Squealing fan belt problem?

[powerjen]

Hi everyone again.

When we drove the RV back from the port last year after about 150 miles the fan belt started to squeal now and again and the engine started to kind of over-rev now and again too.  It got dark as we continued to drive with lights on and in the pouring rain it carried on randomly squealing and soon the battery gauge started dying on the dash panel and the lights started to go fainter and fainter.  But we managed somehow to limp home.  Since then (last October) the only place it has been is to get it registered which was about a 60 mile round trip two weeks ago.  The first 30 miles to get there were fine (daylight, no rain, nothing being used other than engine to drive!), but on the way back the fan belt started squealing randomly again.

Keith thinks that the belt needs tightening which we can do before we go away but the batteries don''t seem to be charging.  We have two in series, one for engine and one for interior RV stuff as is usual.  I guess this could be because the fan belt is slipping that the engine is using it up so there's none spare to charge the battery up.  We will also charge the batteries up before we go too.  Would this cause the engine to do this funny over-revving thing too?  As the engine gets hotter does the fan belt sort of stretch or something?  Why would it only start doing it after a while and not all the time?  As you can see I'm a total idiot when it comes to stuff like this, so please keep answers and ideas simple so I can understand them!!!  ;D

Thanks so much!

Jen

 

[JohnSandyWhite]

Hi powerjen. It's the dreaded FORD belt screech. We have it too on our Newmar. It comes and goes like the UK weather. There appears to be a major problem with the FORD Belt and Tensioner. Some have fitted slightly smaller diameter belts to try and keep the tension. The biggest problem is the weak tensioner.?

 

[King]

Probably, the engine/alternator design did not include the house battery load.? A bank of deep discharge batteries could draw over 100 Amps at a normal vehicle charging voltage of 14.5 volts.? I make sure the house batteries are fully charged before leaving on a trip.? How old are the house batteries?? as they age, it requires ever more current to keep them charged.? If they seem to use a lot of water, they need to be replaced.
The engine over reving would not be related to the belt.? I don't know if this is the case, but I have had the same occurence in the rain.? At cruising speed, the engine would unexpectedly speed up and then return to normal.? I happened to notice the speedometer was climbing at the same time.? If the water on the road was deep enough, the drive tires were aquaplaning and losing traction.? I turned off the cruise control to try to maintain directional stability.? After returning, I replaced the tires with tires supposed to be better in rain.
Art

 

[Karl]

Jen,

Sounds like it's time for new belts. A good belt will only stretch minimally, but a worn one can get quite loose with age and heat. The more power the alternator is asked to put out, the greater the chance of slippage. After a while, the belt will develop a slippery glaze and won't function well at all. Best to replace all the belts while you're at it. As far as the engine over-revving is concerned, look at the ammeter while it's doing that. Does (did) the reading drop significantly? If so, the slipping belt is reducing the load on the engine, allowing it to speed up briefly. Back off the gas pedal a bit and the ammeter will probably go back into the normal range. Let us know what you find.

 

[Gary RV_Wizard]

Replace the belt, per Karl's suggestion. It has stretched and that's a sign of wear/age.

In the future, when you ask technical questons it would be helpful if you identified the year and model of your RV and the chassis/engine as well.

 

[powerjen]

Hi Everyone

Thanks for your suggestions and I forgot to say that it's a 1992 National RV Tropical on a 350 Ford Chassis (7.5L petrol).

We went out in it for a 200 mile round trip and although, yes we did have the fan belt intermittently screeching it never affected the  battery levels this time even though we had rain and the wipers were on and the head lights were too.  We're going to have a better look at it in the week, although it seems hard to get a good look at it from under the cab engine cover.

Will keep you posted what we find out.

Jen