Bleedin’ Brakes!

[Northernraider]

What about getting pressure bleed kit only about £30 in the UK.

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

 

[Lenny HB]

Probably about £600 in Fiddlesticksin France

Yee of little faith.

 

[oldiesontour]

If I had to put money on it I'd go with master cylinder fault,(air is far more likely to enter on pedal release ,may or may not be a tiny fluid leak that will be hidden by the servo

 

[Carpmart]

Vacuum line to the brake servo?

 

[bigtwin]

Vacuum line to the brake servo?

That would make the pedal hard, not soft.

Ian

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[Northernraider]

If you really wanted to try it out as an experiment, just pull the fuse for the brake lights first.

I have to admit, I'm very sceptical of the desired outcome, so probably wouldn't even bother myself.

Cheers,

Jock.

So am I

Same as I was sceptical about there being water in them the last time.

Has to be something else causing the problem Jock

I'm just dammed if I know what.

There's no leaks , the discs have sod all to do with brake fade like that daft mechanic claimed . Calipers were fine , brakes not sticking or binding as far as I'm aware .

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

Makes you paranoid about going on hills though .

 

[Carpmart]

That would make the pedal hard, not soft.

Ian

You're of course 100% correct.,. Maybe he’s used to a hardish pedal as he’s poor vacuum which goes soft occasionally when it gets good pressure, causing the comparative soft pedal feel?

Whatever it is, first thing is bleed the brakes again. Fault find from there! Solves the problem nine times out of ten.

 

[Northernraider]

You're of course 100% correct.,. Maybe he’s used to a hardish pedal as he’s poor vacuum which goes soft occasionally when it gets good pressure, causing the comparative soft pedal feel?

Whatever it is, first thing is bleed the brakes again. Fault find from there! Solves the problem nine times out of ten.

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 .. pump it up you get a better pedal.
But always brakes fine under normal conditions.

When it fades it just goes to floor and the van don't stop which I can assure you is Fiddlesticksin terrifying especially as handbrake wouldn't stop it and the gearing makes engine braking not very good either

 

[bigtwin]

I'm just dammed if I know what.

Thinking about it, it’s possible that whatever the issue is, it has always been there (since you had the brakes done, if not before) and it has only exhibited the symptoms on the recent hill(s) because you, naturally, would be applying more brake pressure than you’ve done since the work was done. It’s possible that the fault is unrelated to your fluid change (which has possibly masked the symptoms a little) but I couldn’t offer any suggestion as to what it might be - others have made suggestions but I can’t comment on those.

Ian

 

[Carpmart]

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 .. pump it up you get a better pedal.
But always brakes fine under normal conditions.

When it fades it just goes to floor and the van don't stop which I can assure you is Fiddlesticksin terrifying especially as handbrake wouldn't stop it and the gearing makes engine braking not very good either

Proper brown trouser stuff!

Sounds like you need to overhaul the whole system then!

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[Northernraider]

Thinking about it, it’s possible that whatever the issue is, it has always been there (since you had the brakes done, if not before) and it has only exhibited the symptoms on the recent hill(s) because you, naturally, would be applying more brake pressure than you’ve done since the work was done. It’s possible that the fault is unrelated to your fluid change (which has possibly masked the symptoms a little) but I couldn’t offer any suggestion as to what it might be - others have made suggestions but I can’t comment on those.

Ian

Yes I think its possible the issue lies elsewhere but last time when it did it the most obvious thing to do was change fluid as it hadn't ever been done.

The mechanic who did it was a bit of a twit and kept saying stuff like it was the brake discs causing the issue which just made him sound like he hadn't a clue . The discs were a bit pitted but that wouldn't cause brake fade it would just cause poor braking...not a disappearing pedal. That's caused by momentary loss of pressure which means a fault in the hydraulic system not the mechanical one. The master cylinder would likely be the next possible cause. I haven't really been on any steep hills where I've been braking long enough for them to get hot though .

I really want to avoid French garages at all costs if I can so I will see how it is tomorrow again and take it from there .

I may have to pay a few brakers yards a visit and aquire a few parts .

