Thread: Catastrophic brake failure like I have never seen before

Originally Posted by JDNSW

My question is, since it has dual circuit brakes, why did this lead to total brake failure? This is exactly the sort of fault that having two braking circuits was supposed to save from leading to total brake failure.

I presume cos the tank got empty and there was nothing in the master cylinder to create pressure

Originally Posted by sierrafery

I presume cos the tank got empty and there was nothing in the master cylinder to create pressure

Exactly, the caliper would have leaked fluid out of the joins so having 10 circuits wouldn't make any difference.

There is SUPPOSED to be a divide in the Master Cylinder so that if one circuit leaks out, theoretically there is fluid in the other circuit. Its part of the ADR's

In practice it is not the case .

Im dealing with this right now with Iveco. One fellows brake hose from master cylinder rubbed through & he had no brakes at all.

So much for Dual Circuit brakes, I also found my brakes failed totally with a broken rear brake hose on a split circuit. That is an ADR non compliance.


simple experiment , undo a brake bleeder anywhere on your car & push the pedal, if it goes all the way to the floor you have zero brakes. Makes a mockery of Dual Circuit & ADR,s

Im replacing the entire braking system on the truck with something that works.

Originally Posted by goingbush

There is SUPPOSED to be a divide in the Master Cylinder so that if one circuit leaks out, theoretically there is fluid in the other circuit. Its part of the ADR's

In practice it is not the case .

Im dealing with this right now with Iveco. One fellows brake hose from master cylinder rubbed through & he had no brakes at all.

So much for Dual Circuit brakes, I also found my brakes failed totally with a broken rear brake hose on a split circuit. That is an ADR non compliance.


simple experiment , undo a brake bleeder anywhere on your car & push the pedal, if it goes all the way to the floor you have zero brakes. Makes a mockery of Dual Circuit & ADR,s

Im replacing the entire braking system on the truck with something that works.

So that front and rear are isolated ?, i believe that is how it is so theoretically you should still be able to pull up with a leak in the front circuit.

Update.
Well I pulled the calliper off and split the halves using nothing more than fingers.
There are rubber seal things? Not o rings or gaskets. I washed the lot with metho and reassembled. Tightened the bolts up a lot to about 100Nm
I put it back on the car and bled the brakes. Put the wheel back on and test drove. So far no leaks and the brakes work!

Now am looking up the receipt and will write all this to the supplier. Calliper was in a green box (bearmach?).

Not happy about this at all but where is the proof? Never seen a calliper ever have those bolts come lose. I would have thought they would have been loctited in and impossible to remove.
I will be asking if they should be loctited as at this stage I did not put any on them on reassembly

James
Zwitter

I'd be checking to see if the bolts on the other caliper are loose .

Originally Posted by loanrangie

So that front and rear are isolated ?, i believe that is how it is so theoretically you should still be able to pull up with a leak in the front circuit.

Yes that is the theory, Iveco is supposed to have a 50-50 split, according to the Official Workshop manual of misinformation. One page shows Front & rear are isolated, the next shows a diagonal split , in either case its moot because there is no divider in the MC , One leak & the lot drains out !

As an asides & off topic, I'm ditching the Iveco Brake system completely & am putting HydroBoost & Master cylinder from Chev Suburban, Yes there is a divider in reservoir, 34mm MC inplace of the 29mm Iveco MC . Mercedes rotors up front already done, F250 Rotors on rear with Cadillac callipers. (will keep the Bosch ABS. )

You should not have to do this to a new car to get brakes as they should be in the 21st century. My 1973 SWB Landy with original dual circuit drums stops better & is safer ( but crack one bleeder & pedal still goes to floor)

That split chamber thing in the master cylinder is useless as only the primary piston is moved mechanically by the rod the secondary piston's movement is achieved through fluid pressure so if any chamber goes out of fluid there will be no pressure in the cylinder... an overcomplicated construction without effect... they should have built a cylinder with bolth pistons actuated mechanically by the rod