Belt squeal on take off

[Duarte 5]

Well a squeal with a air sound usually means boost leak, do you have room where you can remove the belt and do a couple take offs from a standstill to see if noise is still there.

[MO Fred]

We just completed a 160 mile trip yesterday. Heard the squeal one time. I am dropping the motorhome off on the way back at a repair shop to have them check it out and do a couple other things. I will let you know how it turns out. Thanks!

[4Fingers]

Fred,
You could take the belt loose and see if you have a bearing trying to seize. Could be the alternator or possibly the water pump. Another thought is that on take-off the alternator is under high load and causing the belt to slip.

Happy Motoring
Don & Susan

[MO Fred]

Originally Posted by 4Fingers

Fred,
You could take the belt loose and see if you have a bearing trying to seize. Could be the alternator or possibly the water pump. Another thought is that on take-off the alternator is under high load and causing the belt to slip.

Happy Motoring
Don & Susan

Yup, already checked all bearings and all is good. Interesting thought on alternator under high load on take-off. Never heard that before.

[4Fingers]

Fred
By high load under take off I mean a load on the alternator. It has happened on a couple of my vehicles over the years, usually V-belt drives. Charging the battery after starting when the demand for electricity is the greatest.

Happy Motoring
Don & Susan

[MO Fred]

Originally Posted by 4Fingers

Fred
By high load under take off I mean a load on the alternator. It has happened on a couple of my vehicles over the years, usually V-belt drives. Charging the battery after starting when the demand for electricity is the greatest.

Happy Motoring
Don & Susan

Don... when i turn the alternator pulley by hand, with the belt off, it turns freely, no resistance at all. Are you saying that it becomes more stiff or harder to turn under a load? If so... I was not aware of that. Also, my motor is mechanical so I not sure how much of a load that would be. Fred

[twinboat]

It takes about 1 HP, ( horse power ), per 30 amps, to turn an alternator.

As soon as the engine gets up to idle speed, the alternator starts developing output amperage. At idle it is less then 1/4 it's output rating. Its still a few HP.

As you quickly increase engine speed, the alternator works much harder, needs more HP, causing more strain on the drive belt.

With the serpentine belt setup, it is unusual for the alt pulley to slip, since the belt is making a lot of pulley contact.
It could be that your batteries are failing and need high amp recharging or something else is slipping.

[oldbeek]

If it happens when you first start the engine, I would say heavy load on the alternator. If it happens when you start out moving, that is when the turbo really starts boosting pressure, and I would be looking for a turbo out put hose leak. The squeal can be very similar.

[guardrail53]

I would take the A/C belt off, and do a take off, and see if the squeal is still there! If so, then I would suspect the new belt or the tensioner, is the problem, since it just started after they were changed!
The air leak at take off is a problem, and could be part of the sound you are hearing? You need to check the boot's from your turbo to the Air-to-Air charge air cooler, for leaks! Do you have a boost gauge? What does it do at take off?
Just because the belt or the tensioner are new, don't dismiss that they could be bad! If the tensioner is jumping more than the old one, that could be the problem! Do you still have the old tensioner? Swap them out, and see if the problem goes away? Just throwing these idea's out there! Rail!

[MO Fred]

Originally Posted by guardrail53

I would take the A/C belt off, and do a take off, and see if the squeal is still there! If so, then I would suspect the new belt or the tensioner, is the problem, since it just started after they were changed!
The air leak at take off is a problem, and could be part of the sound you are hearing? You need to check the boot's from your turbo to the Air-to-Air charge air cooler, for leaks! Do you have a boost gauge? What does it do at take off?
Just because the belt or the tensioner are new, don't dismiss that they could be bad! If the tensioner is jumping more than the old one, that could be the problem! Do you still have the old tensioner? Swap them out, and see if the problem goes away? Just throwing these idea's out there! Rail!

Yup, the new tensioner (Dayco) jumps when accelerating from idle when taking off. This is causing the squel, a long squel. Anyway, I called cummins care to confirm I have the correct belt and they gave me the part number for the tensioner. I just ordered a new one that is supposedly made by cummins. I didn't know cummins actually made belt tensioners.

[4Fingers]

Fred
Glad you found the problem.