 

[Widge]

Yes, I think that it’s more prevalent in motorbike circles and I can see that in the case of mountain bikes and the like you can orientate the bike in such a way that the bubble can rise.

Air will rise, but, unless there is a clear vertical path from the calliper up to the fluid reservoir any air will remain trapped in the system. Compressing any air bubble doesn’t make it any more buoyant; does it?

Ian

Maybe compressing the brake system that has pockets of air in it for a long period of time. forces the air back into the fluid but in tiny bubbles, maybe like this it doesn't compress so easily, but after a while standing it will probably go back into pockets of air, so even if it works, it would only be a short term fix.

This is all guesswork, i might be talking nonsense, but is sounded like a possible reason it gives the impression of working.

 

[oldiesontour]

You're of course 100% correct.,. Maybe he’s used to a hardish pedal as he’s poor vacuum which goes soft occasionally when it gets good pressure, causing the comparative soft pedal feel?

Whatever it is, first thing is bleed the brakes again. Fault find from there! Solves the problem nine times out of ten.

I would say first thing is unbolt master cylinder from servo (don't loosen pipes ) ease m cylinder away gently maybe ease back gaiter on end of m cylinder looking for evidence of leaks.

 

[oldiesontour]

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 .. pump it up you get a better pedal.
But always brakes fine under normal conditions.

When it fades it just goes to floor and the van don't stop which I can assure you is Fiddlesticksin terrifying especially as handbrake wouldn't stop it and the gearing makes engine braking not very good either

Get what you're saying about Iveco I've had a few and all had a soft pedal ....if you keep pressure on pedal (parked up) they all did the same...go very close to the floor

 

[bigtwin]

Maybe compressing the brake system that has pockets of air in it for a long period of time. forces the air back into the fluid but in tiny bubbles, maybe like this it doesn't compress so easily, but after a while standing it will probably go back into pockets of air, so even if it works, it would only be a short term fix.

The bubbles will certainly compress but as soon as the pressure is released they will return to their original size and there’s no reason why compressing a single larger bubble would result in multiple smaller bubbles being created (and be dispersed around the system which wouldn’t, in any case, reduce their compressibility).

A good try but not sure that it stands scrutiny.

Ian

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[68c]

The 'holding the pedal down overnight theory' works OK with motorbikes. But, as mentioned above the brake lines from the caliper to the master cylinder is uphill. Bubbles will slowly rise but stop at the small hole in the master cylinder that allows the fluid back to the reservoir. Holding the pedal down, or in fact holding the hand lever tight, means when the lever is released it pulls the fluid up and the air bubble with it. I often just jiggle the lever repeatedly, you will see the little bubbles rising. Of course does not work so well with the bike rear brake.
If you are really keen, force the pistons fully in, sucking the excess fluid from the reservoir. Then, while holding the pistons in, bleed normally. Add fluid as you slowly pump the pads back into position. This also means you get the maximum amount of clean fluid in.

 

[mitzimad]

recently changed the fluid in my van using a vacuum oil changer on each nipple in turn

 

[ivorantony]

Quality of the brake pad material is paramount for good braking performance, softer pads will give better braking but quicker wear, harder pads will last longer but with more pedal effort,
Unless you know they are of good quality ( a recognised manufacturer) I would suggest replacing them,

 

[jongood]

This suggestion was posted on Tam’s thread in response to the issues he’s been having with his soft brake pedal.


In response to that, I posted the following:



So, is there a credible scientific explanation regarding why pressurising a brake circuit (by holding the brake pedal/lever on) overnight should assist in removing air from a brake circuit?

Ian

ASFAIK The theory is that there can be tiny air bubbles trapped beyond the inlet port in the master cylinder, so leaving the pedal depressed moves them closer to the point where they can rise. I think its more of a thing with bicycles and motorcycles as the amount of fluid movement is so small. But when I had the clutch changed on our motorhome ( because the slave cylinder was giving notice) they had to leave it under pressure overnight to get the pedal back.

 

[JockandRita]

Has to be something else causing the problem Jock

I'm just dammed if I know what.

