Brake pulsation
 

Hey guys

I'm running into a weird Issue with my brakes and was wondering if someone has a clue or an idea as to what is going on bare with me while I try to explain it


My brake pedal pulsates in accordance to the rpm position. What I mean by that is the higher the rpms the faster it pulsates, it feels like it matches the pumps rotation while its pulsating. If you step on it and push down a bit the pulsation stop but it comes back right away once you lift off.

Here's the weird part, while the car is stopped if I step on the brakes and just push down as hard as I can and hold for about a min the pulsation goes away but comes back after a few braking motions. When you are holding down the brake pedal in the same position I start hearing hissing like as if air is coming out from somewhere, you can hear it inside the car and under the hood once you press down harder it stops for a sec or two the starts again. Once you lift off the brake light comes on and the pulsation continues. And at times the brakes will work for the rest of the day and the next morning it's back to the pulsation😭

Also I did notice this started when it started to get cold here in Calgary

Anyone has a clue what that hissing is? Or what I'm facing here? It's driving me off the wall and can't figure it out

Thanks to anyone for any ideas in advance

Cheers

It sounds like your having more of a mechanical issue but have you bled your brakes lately? Are your brakes spongy, does your brake get incredibly firm when you mash and then slowly go down or or do you have a noticeably spongy feel?

You made it sound like this was an OFF BRAKING event whil cruising, is this true or it this a during braking event?

I can't say I have an idea but the more i formation the merrier.

Sounds like the brake servo or the bomb to me.

If you have an RPM-related pulse in the brake pedal, you're feeling the pulses from the hydraulic pump. If the bomb is holding pressure correctly you'll never feel that, so something is letting the pressure out.

Does your brake warning light come on?

Yes the light comes on. Oddly enough the bomb is new and the brakes have been bled. And now that it got a bit warmer my brakes have been working just perfectly and the light isn't on

I'm really not too sure what it is but its def something that is driving me crazy

brake booster
 

Hey Guys,
what symptoms would i have if the brake booster is at fault?

reason i ask is that hissing is very noticeable inside and out and from what i read could it be as simple as that? a faulty booster?

if it is i'm in the dilemma or fixing/or selling as is which i don't want to do

thanks

You need to find out whether the hissing is air or a gas or a liquid. Air could be air in your power steering/power brake lines. Gas could be the nitrogen that the brake pressure accumulator is filled with. Liquid could be power steering/power brake fluid leaking out somewhere.

Regardless, the fix shouldn't be that expensive. Certainly not enough to cause you to sell your UrS.

Thanks Dave,

its def not fluid leaking i have confirmed that multiple times and if it was i would be short on fluid no? though the bomb is new could it be faulty? im 100% sure its air but would that cause the brake light to be on and pedal to pulsate to the rotation of the pump?


any bit of possible cause would help to check and see what i can find out

thanks

last attempt
 

Hey Guys,

bare with me as i go through all my findings in regards to this matter.

there is no leak in the systems (fluid wise at least). scenario is like this:

if i had the car parked at the train station lets say and then after 8-9 hours i come and turn it on. The light will be off but the pedal pulsates. once the car is warmed up and i start driving the light comes on after 20-30 meters of driving.
From a random trial, i stopped at an inclined hill and stepped on the brakes until the light went out, then i counted to 40 and slowly released the brakes and pressing them again as the car moved backwards slowly. After doing that the brakes work (go figure). what i did notice after that is when you turn lets say right or left in a semi aggressive manner or hit a bump on the road while turning the light comes on for a brief second or two then goes out again, again the brakes keep working just fine. if you turn the car off then back on with in an hour or so they still work, but anything longer and its back to square one.

I'm absolutely beat as to what can cause this, frustrated to say the least. im hoping to have this fixed as the car is seriously dangerous to drive on these snowy roads with minimal braking reaction.

i dunno if i jabbered on long enough for someone to pick up on something that they might have seen before or not, but this is my last hope at having it back up and running

Thank you guys for the help much appreciated for everything

Cheers

Reservoir Cap
 

just curious,

the hydraulic Reservoir tank's cap it has two wires connected to it what are they for?

also does the cap have something that goes into the filter wall? or does mine have something missing?

Are you talking the brake fluid reservoir or the power steering fluid reservoir (which is also the fluid reservoir for the power brake assist system (separate from the actual brake system))? Probably doesn't matter because both have level warning systems associated with them and these have two wires that lead into the dash an the on-board Autocheck warning system.

Which of these lights are you getting:

http://12v.org/urs/UrSWarningLights1.JPG