03 Sub 2500 6 L engine noise

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Posted by OldBuggie73 ( on 02:02:58 03/11/13

I have a 2003 Suburban 2500 with 6L Engine. The engine has developed a new noise in the past few weeks, kind of a metallic grinding/rubbing noise (intermittently, but steadily) - sounds like Ruh ruh... ruh..... ruh...ruh ruh... etc). Noise is not in synch with the engine like a ticking lifter or a thumping rod bearing. Sounds like noise is in (or behind) the water pump. Noise at all RPMS. Maybe gets a little quieter after warming up, but hard to say. Oil pressure at idle about 25 when warm, at highway speed is about 40 or so, per the dash gauge (however accurate it might be).

I used a long screw driver to listen at various places on the engine, trans, and exhaust system, the noise was definitely loudest when touching the water pump. I temporarily disconnected both belts, and the engine made the same noise even with all driven accessories disconnected. The water pump is only 2 years old (maybe ~60K miles on it now). The engine is high mileage, but idles smooth as a new engine, no smoke, doesn't burn oil. Engine makes same noise with both V-belts disconnected also. Water pump (and all accessories - alt, ac comp, ps pump, idler pulleys) turns smoothly by hand without any noise.

Now I will tell you that the Sub has 416K miles on it, engine has never been opened up for anything except the water pump. For that matter, the original transmission filter and oil are still in the truck. I do change the engine oil and filter occasionally...

Any suggestions on what this might be? I am planning to dig in and replace the oil pump since it is so old and has so many (highway) miles, but I can't picture the gearotor pump making a noise like this.


Jim Baker

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