clunk sound whenever i brake

[faiyaz]

hey everyone, for some reason my hilux makes a clunk sound whenever i press the brake pedal while the vehicle is moving , could it be because the rear brakes need adjustment ? or is there air in the system ? its really annoying

[LouisZ]

Start with the Basics.

Bleed the system completely.
Check for leaks.
Check the rear brake shoes
Check front brake pads
Check front calipers securing bolts, they might be loose.
Check rear brake shoes configuration, ie look if you see any springs adjuster or parts missing.

[faiyaz]

alright ill do that thanks!!
does the vehicle need to be on while bleeding the brakes?

[LouisZ]

The engine can be off. Safer that way.

[faiyaz]

ok cool

[Mud Dog]

Do as Louis suggested for a start, check the front callipers especially for loose bolts. Check that the brake pads in the calliper don't have too much play up and down (rotational direction of the disc) - they should be free with very small play but not loose.

Where does the sound seem to come from? Front or rear?

Is it only with braking, or with acceleration as well?

Do you 'feel' anything from the foot well floor when the 'clunk' is heard? Is the torque rod still present on the front axle (from top of the diff to front chassis cross member)?

Check engine / gearbox mountings as well as all the shackle bushes / hanger bushes on the suspension.

[faiyaz]

ok ive checked the caliper bolts they are tight, will check brake pad play, cant really tell im not too sure, only when braking while the vehicle is going forward, yes the torque rod is still there and tight, ok ill have a look at those thanks!

[faiyaz]

the right caliper outer pistons are leaking brake fluid seems to be getting bad so im guessing those have something to do with it, will get rebuild kit if i can find one.

[Mud Dog]

If it got onto the pads, then they're contaminated and will need to be replaced as well. No amount of degreaser and hot water will get the brake fluid out as it gets absorbed deep into the lining. It will compromise the efficiency of the pads and if you replace one side, you have to replace the other as well. Recon both callipers first so that there is no leakage.

[faiyaz]

alright, ill do that, the pads are brand new just replaced them 3 months back, dont think its gotten to the material just the metal plate had some on it, the dust covers had quite abit, ok will have to check around for rebuild kits and of course red rubber grease!

[Mud Dog]

Kits should be easily available. Not a difficult job, just a little time consuming.

Split the callipers after removing them - so much easier to work with them that way. The kit might have the o-rings included for the hydraulic galleries when you split the callipers but if not just get them loose. You might find some pitting in the piston sleeves and on the pistons themselves - pitting on the pistons is not too critical but pitting in the sleeves is a bit more serious. You can give them a quick hone with a honing tool and then polish them up by hand with first a 200grit and then 400grit water paper to bring up a nice bright shine. Do just the emery / water paper on the pistons.

Before reassembly, flush out well with soapy water, then clean water, blow out with compressed air and lastly dry with a hair dryer or heat gun. The rubber grease is a must and when re-fitting the pistons be careful not to hurt the new rubber 'rings'.

If you pinched / blanked off the lines before removing the callipers, you need only bleed the front brake lines.

[faiyaz]

ok ill do that, have checked out some vids and after reading your description it sounds pretty easy, apparently once my dad put cheap qaulity brake fluid that was like oil and made the brakes really spongy we then had to flush the system with methylated spirit im guessing all this caused the caliper to leak, lol yes they kits are readily available overseas but in zambia theres only one place that has the seals for the caliper, ill also have to get new dust covers as the 2 pistons that are leaking have deformed dust covers, im hoping they have the right size, just waiting on the rubber grease ive ordered as even that is unavailable here, have you ever rebuilt a master cylinder for a hilux ? after fitting new seals does it perform well or is it best just to replace the whole unit? as even the original master cylinder was leaking so we fitted a pirate one but im not too happy with it.

[faiyaz]

the hilux was bought brand new 23 years ago it was the top of its range at the time over the years however bad mechanics have made their mark on the vehicle and im in the process of fixing things up the correct way slowly slowly, and im sure you know how it is when you fix one thing , 2 or 3 other problems spring up !!!

[Knuppel]

Check your shackle bush rubbers on on all the springs.
Check your bottle jack is securely placed in its holder!

Also make sure the brandy bottle behind the seat is secured

[Mud Dog]

The dust seals on the pistons are important and IIRC those rubbers come with the kit. A whole new set of callipers will cost you an arm and a leg (the OEM ones anyway), so check out the pitting in the sleeves before going that route - if the pitting is so deep that it won't come out with a light hone, then get new ones.

[faiyaz]

i just replaced the shackle bushes a few months back so i dont think its that, we dont carry the bottle jack around , oh yh it must be the brandi !!!!!!lol

[faiyaz]

however i dont think those bushes were so good they have already started cracking i think also the fact that i used normal grease might have damaged them, next time ill buy RBI bushes and fit them with fuchs renolit lst 0, its vegetable oil based. but ive experience bad bushes before and its definitely not that lol

[faiyaz]

well what im planning on doing is buying 2 complete kits and buying a second pair of calipers if they not expensive and fix the ones on vehicle and also the pair i buy for spare im sure theyll be just as good as new ones if i do it correctly, ill have to check the prices in dubai and south africa, i might aswell also get the kits for the rear drums aswell

[faiyaz]

just for some feedback on this, i removed both calipers and the left caliper pistons had started to seize, they were a real pain to remove, luckily they cleaned up well no pitting, fitted new seals in both calipers and used rubber grease, im guessing the seized pistons only activated once a certain pressure was applied to them and would hit the brake pads with alot of force causing the clunk, also replaced the rear brake cups coz they had just started to seep and bled the whole brake system with fuchs brake fluid, the brakes are much more responsive, and no more clunk!!!

[Mud Dog]

Good to hear!