Engine noise when cold

[SafetyFirst]

My 2007 Holiday Rambler Neptune with a Cummins diesel makes a squealing noise in the engine area and the voltage meter drops off when I first start it on a cool or cold day. This noise happens for about five seconds and then goes away for about twenty seconds, this goes on for about two minutes until the motor starts to warm up. The local Cummins dealer could not find a problem or cure. It has done this since new but so far has not caused a problem. On hot days there is no noise and no indication of a problem. Does anyone else have a similar noise?

[adamfolger]

Your alternator belt it squealing because it is slipping. The proof is that the volt meter drops off. Try some belt conditioner on it.

[onechaddude]

I think what is happening is when you start in the cool or cold your grid heaters cycle off and on. These intake grid heaters draw a large amount of power and puts a large load on the alternator causing your dash gauge to fluctuate. You could try belt dressing that may help. When was your belt last changed, or has it been? I would also want to get a good look at it to make sure it still looks good. Easier to change it at home at your leisure than on the side of the road in the middle of a trip. Hope this helps.

Chad

[clifford j]

I agree about the Alternator theory, I also believe the OP should inspect the belt (s) . Belts age, belts get a glaze, belts stretch. Sometimes noise is a sign that it's time for replacement. I also agree changing at home is better than on a trip.

CLIFFORD

[YC1]

Ditto Chad: The grid heater draws a ton of power.

Just for grins, hold down the Aux start button for a couple of minutes. The extra battery power may reduce the load on the alternator. Just a quick test, not the solution of course.

[RobRoy]

On many diesel applications that use glow plugs and grid heaters, the Powertrain computer commands the alternator off during the initial warm up while the glow plugs and or grid heaters cycle on. Once the glow plugs and grid heaters cycle off and the PCM turns the alternator back on, this is done to take the severe load off the alternator and let the batteries do the work during this initial start up cold. Maybe your coach does not use this strategy and the belt is indeed trying to slip when cold as stated by others.

Another thing to try is unplugging the alternator or pull the alternator fuse and start the coach under the same conditions and see if it still acts up …that will tell you if the alternator load is making the belt slip... or not.... and is or is not your issue.

That being said it shouldn’t slip at all in any normal condition. cold or not.

If the noise goes away with the alternator unplugged or the fuse pulled, you now have a direction to head for a resolution.

It could be as simple as a wrong belt, bad belt or dirty or rusty, pulleys.

Could be a simple belt adjustment and have to be tightened ( if applicable)

Could be belt adjustment even if it has an automatic spring loaded tensioner and is the wrong length belt and that the auto tensioner can not do it a proper job.

You want to make sure the auto tensioner is not at the end of its travel ( either way) once the proper belt is installed.

This auto belt tensioner Pic if for reference only


Happy Hunting

[SafetyFirst]

I had the unit checked out by the local Cummins dealer and had them replace the belt. I have sprayed belt dressing on the belt, listened for a noise in the alternator with a stethoscope, and felt for problems as possible. After about two minutes during cool or cold weather it still makes the noise. Thanks for all the suggestions.

[RobRoy]

Originally Posted by SafetyFirst

I had the unit checked out by the local Cummins dealer and had them replace the belt. I have sprayed belt dressing on the belt, listened for a noise in the alternator with a stethoscope, and felt for problems as possible. After about two minutes during cool or cold weather it still makes the noise. Thanks for all the suggestions.

You say it has done this since new and it's a 2007 coach?

Wow!...Thats 10 years, at least look at the bright side, it apparently isn't hurting anything other than being an annoyance and that you also have a new belt.

[flamebuster]

I had a very similar issue on a large loader. That squealed from day 1 when it was cold or even a large electrical load from all the lights and ac. being on..We had the dealer work on it numerous times changing pulleys and belts..
Finally after several years we replaced the tensioner unit and the problem was solved..Evidently the tension spring was weak from day one...
Also using belt dressing softens the belt rubber and will shorten the life of the belt and allow it even stretch..At least that is what happened every time we ever used the stuff.. JMHO..Doug.

[clifford j]

Dose this belt have a tensioner? Is it a serpentine flat belt or 'v'. What else is driven by the alternator belt. Could the noise be the a/c clutch.

CLIFFORD