Forum Oficjalnego Klubu Mitsubishi - MitsuManiaki

best_x_treme

I wanted to share a recent experience regarding my 4G63T timing belt replacement that might save a few headaches (and engines) for anyone doing this job or dealing with mechanics unfamiliar with Mitsubishi architecture.

Long story short: My mechanic performed the timing belt tensioning while keeping the camshaft locking tool installed between the cam gears throughout the entire process—a common practice on VW/VAG engines (TDI, etc.) where the cam gears are slotted/floating. On a 4G63, however, the cam gears are fixed to the shafts on keyways.

First attempt: Because the cams were locked together, turning the eccentric pulley only pulled tension on the belt section between the crankshaft and the pulley. Once the cam lock was removed and the engine was manually rotated, the belt tension equalized across all spans. The section between the cams loosened up, causing an excessive belt slack between the cams.

Second attempt: Seeing the slack, the mechanic tried to "fix" it by cranking down heavily on the eccentric pulley—again, with the cam lock still in place. Once released, the belt was severely over-tensioned. The hydraulic tensioner was fully bottomed out with zero travel left. Upon starting, the engine had a very loud "supercharger/turbine" whine due to excessive load on the belt and idler/tensioner bearings.

The Fix:
After double-checking the factory service manual, we loosened the eccentric pulley, removed the camshaft locking tool, and set the eccentric pulley correctly so that the hydraulic tensioner rod aligned with its housing hole.

The cam locking tool is ONLY for holding the gears aligned while slip-fitting the belt over the teeth. It must be removed before you set the eccentric pulley tension and perform the final torque down. The 4G63 auto-tensioner is a dynamic hydraulic damper, not just a dummy pulley, and setting it properly requires the belt to move freely across all gears during tension adjustment.

Hope this helps anyone troubleshooting an excessive belt slack between the cams or a whining timing belt!

krzychu

This is exactly what always amazes me about some mechanics: they assume they know better than the service manual and treat every engine as if it's basically the same thing.

On the 4G63, if you mention locking the hidden balance shaft, they often look at you like you're overcomplicating things and say they'll "figure it out." If you tell them the tensioner should be checked after two full crank rotations and a 15-minute wait, or that the grenade pin should slide back in correctly (or that the tensioner travel should be measured), they act as if you're trying to teach them how to do their job.

Then you pick up the car and the entire vehicle is vibrating because the balance shaft timing is off...

Mitsubishi timing systems have their own procedures for a reason. Following the service manual step by step may seem tedious, but ignoring it can easily lead to catastrophic engine failure. Great write-up, and hopefully it saves others from making the same mistake.