Weird Brake Problem - Faulty Servo?

[Guest Watto]

The car (1990 1.9, PAS) has developed the oddest braking fault. When braking the pedal is soft and travels towards the carpet at an alarming rate, as if there is a fliud leak. There are no visible signs of fluid leakage and when the car's stationary the fault can't be reproduced.

 

I wondered if anyone had experienced a similar problem and what the fault was? I suspect it's going to be a problem with the servo.

[Jrod 7]

I doubt it's anything to do with the servo.

 

Sounds more like the master cylinder seals have gone.

[pugrallye 0]

do you have a firm pedal if engine isnt running?

If so pump up foot pedal and hold it on and start car pedal should dip a little, if it dips to floor you have a servo issue (either internal servo problem or a vaccuum leak - disconnect vaccuum hose to test), if its none of this, either you have incorrectly fitted rear pads and they arent adjusting up properly, or you have air in the hydraulics.

Edited April 2, 2007 by pugrallye

[Guest Watto]

Thanks for the suggestions.

 

The pedal pumps up hard when the engine is off, then drops a little on start-up - normal as the servo actuates. There is no spongy feel to the pedal so I doubt that it's air in the system. Although there has been a drop in fluid level there's no trace of brake fluid at any of the calipers, joints or master cylinder connections. If there were a leak I'd expect to be able to find the evidence

 

The odd thing is that the pedal only sinks if the car is rolling; pedal feel is normal when stationary. I'll check the set-up of the pads and report back, although they've been on a few months without any problems.

[Guest Watto]

I'll check the set-up of the pads and report back, although they've been on a few months without any problems.

 

Well I've stripped, cleaned and refitted the brake master cylinder. The seals were in good nick - in fact they looked new - there are no visible scratches or other damage to either the bore or the reservoir seal surfaces, although there was a bit of muck. We checked rear calipers and bled the system, and guess what? No improvement whatsoever.

 

We've enlisted the technical help of a former brake system designer from Lockheed as well as the Mitsubishi RallyArt technicians community but no-one can suggest a diasgnosis. Anyone else want to give their twopennorth?

[welshpug 1,677]

seized load compensators possibly.

 

I has a similar symptom when this failed on my 405 last month.

[Guest Watto]

Load compensators??

 

What are they and where do I find them? (My brother's the genius motor mechanic, obviously not me!)

[welshpug 1,677]

they wont be called a load compensator on a 205 and they work differently to a 405 but they do the same thing thing, limiting pressure to the rear brakes.

 

brake pressure regulators.

[taylorspug 7]

And they can be found in clipped to the very front of the fuel tank either side of the exhaust tunnel, accessed from underneath the car. They are a hexagonal shape, about 2 inches long.

 

Im having similar problems with a low pedal myself at the moment, looking to sort it out tomorrow, so il report back my findings then...