Thread: Snapping sound from alternator area and car won't rev past 3500 ?

I was replacing a thermostat and gasket today because it had been leaking out of the gasket when it warmed up during the last really cold snap (0 degrees).
After changing it I was warming the car up to check it, after it gotten warm and the fans had turned on and run a few times all looked well on the leak and I was putting things away and getting ready for a test ride when I heard a snapping sound from the alternator area. I revved the motor a few time to see if the snapping sped up up with RPM, it seemed to, but I also noticed the car would not rev past 3500 rpm. After checking it more I think the snapping is coming from the alternator itself, it sounds electrical but I cannot see anything amiss such as sparking to ground or such.
Anyone have an alternator start dying by snapping and also have that cause the engine to not rev past 3500?
Car has 252,000 miles and I have had it since around 80,000. I think the alternator and coils on it are original.

2006 Grand Prix 3.8 NA FWD

Short test drive, found out the motor will rev as expected once rolling. I was not aware that the computer limited the no load or park rpm at 3500, but that seems to be what is happening.
Snapping sound at the alternator seems to have stopped after a 5 mile test drive.
battery had 12.3 before starting, 14.3 while running, so it seems to be working.

I will keep test driving it and monitoring the situation and see what happens with it.

It fixed itself... I love when that happens

On a later test drive, there was no snapping but the alternator sounded as if it had a singing bearing on startup, so I am going to plan on getting an alternator soon as I don't need to be told three times.

It spins smooth, the bearings don't feel or sound dry to my hand, but there is certainly a dry bearing sound coming from it when the car is running.
Another thing I noticed on the last test drive, is that the car battery voltage starts out at about 14.3 14.6 which I think is normal, but during the drive it continues to climb, up to 15.5 15.6, I don't think that is normal as I don't recall seeing over 14.6 during the years I drove it. Is that a sign the voltage regulator is failing? Maybe that ties into the snapping sound that is intermittently still happening.

On another note I just went to the garage and the car has blown off the lower radiator hose and purged all its coolant. So I now I know what I should have replaced 6 months ago that might have saved me some pain lately, the stinking radiator cap :bang head on wall:

Off to the zone to get the alternator tested.
They show having a cap for this car but it says its for a 16lb system, the cap that came with the car was rated at 15lbs, not sure it's worth going to the dealer over that difference ?

Got a replacement alternator and now the voltage stays at 14.4 to 14.6 when driving regardless of electrical load, and no more snapping sound.

Got a new cap for the radiator.
Is there a trick to refilling the coolant system on this car?
Unlike most every car I have owned I can't fill it up, start it, wait for the thermostat to open then top it off while it is circulating on this car, the damn coolant never moves unless I pump the hoses like a workout video, annoying. I got a gallon and a half in it, but the top radiator hose is still full of air after two short test drives, what gives?

Thanks Scottydoggs
I will see if that helps when I drive the 3 miles back home and hopefully top it off.

The 04+ alternator bearings are the same as the 97-03, I took mine apart after it burnt out and I got a HO alternator. Now the HO who knows, I think the casing and suchcame froma GM truck to be honest.