds. Open the hood and it seems to get lost in the clatter.
I have run several loads of Diesel Purge (It's an annual ritual for me) through the injectors without any effect. It has had CAT 2 micron filtration on it for the last 40k miles and I always run diesel fuel additives with every tank. MPG continues to average 51mpg, no CELs, no other strange behavior, no smoky or hard starts, no discernible oil usage, etc.
Valve cover, N75 valve, injection pump all sound smooth and comparatively quiet.
What could it be? Should I pop for a new #3 injector, or could it be something I've overlooked? I'm going on a cross-country trip next month and want this addressed before setting off.
Thanks for your help.