Soft Brakes !

[laura_ph85]

I need help!

Brakes on my Rav (02 mark 2 diesel) have gone soft and pedal goes to the floor with moderate pressure in about 10 seconds.

Typical symptoms of master cylinder/rubbers. Cylinder in good order but new rubbers fitted while iit in pieces (£77). No improvement! Rechecked system no air and no leakage.

Clamped off the rubber feed to both front calipers. Brakes now feel as they should. While pressuring just the rear no softness or leakage the pedal is hard and fast.

Released one caliper brakes softer and goes to the floor over 60 sec with moderate pressure.

Released second caliper brakes soft and pedal floors again in 10 seconds.

The problem seems to be with both front calipers (not likley) or some problem within the Anti lock system!

Has anybody experienced similar problems and what was the remedy.

thank for any reply (Lauras Dad)

[pips]

Clamped off the rubber feed to both front calipers. Brakes now feel as they should. While pressuring just the rear no softness or leakage the pedal is hard and fast.

It's years since I played with braking systems (well to be honest, it was my first car a Mini Metro in 1987!) but from what i recall, if the pedal was soft and went to the floor it was symptomatic of either a leak or a rubber pipe that has gone soft, and instead of taking the pressure, it was expanding with the pressure.

As you said that the problem disappears when you clamp off the rubber feeds to the front calipers, I would hazard a guess that these rubber feeds need replacing.

Hope this helps.

Phil

[anchorman]

Turn the engine off and pump the pedal until the servo is exhausted. The pedal should be rock hard and not budge no matter how long it is pressed. With pressure on the pedal, start the engine. If the pedal creeps all the way to the floor, don't worry this is normal as long as it stays hard when the engine is not running.

If the pedal creeps with the engine off it sounds like air in the system or fluid getting passed the seals in the master cylinder which would need changing if you have done the seals.

[laura_ph85]

Turn the engine off and pump the pedal until the servo is exhausted. The pedal should be rock hard and not budge no matter how long it is pressed. With pressure on the pedal, start the engine. If the pedal creeps all the way to the floor, don't worry this is normal as long as it stays hard when the engine is not running.

If the pedal creeps with the engine off it sounds like air in the system or fluid getting passed the seals in the master cylinder which would need changing if you have done the seals.

[Red Yaris 54]

Turn the engine off and pump the pedal until the servo is exhausted. The pedal should be rock hard and not budge no matter how long it is pressed. With pressure on the pedal, start the engine. If the pedal creeps all the way to the floor, don't worry this is normal as long as it stays hard when the engine is not running.

If the pedal creeps with the engine off it sounds like air in the system or fluid getting passed the seals in the master cylinder which would need changing if you have done the seals.

Are you trying to tell us something Laura?

[laura_ph85]

Turn the engine off and pump the pedal until the servo is exhausted. The pedal should be rock hard and not budge no matter how long it is pressed. With pressure on the pedal, start the engine. If the pedal creeps all the way to the floor, don't worry this is normal as long as it stays hard when the engine is not running.

If the pedal creeps with the engine off it sounds like air in the system or fluid getting passed the seals in the master cylinder which would need changing if you have done the seals.

thank for the suggestion; tried it.

With engine off the brakes are hard no sinking pedal, start up the engine and the pedal sinks, pumping the pedal and it still sinks slowly to the floor (10 second).

This I assume clears the any leakage in the master cylinder. It does have new rubbers and to be honest the bore looked in A1 condition. I still have this idea that there may be something wrong / leakiage inside the ABS unit this is on the left hand side inner wing. Hope not that thing looks expensive.

Lauras Dad

[anchorman]

If the pedal is hard with the engine off don't worry. I have a 2006 (pictured to the left) and I can press the pedal to the floor with the engine running and so can everybody else here - its just that nobody ever tries until they have had the brakes in bits!

It is a combination of the servo and ABS/brake assist units working together. If the pedal is solid with the engine off you have tested the integrity of the seals and system. You can replace the lot and it will still do it.

[laura_ph85]

If the pedal is hard with the engine off don't worry. I have a 2006 (pictured to the left) and I can press the pedal to the floor with the engine running and so can everybody else here - its just that nobody ever tries until they have had the brakes in bits!

It is a combination of the servo and ABS/brake assist units working together. If the pedal is solid with the engine off you have tested the integrity of the seals and system. You can replace the lot and it will still do it.

Thanks for that.

Its good to see/hear that a similar car has the same charactistics. My car stops OK and on a sippy road the abs clicks in and out.

Just in case any one else is listening / learning / reading. A salvaged ABS unit is around £200. So would have to get a morgage out to buy a new one from T.

p.s I'm driving a little slower with the price of dev. Achieving 45 to 48mpg non-motorways and 30mpg tugging the caravan (1500kg).

Laura Dad

[Avalon]

Your brakes sound perfectly normal for both the RAV's I have access to. It's perfectly normal that the peddle will go soft over 10 secconds, what did it do before ?

[anchorman]

Your brakes sound perfectly normal for both the RAV's I have access to. It's perfectly normal that the peddle will go soft over 10 secconds, what did it do before ?

Ah ha! Thats the problem - nobody ever checks until they have fiddled with them and then you question if you have done something wrong!!!

If I had a pound for every time somebody has contacted me with a panic stricken voice and said my brake pedal creeps to the floor I would still be in Florida and without the fact that I have been testing brakes for many years there would have been quite a few cars written off!

He's OK now I think.

[bothwell_buyer]

WOT! Back from Floydya already!

One thing not mentioned is whether the fluid has been changed.

Wot you describe is wot happens to my landrover.

With number 1, as you know, the brakes are fairly good - as they need to be otherwise I'd be in the North sea after my 1/4 mile trials!!!

I'd problems with my Humber hawk brakes which we pinpointed to a seal in the servo which hadn't been replaced. Got the servo rebuilt by a specialist down south.

Always found that carrying an anchor and a 12 ton strap can be useful.......

[anchorman]

Not sure its supposed to happen with the landy bothy :o

[Boxsey]

First post to say that I found this thread very useful. I've been just reading these boards for a while now and found some good information on here. In this case I changed the rear pads (they were truly shot and easy to do) and then bled the system because I was concerned about the soft pedal. Like already mentioned here, the pedal was firm with the engine off and then returned to soft when using the car. I know realise that this is how it should be from your posts :) .

FYI prior to changing the rear pads I found the ABS was cutting in very frequently. Too frequently from what I'm used to with my other cars. Changing the rear pads has stopped this. My guess is that the fronts were doing too much work (rears were nearly on the backing plates) and therefore the ABS was being triggered.