Squealing carb
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
Don't reckon how a carb might "squeal" but I have heard whistling vacuum leaks.
A squeal is often caused by belt slippage, often because the belt is too loose, but sometimes because one of the driven accessories is going bad. I had a smog pump with bad bearings one time that sounded okay at idle but didn't like higher RPMs...
A squeal is often caused by belt slippage, often because the belt is too loose, but sometimes because one of the driven accessories is going bad. I had a smog pump with bad bearings one time that sounded okay at idle but didn't like higher RPMs...
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Try playing with some variables to determine if you've got a squealing vacuum leak or a slipping belt.
For example, if you can duplicate the squeal, blip the throttle quickly. You don't need the truck to accelerate much. You just want to briefly reduce the vacuum in the intake manifold. See if the noise changes. You can also let off the throttle quickly. That will increase the vacuum.
For a potential slipping belt, apply some belt dressing and see if that helps. With the alternator belt, for example, try increasing and then decreasing the electrical load (high beams and heater fan) and see if that makes any difference.
There is not much you can do to change the load on the other belts at freeway speeds, though. Can you ever duplicate the squeal while parked? Or is it only at freeway speeds? You're hoping to see if the noise is dependent on vacuum, RPM, or load on the V-belts.
For example, if you can duplicate the squeal, blip the throttle quickly. You don't need the truck to accelerate much. You just want to briefly reduce the vacuum in the intake manifold. See if the noise changes. You can also let off the throttle quickly. That will increase the vacuum.
For a potential slipping belt, apply some belt dressing and see if that helps. With the alternator belt, for example, try increasing and then decreasing the electrical load (high beams and heater fan) and see if that makes any difference.
There is not much you can do to change the load on the other belts at freeway speeds, though. Can you ever duplicate the squeal while parked? Or is it only at freeway speeds? You're hoping to see if the noise is dependent on vacuum, RPM, or load on the V-belts.
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