Outer Limits 4x4 Board

Ok so it sounds weird but thats exactly whats happening.....

Every time the brakes are applied be it either gentle or hard,
the brakes operate as per usual, ........ but...... about 5 secounds after the brakes are applied I get a distinct "pulse" back through the brake pedal, this pulse then happens untill the rig comes to a complete stop.

The pulses are about 1 sec intervals and get progressivly stronger as the rig comes to the stopped position..... the final pulse "feels" to push my foot up about 10mm !!!.

Ive checked ......
pads ................ replaced while I was at it.
fluid ................. dumped the old stuff and flushed and then refilled.
lines ................. checked for kinks etc .... nil to be found !
booster.............. swaped with 3 other rigs, still no change !
brake pedal........ fitted new hinge bolt and greased
master cylinder... replaced, and still no different

rig is a 1980 Nissan MQ diesel..... dead stock standard !!!

any ideas ?????????????????????

Any chance someone fitted a dodgy ABS system while you had your back turned?

sounds like the brake discs need machining

I had the same problem one time, was warped brake discs. A quick machine and it was all fixed.

Sounds like brake shudder. Have you got drum rears. If yes, and the pedal pulsates and ya steering wheel dont shake, id say that the drums out of round. If wheel shakes then either rotors warped or both rotors warped and drums out of round. Machineind rotors and or drums would fix this, but make sure that they are still legal. All discs have a minimum thickness and all drums have a maximum inside diamiter. If these are not adhered to the system is ilegal, and wont dispurse heat properly. When brakes applied hard (emergency stop from freeway speed) they can shatter. NOT GOOD!!!
If ya pads low as well, it is best to change them at same time, They can also contribute to shudder. Anyone who owns VS/VT/VX commadore has probably had this problem(shudder). Its pretty common in them.
hope this helps
layto....

lay80n wrote:Sounds like brake shudder. Have you got drum rears. If yes, and the pedal pulsates and ya steering wheel dont shake, id say that the drums out of round. If wheel shakes then either rotors warped or both rotors warped and drums out of round. Machineind rotors and or drums would fix this, but make sure that they are still legal. All discs have a minimum thickness and all drums have a maximum inside diamiter. If these are not adhered to the system is ilegal, and wont dispurse heat properly. When brakes applied hard (emergency stop from freeway speed) they can shatter. NOT GOOD!!!
If ya pads low as well, it is best to change them at same time, They can also contribute to shudder. Anyone who owns VS/VT/VX commadore has probably had this problem(shudder). Its pretty common in them.
hope this helps
layto....

What he said!

what they all said...

I agree.
Had the same problem with my zuk,turned out to be the rear drums.
Just simply had them adjusted (screwdriver),6 mths on,no problems.

possible also tyre/wheel balance, flat spot or out-of-round tyre, or wheel bearing.

I'd be checking these as well, but suspect discs.

I had this problem too once, trust me it will be the front rotors and rear drums need machining and then the rear's reajusted

there warped due to overheating

The rotors/discs overheat if you are using the brakes late and hard, thus heating them up. Making this worse is heatin them up and sitting at lights with the brake held on, it warps them easily. Having worked in a mechanic shop in sydeney and one in newcastle I can tell ya they get this problem more down there.(or alot more ppl any way due to the constant stoppin)

Wheel bearing play, check it, could cause it, or yopur disks are warped, get them machined and whack some new pads on.. grease your wheel bearings at the same time.

it sounds like brake shudder you can get you disc machine on the car now which is a lot easyer than have to pull then all apart. i do at least 1 to 2 commodores a day with the smae problem

dad's jeep has brake shudder too. started when did trip up to n.t. and back, has had discs machined couple of times, replaced pads, now new slotted discs and new pads. still cames back

might get him to check wheel bearings, thanks for the idea bezerk

im not sure of jeep discs but if they are full floating like the new commodores you have to make sure that the hub face is clean and dial the disc rotors back in when refiiting or it will come back

thanks ruggers. not sure about whether full floating myself.
and, what do you mean about dialing in? is this like running motor in, no hard braking for first so many kays?

its where you set up a dial indicator and spin the rotors aournd and make sure the run is exceeded its normally. .05mm for the front and .08mm for the rear

cool thanks. so i know this wasnt done as dad and i replaced the discs and pads in my garage

they were dba slotted discs and something or other pads. worked real good till emergency braking manouver when found oncoming car on hill crest, other car was going wrong way on divided road

now they shudder

did you end up sorting this problem out?

yep !
































there was a crack in the firewall that allowed the brake booster to flex a bit when the brakes were applied !!!, solution was easy...... weld it !