2002 IH 4300 brake alarm on hyd brakes / booster fine

[RBW]

My 4300's about to drive me into driving it into a canyon.

It's an 02 4300 with hydraulic brakes.
Break booster is / has been operating normally.

Occasionally (though much more frequent lately) the brake pressure warn lamp and alarm will set on start up.
Normally a restart or 10 will get it to go off, but of late it's much worse.
The booster is good, but was recently replaced anyway.

Other possibly related issues:
IC will often go back through boot a second time around after start.
Panel dimmer seldom remembers and usually reverts to full bright.
Engine Warn has started coming on over past week and will stay on till restart, but sys shows no codes stored or shows (can't remember the code now, but supposedly unrelated and not always set).


This is an emergency vehicle and I can't keep sending it to IH only to have them shrug their shoulders. Please help.

Thank you,
RBW

 

[larche]

Well, the second? scariest place for these problems to show up is on a school bus
Unfortunatly, it is common on them and I curse the International engineers everytime I hear this complaint.

I have seeen many show problems when cold, activate the brake pressure light and alarm, but never to reapear once running for a while and no brake problems ever show up. Once warm, or running for a few minutes, if the driver shuts it off, and restarts, the problem does not reappear.
Pretty sad when you can not rely on, or trust a warning system!

Things I have found that can cause this, poor ground on the tail/brake lights, wrong bulbs in tail/brake lights, bad connections in the tail and brake lights, bulb to socket connection problems. Also corroded terminals in the brake pedal switch. If you see any sign of green there, replace the switch. Heck, they are not that expensive, replace it if you are unsure. I hate to throw parts at a vehicle, but we are talking brakes.
Checking with a test light, it is important that both of the terminals that are not normaly powered, have power at the same time when the brake pedal is depressed.

Also, possibly related is your IC going through a second "boot" They are known to have problems with conections on the IC. I have solved many problems by resoldering all the solder joints on the IC as they seem to break loose after a while. Temperature and or moisture (humidity) also seem to aggrivate this problem. Many vehicles have a problem first thing in the morning but do not apear after a few minutes of driving. Time consumeing to resolder them, but cheaper (here anyways) than buying a new IC , if and when you can get them. Usually it is one or more of the solder joints on the IC at one or more of the wiring connectors. So start with them at first.

I hate saying this for the fear some day this may not be the case, but if the brakes feel fine, and you have no problems after the vehicle warms up a bit or driven for a while, there likely is not a problem with the brake systems but just in the warning system and the same for your warn engine light if no codes are present.
I am not saying that so you leave the problem and don't fix it as it is very important that warning systems function properly. I'm just saying it may not be as big a problem (don't take the vehicle out of service type thing if you *need* it). I hope what I am saying makes sense.
Please feel free to ask more questions, I'll do my best to help. The above information is to deal with common problems, but also keep in mind other problems could cause the same or similar problems.

 

[RBW]

Thank you larche!!!

I've gone through the lights and connectors for visual and nothing obvious. Brake sw was good as were terminals, but swapped with a spare just for the sake of sanity and no change. I will ohm the sys out Monday though to be certain.

On the IC issues. Turns out the IH shop is full of idiots. It DOES have codes. I can rem how to show that they exist (cruise control on/resume) but don't rem how to pull them, nor to I have a chart, but it does have codes. That said, I removed the IC and the rear cover to view the solder joints. It seems a good resolder is in order come Monday. For the time being, the peizo is unplugged.

 

[ed mc donald]

i have the same problem

 

[dabunk]

Actually common problem I have found. Try replacing the cap on the master cylinder. Sounds crazy but try it. If you take the cap off after you start it do you hear air going in like the master has a vacuum? The vent gets plugged in the cap and will not let air into the MC. Always worse after morning starts.