Bleedin’ Brakes!

[Lenny HB]

Might it be worth trying an emergency stop on a nice straight flat empty road to see what results you get.

Don't think he would want to risk that with 4 dogs on board.

 

[AdrianChen]

All brakes were stripped wire brushed and cleaned calipers had pistons out and in several times , slide pins removed and greased and reassembled with new pads ,everything greased , no warped discs and no sticking or binding , it was fine

Then when I visited cheddar gorge I had brake fade . It did it once more in Wales and I then had fluid changed and bled. Mechanic claimed no air in old fluid . He wanted me to fit all new discs and calipers but he was reluctant to pay for them . And I'm not in to changing perfectly good parts unless necessary

After fluid changed van has been fine . Until yesterday when once again I got brake fade .. pedal to almost floor and van not stopping .

So changing fluid and bleeding hasn't stopped the original fault so I'm guessing it's something else.

There is no leak and hasn't been any leak as fluid is still slightly above the max in reservoir where that Mechanic put it ...its not far above max so I doubt that's the problem either.

It might be master cylinder I don't know

All looks fine .

With engine off you can pump up a good pedal that goes nowhere

With engine running you can almost press pedal to the floor ...but its done thar on other vans I've had too .

I'm just about to head to cahors so will see how it is today .

View attachment 977036View attachment 977037View attachment 977038

Flexi pipes all good? Had a double skinned one give up once causing some odd symptoms, but no visible leak.

 

[Northernraider]

Flexi pipes all good? Had a double skinned one give up once causing some odd symptoms, but no visible leak.

All look to be OK

 

[growly_bear]

I'd be tempted to crawl underneath and find the load sensing valve. Then look for the bleed nipple, and whether it's been loosened recently ie used to bleed. This is easily overlooked when bleeding, meaning you'll have old fluid in the line (probably from front to back!). I had exactly your symptoms on my 1990 VW Florida. This created 2 issues which combined to make the problem a whole lot worse; the rear brakes weren't as effective as they should be so more pressure on the fronts and increased heat. Mine faded too, even with new fluid until this was done. My nipple had sheared but that's a whole different story

Northernraider anything to report re the load valve?

 

[jongood]

Well after reading this thread yesterday, I went back to my ongoing problem, chocked the pedal down and vigorously tapped the calipers and got a load of new air out and the pedal back to where it should be so thanks guys

Not that it helps Tam at all........

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[L' Hobo]

Well after reading this thread yesterday, I went back to my ongoing problem, chocked the pedal down and vigorously tapped the calipers and got a load of new air out and the pedal back to where it should be so thanks guys

Not that it helps Tam at all........

Are you saying, It really works?
Never heard of that one before.

 

[jongood]

Are you saying, It really works?
Never heard of that one before.

It makes sense really, its like doctors tapping a syringe to dislodge the air bubbles. Otherwise you re just squeezing them where they are sat.

It worked for me, Ive been messing about with this for hours, I'd tried power bleeding, vacuum and even reverse and nothing was getting enough movement on the front calipers. Chocked the pedal down, attached the power bleeder and tapped the calipers a few times and out came a load more air. its a bit of a strange system with a 2 stage master cylinder with 2 dinky little reservoirs and then seprate circuits for front and rear brakes.

 

[bigtwin]

It makes sense really, its like doctors tapping a syringe to dislodge the air bubbles. Otherwise you re just squeezing them where they are sat.

It worked for me, Ive been messing about with this for hours, I'd tried power bleeding, vacuum and even reverse and nothing was getting enough movement on the front calipers. Chocked the pedal down, attached the power bleeder and tapped the calipers a few times and out came a load more air. its a bit of a strange system with a 2 stage master cylinder with 2 dinky little reservoirs and then seprate circuits for front and rear brakes.

Was the route for the bubbles to move a straight forward vertical rise (I.e. no kinks/curves in the pipes that could prevent the bubbles reaching the release point)?

Ian

 

[ivorantony]

Northernraider anything to report re the load valve?

You don’t have load valves on a vehicle with ABS, the wheel sensors take care of it allowing maximum braking at the rear, (regardless of load) without locking up the wheels,

 

[PeterCarole29]

The issue being the water doesn't stay water...it has a lower boiling point than brake fluid , it boils turns ti vapour and the vapour is compressed more easy than brake fluid causing the spongy brakes.

In my case the fluid was only changed last month because I had spongy brakes and the van had sat for years.

Brakes were fine until today and a not very steep hill descent and once again my brakes faded.

Fluid level in reservoir is spot on so it shouldn't be water in brake fluid this time


I'm buggered if I know what it is though

A long shot but if the brake pads were burnt historically (overheated by sticky caliper and not replaced) could this have an effect on there effect when hot down hill
Last year on our 2021 renault our brakes were hot and had to stop and park.I had to leave Carole in the drivers seat with foot on the brakes as the the hand brake would not hold and when coming down to the village before we stopped the front brakes were not holding up to juntions off course we were going slow. But when cold they were fine

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[PeterCarole29]

You don’t have load valves on a vehicle with ABS, the wheel sensors take care of it allowing maximum braking at the rear, (regardless of load) without locking up the wheels,

Thats a good call as they do seize and restrict fluid

 

[jongood]

Was the route for the bubbles to move a straight forward vertical rise (I.e. no kinks/curves in the pipes that could prevent the bubbles reaching the release point)?

Ian

I think thats the point Ian, unless you have a perfectly uniform upward slope with the bleed nipple right at the top then you are going to get small pockets that can trap air. It was Northernraider remark about seeing the mechanic tapping the caliper that struck a chord with me.