Hey gang,

Had the handbrake light on the TJ come up for a while. It would come on, then go off. So naturally I thought it was the brake fluid being a bit low. Then I thought about it some more and realised I recently had the brakes done, so found it perculiar that the light would still come on and off. I left it for a few days/week and now the light stays on all the time.

Brakes feel fine. Today it was booked in as it couldn't get in any earlier and they checked it all over and discovered the master cylinder is leaking/has been leaking and hence why I am loosing fluid.

Gonna cost $300 for a new one, fitted, bled out, all that stuff etc.

Has anyone had a Master Cylinder fail before? Can be quite dangerous, so much so, that despite me wanting to collect the car Mitsubishi refused to let me take it and the part arrives on Tuesday, so I have no car till Tuesday night, but Mitsi are giving me a loan car free of charge, thats how bad it potentially could be.

Nice of Mitsi to stand their ground on that and give me another car at no cost. So has anyone ever had this issue before or heard of it? Car has 169,000 km's on it thus far.

The tiniest bit of dirt under one of the master cylinder cups can cause it to leak out. Yes, it could be dangerous. No fluid = no brakes. On the other hand they can leak and not affect the brakes, provided you keep it topped up. Pressing the brake and holding it down with the engine running, if the pedal sinks slowly over several minutes right to the floor, it is dangerous.
If you could be bothered, and have the skills, you can dismantle it and replace any defective/scored cups. Bit late now though now that it is in the workshop, and probably much safer to let the Mitsu mechanics fix it.

Very uncommon for one to stuff up though. Brake fluid level normally doesn't change much - it will drop slightly as pads wear down - so any major loss needing the reservoir to be topped up needs to be taken seriously and be investigated.

Get the old one back and pull it apart, at least you will be wiser to how one works and what can go wrong. Keep it as a paperweight, after you clean it. lol

Thanks for the reply. Yeah I've requested the old unit to inspect it for sure. Yeah I knew something was wrong cause hte pads were all new and fluid should be high, not low, hence the investigation further.

I'm guessing you've had the brake fluid flushed every couple of years? There is a difference between brands and brake fluid types, with Super Dot 4 being the best to use. The car is fully compatible with it, just Super DOT 4 absorbs water less readily and has a higher heat tolerance (and is rated longer). Costs fractionally more though, for a 500ML bottle its like $1 extra, so for a flush you're looking at an extra $2. Garages tend to use standard Dot 4 though, because those dollars adds up when bulk buying.