Big rig screeching noise - what causes it?

[micd]

My RV makes a screeching noise that sounds alot like I've heard from big rig trucks in rest stops. I've been told this could be dust in the brakes and if so it is likely from us driving on dirt roads. The noise seems to occur when accelerating, braking or turning (basically any time). It does not sound like the noise I've had when brake pads are low and has more of a creaking component to it (if that makes sense).

However if it is a mechanical problem I would like to fix it. It is embarrassing to go through camp grounds with this screeching noise. Does any one have ideas as to what could be causing it and how to get it to stop?

Thanks!
Michelle

[RickO]

Not sure about your chassis but on my DP I sometimes want to crawl in a hole, my cold brakes screech so loudly in CGs. But it only happens when I brake and when the coach is very cold. Freightliner told me to get over it... although I think there is a process for burnishing your brakes located somewhere here on the forum.

good luck.

[Nick-B]

Hard to say without actually hearing it bit I would guess either a dragging brake or maybe your wheel covers are not real tight and rubbing against the wheels and making odd noises.

[Wanabee FTer]

I have a creaking noise in my brakes that is worse when the brakes are hot. If I heard a loud squealing or grinding noise I would be more concerned about it. I have to keep my foot slightly depressed on the brake pedal to quiet the noise when i go through a CG Not sure if this is the same as your concern but I am planning on checking the brakes soon. You may be hearing brake noise from glazed brake pads or shoes. This usually happens over time, the brake material can get very hot. Heat and dirt can build up on the brake pads/shoes and cause squeaking noises, even if you are not using the brakes. Nothing a brake job won't fix, but if the brakes are ok that would be a lot of money just to fix a squeak. Sometimes the glaze buildup can be sanded out of the pads/shoes, and the rotors/drums can be sanded also. There is also an anti squeal coating that can be applied to the back side of the disc pads.

[azloafer]

Burnishing Squealing RV Brakes


Overview:
Air brakes require time to properly bed in. New brake shoes come coated with an epoxy resin. Whenever a new coach is delivered, or new shoes are installed on a used coach, these shoes need to be properly broken in or else the resin will glaze over. Once the pads glaze they will vibrate when applied to the drums and the resonating sound shows up as a squeal.
Even if the new linings are not properly broken in, it is still possible to burnish off the resin glaze if it is caught soon enough. If the shoes themselves have been glazed from overheating after being in use a while the burnishing process may or may not help. If the glaze is light it can still be removed but if it is deep into the shoes, they will need to be relined or replaced.
Freightliner's Recommended Procedure:
Freightliner has a small section on brake burnishing buried in their Recreational Vehicle Chassis Operators and Maintenance Manual that describes this process. It's hard to find so we'll repeat it here for your convenience.

1. In a safe area, make 10 sharp brake applications or "snubs", slowing the vehicle from 40 to 20 mph using light (approximately 10 to 20 PSI brake pressure.
2. Make 10 stops from 20 MPH using moderate (20 to 30 PSI) brake pressure.
3. Make 2 stops from 20 MPH using hard (full application of air pressure) brake applications.
Note: After the hard brake applications, it is normal to notice a hot brake odor.
4. Next drive the vehicle approximately 5 to 7 miles allowing the brakes to cool, and then come to a stop.
Note: After performing the burnishing procedure, there should be no brake noise and the brakes should have good stopping ability.
5. Inspect each wheel and ensure that there is no excessive end-play.
6. Inspect the brake adjusters and air chambers and ensure that the pushrods have proper and equal stroke.
7. If the brakes pull the vehicle to one side or grab after the burnishing procedure, contact a Freightliner RV dealer for service.

If this helps but doesn't totally eliminate the problem you can always try it again after resting a while. You have nothing to lose by trying. Just be sure to secure any loose items inside the RV to keep them from flying around when you make the sudden stops.

[H. Miller]

Last year after having the front bearings repacked, we drove away from the maint. facility and immediately came back with a loud grinding - squealing noise when brakes were applied. Same observation, brake dust in the drums. They blew it out with air - dust everywhere! This helped some but after arriving home I did the same but with a garden hose (and water). 10K miles since and not a squeek!

[speed racer]

If it happens when you are braking ,turning or accelerating it is most likely the fan belt or belts. Upon braking and turning it puts a load on the P/S pump and when accelerating the load comes from the altenator and every thing else and makes the belt slip.

[Cousin Ed]

My guess would be a loose or worn belt.

[micd]

Thanks to everyone for the good information. I'll try washing the brakes out first, have a look at the wheel covers and if that doesn't work have the shop check the belts and brakes.

If it is a belt then I'm going to be pretty ticked. I had the water pump replaced recently. I didn't realize they had to practically take the entire engine apart to get to it and was charged for the belt and hoses removal and reinstall. When I asked them why they didn't let me know so we could get them replaced they said they were all in fine condition and they would have let me know if they needed replaced. The water pump replacement was $866 due to 6 hrs of labor. The belt and hose replacement would have been a small thing to do since they were taking them off and putting them back on anyways.

Thanks again!
Michelle

[Wanabee FTer]

OP said sounds like a big rig screeching, since I seldom hear belt noise on big rigs, but often hear brake squeal noises, I suspect she is hearing brake noise.

[Gary RVRoamer]

Brakes don't squeal when accelerating and turning. Got to be something other than brakes.

[PlayItForwrd]

Just to play devil's advocate, WORN disc brakes that use those "screech indicators" make noises that'll scare the hell outta ya, and once they start making noise, they'll make noise whenever they feel like it.

Been there done that-- our '92 Winnebago pulled that stunt the day a guy test drove it to buy it from us, talk about your dealbreaker!

[micd]

I would like to thank everyone for their input. We had the RV over at the storage lot so weren't able to try out the suggestions until this weekend.

I think my squeaky suspension is due to dust and dirt. My husband washed the brakes out before the trip and we had no squealing on the way down. After all the dusty dirt roads we had a ton on the way back.

However I think I also have a loose belt. When I picked the camper up out of storage I could hear what sounded to be a belt sliding when I started the engine. Just not sure which belt it is and whether it is an emergency to take it in right now or I can wait till the next oil change and have it looked at. Didn't have any problems with it this weekend.

Thanks again for all your help. When we got back from this trip we washed out the brakes again and got all but one tiny squeak eliminated. I think we need a longer hose to get to our back wheels properly.

Michelle