A comment above by oldiesontour (thanks), reminded me that we had a very similar problem with our Iveco 3 x years ago, when it was 15 x years old. Although the pedal never went to the floor, I would find the pedal softer than usual when first braking, and a quick foot off/on to the pedal restored the pressure................until the next time I drove it.
My long time HGV mechanic pal diagnosed the master cylinder at fault. It was changed pronto on our driveway, the system bled accordingly, and I've not experienced the problem since.

Good luck getting it sorted Tam.

Cheers,

Jock.

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[Northernraider]

Quality of the brake pad material is paramount for good braking performance, softer pads will give better braking but quicker wear, harder pads will last longer but with more pedal effort,
Unless you know they are of good quality ( a recognised manufacturer) I would suggest replacing them,

It absolutely is not the pads , the discs or any other mechanical issue . It is not poor braking I'm experiencing it's lack of pressure , brake fade and pedal going to the floor on occasion. It's a hydraulic issue which I thought was resolved.

The pads have all been replaced as they were old , the discs are original , calipers are free and working as normal. Handbrake is a separate system and purely mechanical. Fluid was renewed a month ago and brakes bled , have been fine since until one episode again yesterday which was the Same as the time a month ago which was why fluid was changed.


If it was down to pads or discs etc the pedal would remain firm as too solid surfaces meet , you'd just have poor braking , it isn't that.


Both times it hasn't been a very long or steep hill like I'd expect and hadn't been riding the brakes so I don't think they were that hot either. I've certainly been down a lot steeper longer hills with vans before and not had the brakes just go like they have.

And shortly after the brakes return to normal.

 

[Northernraider]

A comment above by oldiesontour (thanks), reminded me that we had a very similar problem with our Iveco 3 x years ago, when it was 15 x years old. Although the pedal never went to the floor, I would find the pedal softer than usual when first braking, and a quick foot off/on to the pedal restored the pressure................until the next time I drove it.
My long time HGV mechanic pal diagnosed the master cylinder at fault. It was changed pronto on our driveway, the system bled accordingly, and I've not experienced the problem since.

Good luck getting it sorted Tam.

Cheers,

Jock.

Yes the master cylinder is where my thoughts are , it may well have dodgy seals from lying about for years.

 

[JockandRita]

Yes the master cylinder is where my thoughts are , it may well have dodgy seals from lying about for years.

Ours was never stood still for long by the previous owners, so I think it was just an age thing, and ready for replacement.

Can you do as oldiesontour mentioned above, ie, ................

I would say first thing is unbolt master cylinder from servo (don't loosen pipes ) ease m cylinder away gently maybe ease back gaiter on end of m cylinder looking for evidence of leaks.

That might confirm any suspicion without rendering it VOR. It's got to be worth a try.

Cheers,

Jock.

 

[Northernraider]

Ours was never stood still for long by the previous owners, so I think it was just an age thing, and ready for replacement.

Can you do as oldiesontour mentioned above, ie, ................


That might confirm any suspicion without rendering it VOR. It's got to be worth a try.

Cheers,

Jock.

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

 

[Barclaybasher]

Have you got a brake binding?

I had exactly the same braking effect on my Moby - rear brake seized on .

Check wheel temperatures after a run - especially the inside rears....

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[Sue and Rick]

Could it possibly be that one of the rubber type hoses connecting to the calipers is weak and giving way slightly when heavy braking? You know like when you squeeze a balloon.

 

[Landy Andy]

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.

 

[Northernraider]

Have you got a brake binding?

I had exactly the same braking effect on my Moby - rear brake seized on .

Check wheel temperatures after a run - especially the inside rears....

Usually you can feel that though Vic, I had that problem on the last van but this one hasn't given indication of that .

 

[BouncyBoatFolk]

Just aswell you said that as I was going to reply saying most vehicles the brake lights only work with ignition on and guess what


My Fiddlesticksin van the lights are on regardless.

So that plan is gone lol

Remove the fuse or lamps overnight?

 

[Barclaybasher]

Usually you can feel that though Vic, I had that problem on the last van but this one hasn't given indication of that .

I couldn't tell mine was binding - not driving.

Clouds of steam when I chucked water over the wheel.

Drove on, parked for the night, next morning wheel was locked solid.

Edit
No more hills after I freed off the wheel and the brakes then felt normal

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