Brake master screeching when cold - trip planned tomorrow (1 Viewer)

[dbfw]

Hi folks,

99 LX, 204K miles. I jumped in this morning to run an errand and it was colder than it has been in a few years here in the Seattle area (about 25F overnight, 30 when starting this morning). I heard the master cylinder screeching noise for the first time after the booster pump had completed pressurizing the accumulator.

This occured every few pump cycles for the first 20 minutes of my drive. On my way back, all was normal and no screeching could be heard.

In reading @2001LC 's brake info threads, it sounds like there is a seal in the master that starts allowing high pressure fluid to pass when cold, but will then seal back up when warm. This seems to be my exact situation currently. Obviously the writing is on the wall, I need a complete new assembly and will grit my teeth for the big bill to come.

Edit: No alarms, booster pump is quiet and within spec 30-40 sec run time after pumping pedal 40 times with key off.

My question is whether we should still take the trip. What is the collective wisdom, do we fall under 1 or 2?

1. This is in the very early stages, seals back up once there is a little heat in it. You're not at risk of any imminent catastrophic failure, go ahead and take the trip and address this when you're back.

2. This failure mode can progress rapidly, you should park it now and bag the trip until you get that MC replaced.

Thanks in advance to all who have had experience with this and can shed some light on my options.

 

[flintknapper]

Both 1 & 2 occur about evenly from what I've read.

In my case it was #2.

 

[dbfw]

Thanks @flintknapper any other symptoms for you, dash alarms or warning lights? Or, did you get the brief squealing when cold, then suddenly the whole alarm/motor failure with loss of braking?

 

[dbfw]

Also, as I realize much of the terminology can mean different things to different people. When I say "screeching" I don't mean the dash warning buzzer, I mean this noise (@2001LC 's video):

 

[flintknapper]

Also, as I realize much of the terminology can mean different things to different people. When I say "screeching" I don't mean the dash warning buzzer, I mean this noise (@2001LC 's video):

You have the 'dying Seagull'.

Typically that situation degrades slower than what I had (intermittent dash warning and buzzer) and then full time the very next day.

If the experience of others is any indication....you have 'some' time before anything serious happens.

 

[FxFormat]

I honestly wouldn't chance it on a road trip, usually when you get that angry crow screech, you have a couple hundred miles before the unit loses pressure and you get a constant ringing on your dash.

 

[dbfw]

Thanks again for the feedback! That was what my research seemed to be leading me to as well. Helpful to have those with experience chime in. Just went back out after the truck sat for 4 hours, pumped pedal, key on. Normal booster run time, no seagull. Probably will have it first thing tomorrow AM again, but at this point leaning toward going for the weekend and biting the new MC bullet next week when we're back.

Edit: I now see that I have contrasting guidance. I'm not surprised by this, and am thankful for any and all experiences people can give who have had this issue. Normally, we'd just take the camry in this case, but we're predicted to get quite a bit of snow tonight. We'll see, if there isn't too much on the ground in the AM that might be the way to go.

 

[gil12]

I would park it. Braking is more important than accelerating. (Loss of brakes is much more of an "oh S***! moment - memories of my old 403 Peugeot just came back to me!)

 

[nissanh]

The sound at 4 second is an indication of failing motor. How many miles do ou have in the cruiser?

 

[medtro]

Any codes?

 

[badlander]

How's your emergency brake working? Might need it......

 

[2001LC]

The sound is fluid passing seal under high pressure 90% of time IMHO. If bubble(s) seen in front of reservoir at same time, it 100% seal related. Pressure than drops in brake system. So sensor reads low pressure. Brake control CPU than starts pump bring pressure back up. As you can imagine, fluid moving past seal very fast, creates heat as it passes seal. This heat, heat of brake pedal use and engine radiating heat expand parts which includes seals. So leak stops and all seem fine. But every time this high pressure leak ("dying Seagull") accrues, it damage seal. So the "dying Seagull" sound will happen with greater frequency and duration. It's the duration, which causes motor to run excessively long due to pressure drop. This will prematurely wear out motor brushes and or commutator, due running excessively long and heat that creates. Than motor will fail, as it is designed to run frequently, but short duration. Motor failure result in zero booster pressure (NO BRAKES).

 

[CloudCity]

Park it. Mine did this and got worse very quickly, I tried to drive it locally over a couple of days, and like everyone has said, it just gets more frequent. I personally do not think it's worth the risk as inconvenient as it may be to take another car.

