Brakes

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galuk1
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Brakes

Post by galuk1 »

Ok so I warned you I might ask some stupid questions and here’s my first.
I took my car out at the weekend (loved it) and I noticed that when I stopped my foot slowly went further and further down on the break pedal to the point where the car slowly started to move, when I took my foot off and reapplied it the car was ok but repeating the above. Now somewhere in my head I have it that the reason for this is air in the break system and to clear it I need to bleed the brakes? I could be totally making that up as mechanically I’m no expert but I vaguely remember that when I was in my cortina many moons ago. Before I actually start tinkering with the brakes :drive: if any of you know the answer it would be appreciated.
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D366Y
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Re: Brakes

Post by D366Y »

Possible master cylinder replacement - Martin at CapriGear stocks them, I've just got one off him
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Re: Brakes

Post by Mr B »

D366Y wrote: Mon Jul 04, 2022 2:59 pm Possible master cylinder replacement - Martin at CapriGear stocks them, I've just got one off him
:agree:
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pbar
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Re: Brakes

Post by pbar »

As an experiment to find the possible cause, press the brake pedal a few times with the engine off. It should soon feel hard to press. If it remains soft then you could be right in that the brakes need bleeding, which is an easy and cheap thing to try, although it may be something else, as previously mentioned.
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Re: Brakes

Post by Mr B »

pbar wrote: Mon Jul 04, 2022 4:13 pm As an experiment to find the possible cause, press the brake pedal a few times with the engine off. It should soon feel hard to press. If it remains soft then you could be right in that the brakes need bleeding, which is an easy and cheap thing to try, although it may be something else, as previously mentioned.
I always thought this test was for checking the operation of the servo I.e. engine off, pedal should go hard with no vacuum assistance from the engine, have I been wrong all these years? :doh:

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Re: Brakes

Post by pbar »

You're not wrong Wayne, does indeed also verify function of the servo.
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Re: Brakes

Post by Mc Tool »

Sounds like the main seal is worn in the cylinder . What you can do is ( engine running , car stationary ) is apply light pressure to pedal and note the pedal dropping as you describe , release pedal and then quickly stamp on it like your trying to break the back off your seat........if it now holds it usually indicates a worn rear piston seal ( there are two main pistons and seals in a tandem cylinder ) , if it still leaks down you most likely have a worn or corroded cylinder. The added pressure of quickly stamping on the pedal forces the outer edges of the seal out against the cylinder wall a bit more than usual.If the cylinder wall is good it will hold if its not ..... aint never going to seal . The seal is actually like a one way valve which will hold pressure in front of it but when released allows fluid from behind the seal to flow over it .........much like the leather seal in a push bike tire pump.
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Re: Brakes

Post by Peter-S »

Mr B wrote: Mon Jul 04, 2022 8:58 pm
pbar wrote: Mon Jul 04, 2022 4:13 pm As an experiment to find the possible cause, press the brake pedal a few times with the engine off. It should soon feel hard to press. If it remains soft then you could be right in that the brakes need bleeding, which is an easy and cheap thing to try, although it may be something else, as previously mentioned.
I always thought this test was for checking the operation of the servo I.e. engine off, pedal should go hard with no vacuum assistance from the engine, have I been wrong all these years? :doh:

Wayne
Pump it hard and keep foot on the brake and start engine. It will depress slightly if the servo is Ok
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Re: Brakes

Post by Peter-S »

Mr B wrote: Mon Jul 04, 2022 4:01 pm
D366Y wrote: Mon Jul 04, 2022 2:59 pm Possible master cylinder replacement - Martin at CapriGear stocks them, I've just got one off him
:agree:
If it's a 2.8 I don't think Martin has them.
The other day he said he couldn't get them any more.

I do suspect a Master Cylinder though. The fluid will be leaking slowly around the seals so the continued brake pressure means the pedal gradually goes to the floor.

Look for a Granada 2.8 ATE Master Cylinder as they will fit. Martin did suggest they weren't available either but someone said they had ordered one the other day. If not you could try a new seal kit or get the current cylinder bored and sleeved.
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galuk1
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Re: Brakes

Post by galuk1 »

Ok, So as it’s the weekend I took it out again and this time I carried out the experiments you guys have suggested.
1. Engine off and pressing the brakes - all stays hard.
2. Engine on and pressing the brakes hard all ok
3. Take the car for a drive and brake hard - all ok
4. In traffic if I keep hard pressure on the brakes all ok.
5. Engine on and light pressure then it drops.

So it seems that it only does it when I brake gently or keep the pressure light the I can feel the pedal getting closer and closer to the floor. So if I’m going down hill and gently braking the it does it or in light traffic then it does it.

So does this mean it’s a worn seal? If so is that something I can do myself or does it need a more experienced guy to do it?

Thanks
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Re: Brakes

Post by Mr B »

galuk1 wrote: Sun Jul 10, 2022 9:02 pm Ok, So as it’s the weekend I took it out again and this time I carried out the experiments you guys have suggested.
1. Engine off and pressing the brakes - all stays hard.
2. Engine on and pressing the brakes hard all ok
3. Take the car for a drive and brake hard - all ok
4. In traffic if I keep hard pressure on the brakes all ok.
5. Engine on and light pressure then it drops.

So it seems that it only does it when I brake gently or keep the pressure light the I can feel the pedal getting closer and closer to the floor. So if I’m going down hill and gently braking the it does it or in light traffic then it does it.

So does this mean it’s a worn seal? If so is that something I can do myself or does it need a more experienced guy to do it?

Thanks

I still think the master cylinder is shot, as for repairing it yourself only you can really answer that question, but as this is brakes we are talking about I would play it safe and get either a new master cylinder or have the current one refurbished by a pro.

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D366Y
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Re: Brakes

Post by D366Y »

I also think the master cylinder is gone - sounds pretty much identical to what was happening to my GL and that was a master cylinder change and all sorted

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Re: Brakes

Post by SCP440 »

There are companies that will refurb brake master cylinders and in fact most brake components including servos. I had some calipers done for my other classic and they came back as good as new.
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Re: Brakes

Post by Mc Tool »

:agree:
But they aint that hard to sort . Basically pull it to bits ( see you tube tutorials )check cylinder bore , clean the bits , fit new seals where the old ones were and put it back together .
Checking the cylinder bore is a really good look at it ,looking for pitting /corrosion and or scoring .
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Re: Brakes

Post by Mr B »

Mc Tool wrote: Thu Jul 14, 2022 7:15 am :agree:
But they aint that hard to sort . Basically pull it to bits ( see you tube tutorials )check cylinder bore , clean the bits , fit new seals where the old ones were and put it back together .
Checking the cylinder bore is a really good look at it ,looking for pitting /corrosion and or scoring .
I get what your saying but on the flipside Who wants to be a millionaire's questions are easy.....If you know the answers
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