Bleedin’ Brakes!

[JockandRita]

But I think if there were leaks there would be visible signs and the level in reservoir would have dropped wouldn't it?

But no sign of any leak so far and fluid level looks maximum

Does the piston rod from the pedal to the cylinder, feel sticky to the touch at all?

Cheers,

Jock.

 

[Diabalo]

Tam, Does your van have ABS?

 

[Onemanandhisdog]

mostly from mountain bikers

Yep, done it many times on mountain bikes and it certainly works.

 

[L' Hobo]

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

When you bled your brakes, did you also bleed your clutch?
It probably contains 12yr+ fluid and shares the same reservoir.

Shouldn't make a great deal of difference to the brakes BUT as Mr Tesco states, every little helps.

PS. The few times I have had to back bleed my CLUTCH to get any pressure, I have always got something to compress the pedal (because that's how it was taught me 70yrs ago,) perhaps it allows a free flow back to the reservoir or reseats the seals??

 

[Onemanandhisdog]

If that works, you’ve got a leak in the hydraulic system somewhere!!!

Surely the pedal would go down as fluid escaped?

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[pagey]

It's got to be either the mastercylinder or the load sensing valve to the rear brakes

 

[L' Hobo]

No idea .
Loads of folk say no idea why it works but apparently does ..

Can't do it anyway as not leaving brake lights on all night

Can't you pull a fuse?

 

[Carpmart]

I think I need a recap on this!

You had a Long brake pedal so you get the fluid done changed. All fine post change (so not air as you’d have felt that before) until you hit a descent which applies a proper test and you get a long pedal. Does pumping resolve? Once you pumped, did you have a good pedal again? You’ve lost no fluid, is that correct?

Did you service the brakes? If stood for so many years corrosion is a problem. Servicing for me would have had a big focus on mechanical aspects. If they didn’t get properly looked at, I would wire brush off the pad carriers and contact surfaces the pad lugs run on. Copper grease these. Push (apply brakes but keeping piston from fully exiting) the pistons out a bit, check for corrosion and pitting and clean around and check the boots. Spin disc and try and ascertain how true the disc spins… hard to do by eye but you can mock up a guage to check. You problem could have been a sticking piston, pad etc suddenly releasing, so giving a long pedal as the hydraulic slack is taken up?

How easy is access to the brake master cylinder and booster? It needs checking..

Once you’re sure the master cylinder is dry, all the surfaces are interacting as they should, the discs aren’t warped and knocking the pads/pistons back, then I’d do a fresh bleed with a new sealed bottle of Dot4 and an easibleed kit, or some assistance from a willing Motorhomer.

 

[L' Hobo]

He has two.

But he MUST reduce one to VERY, VERY low pressure!

 

[bigtwin]

You problem could have been a sticking piston, pad etc suddenly releasing, so giving a long pedal as the hydraulic slack is taken up?

That scenario would result in a drop in the reservoir level and he’s reported that the level hasn’t changed.

Ian

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[TDub49]

The local garage told my wife she needs her brakes bled. The symptoms are that it’s spongy on the first press and more resistance on the second. Not an explanation but anecdotal evidence that the pressure in the sealed system does change does seem to change after a pedal press. Maybe it’s water in the system and not air and the water is slightly more compressible, isn’t it?..

I think it is the other way around - air is compressible, water is virtually incompressible under normal conditions.

 

[L' Hobo]

Probably about £600 in Fiddlesticksin France


I shouldn't have to bleed the brakes everytime I go downhill though.

There has to be an other issue

Something I have noticed lately in Car Mechanic magazine that I still have delivered is, the sequence of bleeding has changed on some modern vehicles.

I used to start at the nipple furthest away from the reservoir and slowly work on the wheels, getting closer and finishing, usually, with the Front Offside.
NOW, often it's at the front that they START???

Is your vehicle the Old or New sequence of bleeding?

 

[Widge]

I know the pressing pedal over night works on a hydraulic clutch system as I have done it myself.

