International Air Buzzer?

[eethan]

A few weeks ago i was out and about in the bus. When i was driving home the low air alarm started going off. Its a 2002 international, and the dash has a buzzer/beeper that sounds when the brake air pressure is below a certain threshold. I know i definitely have brake pressure, as the mechanical gauge still reads good pressure, and the parking brake and regular brakes still work as expected. For a while it was going on and off, but now its just stuck on. I ended up taking out the beeper just for my personal sanity, and drove the rest of the way keeping a careful eye on the gauges at all times.



Is there some kind of electronic sensor that might've gone bad? Can anyone else with an international provide any guidance on this?

[musigenesis]

Originally Posted by eethan

A few weeks ago i was out and about in the bus. When i was driving home the low air alarm started going off. Its a 2002 international, and the dash has a buzzer/beeper that sounds when the brake air pressure is below a certain threshold. I know i definitely have brake pressure, as the mechanical gauge still reads good pressure, and the parking brake and regular brakes still work as expected. For a while it was going on and off, but now its just stuck on. I ended up taking out the beeper just for my personal sanity, and drove the rest of the way keeping a careful eye on the gauges at all times.



Is there some kind of electronic sensor that might've gone bad? Can anyone else with an international provide any guidance on this?

Same problem here. I dunno what the problem is. It's infrequent enough that I can just ignore it.

[CHEESE_WAGON]

Likely the sensor has gone bad. It should be a simple pressure switch. Might be threaded in to the supply tank maybe?

[Booyah45828]

Or near the governor. I've also seen them near the compressor too.

It should look like this.


Or this.



The latter being more rare.

[eethan]

Originally Posted by Booyah45828

Or near the governor. I've also seen them near the compressor too.

It should look like this.


Or this.



The latter being more rare.

Thanks for the info. It seems to have gone away for now but I’ll take a look soon.

[musigenesis]

Originally Posted by eethan

Thanks for the info. It seems to have gone away for now but I’ll take a look soon.

This is what I said a year ago.

[Brad_SwiftFur]

It's very likely the air pressure sensor/switch. I've had a few go bad over the years on various vehicles, not just Internationals. Removing or disabling the alarm on a commercial vehicle is a violation of the Federal Motor Carrier Safety Regulations (to paraphrase, there must be an alarm and it must work). I doubt anyone would check a decommissioned school bus and as a rule you'll want this to work, better to fix the sensor than to remove the alarm permanently.

[musigenesis]

Originally Posted by Brad_SwiftFur

It's very likely the air pressure sensor/switch. I've had a few go bad over the years on various vehicles, not just Internationals. Removing or disabling the alarm on a commercial vehicle is a violation of the Federal Motor Carrier Safety Regulations (to paraphrase, there must be an alarm and it must work). I doubt anyone would check a decommissioned school bus and as a rule you'll want this to work, better to fix the sensor than to remove the alarm permanently.

I have a wig-wag in addition to the beeper - is that sufficient as an alarm, such that I could just disable the beeper?

[sepudo]

ANY INFO TIPS on the same experience but on a THOMAS /Freightliner?

I have been experiencing the same low air buzzer while still having proper air pressure and all other gauge values looking good.

I wonder if my problem would be a bad sensor as well

I'm on a 2003 Thomas on a Freightliner chassis with HYDRO brakes, AIR parking brakes, air door and air seat

[Booyah45828]

Originally Posted by sepudo

ANY INFO TIPS on the same experience but on a THOMAS /Freightliner?

I have been experiencing the same low air buzzer while still having proper air pressure and all other gauge values looking good.

I wonder if my problem would be a bad sensor as well

I'm on a 2003 Thomas on a Freightliner chassis with HYDRO brakes, AIR parking brakes, air door and air seat

You have to see if it's a low air buzzer, or if it's a low hydraulic pressure buzzer, or some other kind of buzzer.

[Brad_SwiftFur]

Originally Posted by musigenesis

I have a wig-wag in addition to the beeper - is that sufficient as an alarm, such that I could just disable the beeper?

I would accept that as a reasonable substitute as a short term measure, if it were me, I'd still be fixing the cause of the problem eventually and re-enabling the beeper.

Originally Posted by sepudo

ANY INFO TIPS on the same experience but on a THOMAS /Freightliner?

I have been experiencing the same low air buzzer while still having proper air pressure and all other gauge values looking good.

