Brake pressure light and buzzer

[DRoberts123]

Picked up a 1998 3800 with the T444e and the good ole 545…lol.

The bus was owned by a preschool before me and they had it sense 2007, when it was decommissioned from service.

The bus as it sits today has 25,000 original miles on it and a reman transmission…. Which I thought was strange at first, but makes sense to me now and hang on I’ll explain deeper into the story…

I didn’t actually get it from the daycare themselves…

I got the bus from a local tow truck company… they towed it from a local shop where the preschool owners apparently have been taking it back a whole lot to them with issues have not been able to start it, and I would assume other drivability issues as we will get into in a bit.

So this preschool abandoned the vehicle and the tow truck company picked it up and that’s where I come into the story.

I went to go look at the bus and it looked OK, the motor was clean and started up real well, I didn’t have any blow by. So a test drove it and everything seemed good.

So I asked the guy what his best price was and he told me if I gave him 4000 he’d put new tires on it.

So that sounded like a heck of a deal we shook hands. I bought the bus and left for my one hour trip on the interstate home.

With only about 20 minutes left in my trip the brake pressure light came on as well as a super annoying buzzer beep or something like that…. After some examination real quick of the system which this is a hydraulic system with a Hydro max booster… and I do not have ABS either…. But after examining my system and what was going on, I concluded that it would be OK to continue to drive it to the storage unit right around the corner from my house where I was already headed to.

I kept more of an eye on the gauges ever since the brake pressure light came on… and well I can’t say my gauges are super accurate, they are all I had to try them monitor the systems

My water temperature look like it was getting somewhere around the 215-230° mark depending on if I was going up the hill or not, which seems a bit high to me… ( as of today I have ordered a 180 thermostat for it and it just came in, but I haven’t installed it yet)

So my wife is following me in the vehicle that we drove to go get the bus in… and she calls me and asked me why my brake lights are on all the time, and if I was riding the brakes and she also told me she could smell some brakes… well I wasn’t riding the brakes.. so I figured I had some calipers that were not releasing at minimum.

So, because of all that in the system’s age and I knew it had sat for a while, I decided to go ahead and put all new calipers all the way around as well as new rubber lines on all four corners and a new master cylinder and a new Hydro max booster with a new electric backup pump as well…. So essentially a whole new breaking system minus the hardlines.

It took me and another buddy of mine about eight hours, but we got it all knocked out and the brake system and power steering system flushed with new fluid.

Once I went to hook the battery back up, the second I hooked up the very last cable, which was the negative, the electric back up pump for the Hydro max system kicked on and started pumping, and I knew with the key off and the bus just sitting there, it should not do that.

I’m almost certain I did not fiddle with anything in the system that would make it do that…. Essentially all I did was replace all the hard parts and the sensors for the system already came in the master cylinder and the Hydro max so that’s not something I had to put in, I just had to plug the old wires up to the new sensors in the new parts.

So I left the battery disconnect disconnected so that I could disconnect the power switch at the electric backup pump so that we could start the bus and at least get the bleed the steering and the brake systems properly.

So after properly bleeding the power steering in the hydraulic brakes, I hooked up the emergency back up pump, and with the key on the pump would not run, but with the key off the pump would automatically start to run… I knew this wasn’t right, but it was a long day and I was tired but the brakes feel great. The power steering feels great as well.

at this point it was pretty late in the evening on the day that we changed the brakes so I just drove it back over to the storage unit and put it back for the night…

The next day, I went back to the storage unit to get the bus again, but this time when I started the bus, the brake pressure light was on, but the beeping was not on…. And I didn’t have the emergency backup pump connected at this point , but because the beeping wasn’t happening, I decided to hook it up real quick with the key off again and try it and this time the backup pump doesn’t kick on on its own with the key off… and I thought to myself well that’s great news, but what the heck was that about?

So I drive the bus for about 30 minutes during a test drive, and while the brake pressure light has been on the entire time, again, I will mention the brakes felt great, and the steering system felt great as well… but the beep started going off again…. So I took the panel off where the beeper was and I removed that beeper that looks like a relay.

