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Old 06-13-2022, 02:21 PM   #1
Mini-Skoolie
 
Join Date: Mar 2021
Location: Pennsylvania
Posts: 16
Year: 1991
Coachwork: Thomas
Chassis: International 3800
Engine: T444E
3800 Hydraulic Brake Pressure Light

I've got a '91 International 3800 with a T444e and hydraulic brakes, which has been working fine for the past year. On my last trip, the brake pressure warning light went on, its buzzer started beeping and the amount of stopping from the brake pedal was much less than I was used to. This went away after a bit and my brakes returned to normal, but then it returned before the end of my trip and now comes on whenever I start up the bus. Any ideas where I should start looking? I've seen suggestions about taillight grounds in similar threads but I don't have a service manual and am unsure how to check those or what I'm looking for. I have confirmed that there is sufficient brake fluid in the reservoir, so it's not that.

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Old 06-13-2022, 06:23 PM   #2
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Location: Southern Oregon
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Engine: DT444E (7.3L) International
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Quote:
Originally Posted by skykooler View Post
I've got a '91 International 3800 with a T444e and hydraulic brakes, which has been working fine for the past year. On my last trip, the brake pressure warning light went on, its buzzer started beeping and the amount of stopping from the brake pedal was much less than I was used to. This went away after a bit and my brakes returned to normal, but then it returned before the end of my trip and now comes on whenever I start up the bus. Any ideas where I should start looking? I've seen suggestions about taillight grounds in similar threads but I don't have a service manual and am unsure how to check those or what I'm looking for. I have confirmed that there is sufficient brake fluid in the reservoir, so it's not that.
This is NOT going to be something like a bad ground that causes a tail light to flicker or not light at all. You have a SERIOUS and DANGEROUS problem that needs to be addressed BEFORE going any distance on the road. The fact that you recognized the loss of stopping power initially tells you that it is a real and dangerous condition.
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Old 06-13-2022, 08:54 PM   #3
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Year: 1991
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Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
if its a 91 it doesnt have a T444E.. most of these busses with hydraulic brakes use the Powered steering for the power assist.. the first 2 places I would go would be brake fluid and also power steering fluid..



when the engine is not running there is supposed to be an electric motor come on when you turn on the key, this is your backup motor for the hydroboost system.. your brake pedal will be hard as a rock without it.. and a buzzer goes off if that motor fails.. when the engine is running, power steering pressure is the power assist for your brakes..



you didnt indicate whether the pedal was hard, went straight to the floor, etc just that you lost stopping power.. its hard ot tell if your issue is in the power assist or in the brake circuits themselves.. but like Hamskoolie says this is serious and needs fixed before the bus is driven anywhere at all!!
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Old 06-13-2022, 09:20 PM   #4
Mini-Skoolie
 
Join Date: Mar 2021
Location: Pennsylvania
Posts: 16
Year: 1991
Coachwork: Thomas
Chassis: International 3800
Engine: T444E
Quote:
Originally Posted by HamSkoolie
This is NOT going to be something like a bad ground that causes a tail light to flicker or not light at all. You have a SERIOUS and DANGEROUS problem that needs to be addressed BEFORE going any distance on the road. The fact that you recognized the loss of stopping power initially tells you that it is a real and dangerous condition.

I recognize that, which is why I'm asking for help online rather than trying to drive it to an International mechanic.



Quote:
Originally Posted by cadillackid View Post
if its a 91 it doesnt have a T444E.. most of these busses with hydraulic brakes use the Powered steering for the power assist.. the first 2 places I would go would be brake fluid and also power steering fluid..

I may have got the year wrong, I'll check the title. It's definitely a T444E, it's got the badge on the side of the hood. Where would I find the power steering fluid reservoir? I didn't notice any lack of power for steering.



Quote:
Originally Posted by cadillackid View Post
when the engine is not running there is supposed to be an electric motor come on when you turn on the key, this is your backup motor for the hydroboost system.. your brake pedal will be hard as a rock without it.. and a buzzer goes off if that motor fails.. when the engine is running, power steering pressure is the power assist for your brakes..
Yes, and this is still working.