I wonder if my problem would be a bad sensor as well

I'm on a 2003 Thomas on a Freightliner chassis with HYDRO brakes, AIR parking brakes, air door and air seat

I'm going to assume yours is the low air alarm too, and yes, it's likely a failing sensor.


Most diesel powered buses, with hydraulic brakes, will have hydraulic power assist, typically driven by the power steering pump. However, should the P/S pump stop working for any reason - including a stalled engine - this makes braking *VERY* difficult and runs the risk of causing a crash. Since this tends to be a *Very Bad* thing, manufacturers install auxiliary electric pumps to kick in and provide pressure, usually when the brake is applied (sometimes simply when the ignition is on but no pressure is sensed). The bus I had with such a system did not have a warning alarm, or if it did, it did not work.

[Jolly Roger bus 223]

for the ones thinking about or looking into replacing there faulty pressure sensor or pretty much replacing anything air pressure related?
please make sure to release all air pressure before attempting to remove anything.
depending on what part you are working on?
your guage might read zero but some are at least one of your tanks and lines are/ is still holding pressure to feed your air powered parking brake.

[CHEESE_WAGON]

Originally Posted by sepudo

ANY INFO TIPS on the same experience but on a THOMAS /Freightliner?

I have been experiencing the same low air buzzer while still having proper air pressure and all other gauge values looking good.

I wonder if my problem would be a bad sensor as well

I'm on a 2003 Thomas on a Freightliner chassis with HYDRO brakes, AIR parking brakes, air door and air seat

Hydraulic brakes with an air parking brake? That's a new one to me. Hope that's not the next-generation Lucas-Girling. But yes, if your low-air warning is going off for no reason, likely a bad sensor/switch. I would verify your air pressure readings though, if possible.

Originally Posted by Jolly Roger bus 223

for the ones thinking about or looking into replacing there faulty pressure sensor or pretty much replacing anything air pressure related?
please make sure to release all air pressure before attempting to remove anything.
depending on what part you are working on?
your guage might read zero but some are at least one of your tanks and lines are/ is still holding pressure to feed your air powered parking brake.

I second this, and chock the drive wheels just in case.

[CHEESE_WAGON]

Originally Posted by musigenesis

I have a wig-wag in addition to the beeper - is that sufficient as an alarm, such that I could just disable the beeper?

I agree with Booyah - these two different devices could indicate problems in either system. The wig-wag may be for the air side, and the buzzer could be for the hydraulics. *EDIT* had two different buses jumbled in my mind, was thinking about the Thomas with air over hydro.

It also depends on the year of manufacture. The wig-wag arm was the predecessor to the buzzer / warning light arrangement. At some point the wig-wag was no longer used. I'm thinking BSF could clarify specific years in relation to this, the wig-wag was before my time, as I didn't get CDL training until 2013.

But basically, if it's factory safety equipment, it's best to repair / replace it as factory delivered. Chances are low that you would get a ticket for it, but as for me, I would want all the warning I could get, and I believe this would be tampering with federally mandated safety equipment. My knowledge of the wig-wags is limited, but they may only trigger at 40 psi, the warning lights trigger at either 60 or 85, depending on the chassis. Specific purpose-built bus chassis are supposed to trigger at 85, skoolies built on truck chassis will still be 60.

[sepudo]

Originally Posted by CHEESE_WAGON

Hydraulic brakes with an air parking brake? That's a new one to me. Hope that's not the next-generation Lucas-Girling. But yes, if your low-air warning is going off for no reason, likely a bad sensor/switch. I would verify your air pressure readings though, if possible.

Air pressure is good. Sitting right at 120psi. My air door, air parking brake and air seat work as they should.
What throws me off recently is I notice when I apply the brake pedal, I hear what sounds like a hiss coming from under the steering wheel/left leg area. As if air is somehow assisting the hydro brakes???

I'm stumped but eager to get to the bottom of it.

My biggest concern was if I can safely be driving the bus if it *did * have a slow air leak, as I've read that air brakes lock up with loss of air as a safety precaution.

(photo of my red light and proper air pressure)

[CHEESE_WAGON]

Originally Posted by sepudo

Air pressure is good. Sitting right at 120psi. My air door, air parking brake and air seat work as they should.
What throws me off recently is I notice when I apply the brake pedal, I hear what sounds like a hiss coming from under the steering wheel/left leg area. As if air is somehow assisting the hydro brakes???

