Mystery rotating noise (engine accesory?)
09-15-2015, 10:27 AM
#1
Le Mans Master
Thread Starter
Mystery rotating noise (engine accesory?)
Perhaps this should be in Tech. If so, MODS, please move it.
1978 L82, auto. 7 blade fan, two new belts, new fan clutch. AC deleted, three groove pullies.
New Gates belt from crank around the PS pulley and another new Gates belt around crank, alt and WP. No tensioners.
I have a new WP to install (preventative). No overheating issues. Runs 200 all day long.
I get a fairly loud squeak at startup. Idles fine. Drop it into 2nd gear and its fine. As RPM's increase its all good right up to about 2500 or so then I get a squeal. 3000 its louder, if I bump it into 3rd the noise goes away until its back to 3500 or so then after about 3 minutes at RPM's above 3000 the noise goes away. I can shut the car off for a couple of hours and the noise doesn't come back. Makes me think something is getting hot.
Current WP spins freely, alt spins free. I'm thinking one of the accessory bearings are getting hot and goes quiet once hot. I can replicate the squeal with the car in park and manually manipulating the throttle on the side of the carb. I cannot tell where the squeal is coming from with the hood open.
If an accessory bearing was bad wouldn't it squeal all the time, not just at 3000+? If its the belts squealing wouldn't it also be all the time?
Would a PS pump make this noise? Ive never done anything with the pump in the 10 years I've owned the car. When I replaced the PS belt I didn't notice any abnormal movement in the pulley.
Im going to pull the Alt belt and eliminate that first, then I'll pull the PS belt to eliminate that.
Really it can only be a few things. Crank bearings (
) Alt bearing, WP or PS.
Thoughts?
dodosmike
1978 L82, auto. 7 blade fan, two new belts, new fan clutch. AC deleted, three groove pullies.
New Gates belt from crank around the PS pulley and another new Gates belt around crank, alt and WP. No tensioners.
I have a new WP to install (preventative). No overheating issues. Runs 200 all day long.
I get a fairly loud squeak at startup. Idles fine. Drop it into 2nd gear and its fine. As RPM's increase its all good right up to about 2500 or so then I get a squeal. 3000 its louder, if I bump it into 3rd the noise goes away until its back to 3500 or so then after about 3 minutes at RPM's above 3000 the noise goes away. I can shut the car off for a couple of hours and the noise doesn't come back. Makes me think something is getting hot.
Current WP spins freely, alt spins free. I'm thinking one of the accessory bearings are getting hot and goes quiet once hot. I can replicate the squeal with the car in park and manually manipulating the throttle on the side of the carb. I cannot tell where the squeal is coming from with the hood open.
If an accessory bearing was bad wouldn't it squeal all the time, not just at 3000+? If its the belts squealing wouldn't it also be all the time?
Would a PS pump make this noise? Ive never done anything with the pump in the 10 years I've owned the car. When I replaced the PS belt I didn't notice any abnormal movement in the pulley.
Im going to pull the Alt belt and eliminate that first, then I'll pull the PS belt to eliminate that.
Really it can only be a few things. Crank bearings (
) Alt bearing, WP or PS.Thoughts?
dodosmike
09-15-2015, 12:56 PM
#2
Safety Car
Member Since: Jun 2004
Location: Beecher Illinois
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As I am currently in the middle of my second water pump rebuild on my white79(black79 was done 3 years ago) I'd go with water pump.
Neither of mine leaked at all, just made noise. Could detect some wobble in the fan.
The one I'm working on now had all the grease pushed out of it and collected inside the back side of the pulley.
On the bench turning the shaft by hand you could feel and hear the bearing grinding.
Neither of mine leaked at all, just made noise. Could detect some wobble in the fan.
The one I'm working on now had all the grease pushed out of it and collected inside the back side of the pulley.
On the bench turning the shaft by hand you could feel and hear the bearing grinding.
09-15-2015, 05:48 PM
#3
Racer
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Location: Brisbane Australia
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Mystery rotating noise (engine accesory?)
Had the same sounding issue on my 68. Most apparent once over 2900rpm. I had removed the a/c belt and the remaining alt belt was slipping trying to drive the water pump from the crank pulley at higher revs. A/c belt back on and belt squeal disappeared. A friend had same issue in his Camaro and swapped to a different belt setup for non ac cars where as well as the alt belt there is a small belt just between the crank and the water pump for the extra tension.
09-20-2015, 08:39 AM
#4
Le Mans Master
Thread Starter
New alt, new alt/wp belt.
No noise.....yet? Really raining yesterday so no road trip to get everything hot.
Heading out on the ATV this morning for a group ride for a few hours, hopefully this afternoon I can get it out for a test drive
No noise.....yet? Really raining yesterday so no road trip to get everything hot.
Heading out on the ATV this morning for a group ride for a few hours, hopefully this afternoon I can get it out for a test drive