Hey all, I'm fairly new to this site but have owned a 1990 Executive EFI TP sedan for about 8 months now. Bought it for $1000 with rego and roadworthy and it's been incredibly reliable up until now.

My brakes failed to work the other day as I was driving home. I was driving up a hill (fortunately) when I saw a dog on the side of the road and instinctively braked lightly but instead the pedal went to the floor. After rolling to a stop I turned off the car and looked underneath for any brake fluid leaks and checked the reservoir. Couldn't see any leaks and the reservoir was showing close to max so I turned on the car and the brakes were working fine again. Drove another 50m or so and they failed again. By this time I was about 100m away from my home so I turned off the car again, waited 15mins and drove home with working brakes again. I thoroughly inspected the car for leaks at home but couldn't find anything and have driven it up and down my street a few times without any braking issues.

Could this be the brake master cylinder or perhaps the brake booster or...? Any help would be greatly appreciated as I don't want to drive it too far in case the brakes fail again.

how to test the booster
http://www.mbmbrakeboosters.com/index.php?option=com_content&view=article&id=12:what-to-do-if-you-suspect-your-brake-booster-is-not-working&catid=7:diagnosing-brake-system-problems&Itemid=15

the master cylinder for a replacement . ..not cheap $281.95 (shop around)

another other way ....the brake shop will want to sleeve and rebuild yours ..$ ?

your not supposed to drive the car far without brakes
I have done some times on different cars and trucks to get the to a workshop
using the gears /handbrake and constant pump of the brake pedal .. needs experience

the TM master will fit . same brake set up on the TP

Could be the brake booster

Brake booster failure will give you a harder pedal, but your brakes should still work as normal. Just needs a heavier push on the pedal. If the pedal just sinks to the floor it is the master cylinder.

I've come across this problem several times, with the earlier Sigmas.
You won't find any leaks, it is due to the cups in the master cylinder not holding pressure, ie it is leaking internally.
Simple solution is to pull the master cylinder off, dismantle and clean out. Then look at the bore, if it is scored it will need to be replaced. Also look at the rubber cups, if they show wear on the lips (fine lines) just replacing those will fix the problem. A serious brake shop will be able to sell or order in the bits needed to recondition the master cylinder.
Alternatively, buy a new master cylinder and just swap them over.

Ok, so the car is back on the road - finally. After taking the master cylinder off and inspecting it there wasn't any scoring and the cylinder itself looked pretty good. The brake fluid was pretty old and dirty and we suspected the inner cup seal needed replacing. So for $130 a brake specialist would recondition the cylinder. They messed it up the first time and must have put the wrong size seal on it because when I went to put it back on the car it began leaking fluid from the rear/outer seal (where it joins on to the brake booster). Anyway, after taking it back and getting it properly fixed I've put it back on the car and now have working brakes again. Won't be going back to that brake specialist again though. Thanks magna buff and MadMax for the advice!

No problem! Us old farts are here to help.

And thanks for the feedback, some people don't bother.

not bad for a hone and rebuild

correct - rubber kits are not all the same