Ok a little light reading for Thursday, we all know prevention is the best way forward with service items and but many times those little warnings are too subtle or just missed as little annoyances or the character of the car and the 300zx brakes is a case in point.

 

So two points, the master cyliner and the front calipers these are the two area`s where most problems occur in the breaking system and are often overlooked as the cause at the time, of course ensuring no air is in teh system is a biggy too.

 

So we will deal with the master cyliner in this thread and the calipers in the next one, the bmc is so easy to service ( kit part number shown in picture for Twin Turbo ) assuming your cyliner body is in good order its a case of removing it from the car which is a 20 minute job, probably best if you use a turkey baster or similar to remove as much fluid as possible, and have lots of paper towel around keeping everything covered as brake fluid and paint do not get on!! be warned do not spill it on you paintwork if so immediately wash down with soapy water.

 

So once the bmc is on the bench is a simple case of releasing the lock pin and end stop and tapping the unit down on the table until the bits fall out.

 

 

 

 

Once out clean everything with brake cleaner and dry off, inspect the inside of the cylinder and if all good wet the new seals down with fresh brake fluid and refit to the piston in the same order and orientation they came off, ( make a drawing before hand or take a photo to refer to later) then refit to the cylinder and lock it off. Refit to the car and fill up with fluid, you only need to bleed the two nipples in on the ABS unit in the boot not at the wheels unless you want to change the whole fluid, however if you have a rare non abs zed ( some non turbo`s ) you will have to bleed at each wheel, even with new cylinder seals fitted I recommend you do not push the brake pedal all the way to the bottom when bleeding, place a small piece of wood or similar under the pedal to prevent this.

 

The bleeding should not take long as the lines go direct to the ABS and are of only small bore, of course you could buy a new unit but at near £200 this can save a lot of petrol money at a little of £20 for the seal kit and your master cyliner will be in good order and ready for another service.

 

Jeff

Edited October 15, 201510 yr by JeffTT

Not sure the images are working Jeff?

Strange I can see them from here ?? just re-saved the post any better?

 

Jeff

Edited October 15, 201510 yr by JeffTT

Images are fine now:)

Works now - thanks Jeff! :)

Nice one Jeff, thanks. When you say 'inspect the inside of the cylinder', what should we be looking for? Do they wear out increasing the bore or can they get scored etc?

What are the symptoms of a failing BMC Jeff?

Nice one Jeff, thanks. When you say 'inspect the inside of the cylinder', what should we be looking for? Do they wear out increasing the bore or can they get scored etc?

 

Yes they actually tend to wear quite evenly unless of course some debris travels down the side of the seals and scratches the bore as you mention but do not confuse the swirl effect marks caused by the seal rotating as it travels down the bore a few thousand times a year!!

 

Jeff

 

What are the symptoms of a failing BMC Jeff?

 

Sinking pedal mainly from fluid by-pass at the main seal and increased pedal travel from air getting in at the back seal, you can check the back seal quite easy, get someone to press hard on the pedal and hold it whilst you watch the fluid in the reservoir, then release and hold down hard again do this a few times, if you see any air bubbles rise through the fluid the back seal is drawing air in.

 

Jeff

Interesting as since my brake upgrade I haven't been able to get my brakes feeling hard, they are continually soft a few pumps changes it for that brake then soft again. I've bled them as per the manual. Whilst it's got better it's still not right. The car also pulls to the left under hard braking. The calipers aren't seized. I think I just need to bleed them again.

Yes they actually tend to wear quite evenly unless of course some debris travels down the side of the seals and scratches the bore as you mention but do not confuse the swirl effect marks caused by the seal rotating as it travels down the bore a few thousand times a year!!

 

Jeff

 

Jeff

 

Cheers Jeff, another question, are you talking a piece of 2x4" under the brake pedal when bleeding?

Cheers Jeff, another question, are you talking a piece of 2x4" under the brake pedal when bleeding?

 

Yes that will do it.

 

Jeff