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fullmoonguru · 10-30-2021, 07:12 AM

I know this topic has been much discussed but the answers I've seen aren't clear.

I have two questions about brake noises.

Q1: I have a 2001 F53 chassis and when I turn the key to the on position I hear a loud noise which I think is the electric motor for the hydroboost system. If I press on the brake pedal the tone of the noise gets lower pitched.

The confusuion is that I have read that there should be no noise until the brake is pressed AND that there is noise even if not pressing the brake. Which is right?

Q2: When driving, any time I am applying more than very light pressure on the brakes, I get what can be best described as a squealing/wheezing sound. Not too loud but definitely not minimal either. Is this normal or does it indicate air in the power steering fluid or some other problem?

TeJay · 11-01-2021, 10:29 AM

fullmoon,

Your unit is a 2001 which means the electric motor for the hydroboost might have a bearing that is going out or at least not as quiet as it was 20 years ago. The best I can think of is to locate the motor and listen to it with a stethoscope where you think a bearing might be located as somebody turns on the key. That should locate it easily and give you a better idea of how bad the bearing might be.

As far as noises when applying brakes that is not an uncommon happening. The first thing I'd check is the thickness of the pads. If the pads are worn down enough to cause the low pad wear indicator to scrape the rotor that will cause the squealing noise. In fact it's there for that very reason. To indicate to the driver the pads are low and need changing. Even if they are not to low making the noise might mean the pads are glazed enough so you are not getting good enough friction being generated by the brake system.

Do you know or have the repair history for your RV and know when the pads were last changed? If they were changed recently and the repair did not use new rotors or have the old rotors machined that could very well be the problem.

Contrary to what most folks do on these forums if an RV has 70,000 + miles on it and needs new pads the old rotor has brake pad particles imbedded into the rotor surface. This is designed to happed to improve braking. If the rotor is not new or the old rotor is not machined the rotor surface WILL not act as a good friction surface for the new pads to burnish (break in) properly. Brake pads that are not burnished properly will not reach their best friction creating condition. That in itself will result in premature glazing and poor braking as well as early and excessive noise.

The DOT manual for brakes published by the FEDS states that 200 stops and starts with both surfaces being properly prepared will result in a properly burnished brake system and therefore maximum braking for a vehicle. If the two surfaces (rotor/pads) do not create sufficient friction proper break in won't happen and poor braking will result.

Those are not my words but the DOT!!!! Proper burnishing does not mean to stop hard enough to cause pads to smoke either. All that does is cause early glazing and poor stopping ability. Again not my words!!!!!

HarryStone · 11-01-2021, 11:40 AM

On my 2006, the noise is there as long as the key is on, and the engine is off.

US1 · 11-01-2021, 09:01 PM

Agreed, My boost motor sounds as soon as key is turned, or if the brake pedal is pushed, either while the motor is not running.

fullmoonguru · 11-02-2021, 08:32 AM

Thanks all, I think that answers question #1.

What about a wheezing/squeaky sound when driving and applying more than slight brake pressure? This sound is not coming from the pads.

TeJay · 11-02-2021, 01:43 PM

fullmoon,

This is the first you mentioned a wheezing sound. You say it's not coming from the pads and you know this for certain? When you apply a slight to moderate pressure to the brakes what has or is changing? The pistons press against the pads and are then pushed into the spinning rotor.

What else is moving at the same time? The calipers will move & shift due to the rotation of the rotor and any give in the caliper attaching bolts, along with any bushings or just play between the caliper and the cast iron attaching slide part. I can't think of a name for all that but it's how the caliper is attached to the front wheel assembly. At any rate the caliper movement is very slight.

I've never heard of any caliper noises being created by the brake system unless it's from the wear indicator which is part of the brake system plan. Calipers will move if an attaching bolt is loose or missing. That's usually a clunking noise as the caliper shifts.

The wheezing noise may be brake fluid noise coming from the hydro boost pump.

fullmoonguru · 11-03-2021, 08:22 AM

I asked about the wheezing in Q2. It's definitely not the pads/calipers. It does sound like something that would be coming from the hydroboost. Just curious if it's normal for the F53 or something I should be tracking down.

TeJay · 11-03-2021, 09:05 AM

Based on the age of your unit I'd just monitor the noise and hope for the best. The hydro boost motor is getting older and is making more noises. That does not mean that it will quit or die tomorrow. We get older and have more pain as things break down but we still keep on keeping on.