Self bleeding of brakes isn’t too hard with the correct kit. I use. https://www.ebay.co.uk/itm/28614678...pid=5339023013&customid=&toolid=10001&mkevt=1

Brake material has a big effect on brake feel, so good pads are a must. Also be aware that if a vehicle has been standing or brake pads are old they can start to come off the metal back plate that with give a soft pedal. Another obvious check is that the wheel bearings have no play, as a faulty bearing will push the pads back further.

I didnt have a bleed tube handy last time i needed one, so used a piece of rubber gas pipe, put a bolt in the end to seal it, then cut a slit about 2-3cm lengthways along the tube about 3cm from the end to let the fluid out and act as a non return valve, it worked great.

 

[L' Hobo]

I didnt have a bleed tube handy last time i needed one, so used a piece of rubber gas pipe, put a bolt in the end to seal it, then cut a slit about 2-3cm lengthways along the tube about 3cm from the end to let the fluid out and act as a non return valve, it worked great.

You used to be able to buy self bleeders like that at Halfords before everything got so technical!

 

[Northernraider]

Does the piston rod from the pedal to the cylinder, feel sticky to the touch at all?

Cheers,

Jock.

Nope clean and dry

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[Northernraider]

Tam, Does your van have ABS?

Yes

 

[Northernraider]

When you bled your brakes, did you also bleed your clutch?
It probably contains 12yr+ fluid and shares the same reservoir.

Shouldn't make a great deal of difference to the brakes BUT as Mr Tesco states, every little helps.

PS. The few times I have had to back bleed my CLUTCH to get any pressure, I have always got something to compress the pedal (because that's how it was taught me 70yrs ago,) perhaps it allows a free flow back to the reservoir or reseats the seals??

Different system the clutch fluid master and slave cylinder is what I replaced the other day . Not related to brakes

 

[Northernraider]

I think I need a recap on this!

You had a Long brake pedal so you get the fluid done changed. All fine post change (so not air as you’d have felt that before) until you hit a descent which applies a proper test and you get a long pedal. Does pumping resolve? Once you pumped, did you have a good pedal again? You’ve lost no fluid, is that correct?

Did you service the brakes? If stood for so many years corrosion is a problem. Servicing for me would have had a big focus on mechanical aspects. If they didn’t get properly looked at, I would wire brush off the pad carriers and contact surfaces the pad lugs run on. Copper grease these. Push (apply brakes but keeping piston from fully exiting) the pistons out a bit, check for corrosion and pitting and clean around and check the boots. Spin disc and try and ascertain how true the disc spins… hard to do by eye but you can mock up a guage to check. You problem could have been a sticking piston, pad etc suddenly releasing, so giving a long pedal as the hydraulic slack is taken up?

How easy is access to the brake master cylinder and booster? It needs checking..

Once you’re sure the master cylinder is dry, all the surfaces are interacting as they should, the discs aren’t warped and knocking the pads/pistons back, then I’d do a fresh bleed with a new sealed bottle of Dot4 and an easibleed kit, or some assistance from a willing Motorhomer.

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 .

 

[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

 

[L' Hobo]

Different system the clutch fluid master and slave cylinder is what I replaced the other day . Not related to brakes

So don't share the same reservoir, good, a lot do!

As you have ABS, have you checked the bleeding sequence as I suggested.
It seems the starting to bleed at the front came in as more and more cars were fitted with ABS?

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[jongood]

Possibly

But I think if there were leaks there would be visible signs and the level in reservoir would have dropped wouldn't it?

But no sign of any leak so far and fluid level looks maximum

sorry havent read eveything in detail but after12years stood I think it is quite likely that a seal has gone hard/perished somewhere. why dont you try and pick up a master cylinder seal kit somewhere? Is it LHD? if so then shouldnt be a problem and get the moroccans to do it. Have you had the rear drums off? would you know if one of the rears was weeping?

 

[Northernraider]

So don't share the same reservoir, good, a lot do!

As you have ABS, have you checked the bleeding sequence as I suggested.
It seems the starting to bleed at the front came in as more and more cars were fitted with ABS?

I haven't. I assumed the truck garage who did it would know/check that . I believe he did front lhs first which was directly under reservoir. That's the one I saw him hitting with a hammer.

