Technical strange brake fault

[ken page]

hi guys i have a strange fault on my brakes on a 2005 2.3 jtd 244 every now and again i will apply the brakes and the pedal will go halfway down although i have full braking and then next time it will be where it should be at the top,and will stay like that for many miles/weeks since this started last yr it has had a new wheel bearing and new discs and pads it has just been for a mot and passed with no faults, its as if the pads are being pushed back a bit and extra travel on the pedal is required to make contact with the discs. any advise on whats wrong welcomed thanks ken

 

[corcai]

hi guys i have a strange fault on my brakes on a 2005 2.3 jtd 244 every now and again i will apply the brakes and the pedal will go halfway down although i have full braking and then next time it will be where it should be at the top,and will stay like that for many miles/weeks since this started last yr it has had a new wheel bearing and new discs and pads it has just been for a mot and passed with no faults, its as if the pads are being pushed back a bit and extra travel on the pedal is required to make contact with the discs. any advise on whats wrong welcomed thanks ken

If its not the master cylinder, sticking caliper slides would be my guess.

 

[ken page]

thanks corcai i will start there its a motorhome and stands around for a time as said the brakes work fine but its unnerving when it does it regards ken

 

[Techno100]

Pedal normally drops after starting the engine if foot is on it. This is the vacuum servo assist.

 

[ken page]

thanks tecno it only happens every now and again after a run when i use the foot brake the pedal goes halfway down the van stops fine if i let the brake off and re apply the pedal is back at the top regards ken

 

[errolmorris]

My initial thought is a master cylinder fault.
I would be testing the fluid with an hygrometer for water content first up and then check the bottom of the master cylinder for sludge.
If the water content is too high and/or there is an accumulation of sludge, a new master or perhaps a kit would be worth looking at.
Most times you can get away with suctioning out most of the fluid and replacing it with fresh stuff and do this a couple of times over the next few weeks. This would only be an advantage if the water content is too high, but then with water in the fluid then 'rust'/sludge will build up.
You could be lucky with a fluid change only, but safety is paramount, so don't spare the parts if you are able.

 

[errolmorris]

I forgot to mention that a water content of 2% - 3% is not really acceptable. If the percentage is greater than 3% then all bets are off.
The water lowers the boiling point of the fluid and may have devastating effects on your braking capacity.
In high humidity and very cold climates, the fluid will have access to more moisture than a dry climate. Think condensation.

 

[ken page]

thanks errol i cant test for water but will do a fluid change regards ken

 

[Techno100]

http://www.ebay.co.uk/sch/i.html?_f...+fluid+.TRS0&_nkw=brake+fluid+tester&_sacat=0

 

[Techno100]

 

[ken page]

thanks thats the way to go regards ken

 

[Techno100]

Yes no pedal pumping and take as long as you like is the way. So unbelievably easy like that.

 

[rolandbrindley]

I change brake fluid on all my vehicles every 2 years or whenever any braking problem surfaces, even a slight pedal level change. Water in the fluid will rust cast iron brake cylinders and calipers very rapidly, and they will sieze up.

A pressure bleeding tool or a vacuum pump is the way to go, avoid pumping the pedal if possible. If bleed screws are looking rusty change them and only open them far enough to let the old fluid flow.

But in your case I would suspect handbrake mechanismtrouble or rear brake adjusters stuck, first of all.

RB

 

[Ocwobio]

thanks tecno it only happens every now and again after a run when i use the foot brake the pedal goes halfway down the van stops fine if i let the brake off and re apply the pedal is back at the top regards ken

I get this all the time (05 Burstner i821 3 axle) and put it down to lack of dispalced volume of fluid into 2 extra calipers- assuming it is a standard master cylinder. Don't even think I'll get an answer if I ask around, either Fiat or Burstner, experience tells me!

 

[ken page]

hi Ocwobio i had a fluid change done but as this problem is random i did not know if it had cured the fault,, i went away for 5 weeks down to spain and it only happened once when i was in the mountains i dont think i will find the cause either , i have had brake fade before on the racers but that manifests its self as a rock hard pedal and no stop so i just dont know regards ken

 

[Ducatiman]

Might be worth thinking about another alternative.....I've had this happen before:

The piston on the master cylinder is ported to allow fluid to enter the system as the piston moves back and forth, if the piston isn't always returning fully when the brake is released it doesn't always get enough fluid for the next pedal push.

My dear old Dad, now sadly departed, once had a problem with brakes pumping up and I suggested he move the carpet that was slightly restricting the pedal travel. He chose to strip down the complete braking system then when nothing helped the problem moved the carpet, job done LOL

I had the same thing but the other way around on a hydraulic motorcycle clutch once, the timing of the piston was out (post service NOT one I did!) and wouldn't let the fluid back into the reservoir, clutch kept slipping and we kept it going by releasing the bleed nipple on the slave cylinder and using the clutch as little as possible. Got it home and checked out the master cylinder, just needed a couple of turns adjustment and it was fine.