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I am about midway done with changing the timing belt & water pump on my 1999 Toyota, which features a 6-cylinder 5VZ-FE engine. After getting the front timing cover off, I discovered that there were some paint dots on the rear timing cover, and also both cam pulleys.

(Despite the vehicle's age in years, it has rather low mileage on it and so might very well still have had the factory timing belt on it. So, I think these paint splotches are from the factory.)

For the most part, these splotches coincide with the TDC notches that are cast/cut into the cams & the back cover, but somewhat sloppily.

On the passenger-side cam sprocket, the painted dot is directly over the pulley's timing mark, but the corresponding painted dot on the rear cover is to the left of the 'V' notch.

engine photo 1

And then on the driver-side, the painted dot on the pulley is immediately to the left of the pulley's timing mark, and the painted dot on the rear cover is to the right of the 'V' notch.

engine photo 2

What is the point of these paint marks? What meaning are they conveying that the actual TDC markings don't? Do I need to interpret their positions relative to the TDC alignment notches in a particular way? ... And if not, why did Toyota even bother with the paint?

(There is also the puzzling matter of the additional paint splotch ~170 degrees out of phase with TDC, on the passenger side. But I'm content to ignore that one.)

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    I don't know why, but I'd bet the reason for the dots is not to show the alignment notches, but are rather to show the technician who put the engine together has checked to ensure the alignment of the timing marks. I don't know this for a fact, so am leaving this as a comment. – Pᴀᴜʟsᴛᴇʀ2 Oct 8 '16 at 2:20
  • That is a reasonable guess. – Ryan V. Bissell Oct 8 '16 at 2:26
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    They wouldn't need to worry about aligning the paint splotches, the splotches are just there to show they've done their job. – Pᴀᴜʟsᴛᴇʀ2 Oct 8 '16 at 2:29
  • They may also be there to make the existing marks clearer - if you're using a strobe to set the timing, it can sometimes be difficult to see the cast-in marks, so people add a paint mark to make it clearer - especially as both marks seem to be done to line up a few degrees before TDC – Nick C Apr 5 '18 at 8:34
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Despite the vehicle's age in years, it has rather low mileage on it and so might very well still have had the factory timing belt on it.

I would say this is very unlikely a belt of this age regardless of mileage would probably be well perished by now.

I don't know for a fact but usually, the technicians who time these engines have more efficient methods of timing and installing the belts than the official guide instructs. Tricks like turning cam pullies half a tooth off etc. to make it easier to fit the belt around idle pullies and tensioners. This is even more common on V, DOHC and engines with split timing.

Ignore the paint marks and always time using the machined notches.

  • I think @Paulster2 had the correct answer, as a comment: the paint marks are just quality-control. The factory worker will never have to ask themselves "did I forget step #13?" when #13 ends with making a paint mark. I think I may have gotten confirmation of that elsewhere. As to your comment about age of the belt: I later saw that the water pump was not original (based on date stamp.) – Ryan V. Bissell Apr 6 '18 at 17:07

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