They used a machine to do fluid change

 

[Northernraider]

sorry havent read eveything in detail but after12years stood I think it is quite likely that a seal has gone hard/perished somewhere. why dont you try and pick up a master cylinder seal kit somewhere? Is it LHD? if so then shouldnt be a problem and get the moroccans to do it. Have you had the rear drums off? would you know if one of the rears was weeping?

I'm thinking a seal too just not sure why there wouldn't be signs of leaking.
If I can get one I'm just going to buy a replacement master cylinder . But don't want to pay French prices.

It has separate shoes for handbrake on this like the fiat's but completely mechanical no fluid in there and not operated by service brake .

 

[Bessy765]

One of the problems that may or not been raised is if the vent in the fluid master cylinder is obstructed, a vacuum can be formed pulling the callipers back from the disc. When you pump the pads are forced back out and the second pump gives a firmer pedal. One way to check is to loosen the fluid cap and try again.

 

[Silver-Fox]

He knows this but the challenge is doing it on his own.

Ian

It’s simple with a pressure bleeding kit.

Around £40 from a motor factors.
Fits on top of the master cylinder, generally how it’s done at a garage.

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[Diabalo]

Yes

So if all else fails the ABS module is in the mix for checking as that could be having a hissy fit. They are complicated and do control the brake pressure with relief valves and sensors.

 

[Driventemple]

The local garage told my wife she needs her brakes bled. The symptoms are that it’s spongy on the first press and more resistance on the second. Not an explanation but anecdotal evidence that the pressure in the sealed system does change does seem to change after a pedal press. Maybe it’s water in the system and not air and the water is slightly more compressible, isn’t it?..

Water is not compressible, but air is.

 

[gus-lopez]

Could be seals in master cylinder or something

This ^^^^^^^^ I have had it on 2 vehicles previously. Go to brake % straight to the floor, off the pedal & back on & perfect .

Not sure if seals in master cylinder would cause this problem. But you'd think it would be constant and not just happen randomly.

No it just can happen randomly .Frightening when it does

The pedal on this like my last iveco has always been relatively soft . If you press it you can practically put it down to floor

Anything with ABS is like that .If you rest your foot on the pedal it will sink slowly to the floor yet under normal braking they work perfectly.
It isn't a fault but a peculiarity of abs systems. There was a thread here a while back where it was pointed out & what it was called?

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

That is only because all the vacuum for the servo has gone & you are attempting to brake using the master cylinder directly which will never stop the vehicle if you tried.

With engine running you can almost press pedal to the floor .

As above.
The only thing it is likely to be if there is no leak anywhere ,is the master cylinder.It cannot be the servo or vacuum as that just gives assistance to your effort when braking.

If going to change the master cylinder then it would be best to'bench bleed' the cylinder before fitting.That way the least air is being pumped around the system.

 

[AdrianChen]

He knows this but the challenge is doing it on his own.

Ian

Slightly easier with a mityvac I guess.

Cant understand how air compressed for a few hours will not just come back when the pressure is off.

DOT5 (Silicone) can absorb air, and is a nightmare to use, since even if you shake the bottle before filling the reservoir you introduce air, and get spongy brakes.

Dot 3, 4 and 5.1 I don't think absorb air, water yes but not air....

So unless lucky enough to dislodge a bubble that finds it's way back into the reevoir, if it does harden the brakes permanently, then I guess the air must get past the seals in the master/slave and calipers? If so then can it get back the same way?

 

[berni109]

Northernraider Intriguing problem you have there tam and a real bu§§er for you and where you are.
Did a bit of reading which I am sure you have done as well.

Worn master cylinder​

As the heart of the brake system, the master cylinder ..... an internal leak from a damaged piston seal. ...... results in the brake pedal failing and going to the floor.

ABS hydraulic assembly malfunction​

Vehicles equipped with ABS have a hydraulic assembly also called an ABS modulator. This assembly contains multiple internal solenoids and valves. An internal failure, corrosion or debris in the brake fluid can cause a valve not to operate properly, resulting in a low or spongy pedal.

A number of peeps have suggested the worn master cylinder theory which I think is the most likely. Have you been applying more brake pressure (or at least trying) on the down hills. Could that extra effort cause a weak seal to leak whilst a normal light touch does not.

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

But then I might just be talking out my posterior.

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