 

[dbfw]

Yep, thanks everyone for chiming in. We ended up just staying home due to the amount of snow we got, and I'm planning to get the unit replaced ASAP. Not sure yet whether it makes sense to just take it to a dealer, or try to drive it up to Torfab. I'm inclined to just drive it to the closest dealer rather than risk the 60 or so mile trip. Doesn't seem like there is really much savings going indy with this one as most of the cost is the part.

I'm also not too into crawling around in the snow on my driveway bleeding, etc. so probably best to just bite the bullet on this one and know I'm good for another 22 years and 200k.

 

[CloudCity]

Yep, thanks everyone for chiming in. We ended up just staying home due to the amount of snow we got, and I'm planning to get the unit replaced ASAP. Not sure yet whether it makes sense to just take it to a dealer, or try to drive it up to Torfab. I'm inclined to just drive it to the closest dealer rather than risk the 60 or so mile trip. Doesn't seem like there is really much savings going indy with this one as most of the cost is the part.

I'm also not too into crawling around in the snow on my driveway bleeding, etc. so probably best to just bite the bullet on this one and know I'm good for another 22 years and 200k.

I think that's best for such a vital system. I feel so much better knowing mine is brand new and working. It's a BIG bite to take, but these vehicles are worth the investment if you're keeping it for the long term.

 

[flintknapper]

For most folks....replacing the booster pump motor and accumlator (as a set) AND rebuilding the Master Cylinder....will restore your ABS system to a reliable unit. That is what I had to do to with mine @ 235K miles.

 

[grundsethp]

I had the same problem and after changing out the pump and rebuild, I still had the issue. I got a copy of the service manual and figured out the high pressure switch stays stuck and does not switch. How the system works is there are two pressure switches in the system. If the pressure is too low, the low pressure switch switches and the pump turns on and fills the accumulator to the high pressure switch. It then turns off. If the high pressure switch is sticky, it will not turn the pump off and the system will over pressure and creates the screech. The pressure switch is in the unit and not the pressure switch that you see outside the abs unit. It is not replaceable.

The only thing that i have seen work is to let the pressure switch depressurize after keying off. Normally when you shut off the truck, the system is at high pressure and the switch is switched. Press the brake pedal 10-15 times to depressurize. When you turn the truck on the next time, you will hear the pump and then it should stop when it reaches the high pressure switch.

I have done this pressure switch cycling a couple times to also get the system working.

if the pump runs for more the 5 min without stopping, the brake light and alarm will sound. If the preasure switch starts working correctly before the 5 min, you will not get the alarms.

 

[2001LC]

I had the same problem and after changing out the pump and rebuild, I still had the issue. I got a copy of the service manual and figured out the high pressure switch stays stuck and does not switch. How the system works is there are two pressure switches in the system. If the pressure is too low, the low pressure switch switches and the pump turns on and fills the accumulator to the high pressure switch. It then turns off. If the high pressure switch is sticky, it will not turn the pump off and the system will over pressure and creates the screech. The pressure switch is in the unit and not the pressure switch that you see outside the abs unit. It is not replaceable.

The only thing that i have seen work is to let the pressure switch depressurize after keying off. Normally when you shut off the truck, the system is at high pressure and the switch is switched. Press the brake pedal 10-15 times to depressurize. When you turn the truck on the next time, you will hear the pump and then it should stop when it reaches the high pressure switch.

I have done this pressure switch cycling a couple times to also get the system working.

if the pump runs for more the 5 min without stopping, the brake light and alarm will sound. If the preasure switch starts working correctly before the 5 min, you will not get the alarms.

Did you have the same (angry crow screech with simultaneous bubbles coming up front of reservoir) before replacing the "pump"?

"pump" Did you replace pumps motor also?

 

[Mike NXP]

Hmmm, I also have a dying seagull in my engine bay but I didn't think it was coming from the brake system. Fades away after a few seconds and happens when it is very cold out.

14 Seconds
>>

 

[grundsethp]

Did you have the same (angry crow screech with simultaneous bubbles coming up front of reservoir) before replacing the "pump"?

"pump" Did you replace pumps motor also?

I had the same issue. The reservoir would fill and then screech and bubble.
I consider the pump = pump and motor unit. You cannot purchase the pump or motor on its own, they are a unit. You can purchase the whole unit, the pump/motor and the master cylinder.