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The mkiv Supra Owners Club

Brake failure


imi

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Hey all

 

Just got back home safely.

 

Got the brake fluid changed 2 weeks ago to 5.1

 

Today on my way back home, the brake warning light came on and the pedal went all soft.

 

I parked the car up, lifted the bonnet and the brake fluid level was low. Strange as I just got the fluid changed a couple of weeks back.

 

Anyway, got myself 0.5l of brake fluid from a shell garage, toped it up (300ml) however the pedal is still soft despite a lot of pumping and the light will not go off.

 

I managed to creep back home.

 

What should I be looking at? What could it be? Could it just be air or something more sinister?

 

many thanks

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If it was fine for a couple of weeks and has now suddenly dropped then it must be a leak somewhere along the line. Either that or it wasn't bled properly last time it was changed... Do you know if they did the master cylinder and ABS unit bleed after the swap?

 

Check along all the brakes lines for a sign of a leak, especially the lines from the caliper to the hard pipes.

 

If you are not 100% confident to check things yourself it's advisable to get it to your garage again and let them sort it out.

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topped it up with brake fluid yesterday and the brakes have been functioning again (albeit pedal travel is not consistent - perhaps air in the system).

 

Just got back home and the brake light went on again, seems like the fluid is low again. seems like a leak in the system perhaps.

 

will take it to the monkey tomorrow....

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Thats almost certainly a leak rather than a bleed issue Imi, as has been mentioned before check the usual spots. Although any half competent garage should be able to find fault I'd personally recommend you get it to a specialist to look at. AFR?

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If you managed to fit half a litre of fluid in the master cylinder, you have a major problem and will now have air all over the system. You must be really careful if you drive it anywhere, which you shouldn't, you could cause an accident. If on investigation it was found that you knew there was a problem with the brakes, you would be stuffed royally.

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Took that car to the mechanic this afternoon.

 

No signs of leaks under the car, from the calipers, etc.

 

Nothing in the engine bay either.

 

A quick unbolt of the "servo" (silver metal bit under the brake fluid reservoir) and he said that the master cylinder i leaking and needs changing.

 

Does that sound about right (appreciate that advice is based on my description alone)?

 

Is it possible to recondition the existing cylinder or does it just make sense to go for a new one?

 

If so, then approx idea as for costs for a new brake master cylinder, if anyone knows that specific parts that I need to change it then please post or PM me.

 

times like these I really do miss Pheonix. :(

 

Mark gave me his email addy but sadly I have misplaced it. If anyone has that handy, could you kindly PM it to me so I can send him a quick hello.

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Anyone?

 

been searching on the forum and there is mention of different master cylinders on offer from toyota.

 

does anyone have the part number of the different versions?

 

I have UK brakes all round with ABS.

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Hi Imi,

 

I had the master cylinder on my Manta leak. This car had a dual circuit break system so if one failed you still have some breaks. The master cylinder was effectivly two pistons, on behind the other, and the seals on one of them started to leak.

As the seal only leaked slightly, when I stamped on the breaks they initially felt firm and worked ok. However if I kept the presure on, the pedel slowly sank as the fluid leaked past the bad seal. Had to keep pumping....... ! It was the rear seal that failed so the fluid was leaking into the foot well and being absorbed by the sound insulation.

 

As I recall the refurb kit (new seals) didn’t cost much. A lot less than the master cylinder. This will be fine if the cylinder bore is smooth and free from corrosion. If your not confident to check this take advise from a specialist.

 

Air in the system will feel spongy as you press the pedal, then feel harder as the pressure rises. You may have air as well as a leaking master cylinder, if the fluid level fell to far.

 

One things for certain, if you're losing fluid, it's going somewhere. When you find where its going you will have the answer.

 

Good luck

 

Mark

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If you've got fluid disappearing from the master cylinder there is ONLY one cause... it's leaking out. Check every brake line, but particulary the pipe joints. The most likely place for the leak to be is at the calipers or bleed nipples. Any sign of any fluid at all will be a leak. The Supra (with ABS) is not a difficult brake system to bleed.

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If you've got fluid disappearing from the master cylinder there is ONLY one cause... it's leaking out. Check every brake line, but particulary the pipe joints. The most likely place for the leak to be is at the calipers or bleed nipples. Any sign of any fluid at all will be a leak. The Supra (with ABS) is not a difficult brake system to bleed.

 

did all that, no physical viewable leaks from any of the places you mentioned when the car was on the ramp.

 

mechanic points towards the master cylinder (even though we cannot see any signs of leaks there either)

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Sorry, I missed the bit in the post about the master cylinder leaking :( You can put new seals in a master cylinder if a) you can get them and b) if the bore of the master cylinder is not scored. If you're not a competent mechanic, replacing the master cylinder would be the easiest solution. There should never be any loss of fluid anywhere in a correctly functioning brake system.

 

Toyota dealer is the best place to get them and if you replace the master cylinder, get the correct one for the car - it's well up to the job.

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Looks like I need a new Master Cylinder

 

Does anyone have the part number handy?

Talk on this forum about a version with a bigger piston - if you have the part number of that then that would be appreciated too.

 

imi

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Got a replacement master cylinder from Mike today, took it to the mechanic and he changed the brake master cylinder however no joy. Looks like the servo is full of fluid and cannot be drained.....so a long job required to switch the servo too.

 

I was hoping that by draining the servo we'd be able to get the required compression.....

 

Love the car to bits....getting to a stage where I dont have the time to dedicate to it anymore.

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