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T900 and T630 water pump pulley
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Author:  Joshua [ October 29th, 2013, 8:47 am ]
Post subject:  T900 and T630 water pump pulley

We have seen a few instances of TracStar water pump pulleys failing. The part is replaced and they fail again.
The part number is MDA00234. Here is what the engine people are telling us:

Here are a couple of pages from the workshop manual for these engines. I have highlighted a couple of areas that may be causing the problem. On the first page, “Tightening Torques”, I have highlighted the fan-pulley screws (which are 6mm). Notice that the left-hand value is for screws with the number ‘4’ on the head, and the right-hand value is for screws with the number ‘7’ (these represent different metals and processes). It’s important to note that these screws MUST be tightened in steps, with the belt loosened, so as to prevent warping or cracking the pulley.

The second page depicts the proper alternator/water pump belt tightness. I have included this for two reasons: 1) over tightening the belt would exert excessive forces of the water pump pulley and bearings, as well as the alternator bearings, and 2) the belt MUST be loose when tightening the pulley screws; otherwise, the values indicated on the torque wrench will be inaccurate. Of course, once the pulley screws are properly tightened, the belt must be tightened with the proper tension.

Lastly, because the overwhelming majority of torque wrenches are not accurate below 10 foot-pounds, I recommend using an “Inch-pound” torque wrench; those converted values are:

Foot Pounds Inch Pounds

‘4’ 5.8 – 6.8 69.6 – 81.6 (First step = 40 inch-pounds)
‘7’ 7.24 – 8.31 86.9 – 99.7 (First step = 45 inch-pounds)

Please have the techs verify these torques and procedures, as this usually proves to be the root cause of the failures they’re experiencing.

Pulley Info.jpg
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