My 500x has just suffered brake failure. I put my foot on the brake, it slowed right down but then the peddle went to the floor. Took my foot off and the pressure was back, then sunk to the floor again.

Managed to get home and had a look underneath. The offside rear brake lines and around that area is soaked in fluid and there is a drip every few seconds. Hopefully it’s just something come loose.

The fluid level is down a bit. Drove it down the M25 yesterday, thankfully it didn’t go then.

That's a little worrying, glad you're ok.

The point of dual-circuit brakes is that a failure in one circuit will leave you with the other. Pedal travel will increase, and braking effort reduce, but still able to stop. Should be able to cope with complete fluid loss of either circuit.

Is this a car you've repaired? And if so, have you worked on that area of the brakes, or was that area affected by the collision if it is a damaged repaired car? If all should still be standard, might be an idea to alert Fiat once the diagnosis is done, if the braking system cannot cope with one circuit failure.

portland_bill said:

That's a little worrying, glad you're ok.

The point of dual-circuit brakes is that a failure in one circuit will leave you with the other. Pedal travel will increase, and braking effort reduce, but still able to stop. Should be able to cope with complete fluid loss of either circuit.

Is this a car you've repaired? And if so, have you worked on that area of the brakes, or was that area affected by the collision if it is a damaged repaired car? If all should still be standard, might be an idea to alert Fiat once the diagnosis is done, if the braking system cannot cope with one circuit failure.

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It was a Cat S. Both doors and the ABS sensor. A couple of wheel speed sensors were replaced including one on that wheel. The ABS pump/sensor was replaced by Fiat about 6 months ago.

There was no impact on that corner and I’ve been happily driving it for about 18 months.

Rather worrying

Not run over anything recently wire plastic twine ect?

typecastboy said:

It was a Cat S. Both doors and the ABS sensor. A couple of wheel speed sensors were replaced including one on that wheel. The ABS pump/sensor was replaced by Fiat about 6 months ago.

There was no impact on that corner and I’ve been happily driving it for about 18 months.

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Have a careful look at the leak area. Try to diagnose as much as possible without disturbing anything. Then once the problem is identified, you'll know where to go from there.

Take some pics, and contact Fiat Customer Care on Monday. Thinkiing more since my last post, whatever the cause of fluid loss, it should not result in total brake loss.

typecastboy said:

It was a Cat S. Both doors and the ABS sensor. A couple of wheel speed sensors were replaced including one on that wheel. The ABS pump/sensor was replaced by Fiat about 6 months ago.

There was no impact on that corner and I’ve been happily driving it for about 18 months.

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Its not old enough for traditional fluid loss issues

Corrosion.. doubt it

Perished rubber.. also doubtful

Wheel cylinders would normally be the 'weak link'

As others have hinted.. there is always the chance of impact damage.. or a sub.system failure

I’m not aware that I’ve been over anything, went round the M25 yesterday to Dartford Fiat dealers ironically.

Will try and clean up the area tomorrow and have a look.

Got my trustee mobile mechanic coming over later this afternoon to have a look. Fingers crossed.

typecastboy said:

Got my trustee mobile mechanic coming over later this afternoon to have a look. Fingers crossed.

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Will be good to know what is found ..

Hope its a simple fix

It’s the flexible brake hose. 1 big cut and a couple of smaller ones. Mechanic is getting the part and will fit for me. I can only think something has caught it. Either that or the missus is trying to do me in.

Is it a location facing the road ?

An MOT tester should have spotted that.. if it was there at that point..

Wow those hoses are tough and it takes something very sharp to cut them.

Check tyres for cuts too?

typecastboy said:

It’s the flexible brake hose. 1 big cut and a couple of smaller ones. Mechanic is getting the part and will fit for me. I can only think something has caught it. Either that or the missus is trying to do me in.

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Should still be able to stop the car with the unaffected circuit. If mine, I'd be squeaking at Fiat about the dual circuit not doing what it should. If no joy there, send an email to Dept of Transport.

It is parked on the road. Sometimes that wheel facing into the road , sometimes towards the pavement.

When he fits the new one I’ll get pictures of it.

The car would almost come to a stop, then the pedal would hit the floor. If I raised it again the pressure would come back then to the floor again. If I stamped on it when on the floor it would snatch and stop all of a sudden.

I’m just glad it went when I had just popped down the road and not when a lorry had stopped in front of me.

I’m going to check my cctv tomorrow just in case!

typecastboy said:

It is parked on the road. Sometimes that wheel facing into the road , sometimes towards the pavement.

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I will ponder that one..

Update on my brake failure. The flexible pipe has now been replaced.

This is the one that failed. It’s a mystery how. Fox chewing, caught on something or someone has cut it.

Checked my CCTV from the night before and picked nothing up with motion recording but a fox would not activate it.

portland_bill said:

Should still be able to stop the car with the unaffected circuit.

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As PB says, it should still stop even with this hose cut - That's what tandem master cylinders are all about! You would expect the pedal to be going much nearer the floor but even then, once it has finished fully depressing the half of the master cylinder which has ceased functioning then you should still get quite a hard pedal and the braking effect should be reasonable.

What is being described here is a pedal which slowly goes to the floor but can be recovered by "pumping" - typical symptom of defective master cylinder seals don't you think?

If it were my car I'd be very carefully and in great detail, checking out the entire braking system before I would have any confidence in it again.

Ps. As someone mentioned above brake flex hoses are extremely tough bits of kit. The picture you've posted of your hose shows damage such as I've never seen in normal use. Much more like the sort of thing you might expect on a serious complete write off.

I would initially say that has been chewed or otherwise attacked by animal or road debris

BUT

If you look and the lowest part of the tube picture, next to the white lettering and almost off frame, then you will see a hairline crack / line crossing 5 of the pipes longitudinal rib lines.

Suggest you try flexing, stressing, teasing that minute hairline crack/marking to see if it develops further.

you could have encounter a pretty serious issue with a given production batch of 500X that has taken all this time to come to light.

Can you PM me your VIN/Chassis number just so we can establish a production date.

With modern "just in time" parts and production lines then we should be able to establish a window of potential other possibly affected vehicles so vehicle owners can check for themselves.

Also I gather from a previous post it is a front wheel brake pipe but not clear id a N/S or O/S front pipe?

I think it looks like it has been chewed. Mice and rats will chew anything, but will probably stop when they get a moouthful of fluid.

A good idea, if not already done, is to check all the rest.

Then inform Fiat. Tell them that the pedal went all the way to the floor, as that should not happen. Be prepared to send them the hose if necessary. If they do not take action immediately, contact Dept. of Transport - website will help, possibly near recalls section.

The hose damage may not be a Fiat fault, but the pedal to the floor is serious and needs to be addressed.