I have had this happen twice now. I heard this noise and right after my video cuts out, the ABS, Trac and brake lights light up on the dash and the constant beep. This has only happened in the morning when it was cold outside, like in the 40's. If I press the brake pedal it does away for a second and then comes back. After the truck heats up the alarm goes away and doesn't come back. I didn't have time to stick my code reader in to see if it showed a code or not.
is this sound the accuator or the pump on the brake system? (1 Viewer)
- Thread starter aroq
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #2
ok, I must have the only 100 that has had this sound come from the brake booster area. I just can't tell if it is the pump or the accuator itself and want to avoid the $1200 replacement if I can help it. Maybe I'll try and find a donor from a junkyard or something. Really weird as it has only started happening when its cold outside. I figure it may be that the contacts in the motor/pump are shrinking in the cold or possibly the pressure sensor. This does not effect the braking of the truck, but I still want to get to the bottom of it. ANY info would be helpful.
Have you figured this out yet? I have a 2005 LC with the same issue. Strange buzzing in the dash in front of me on cold mornings, runs until it finally times out and I get the ABS, VSC, Brake lights and awful siren. Brakes work fine, I can feel the ABS go out when the lights kick on. Only happens first thing when it's cold out, low to mid 30s. Then it doesn't happen the rest of the day. Took it in and had all the sensors looked at and make sure there isn't an electrical issue. My guess is the brake booster and accumulator assembly which is a hefty price. But to me, if those were failing, it would happen all day, not just first thing in the morning only on cold days.
- Thread starter
- #5
I have not figured this out yet, but all the things you describe are exactly my issues as well. Only when cold and ABS,VSC, Brake lights all on plus the constant beeeeeeeep, for about 15 20 min of driving and then it goes away. The buzzing is the pump pressurizing the booster. If you take and pump the brakes, without the key in, for about 5 or 6 times it releases the pressure. Then pop the hood and look at the brake reservoir and turn the key on but don't start the truck and watch that fluid level. It will drop about 1/4 inch as it adds it to the system (pressurizing it). I figure it is the elec pump most likely. Looking to source another pump first and have it rebuilt ready to slap in there once this one goes.
- Thread starter
- #6
also to note, I figure that the temp being low IS the factor. I mean the copper is condensed and once the engine warms the engine bay it expands a bit to make better contact. I don't know for sure, but it makes sense to me.
uHu
Bridgeburner
Sounds like you have faulty brake boosters, guys.
That alarm means that there is too little pressure in the brake booster for safe stopping. Don't drive when the alarm goes off. Park and get it fixed -- if you value your safety, and the lifes of others.
A 100 without a working brake booster is not fun. I've tried. Scary.
That alarm means that there is too little pressure in the brake booster for safe stopping. Don't drive when the alarm goes off. Park and get it fixed -- if you value your safety, and the lifes of others.
A 100 without a working brake booster is not fun. I've tried. Scary.
Would the brake booster only be affected by cold weather at first startup? I was leaning towards the brake pump motor based on sound and occurrence. I am going to pony up and replace the brake booster and accumulator pump assembly. Other than the crazy lights and siren on cold mornings I've had zero mechanical faults or indications that my brakes are possibly failing. Everything works as it is supposed to.
Yes, a failing booster pump motor could be affected by cold. As @uHu noted above, you almost certainly have a failing booster pump motor and you should not be driving it with the alarm going off. There is residual pressure in the system under some circumstances, so you might not feel a difference in the brakes if the pump runs a bit. But, with your symptoms, I would definitely replace/rebuild the booster pump assembly immediately and consider replacing/rebuilding the master cylinder too, depending on the mileage and age of you truck.
Thanks, I will update once I find the fix.
- Thread starter
- #11
I have 295k on my truck. I agree it is the pump and not the whole assembly. I also agree that this is important to fix, now. however, I still have the pump pressurizing the circuit and making it work when warm. So I have a day or two of working pressure. I feel that if I have brake pressure and not abnormal, as of yet, I can still drive it. Maybe you all think I'm stupid, but it works for now and I am FULLY aware of the problem. will work on it when I have the funds. Mind you I have another vehicle in the mean time.
I had this happen on my LX twice in one month well over a year ago. The second time I immediately pulled over, shut it off, pumped the brakes for a few minutes, started it back up and no problems since, over a year later.
Freaked me out at the time, but no issues so far.
Freaked me out at the time, but no issues so far.
I have this issue also. The high pressure cutoff switch is sticky at low temperatures. The abs pump will pump until a certain pressure is reached and then cutoff. The pressure switch stays closed even if the pressure in the accumulator is maxed out. It will keep running for the time out time of 5 minutes. This sensor is in the abs module. To keep the pressure sensor from sticking, I press the brake pedal after I remove the key to reduce the pressure in the accumulator. This tends to work if I remember. The only other option is changing the abs module.
Forgot to mention that after the 5 minutes of abs pump run time the alarm will sound and the abs lamp will turn on and there will be a fault code. After the abs sees the switch cycle correctly then the alarm will quit.
uHu
Bridgeburner
This is important information -- another factor when analyzing booster problems. Thanks for sharing.
Here is some more abs brake info
Diagnostics
More
Thanks for the video. I am having this exact problem. It has done it about a half dozen times but it is happening more frequently now.
It's not cold weather because it's 100+ degrees here right now.
At first it was just the sound like in the video at start up but would stop after a few seconds. Then today, it did it again but I also got lights on the dash and a high pitch alarm. I turned off the truck and let it sit. Started it again and everything is back to normal.
I'm reading now but it's definetly abs related.
Brake booster or bigger job? The sound is identical to the one in the video. It sounds like metal on metal.
It's not cold weather because it's 100+ degrees here right now.
At first it was just the sound like in the video at start up but would stop after a few seconds. Then today, it did it again but I also got lights on the dash and a high pitch alarm. I turned off the truck and let it sit. Started it again and everything is back to normal.
I'm reading now but it's definetly abs related.
Brake booster or bigger job? The sound is identical to the one in the video. It sounds like metal on metal.
