Poor fuel consumption - answer found Mk2 (I think) !!

[Alacrity]

OK, further to my previous posting where I thought the transfer box viscous coupling had siezed, I have finally had time to look again. This time I am confident I have found the cause of the tight wheels (well I know I have), but I don't know the answer is.

On closer inspection (this time I did it myself ) I could hear the brake pads dragging & clicking in the caliper if I rocked the wheel. All four the same pretty well. So I cracked a bleed nipple on a caliper & bingo, the wheels instantly ran free, due to the split breaking system I had to crack one on the front & one on the rear, but same effect on both. As soon as I apply the brakes they are tight again. So, for some reason, the brake system is holding pressure all the time. This one does have ABS fitted.

Any idea's what could be the problem ladies & gentlemen?

[mikeonb4c]

OK, further to my previous posting where I thought the transfer box viscous coupling had siezed, I have finally had time to look again. This time I am confident I have found the cause of the tight wheels (well I know I have), but I don't know the answer is.

On closer inspection (this time I did it myself ) I could hear the brake pads dragging & clicking in the caliper if I rocked the wheel. All four the same pretty well. So I cracked a bleed nipple on a caliper & bingo, the wheels instantly ran free, due to the split breaking system I had to crack one on the front & one on the rear, but same effect on both. As soon as I apply the brakes they are tight again. So, for some reason, the brake system is holding pressure all the time. This one does have ABS fitted.

Any idea's what could be the problem ladies & gentlemen?

I'm no expert, but it sounds a bit like maybe slave and/or master pistons are not moving as freely as they should but are binding a bit. Given that the slave seemes to have released its grip when the bleed niple was opened (did a little fluid come out of it?), does that point to it being the master that is binding a bit? Could this apply to many of our old Bongos and how tricky would it be to overhaul the master cylinder and/or the slaves. As for pulling the pads back off the discs, as you would think is desirable, is there a component that does this (brake pedal return spring or whatever?).

[helen&tony]

Hi
I've not heard of ALL the brakes siezing in that way...could it be a faulty ABS connection, or the motors/ relays in the ABS controller. In older systems I might suspect the unit that controls the balancing front/ rear...but I can't see one in the Bongo diagrams
Anyway...could you possibly jack the Bongo up, disconnect the ABS unit, and test again?...would this find the problem????
Cheers
Helen

[mikeonb4c]

Hi
I've not heard of ALL the brakes siezing in that way...could it be a faulty ABS connection, or the motors/ relays in the ABS controller. In older systems I might suspect the unit that controls the balancing front/ rear...but I can't see one in the Bongo diagrams
Anyway...could you possibly jack the Bongo up, disconnect the ABS unit, and test again?...would this find the problem????
Cheers
Helen

Master cylinder binding? Speak to me, oh great one

[Alacrity]

I have checked the master cylinder pushrod (from the pedal) isn't tight - & it isn't. Not sure how to disconnect the ABS valve block, that would seem like a huge amount of work to re-pipe the whole system or am I being stupid here? My suspicion is the ABS system somewhere as all four calipers are being held on.

Mike, the pads don't have anything to push them back, they just move back the fraction needed to clear the disc of their own accord once the pressure is released (or should be) when you release the brake pedal. I have proved the calipers (slave as you call them) are not at fault by releasing the pressure from the system when they immediately free off.

[helen&tony]

Hi
Never had that one, Mike...total master cylinder failure and no brakes at an exciting moment...had that one!
Alacrity...
The Lushprojects diagram shows a couple of wires and a pair of connector blocks...try removing the connectors to test...
Cheers
Helen

[Alacrity]

Oh I see, disconnect it electrically. I will try but I doubt there is any power to the valve block when the key is out? Worth a go though.

[Northern Bongolow]

first thing i would do is change the fluid, when i did ours there was lots of black staining of the fluid in the cylinders, both master and at the wheels, this is the seals decomposing.
i would remove each calliper and clean out the internals.
the pistons/pads run very close to the disc normally, but yours does sound like its a pressure relief problem, hopefully a fluid change would clean the valves out.

[lpgimports]

Had something similar on a Regius and it was the servo push rod inside semi ceased and not returning 100%.

[dandywarhol]

I can't see how a deactivated ABS system causing the brakes to bind. Sounds more mechanical to me, lpg's theory or something allowing the servo to apply light pressure to the system.
The caliper seals are square section and when the pressure is applied the square section becomes a parallelogram shape, returning to square when the brake pressure is released which brings the caliper piston back to where it originally was.

An outside possibility is that some uneducated spannerperson has used mole grips on the flex hoses to stop the fluid escaping when working on the system - the grips damage the inner membrane of the pipe which act as a one way valve which won't allow the fluid return, making the brakes bind, causing heat build up which allows the fluid to expand and so on....................blah, blah

[The Great Pretender]

Don't you just hate it when you read through a post looking at the problem, considering the alternatives, thinking BINGO, only to find LPG got there first......................

[teenmal]

Hi,
Could be the plunger in the master cylinder not returning,I would remove the master cylinder and do a bench test on it.
Check that the pressure is releasing when it should,might just need a strip and clean.

This system does have a balance valve,worth looking at it also.

Cheers.

[gmaczbongo]

Try exhausting the brake servo and see if this also lets the brakes release.
Just press the brake pedal a few times until it is empty, engine off.
This assumes that a bongo runs a normal servo.

[bigdaddycain]

Have you checked that the brake fluid reservoir isn't filled to the brim?

[Northern Bongolow]

Have you checked that the brake fluid reservoir isn't filled to the brim?

.the simple ones are sometimes the hardest to think off . .