Brakes a bit hard

[iainfm]

Hi,

 

The brakes on our 2001 Fabia have always been a bit rubbish (well, in the 18 months we've had it). I was going to put new front discs and pads on the other day, but they're really in quite good nick. The calipers look ok too, and I recently changed the rears (drums, shoes, springs and cylinders).

 

The car stops ok, and passed its MOT recently, but the pedal seems to take a lot of effort to press, as if not all vacuum assistance is there.

 

Is there any way or thing I could check? I've not tried holding the pedal down while starting the car (yet). Should it drop slightly when the engine starts if the vacuum is good?

 

Cheers,

Iain

[Alexandru]

Yes, it should drop a bit. It should feel the same when downshifting, engine braking and applying light pressure on the brake pedal. 

[iainfm]

Thanks, I'll test that next chance I get

[TMB]

The plastic servo pipe can crack and leak vacuum, so check that out. If anything I find the brakes to be a bit too grabby and sharp (over-servoed), so yours don't sound like they are working properly.

Edited 29 April, 2016 by TMB

[Alexandru]

The vacuum pipe that goes into the pump doesn't have a fastener, or at least mine doesn't have. I think it worths inspecting it.

Sent from my iPhone using Tapatalk

[TMB]

The vacuum pipe that goes into the pump doesn't have a fastener, or at least mine doesn't have. I think it worths inspecting it.

Sent from my iPhone using Tapatalk

 

Into the servo you mean?

[Alexandru]

Yes, I'm talking about the pipe that goes from the servo pump to the intake manifold.

[iainfm]

Thanks guys, I'll check these things out.

[iainfm]

Ok, so from the vacuum pump there's one pipe that goes around the back of the engine into the servo. There's a 90deg rubber bend that's clipped to the vacuum pump, which is a bit loose. I'll find/get a jubilee clip to replace it with tomorrow. The rubber part of the pipe is a bit perished, but I don't think it's split/leaking.

 

While the pipe's off I'll try testing the vacuum. There's a bit of engine oil showing at the vacuum pump. Could that be an indication the pump itself is past it?

 

The pipe into the servo is a bit wiggly too, but again there doesn't seem to be a leak.

 

Thanks,

 

Iain

 

PS I tried starting the engine with the brake held down, and it didn't drop at all, so something's wrong somewhere.

Edited 29 April, 2016 by iainfm

[iainfm]

PPS I forgot the important bit - it's a 1.9 SDI, hence the vacuum pump.

[TMB]

Take the vaccum pipe off before the pump and see if there's any vacuum with the engine running. The pump might have failed.

[Alexandru]

After leaving my car 2 weeks my brakes seem to be a bit hard as well, but the discs are rusty and I drove it only 15miles or maybe less. This feeling I get is after driving some other cars meanwhile. Are you sure the way your car is acting isn't normal ? Have you opened the bonnet and check the brake fluid level? Try giving it a run and pump the pedal several times and/or apply high pressure on the pedal for a couple of times.

 

Have you tried to adjust the rear brakes? IIRC, 1.9 sDI doesn't have discs on the rear by default. The procedure is the following (with the engine running):

1. push hard the brake pedal (as hard as you can);

2. pull the handbrake lever (as hard as you can);

3. release the brake pedal;

4. release the handbrake;

5. repeat for a couple of times;

6. check if your service brake is acting better.

Edited 30 April, 2016 by Alexandru

[iainfm]

Hi,

Checked the vacuum pump this morning, and it seems to be find. It's creating enough of a vacuum to stick my finger to it quite hard. Replaced clip-on clip with a jubilee.

Brake fluid ok, and rears are adjusted.

Is it safe to disconnect the vacuum pipe at the servo, in case it's a blocked pipe or the non-return valve is faulty? Other than that, it's either the servo (which looks fiddly to get out) or it's just normal for a car of that era.

Cheers,

Iain

[TMB]

 Is it safe to disconnect the vacuum pipe at the servo, in case it's a blocked pipe or the non-return valve is faulty?

 

Yes perfectly safe.

[iainfm]

Yes perfectly safe.

Thanks, will check next opportunity

[Breezy_Pete]

Did you get to the bottom of this, iainfm? 

 

My missus's car has seemingly gone from being epic at stopping to now requiring a noticeably harder pedal press.  Been all round the drums/shoes and disks/pads, fluid change, and servo vac pipe without finding anything amiss or improving anything. It really feels like the servo's somehow not as good as it was (but not doing nothing either). Doesn't seem to be worsening over time, just a step change for the worse.

 

She's not complaining about it much, so it's not dramatically bad, just not as it should be, in both our opinions.

 

I might stick VCDS on it and see what the manifold vacuum is at idle, and compare with my Polo. I guess it should be reasonably similar. Barking up the wrong tree though I shouldn't wonder.

[Alexandru]

Does the car has ABS ? If if fails, the brake pedal will feel stiffer.

[iainfm]

Hi,

 

No, not had chance since - combination of other things getting in the way!

