Lost Stopping Power

[blue62]

Originally Posted by particlewave

I took it for a test drive today. Results:

1) After a 10 minute drive with some hard braking, front drivers side rotor was at 210f, front passenger 145f (oddly with a 1cm band in the middle of the rotor reading 190f), rears 90f (50f outside).
2) Braking power is still there, I just have to press a lot harder (pedal not hard or soft, feels normal).
3) The front end wandered a bit under hard braking, but only a couple times (didn’t seem significant).
4) Brakes lines are not swelling under pressure, but I’m going to replace them anyway.

Maybe low vacuum?
I think I should order a good manometer as I don’t trust my diy tube setup.

Sounds almost as if you have a torn diaphragm in the brake booster.
If you have something like a mighty vac with a gauge hooked to it you could pull a vacuum on the vacuum hose side of the brake booster and see if it holds.

Or in a safe place roll it down a hill with engine off hit the brakes then compare braking to normal engine running braking. If it feels the same both ways I would look at the booster more closely.

[JayG]

If the booster is out, the pedal will be REALLY HARD to press to get any stopping power
You can pull that hose and see what I mean

[blue62]

Originally Posted by JayG

If the booster is out, the pedal will be REALLY HARD to press to get any stopping power
You can pull that hose and see what I mean

yes if it is a total failure that is true.
If the diaphragm has a pin hole leak it will still have some pressure differential from the vacuum side to the atmospheric side of the diaphragm.
It will just be less pressure differential then spec. So it could take more pressure (maybe a little more maybe a lot more) on the brake pedal to apply the brakes.
If you remove the hose there will be no pressure differential from one side of the diaphragm to the other. So it will take maximum (REALLY HARD) pressure on the brake pedal to apply the brakes.

[particlewave]

To rule out a leak, I let it sit for a week before pulling the vacuum line. It was definitely still holding a lot of vacuum (not the greatest test, but good enough).

This one has me puzzled...

[blue62]

Originally Posted by particlewave

To rule out a leak, I let it sit for a week before pulling the vacuum line. It was definitely still holding a lot of vacuum (not the greatest test, but good enough).

This one has me puzzled...

PW
It gets you closer to the root cause.
It's not an issue with the booster or vacuum at the booster

[maytag]

Guys, I'm telling ya..... don't overlook this from his test drive:

"...front drivers side rotor was at 210f, front passenger 145f (oddly with a 1cm band in the middle of the rotor reading 190f),..."

I'd be pulling that pad, front right, checking that pad first, then the rotor. You've got something going on there.

Sent from my SM-G970U using Tapatalk

[particlewave]

Originally Posted by maytag

Guys, I'm telling ya..... don't overlook this from his test drive:

"...front drivers side rotor was at 210f, front passenger 145f (oddly with a 1cm band in the middle of the rotor reading 190f),..."

I'd be pulling that pad, front right, checking that pad first, then the rotor. You've got something going on there.

Sent from my SM-G970U using Tapatalk

It’s on the agenda for tonight or tomorrow

[piper6909]

Originally Posted by maytag

Guys, I'm telling ya..... don't overlook this from his test drive:

"...front drivers side rotor was at 210f, front passenger 145f (oddly with a 1cm band in the middle of the rotor reading 190f),..."

I'd be pulling that pad, front right, checking that pad first, then the rotor. You've got something going on there.

Sent from my SM-G970U using Tapatalk

+1

The passenger side is making the driver's side do most of the stopping. That would also explain the front end wandering. It could be a stuck piston or 2, glazed pads/rotor, or bad brake hose. Either way, I'd concentrate on the front passenger side.

My guess is that if you let go of the wheel when braking, it would pull to the left.

[particlewave]

I spent the last hour pulling the pads and checking the pistons. Pads look great and pistons moved freely.

I’ll try to take it for a longer drive soon and get updated temps. I don’t think ten minutes was long enough (engine wasn’t even fully warmed up).

