newport dave
Chief Petty Officer
- Joined
- Nov 21, 2004
- Messages
- 458
The engine is a 2001 Volvo 4.3Gi (Vortec V-6 roller cam / balance shaft engine) 250 hours. The problem: Unidentified engine noise. <br /><br />Sounds similar to a lifter noise at idle. It is very noticeable tap tap tap at idle, and goes away when engine is running (no load) at a slightly higher constant RPM, but you hear a loud clatter as the engine decelerates back to idle where it resumes the tap tap tap noise.<br /><br />The first thing I did is try to locate the noise with the valve covers on. I could not really tell which cylinder it was coming from. It sounded loudest at the front timing cover. I know the timing cover is plastic and you will hear any noise in the lifter valley through the cover. <br /><br />I put my PC based scan tool/scope on it to see what was going on performance wise. The scan tool showed no fault codes, perhaps a bit more IAC activity than normal, but nothing other than that. The scope indicated the need for a tune-up, but normal compression, and normal idle ignition patterns. Watching the scope at a higher RPM, there seemed to be more turbulence in #4 cylinder than the others. I thought that may be where the problem was. Cranking compression test showed all cylinders between 150 to 160 PSI.<br /><br />Next step was to pull the valve covers and look for loose rockers and such. No sign of any problem on either side. Ran engine with valve covers off. Still could not pin the noise down to any one cylinder, nor was there any obvious problem. Off came the intake manifold. Inspected all rockers, pushrods and lifters. Found a small crack in the intake lifter of #3 cylinder. Didnt really think it was the problem, but it was replaced. No other signs of any problems, other than my engine guy who inspected the lifters said they looked excessively worn for an engine with 250 hours. He says they look like they have 1000+ hours on them. Also checked the balance shaft for play. It was fine.<br /><br />The engine goes back together and the noise has not changed. Spent some more time listening to the sound at various RPMs. It is still loudest at the timing cover. I start to wonder if it the balance shaft drive gears or timing chain could be the problem. So the timing cover comes off and thats where I am now. <br /><br />The balance shaft drive gears look fine, but the timing chain and cam sprocket look to me to have a lot of wear. See the pictures below. Could this wear indicate a problem? If so what? Just worn out? Is it the cause of the noise perhaps? Any suggestions or comments would be welcome.<br /><br />Thanks,<br />Dave<br /><br />
<br />
<br />
