NG900 engine noise??? help...

[TurboWookiee]

question for you guys, the car in discusion is a 97 ng900 set, got a noise in the motor between just above idle and a bout 3k, sounds like a rod knock, but it stops after 3k, which if it was a rod it would persumable only get louder, compression is staight across the clys. could this be a balance shaft faliure?? never really heard a bad balance shaft so im not sure what it would sound like if this goes bad. any ideas??? just put on a new turbo and was planning on doing software nxt week. but obivisouly this need to be dealt with first. i should lose compression if a rods going bad right? possibly a valvetrain issue?? bent valve hitting?? im sorta lost atm. any input would be great.

thanks sorry my spelling sucks

[Crazyswede]

the balance shafts in that engine are driven by seperate chains from the main timing chain....so it could be that the chain broke or something is damaged. So did this noise happen all of a sudden or has it been getting progressively louder over a period of time? Have you been doing regular oil changes? do you run synthetic oil? have you checked your oil pan for sludge? What octane gas are you running?

[rsp57]

If the balance chain broke the engine would have a vibration which you could describe as as a harshness. I have seen a big end rattle and go away at revs with no load due to the oil pressure increase. If the pick up is blocked the pumps usually whine due to cavitation. this is a common problem. You can remove the sump by lowering the subframe on the sump side. Remove the frame bolts on this side and just loosen the other side. The frame will hang enough to remove the sump. Sand blast the pick up and punch some bigger holes in the gauze. You can check the big ends once the sump is off. lHope this helps.

[Sam]

rsp is talking about sludge diagnosis. You can also have a look under the valve cover but in many cases people have seen no sludge in the cam area and have had totally clogged pickup screens. If it were sludge your oil light would be flickering.

If it actually is the balance chain you can actually remove that. Many indie shops will roll in a new timing chain and just leave the balance chain removed.

[Raul]

I heard these models had problem with oil pan design make it prone to sludge clogging and starving the rod bearing from proper oil lube.

[Crazyswede]

The sludge issue does exist but can be minimized from regular oil changes and running good quality synthetic oil. You can always drop the pan and clean it out too. Im at 184,000 miles so far. I have not checked for sludge yet so hopefully yhr 10 years of mobil 1 oil changes is paying off.