Quote:
Originally Posted by cadillackid View Post
you didnt indicate whether the pedal was hard, went straight to the floor, etc just that you lost stopping power.. its hard ot tell if your issue is in the power assist or in the brake circuits themselves.. but like Hamskoolie says this is serious and needs fixed before the bus is driven anywhere at all!!

The pedal seems to take about half as much force to press as I'm used to. I was still able to apply a decent amount of braking force by really standing on it, but not easily.
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Old 06-14-2022, 07:41 AM   #5
Bus Geek
 
Join Date: May 2009
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Year: 1991
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Chassis: International 3800
Engine: DTA360 / MT643
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Quote:
Originally Posted by skykooler View Post
I recognize that, which is why I'm asking for help online rather than trying to drive it to an International mechanic.






I may have got the year wrong, I'll check the title. It's definitely a T444E, it's got the badge on the side of the hood. Where would I find the power steering fluid reservoir? I didn't notice any lack of power for steering.





Yes, and this is still working.




The pedal seems to take about half as much force to press as I'm used to. I was still able to apply a decent amount of braking force by really standing on it, but not easily.

if the pedal is going down far and easy then I would look to the brake circuits thenselves.. ie low fluid, air in the lines, master cylinder, etc..



once you get past the booster and into the master cylinder your brake system is similar to that of a car just much larger..



if your bus is new enough (my 444E bus is a 2000) there will be an ABS module most likely and those are somewhat notorious for causing issues.. esp if they think a wheel is stopped when its not.. you'll get lots of push back in the pedal when trying to stop.. on mine the ABS module is on the frame rail about halfway back.. its obvious as there are 2 or 4 brake lines in and 2 or 4 out, and a wiring harness..
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Old 09-19-2022, 08:30 PM   #6
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On my '97, the power steering fluid reservoir is bolted outboard of the radiator, driver's side.
Did you resolve the problem, and if so, what was the solution..?
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Old 09-20-2022, 07:23 PM   #7
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Year: 2008
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Chassis: IC CE300
Engine: Maxxforce DT
Hi Skykooler, you have a much older model than mine, so hydraulic system May be different. However, you may want to read my thread on my hydraulic brakes debacle. For sure (looks like you are indeed conscious of that) if you get a brakes light related come up red on dash and even more with buzzer, do not drive thinking that it is intermittent “so it is OK”. I had complete service brakes failure (master cylinder) with NO fault light on dash. Maybe if I had had more experience, I would have detected the premises of a severe issue just by the feel of the pedal. Even for a yellow brakes related light (even if intermittent) take your bus immediately to be serviced. I had mixed experience with international dealership (last one contaminated my system with wrong fluid), but I would still take it to a dealership, paying big $$ : I am not comfortable enough to work on the number one safety system.
Very simple thing to check first is your brakes fluid level as well as color.
Is your system a wabco ABS/ATC ?
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Old 10-04-2022, 10:58 AM   #8
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If you have Wabco brakes, you shouldn't fill your reservoir without first depleting the accumulators. I only have experience with the Wabco system, and if that is also your system, get the Wabco Toolbox software to communicate with the brake system ECU. This software is super helpful in conjunction with Wabco technical support. If you aren't a mechanic, this is a scary situation, but if you can precisely follow directions and are in touch with Wabco technical support, you should be able to diagnose and repair your issue. They will hold your hand the whole way. You will need Nexiq, laptop, and Wabco toolbox if this is the case. In the case of Wabco's Hydraulic Compact Unit, it's components were basically unserviceable for an amateur like myself. They sell it as a unit. I got one at finditparts for 3700$ + 1100 core. If you are in a position that you have to replace anything, you will need a pressure fill/bleed tool and a master cylinder adapter to fit where the cap goes. A universal adapter can work, but use a c-clamp to squeeze it tight to the reservoir to avoid an eye-level spew of brake fluid.

I am beginning to think that you don't have a Wabco system because it has a failsafe that should prevent you from disengaging the parking brake when there is a brake system fault.

If you have a Wabco system, give them a call. They are super helpful.

Old post, oops
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