2G Why is my timing belt riding like this?

[shinzon]

So the water pump went out on my 96 TSIAWD and I'm in the process of replacing it and all the timing components while I'm in there. Is it normal that my timing belt rides so far to one side of the cam gears? It's always been like this, and I'm not sure what, if anything, is wrong. Also notice now far forward it sits on the idler pulley. The belt lines up fine on other pulleys, and the sprockets on the crankshaft.

New with this timing job are:

Timing and balance shaft belts - Gates
Balance shaft and timing belt tensioner pulleys - ITM with NTN bearings
Idler pulley - ITM/NTN
hydraulic tensioner - AISIN
New OEM idler arm

Any ideas? Thanks, guys!

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[DSMPT]

Most likely your tensioner arm bushing is worn.

 

[shinzon]

Most likely your tensioner arm bushing is worn.

Brand new OEM. The shaft on the engine mount bracket the tensioner arm rides on was in perfect condition too--not so much as a score mark.

 

[DSMPT]

Is this still happening after starting the engine with proper belt tension?

 

[shinzon]

Is this still happening after starting the engine with proper belt tension?

Yup, it still happens after the engine has ran; in fact, it was like this before I did the 120k service on this car back in 2014, and it's ran like that for roughly 20-30k miles. I followed the procedure in the manual exactly, and had about 4mm clearance between the body of the hydraulic tensioner and the tensioner arm after turning the engine over and letting it sit. Verified that 4mm clearance after running the engine briefly and letting it sit, too.

 

[luv2rallye]

I wouldn't worry about it. As long as the belt doesn't go over the cam sprockets edge and is tensioned correctly you're ok.

As far as why, here's one possibility I've experienced on my 99 GST. A different "offset" of the idler or tensioner pulleys can do this. [Offset is the distance from the outer edge of the pulley to the pulley face where the bolt head is against the pulley. If changed, this causes the pulley belt holding force direction to be slightly different which can affect the belt riding position to be off center.] I've also had your exact problem and noticed some after market pulleys have a slightly different offset than factory. Using an aftermarket pulley caused my belt to not be centered (went all the way to the edge of the cam sprocket). Changing nothing other than the pulley to a factory oem one centered the belt immediately. That's when I looked closely at the 2 pulleys and discovered different offset. The aftermarket one had more offset. I theorized the extra offset made the tension force direction not be perpendicular to the belt which would cause the belt to want to move outward (as riding near the cam sprocket edge proved). I also discovered Mitsubishi changed vendors with the same part number and the idler pulley was now slightly different. Enough so that I went around to all the Mitsu dealers to find the "old stock" pulley just in case the new one would cause problems.

 

[BLACK'98DSM]

+1 on that theory. Back when I was still running all OEM timing components my belt was centered on the gears. But now I've replaced everything and it looks similar to yours.

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[DSMPT]

Worn tensioner arm is a known thing, but I know this is not the only cause. Long time ago I had the same experience and actually was driving the car like that without any issues as I was sure all components were all good and installed properly. But this has never happened again even with the same tensioner arm and bracket since I changed the head/cams and started to use OEM components.
So another possibility I have thought besides worn bushing and aftermarket components design is, perhaps some combination of condition of head/cams/block would cause this, too.

 

[shinzon]

So another possibility I have thought besides worn bushing and aftermarket components design is, perhaps some combination of condition of head/cams/block would cause this, too.

This was my thought too. The car wasn't with me for it's first timing belt change, but I did the second and third, and despite changing to various different brands of components, and replacing the idler arm, as long as the car has been mine this is where the timing belt has been on the gears. The engine has never been taken apart, so for lack of a better explanation, maybe manufacturing tolerances in the various components added up to this?