The Stovebolt Site Forums The Shop Area Engine Shop 228 Engine Noise - Prelim Diagnosis

Hello all. Was wondering if any stovebolters might be able to help suggest some initial diagnosis/places to check on a very recent engine noise in my 51 GMC Burb. Upon acceleration, it is making a fairly nasty clattering noise. First thought it was the water pump, but now I worry is it a bearing or something. Check out the video and let me know what you think:

http://sharing.theflip.com/session/6b634d09c0b91617e03d5d49a2dfec56/video/18046686

Hard to tell but to me it seems more like a rubbing sound than a knock and the water pump does seem suspect. Is anything hitting the bottom pulley and have you eliminated the generator? Just some thoughts but doesn't sound like bottom end to me, could I suppose be the valve train but I don't lean that way. Everyone will hear it differently.

WIll check the bottom pulley. Do you mean the generator bearing might be going? I just took the belt off and spun the generator pulley .... no strange sound or play.

Okay. I disconnected the fan belt and generator, so that the only thing turning when the engine is on is the crankshaft/CS pulley. Wallah, no more noise. I assume it is the water pump. I am missing something?

The generator or water pump could be the problem. I'd suggest changing the water pump first, especially if the old pump has some mileage on it. It's just a matter of time and mileage until the pump starts to leak, so a little preventive maintenance will probably save you a possible on-the-road problem. If it springs a leak, you could be dealing with an expensive towing job, or a roasted engine.
Jerry

Yeah, not leaking yet. But sound like the impeller bearing is rattling. So, yes, I'll change it and hopefully that will be it. Thanks!

I was watching the video, and it looked like the fan belt was wobbeling from the bottom. I would check the harmonic ballancer. It may have walked off the crankshaft. I don't believe there is a bolt on your 228 to hold the harmonic ballancer on like the later 270s and 302s have.

John

Really? What holds the HB on?

Yes, the fan belt is loose and I am going to get a new one as the current one is a bit worn.

When I took the fan belt completely off and started the engine, I couldn't reproduce the sound.

When I put it back and engaged the water pump pulley, it started making noise again.

The HB is a press fit. It is not uncommon for them to walk off. If the HB walks completely off it can cause a lot of damage as it will likely go through the radiator. It may not be your problem, but I would definetely take a good look. The fan belt may be pulling the HB enough when it is on to cause that sound. In my experience water pumps usally ring when they go bad.

John

"Ring"? I'll definitely check the HB ... I assume it would be noticeably loose.

Sometimes when the bearing in the water pump is going, you can feel thre play in it with the engine stopped. Grasp the fan and try to wiggle it sideways, sort of tilting it. If you can do that, it probably needs to be changed

Thanks all .... pretty definite now it is the water pump bearing.

Also.....have you inspected the blades of the cooling fan? If a blade is bent or cracked it will flex at higher RPM's with higher air flow and strike the front edge of the harmonic balancer. The clearance between the two components can often times be VERY close and the slightest wobble or flex can cause a scraping sound. My 216 suffered from this ailment.

I had the fan off and it seemed fine. I'll check the HB for any signs of striking. Thanks!