Random Brake Pressure Loss

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Hey all,

I'm confused, what can cause brake pressure loss on a well maintained VT series II executive?
uses brake fluid quite a bit i think, but no leaks.

Not my car but dads unsure what to check.

any ideas?

Thank you

[Sabbath']

Technically you should never lose "quite a bit" of brakefluid as it's a sealed system so to speak. If the level is going down at that rate, it would suggest there is a leak. Check calipers and master cyclinder seals for leaks.

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I will do.
Also it's total brake loss.
and then it'll work fine again.

[lout]

If it is losing brake fluid you have a leak
If you can't locate a leak it is possible the master cylinder is leaking into the booster (unlikely)
If it is not losing fluid most likely the master cylinder.
If it was me I would replace the master cylinder as a precaution.
If you don't find anything conclusive
get it checked by a professional, you don't want to take chances with brakes

[RiCeY]

When you say it uses fluid how much does it go through over how many kms?

Does the pedal sink to the floor or just requires a lot more effort to pull the car up?

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i'll find out about the fluid loss, i did briefly ask him yesterday he said something like it doesn't use all that much, my assumption based on what his said in the past
maybe from full to half way in less then 6mths.

pedal is kinda strange you can hear a kind of hissing sound when depressed, even when not driving just motor idling, also it seems like you need to press the brake pedal maybe 20-30% down before it starts to brake but you don't have to push it to the floor.

[1SIKR8]

you might have a air lock in the brake lines mate, try bleeding the brakes ? also how olds the brake fluid ? old brake fluid can turn to a water substance and then evaporate ....

[RiCeY]

Could be an issue with the brake booster.

With the engine off pump up the brake pedal till its hard then while keeping pressure on the pedal, start the engine.

The pedal should sink if the booster is working correctly.

Check the vacuum line that goes from the engine to the brake booster and make sure its secure and undamaged.