Catastrophic water pump failure 300Tdi


Well-known member
Fortunately I was at a Maverik station getting fuel when I noticed all the coolant pouring out. The core bearing was being pulled out of the water pump and the pump vanes were grinding away the housing interior. Here's why.
The center of the belt tensioner has a ~2" diameter plastic ring facing forward on it about 1/8" thick. That plastic layer wears over time.
That wear also causes the serp belt to squeek as many here correct by shimming a penny between the housing and the engine block.
So as the tensioner leans forward, it puts forward pressure on the pulleys causing a forward pulling pressure and that caused the center of my water pump to pull forward wanting pull out it's core, bearing & impeller, and when it got far enough forward exposing the weep hole the coolant was gushing out of it. In the 4 miles it took to get home, I went through over 4 gallons of water (remove res. cap so there's no pressure) on that short drive. So IF your serp belt is squeeking, it's most likely because that center forward facing 1/8" ring of plastic is worn causing the serp belt to not be aligning correctly and it may cause you water pump to fail quickly like mine.
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Staff member
Your truck hates serpentine belts!:LOL: Roosevelt Lake and now this. Hope this is the last fix and don't be a stranger when you come down the hill.


Technical Excellence Contributor
Been a while since I’ve seen you post! Not that I’ve been very active after selling my 90, but still good to see you about. You helped me a lot with my Tdi swap, always appreciated that.

Good advice on the persistent squeak! I wondered what was going to be the giving point for that squeak that 300Tdi owners can come across.