V70 Brakes: Double tapping plus travel....

[Bashy]

Hi folks, is this a known thing or a known issue please? When i press the brakes then work ok, but if i release and brake again, they seem so much better, always in pairs, though, i cant hold on the brakes then tap them again, makes no difference, but if i double tap, then they make a difference.

Something else occurred the other day too, i cant remember what cause me to brake but i did have to (oh a dear ran out) brake hard, hard enough for the ABS and tyre squeal, whilst all worked great missed the deer so thats deffo great in my book), the pedal travelled a lot further than i thought it should have, im not overly confident as to whether there was much travel left to be honest and it never travels like that during normal use even under high speed braking

Thoughts please?

[VroomVroomClonk]

In my experience the number one cause of brake pedal improving on a second tap is air in the brake pipes. Basically the master cylinder is not able to generate enough pressure at the first push but a second push adds to the pressure and applies the brakes more firmly the second time.
However, adding in that your foot nearly went to the floor in an emergency stop, and I'd be more inclined to suspect a faulty master cylinder which is allowing fluid to leak back past the seals. It doesn't leak out under the car, just basically stays in the reservoir rather than all going down the brake pipes.
I will just add one final cause of brake pump-up (double tap) that I've only experienced once and that is the brake pads coming unstuck from the brake backing material and rust forming between them. This basically put a bit of a spring between the brake friction material and the backing plate and resulted in a lot of pedal movement and needing to double-tap the pedal to get a good response.

PS. All the above assumes that you have plenty of fluid in the reservoir and that it in not leaking out under the car anywhere.

[davebb]

Originally Posted by Bashy

Hi folks, is this a known thing or a known issue please? When i press the brakes then work ok, but if i release and brake again, they seem so much better, always in pairs, though, i cant hold on the brakes then tap them again, makes no difference, but if i double tap, then they make a difference.

Something else occurred the other day too, i cant remember what cause me to brake but i did have to (oh a dear ran out) brake hard, hard enough for the ABS and tyre squeal, whilst all worked great missed the deer so thats deffo great in my book), the pedal travelled a lot further than i thought it should have, im not overly confident as to whether there was much travel left to be honest and it never travels like that during normal use even under high speed braking

Thoughts please?

when did you last change the brake fluid ?
Dave

[MikeGMT]

Originally Posted by Bashy

Something else occurred the other day too, i cant remember what cause me to brake but i did have to (oh a dear ran out) brake hard, hard enough for the ABS and tyre squeal, whilst all worked great missed the deer so thats deffo great in my book), the pedal travelled a lot further than i thought it should have, im not overly confident as to whether there was much travel left to be honest and it never travels like that during normal use even under high speed braking

Thoughts please?

That could be due to the EBA.

From the manual,

Untitled.jpeg

[barrybritcher]

Originally Posted by MikeGMT

That could be due to the EBA.

From the manual,

Attachment 127026

exactly what I was about to post!

Also don't forget you aren't supposed to use dot 4 regular in p2,
it's meant to be DOT4+ (which is basically the spec of 5.1 ESP)

[barrybritcher]

Brake Fluid Spec

[Bashy]

Thanks guys, i haven't done a replacement of the fluid, bought the car late last year, i did however top up the fluid as there was about a 5th missing maybe less, BUT, i didn't look at the dot type, i just bought brake fluid, hoping i haven't damaged anything by doing this? Now i am wondering if i dreamt even doing it now lol Will have to check to see whats on the shed shelf

[barrybritcher]

There's probably literally millions of cars running plain dot4. But it's definitely out of spec dot4 plus is a lot thinner in the cold I think.

I wouldn't worry about it. New fluid is better than old

[Bashy]

Originally Posted by barrybritcher

There's probably literally millions of cars running plain dot4. But it's definitely out of spec dot4 plus is a lot thinner in the cold I think.

I wouldn't worry about it. New fluid is better than old

Ah, nothing overly serious where it will make stuff rot then, phew, prob not enough in there, i was quite generous with the 1/5th guess

The brakes didnt falter either when the pedal travel extended some, they still worked as they should, thankfully, else it may have been a deerer outcome, see what i did there

It will be on a to do list

[barrybritcher]

I use genuine Toyota 5.1 as it's widely available and the closest thing to super dot4 spec for the price. But the one that is the ideal match is 5.1 ESP.