The only thing that I would say is odd about the system that I can visually notice myself is the sensor on the Hydro max booster that points right at the master cylinder, the lock tab on the old one is in the 12 o’clock position, but on the new one, it is in the 7 o’clock position, almost like the Sensor is not screwed in the same amount or something like that … I haven’t gone back over there to put a wrench on it to see if the sensor goes in any further yet… but has anyone had any kind of a similar issue?

Also, one thing I didn’t think, helped the original issue of the brake pressure switch, was there were some heater hoses that they had run from the passenger side firewall over to the driver side firewall but for some reason the person that had installed those had run them over top of the master cylinder and they were actually resting on that pressure switch with quite a bit of weight…. When I reinstalled everything, I rerouted those lines underneath the master cylinder and Hydro Max system so they’re not pressing or tugging or pulling on anything.

I sure would like the backup system to work as it was designed… but but if I have to, I’ll put the back up pump on a switch wired up at my panel inside the cab where if I need to, I can keep it turned off, but if the engine dies, I can just flip the switch and have the emergency back up pump work

What do y’all think?

 

[DRoberts123]

Here you can see the original routing of those heater lines

 

[DRoberts123]

The old calipers, at least the rears were really bad

On one side, one of the pistons had actually started to disintegrate into rust

I’ll post some pictures of them soon… it was pretty wild

 

[nikitis]

I don't know enough about the hydraulics to give you a good answer. I have air brakes in mine. The issue almost sounds electrical to me like there's a power wire shorting the brake light lines. I'd trace those and ensure nothing was chewed on by rat being parked for awhile, causing two wires to touch that shouldn't be touching.

 

[DRoberts123]

I don't know enough about the hydraulics to give you a good answer. I have air brakes in mine. The issue almost sounds electrical to me like there's a power wire shorting the brake light lines. I'd trace those and ensure nothing was chewed on by rat being parked for awhile, causing two wires to touch that shouldn't be touching.

the wild thing is ... the light was not on for the first 20-30 min of driving, then it came on and even after replacing pretty much the entire system, but the light is on still and wont go off as long as the bus is on and running.

I do kind of think its either the pressure switch what came with the hydromax system... i feel like the lock tb shoudl be in the 12 oclock position , not the 7 oclock it is the way the new part came. some sort of ground or module issue...

And just for info, I purchased brand new hydromax booster and back up pump... not reman.

 

[magnakansas]

Have you read the service manual for this system? If you dig around on the internet, you will find the service manual in .pdf format. I believe you will your answers there.

William

 

[DRoberts123]

Have you read the service manual for this system? If you dig around on the internet, you will find the service manual in .pdf format. I believe you will your answers there.

William

Yes, here it is, I read it and it doesn't really help with my situation. My brakes feel really good and my power steering feels great too.

https://share.google/FYwBPgc6nc1kbBO19

 

[magnakansas]

I believe your problem is electrical.

William

 

[DRoberts123]

I believe your problem is electrical.

William

I believe so as well, I just haven't gotten time to troubleshoot the electrical side of it just yet, which I will get to, no problem, but wanted to dost what was going on incase someone had this issue before.

Thanks for the help as well

I will update the thread once I find the issue incase it happens to someone else

 

[skydawg]

So after properly bleeding the power steering in the hydraulic brakes, I hooked up the emergency back up pump, and with the key on the pump would not run, but with the key off the pump would automatically start to run… I knew this wasn’t right, but it was a long day and I was tired but the brakes feel great. The power steering feels great as well.

If that happens again, check your brake lights and see if they are on. The pump is supposed to be able to run with the key off, but only when the brakes are engaged. There is an adjustment on the sensor for the brake pedal lever. I would suspect it is right on the edge of the adjustment where sometimes it is engaging the brake lights even though the pedal isn't down.

As far as the brake pressure light, I noticed mine will come on and stay on if I cycle the ignition power while the engine is already running (I have a manual fuel shutoff so the engine is still running in this scenario). If you have a loose connection somewhere and the sensor is losing power, I would suspect yours would behave in the same way as when I cycle the ignition and illuminate, at that point staying on until the engine is shut off and power cycled.

I will also note that the connector on my boost pump was in pretty terrible shape (on the wiring coming off the bus), so you might want to inspect/replace that. I had to wire in a new pigtail/connector plug on mine, since the replacement boost pump had a different connector on it than the original.