Water pump squeal...maybe?

[CharlieB]

Hi all,
My '76 Spider is having an intermittent high pitched squeal coming from under the hood. The noise doesn't show until after I have driven for 15 miles or so. My best guess is that the sound is coming from the water pump. Once the noise starts it is a constant high pitch sound that does not change with engine speed. I have tried several times to put the car in neutral with the engine running to see if I could pin down the location of the sound, but after 10 to 15 seconds of idling the sound stops.
I did have a friend drive it and i was able to check under the hood and listen for a few seconds and determined it was at least near the water pump.
My first question, if it was the water pump making the sound wouldn't the sound be there even before the car warmed up?
My second question, if it's not the water pump making the sound, what else could it be?
Any help is greatly appreciated.
Charlie

[RRoller123]

Also check Alternator and Belt Tensioner bearings.

Here is an oddity too. I had a consistent chirping sound, like birds or grasshoppers, that I would hear as I was driving along. Literally thought at first it was the night time critters. It turned out to be the AFM door flap, just slightly bearing upon the housing. These things wag back and forth with a surprisingly high frequency. I ran the engine and drove around a little with the cover off to observe it. Sanded the housing down very slightly with 400 grit to free it up and the chirping noise went away.

Anyway. with a cheap mechanic's stethoscope from Harbor Freight or wherever, you can isolate that squeal quickly to either the water pump, alt, tensioner, or God forbid something more difficult to fix.

[CharlieB]

Yeah chasing down the gremlins is part of the fun I guess. The tensioner bearing is fairly new. I'll check the alternator.
If the water pump was the problem, would it make a high pitch noise all the time? Or only after the car warmed up?
Thanks for the response.

[RRoller123]

My guess is that a bad water pump bearing usually makes more of a constant grinding noise, but yes, usually constant, when one of mine has gone bad.

[18Fiatsandcounting]

A squeal is usually metal-on-metal contact, but you've got me puzzled when you say that the noise doesn't change with engine speed. Do you mean the volume doesn't change? And the pitch doesn't change? That would be very odd if the noise is the same volume and pitch regardless of engine speed.

Could it be a loose water pump/alternator belt? When these are too loose (or glazed due to age and oil), they can squeal, but this is usually when you accelerate the engine from idle. Try tightening this belt.

Other common sources of squeals: water pump bearings or its impeller hitting the block, timing belt tensioner bearings, smog pump bearings/vanes, alternator bearings, alternator pulley cooling fins hitting the alternator, air conditioner compressor.

The fact that the noise only appears when the engine gets warm isn't surprising, as metal parts expand when hot. Try this: Remove any covers so you can quickly get to the alternator/water pump belt, warm up the car until you get the squealing, turn it off and quickly remove the alternator/water pump belt, and turn the engine back on. Don't run it very long like this as it will overheat. If the squeal is gone, then it's being caused by something driven by that belt. You can play the same game if you have any smog pump or air conditioner compressor belts.

-Bryan

[CharlieB]

Thanks for the input Bryan. The pitch of the noise stays the same no matter what the engine speed is. Also, now that I've heard it a few more times I should have described the noise as more of a whistle sound than a squeal (sorry).
I'll try removing the belt like you describe over the weekend and see what I can find.
Thanks again
Charlie

[18Fiatsandcounting]

Hmmmm, a whistle you say... Leaking air injector system? Emission control device gone awry?

-Bryan

[DieselSpider]

Or like an electric motors constant speed such as when the engine warms up and the electric cooling fan comes on?

[18Fiatsandcounting]

Or like an electric motors constant speed such as when the engine warms up and the electric cooling fan comes on?

Ding, ding, ding! I think Ol' Diesel is on to something here. You could connect the cooling fan directly to the battery and see if it produces the sound you're experiencing.

-Bryan

[CharlieB]

I certainly had not thought of the fan. I'll check that out over the weekend too.
Thanks Diesel and everyone for the help

[RRoller123]

Good idea. Just jumper across the temp sensor at the bottom of the radiator and the fan will come on.

[CharlieB]

Quick update:
I tested the fan and it is not the source of the noise. I had to help my wife's grandparents move over the weekend so I'll look into the issue further this week.

[18Fiatsandcounting]

This is a long shot, but how about a very small pinhole leak in one of the coolant hoses? Usually small coolant leaks sound like, "Psssss", but I suppose it could sound like a whistle. That would explain why it only does it when fully warmed up, and when the car cools down just a bit when you're idling, the coolant pressure drops, the leak "closes", and the whistle stops.

Are you losing coolant over time? Any evidence of coolant leaking around the radiator hoses at the front of the engine, specifically the connections near the water pump as that's where you thought the sound was coming from?

-Bryan

[DieselSpider]

Quick update:
I tested the fan and it is not the source of the noise. I had to help my wife's grandparents move over the weekend so I'll look into the issue further this week.

How long did you let the fan run? It may take a few minutes before the bearings get warm enough to squeal.

The only other thing I can think of that would not be impacted by engine rpm or vehicle speed would be electric fuel pump related and possibly the fuel return line making fluid noise. Squeals from coolant hoses leaking or collapsing should vary with engine speed but...

[manoa matt]

IIRC the water pump has two shaft bearings. One inside the pump behind a rubber seal, and one outside the pump behind the pulley. The typical failure mode of the pump is the rubber seal on the inside starts to loose elasticity and shrinks. When the car is cool, the seal is shrunken allowing water to the bearing. When the car heats up, the seal swells and somewhat prevents water from getting to the bearing. On most pumps there is a weep hole on the bottom of the housing under the shaft. When the inner rubber seal goes bad, you will see coolant weep from the hole when the car cools down. I can't remember if the Fiat pump has a weep hole.