NG 900/9-3 Valve Cover and Timing Gear

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B204 (2.0 liter, 4-cylinder 16-valve) engine at 100k miles after oil changes with conventional oil every 3-5k miles and after treatment with a quick (20-min) engine oil flush. Compression and leak-down tests show moderate engine wear. An oil test (Used Oil Analysis) performed by Blackstone Labs shows high lead and just over 2% fuel in the oil, but no coolant or any other abnormal metals.

  • Dry compression test: 142-145 psi
  • Leakdown test: 12-18% leakage
  • Oil pressure test: 50psi at 2000 rpm

Valve cover removed for inspection.

Valve Cover

Inside of valve cover, covered with baked-on oil deposits. For details of valve cover removal and gasket replacement, see Valve Cover.

Fig. 1 - Valve Cover


Top of the engine after valve cover removal, timing chain and sprockets on the left. Picture shows moderate to heavy tar-like oil deposits.

Fig. 2 - Top of Engine

Timing Chain and Sprockets

Light areas show normal discoloration. Dark areas are layers of accumulated oil deposits. The timing chain was too covered with oil deposits to inspect properly, but there were no obvious signs of wear on the sprockets. For more information on the timing chain, see Timing Chain Tensioner.

Fig. 3 - Timing Chain and Sprockets

Timing Chain Gear

Close up showing a section of timing chain on one sprocket. View shows difference between light areas (varnish), and dark areas covered with oil deposits (sludge).

Fig. 4 - Timing Chain Gear


Valve cover, after a chemical wash. Oil deposits were removed fairly easily in a parts washer, but the engine cannot be cleaned as easily.

Fig. 5 - Clean Valve Cover