[Gilles]

Originally Posted by piper6909

+1
It could be a stuck piston or 2, glazed pads/rotor, or bad brake hose. Either way, I'd concentrate on the front passenger side.

Yes, a glazed rotor or pads could cause this as well.

Some times you can remove the glaze from the pads by sanding them, but I don't believe you can fix a glazed rotor with sand paper..

PS: you could swap the front pads from one side to the other and measure the temp again

[blue62]

Originally Posted by particlewave

I spent the last hour pulling the pads and checking the pistons. Pads look great and pistons moved freely.

I’ll try to take it for a longer drive soon and get updated temps. I don’t think ten minutes was long enough (engine wasn’t even fully warmed up).

PW
Interesting dilemma:
If everything is up to snuff on each end.
Calipers, pads, rotors on the down stream end
Brake booster on the upstream end.
That leaves mechanical leverage of the brake pedal components, master cylinder function, hydraulic pressure, and brake line condition.
Unless I overlooked something- but I am just looking at a computer screen not the car.

Did settle in Kalama????

[JayG]

Originally Posted by particlewave

I spent the last hour pulling the pads and checking the pistons. Pads look great and pistons moved freely.

I’ll try to take it for a longer drive soon and get updated temps. I don’t think ten minutes was long enough (engine wasn’t even fully warmed up).

When I had my similar problem, the pads looked fine as did the rotors.

I wouldn't worry too much about the rotors as if you bed pads, that will clean off just about anything on the rotors.

I still say, try a different set of pads, even if they are old used ones

[particlewave]

Originally Posted by JayG

When I had my similar problem, the pads looked fine as did the rotors.

I wouldn't worry too much about the rotors as if you bed pads, that will clean off just about anything on the rotors.

I still say, try a different set of pads, even if they are old used ones

I’d love to, Jay, but i don’t have another set, a new set is not in the budget and these pads have less than 5k on them.
I wish I’d saved the old pads...

[JayG]

Originally Posted by particlewave

I’d love to, Jay, but i don’t have another set, a new set is not in the budget and these pads have less than 5k on them.
I wish I’d saved the old pads...

Ill check and see if I have a set I can send you. I'm in the process of moving and I have packed most of my car parts.
Do you have an S or Base?

Another option is a set of Powerstop ceramics. They are pretty inexpensive and I have been running them for a while for my street pads and like them a lot

[particlewave]

Thanks for the offer, but mine is a base

I’ll look into the Powerstop pads. Finances are tight due to the cross country move, but things will even out in a month or two, so it looks like this may be a winter project.

[JayG]

Originally Posted by particlewave

Thanks for the offer, but mine is a base

I’ll look into the Powerstop pads. Finances are tight due to the cross country move, but things will even out in a month or two, so it looks like this may be a winter project.

and I only have pads for an S.

Where did you move to?

[Racer Boy]

He moved to Kalama, WA. The problem is likely that his rotors are probably super rusty because of the incessant rain pouring down 24/7.

Or, his car is so waterlogged from the incessant rain pouring down 24/7 that the car weighs twice as much, and just doesn't stop as well.

[particlewave]

Originally Posted by JayG

and I only have pads for an S.

Where did you move to?

I appreciate the offer, anyway

Originally Posted by Racer Boy

He moved to Kalama, WA. The problem is likely that his rotors are probably super rusty because of the incessant rain pouring down 24/7.

Or, his car is so waterlogged from the incessant rain pouring down 24/7 that the car weighs twice as much, and just doesn't stop as well.

Ha!
It’s actually been 60 and sunny every day for weeks, now. I’ve been missing out on amazing driving weather

[Racer Boy]

Shh! Don't give people the idea that it doesn't rain here all the time! They might want to move here, and Seattle does NOT need any more newcomers!

[P_Carfahrer]

PW,

Though not sounding likely, if you need a MC you can have mine I just pulled out with 66K miles.