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View Full Version : What is that noise? (water pump)



Charlie Foxtrot
02-18-2017, 08:11 PM
My guess is that most readers will already be familiar with the water pump on the 4.0L 6 cylinder engine. It's one of the most basic pumps out there, and replacement is very straightforward. How to R&R is not the point of this short posting. I had an intermittent squawking, scraping noise that sounded like a failed bearing on the front of the engine, not in it. Kind of like an idler pulley or maybe a water pump. Took the belt off, no noise. Rotated/spun every pulley, no noise. Replaced the belt. Noise re-appears. This was driving me crazy. Replaced both idlers, still had the noise. Used the stethoscope, and it sure seemed like it was coming from the water pump area, but the pump was not leaking. In over 40 years of turning a wrench, I've never seen a failed water pump bearing with out a leak, but what the heck. Pumps are cheap, I had some antifreeze on the shelf, & I'd tried everything else. Pulled the pump. This is what I found. Even though the pump rotated freely w/o noise when I spun it by hand, the minute the tension of the belt was on it, the impeller was touching the cylinder wall. (see photos)

bluedragon436
02-22-2017, 12:57 AM
WOW.. WTF?!! Yeah can't say I've seen or heard of bearing failure without leakage.. that is what happened to the water pump on my 98 XJ.. was driving down the highway, belt popped off.. was like WTF?!! so pulled over cut the engine off... had the wife come pick me up and take me to the auto parts store to get a new belt, since the old one was thrashed.. was fighting to get it on, went under the engine to get it over the harmonic balancer correctly, and got dripped on... and was like WTF?!! Pulled the belt back off and touched the water pump pulley, and all hell broke loose...