I'm stumped but eager to get to the bottom of it.

My biggest concern was if I can safely be driving the bus if it *did * have a slow air leak, as I've read that air brakes lock up with loss of air as a safety precaution.

(photo of my red light and proper air pressure) Attachment 43546

A very valid concern, but are you ABSOLUTELY sure this is a hydraulic system with an air-chamber parking brake? I see 120-ish psi on that gauge, way more than a simple spring brake would need. Typical air systems warn at 60 or 85 psi, and the spring brake engages at 20-40. Seems to me it wouldn't need that kind of pressure for something that simple. As I said earlier, it sounds a lot like an adaptation of the old Lucas-Girling setup. If it truly is what it sounds like, and it maintains 120-ish and never drops below 90 or so, I wouldn't worry about it. Get it checked by someone familiar with those systems though.

A slow air leak, well that depends on how slow. If it takes more than a day or two of sitting to show noticeable loss (15-25 psi), I wouldn't worry too much about it. DOT regs require professional drivers to note any loss greater than 3 psi with the brakes set, engine off. Most systems should be able to maintain >110 psi, nominal pressure is 90-120. Safety blow-off valves are supposed to regulate pressure to 150 psi, but have been known to leak. But that is for systems where the air system actually controls the brakes.

In the case of a simple air chamber actuating a hydraulic parking brake, a typical spring brake only needs above 40 psi to disengage, so there's a much narrower margin of error. But your gauge shows way more than that, so no danger there. A slow leak could be a larger problem in a lower-pressure system. I would get that checked just to be sure.

That red light appears to be a typical warning light to show that the parking brake is set. On some models, that can also serve to indicate a pressure problem in the hydraulics, which could mean air in the system. When an air system's pressure is low, there should be a buzzer or other audible warning device, and most modern air gauges have a red warning light built in as well. That's not what this appears to be.

Also, low air pressure will usually trigger a low-air warning light on the dash or console. The red light in your photo is purely for the parking brake, methinks, but if it's on when you're moving, something isn't right and should be checked. The air chamber for your parking brake could be bad and not completely disengaging the parking brake.

I think you're okay, but if the light is staying on when driving, I would be concerned about a sudden air pressure drop engaging the parking brake while moving. Check the system for leaks and issues with the air chamber.

As for the hiss when using the brake pedal, that could be one of a few things...

Your thought of air assisting the hydraulics could be on the money, but I'm leaning toward a vacuum pump generating vacuum assist as though it had a booster. This is necessary on diesels because they cannot generate vacuum.

Could also be air in the hydraulics showing up, but this would result in a soft, mushy pedal, would also explain the red light if it is staying on when driving in. If the brakes are responsive, not likely, but still worth checking, as there could be a problem with the parking brake disengagement.

Just my $0.02. Hope that helps...

[sepudo]

Originally Posted by CHEESE_WAGON

That red light appears to be a typical warning light to show that the parking brake is set.

All useful info.

Only thing I'd like to clarify is that I do know it's not the parking brake.

When I was cleaning up the instrument panel I removed the guages and noticed all the different lights and symbols. Granted, I don't know if they're all active on my rig since several slots don't have light bulbs in them but at least I do know the parking light is bottom right

And thoughts on that?

Thanks all

[CHEESE_WAGON]

I see what you're talking about now. Didn't realize you had a separate parking brake warning light.

I would be leaning toward a pressure problem in the hydraulics / possible air in the system. Or, alternately, there could be a problem with the disengagement of the air mechanism on the parking brake, if it is not disengaging fully. I'm leaning toward air in the hydraulics though.

[Booyah45828]

That light is a brake warning light.

Seeing as how he only has one air pressure needle, I imagine it's a hydro system with and air released parking brake. I've never worked on one but they do exist.

I'd guess that it's warning about a lack of hydraulic pressure for the booster or a brake pressure fault sensed by the combination valve. It could also signal for low brake fluid level in the master cylinder as well.

Inspect all of the systems. If no faults are found you can unplug the sensors/switches one at a time to find which one is giving the fault.

[Dirtdoctor]

Ok folks- the air brake system is Important!Tamper with it and get in a accident and you will find your insurance not covering you and your butts being sued. Ignorance is not an excuse.
Get it to a reputable truck shop
And keep the system up to Date and working.


Cheers