 

I'd be interested to see your pressure readings though. I could compare and contrast

 

I have noticed the front disks are getting a bit corroded though, so suspect the calipers aren't what they used to be.

 

No ABS on this one.

 

Cheers,

Iain

Edited 21 June, 2016 by iainfm

[Breezy_Pete]

Cheers for the reply Iain, and apologies Alex for not seeing your question.  The car you're referring to, Iain, has a diesel engine, judging by references to vacuum pump? Edit: Ah yes, post #10.

 

The car in question for me has ABS, but as far as I (and VCDS) know it's working fine.

 

I did check inlet mani pressure at idle, but forgot to update.  It seemed to sit at about 316mbar, I think.  Not sure how to compare a petrol engine's manifold vacuum with a diesel engine's pump-created vacuum though, I know nothing about the latter.

 

Having tried a brand new servo vac pipe (and found not a thing wrong with the old one) I'm starting to think it must be a servo problem, but I can't understand how it can get a bit worse, and then not carry on deteriorating?

 

Edit: interesting possibility here?

Edited 21 June, 2016 by Wino

[rum4mo]

I'm guessing here based on very old experience, but I thought that there is no need for a seal there normally as that is a sealed void giving the master cylinder access to the diaphragm face?

Edit:- I seem to remember a 1979 Ford Escort Ghia 1.6 having a weeping master cylinder that filled that void and was coming out that hole. I think that a seal from a 1976 Escort van rear brake cylinder sorted that enough to get its first MOT!

Edited 22 June, 2016 by rum4mo

[Breezy_Pete]

Not sure, but my plan is to have a listen around that area with my stethoscope this evening, hoping to hear some suspicious hissing.

 

Looking at a photo of one off a car, I assume the o-ring does need to seal there, 'cos I can see a big spring that must be the diaphragm return spring, through the hole. That's the main front chamber area.

The blue arrows point at the surface I guess the o-ring seals against, and the red arrow where - judging by the dirt where the o-ring should have kept it clean - it might have been leaking on this ebay one?:

 

Edited 22 June, 2016 by Wino

[rum4mo]

Stethoscope, you are lucky, I'm vanished almost 20 years when we moved house along with a single (out of a set of 4) spark plug for my Cav GSI 4X4 2000 and wife's camera and binocs ( camera and binocs were stashed in GSI 4X4 due to me being at the local BTCC meeting the day before moving ). 

 

Anyway, I can understand a dust seal being in that location, but still a iffy about a vac seal, consider this if there is/needs to be a vac behind that face, then unless the master cylinder can operate with that vac and not ambient pressure  at that point in it then maybe okay.

 

Edit:- loose clips on vac pipes rarely cause issues as the vac should pull the pipe in seal, not so with positive pressure system pipes. Why not try to get a tee piece and check that you are still getting a vac when the pipe work is all connected - ie is the servo body leaking?

Edited 22 June, 2016 by rum4mo

[wiredsoftware]

Hi Wino, did you ever get to the bottom of this?

 

I'm in a similar situation, brakes are OK but not great, I've replaced disks, pads and fluids which has helped a bit but they're still a bit crap. I've checked all the vacuum hose, all in great condition and no leaks (tested with bubble mixture all around). The hoses continue to hold a vacuum after leaving the car off too. Passes the "pump the brakes then hold and start the car" test fine too. No ABS on mine. I think this may be time to replace the servo, but like you I'm surprised that it could be working to some extent, but not at full efficiency.

 

 

Not sure, but my plan is to have a listen around that area with my stethoscope this evening, hoping to hear some suspicious hissing.

 

Looking at a photo of one off a car, I assume the o-ring does need to seal there, 'cos I can see a big spring that must be the diaphragm return spring, through the hole. That's the main front chamber area.

The blue arrows point at the surface I guess the o-ring seals against, and the red arrow where - judging by the dirt where the o-ring should have kept it clean - it might have been leaking on this ebay one?:

 

[pic]

Edited 21 July, 2016 by wiredsoftware

[Alexandru]

No ABS on mine.

That's the point. The non ABS models have a mechanical brake distributor, connected to the rear axle. The ABS equipped ones have a computer which decides how much brake pressure you need. Maybe you're just used to driving cars with ABS which are braking a little bit more 'aggressive'. That's the main reason why I've dumped my project of replacing the rear drums with disks. I don't know how yours is, but my mpi had not it's pads, discs or drums ever replaced since I got it (and without a FSH, I cannot tell when those have been replaced). I can plant my foot hard on the brake pedal, it stops right up and it stays as straight as it could be. My other Fabia, the 74kW model has ABS and it has that first 1/2 if inch when you really need to be careful how much pressure you apply on the pedal. Other than that, it's the same. Just make sure your tires & shocks are in good condition.

Edited 21 July, 2016 by Alexandru

[wiredsoftware]

Could be, although it does feel like I have to give it some welly to get it to stop. I appreciate that it's never going to be as good as my other car with ABS, but if I exerted this much effort in the other one my back wheels would leave the ground!

Edited 21 July, 2016 by wiredsoftware