brake problems

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406jim
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brake problems

Post by 406jim »

hi all, got some problems with my brakes 1997 406 2.1 150k, occasionally when driving the pedal becomes stiff and unresponsive and i really have to stamp on it to slow down, its only started over the last couple of weeks but prior to that i found it happened when rolling into a parking space slowly. the fluid level is ok, any ideas welcome, thanks in advance
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Post by addo »

It's well possible the flex lines are failing internally. This on occasion creates a blockage that increases with pedal pressure.

Cheapest good quality brake line sets I've seen are on Fleabay - look for seller "dusty789blue" from memory. They're Teflon lined, stainless outers and will not break down like the originals.
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Post by spider »

I'd agree with Addo. It does sound like that, although fortunately its not common. I've only experienced it on old cars.

What happens is the hose collapses internally, so it starts to act like a one way valve, so the pressure cannot return (hence brakes staying on) , over a time it releases.


The even less common (I've only ever seen this once and it was on a 406, took some head scratching to see what was happening) , if you have ABS, look at the 'rings' on the driveshafts. If these become detached its possible the ABS will detect the front wheels as locked and reduce pressure available to them, this causes a lack of braking as only the rears are doing the work. This is fortunately rare.
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406jim
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Post by 406jim »

addo wrote:It's well possible the flex lines are failing internally. This on occasion creates a blockage that increases with pedal pressure.

Cheapest good quality brake line sets I've seen are on Fleabay - look for seller "dusty789blue" from memory. They're Teflon lined, stainless outers and will not break down like the originals.
what should i do then? buy the line and re-fill and bleed the system?
if so is there a tutorial knocking about for this?
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Post by addo »

The other simple first check is to wiggle the vacuum hose out of your brake booster - there should be a "hiss" of incoming air, even thirty minutes after the motor last ran.

Your generation of 406, has four flex hoses - two front, two rear. During replacement and bleeding, remove the fuse for your ABS controller - which one this is, will be noted in the owner's handbook. Do not drive the car while this fuse is out, except in the most significant of emergencies.

To replace the flex hoses, you will probably need to purchase two "flare nut spanners" - as use will be infrequent, cheaper ones should be fine. I expect they will be 12/14 and 8/10mm but check with both your new hoses to hand, and against the inbuilt coupling nuts.

You can do both the fronts or rears with the car up securely on stands - subframe bolt locations aren't a bad option for these. The following isn't quite a "step-by-step" but some guidance for getting the job sorted reasonably.

DOT4 fluid is used for the topping up (buy a litre), and something like Plus Gas for any connections a little frozen with age or cold. Some clear push on tube for the bleeders is essential, and an old soft drink bottle or similar with hole bored in the cap for the far end of this tubing - the tube should be about 18" or so long, and reach to the bottom of the bottle.

Always refit the bleeder rubber caps BEFORE rinsing away spilt fluid. If they're missing, buy new caps (and new bleeders if corroded).

There's more to it than this, but the other basic rule is to not let the reservoir run too low - when you disconnect a hose, it will begin to siphon fluid out. So you need to be ready; crack the union first then unscrew at the top end, install the new hose and nip up ever so lightly. Keep a fingertip on the new hose lower end as a seal while unscrewing the lower end of the old hose.

Carefully yet quickly, thread in the lower end of the new hose and tighten firm but not gorilla-tight. Now similarly tighten the upper, making sure that it doesn't impart a twist in either the metal line or the flex.

I bleed each after installing - sometimes you need to do another round once all are fitted. You do need a helper to push the pedal; check before commencing that the reservoir is slightly past "Max" (and top up every four or five strokes). With the clear pipe fitted into the bottle via cap and pushed onto the bleeder, use your spanner to crack the fitting ¾ turn just as your helper applies pedal pressure (engine off).

Expect a spurt of fluid. Once the pedal is at the bottom, the helper needs to hold the pedal there while you quickly nip the bleeder shut. You'll notice trapped air in the expelled fluid as a series of fine bubbles - what has to be done, is fluid pumped through until the air bubbles are all but disappeared. This could be ten or more strokes of the pedal; remember to top up the fluid.

With the caliper bled, pedal pressure should be rock hard as the booster has been exhausted of reserve vacuum.
406jim
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Post by 406jim »

Thanks addo,will try and track down those lines and get cracking
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Post by panason1c »

Sounds much more likely to be the brake servo that's faulty to me, its either faulty or not holding sufficient vacuum due to another reason such as the vacuum pump or connecting pipe having a fault.
Last edited by panason1c on 30 Dec 2010, 16:02, edited 5 times in total.
panason1c
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Re: brake problems

Post by panason1c »

406jim wrote:i found it happened when rolling into a parking space slowly. the fluid level is ok, any ideas
A non-working brake servo will cause the brake pedal to be very hard and require quite a lot of foot pressure to activate the brakes even just to slow down............A possibility is that the engine driven vacuum pump is weak and when the engine is at low revs (ie, when parking) it is not producing enough suction for the servo to operate efficiently, also, check the vacuum pipe connections from the pump to the servo for any sign of a leak or damage.

Either way, i strongly suspect either the brake servo booster or servo pump, or the connecting pipe/valve to be the root cause of the problem.
406jim
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Re: brake problems

Post by 406jim »

panason1c wrote:
406jim wrote:i found it happened when rolling into a parking space slowly. the fluid level is ok, any ideas
A non-working brake servo will cause the brake pedal to be very hard and require quite a lot of foot pressure to activate the brakes even just to slow down............A possibility is that the engine driven vacuum pump is weak and when the engine is at low revs (ie, when parking) it is not producing enough suction for the servo to operate efficiently, also, check the vacuum pipe connections from the pump to the servo for any sign of a leak or damage.

Either way, i strongly suspect either the brake servo booster or servo pump, or the connecting pipe/valve to be the root cause of the problem.
that sounds abit more more like the problems im getting, am i right in thinking that the vacuum pump uses the exhaust manifold to provide the back pressure needed?
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Post by dieselnutjob »

spider wrote: so the pressure cannot return (hence brakes staying on) , over a time it releases.
when did he say the brakes are staying on?

if the brakes work but you have to press really hard that's the classic symptom of the servo not working, either due to a broken servo or lack of vacuum supply to it
406jim wrote:am i right in thinking that the vacuum pump uses the exhaust manifold to provide the back pressure needed?
No, it uses a pump driven off the engine. Also check that all of the hoses between the pump and the servo are present and not split. You need to check every hose that has a vacuum supply. I don't know how many things that is on a 2.1. On a 1.9 it's only the brakes, on a HDI it's many things.
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Post by 406jim »

dieselnutjob wrote:
spider wrote: so the pressure cannot return (hence brakes staying on) , over a time it releases.
when did he say the brakes are staying on?

if the brakes work but you have to press really hard that's the classic symptom of the servo not working, either due to a broken servo or lack of vacuum supply to it
406jim wrote:am i right in thinking that the vacuum pump uses the exhaust manifold to provide the back pressure needed?
No, it uses a pump driven off the engine. Also check that all of the hoses between the pump and the servo are present and not split. You need to check every hose that has a vacuum supply. I don't know how many things that is on a 2.1. On a 1.9 it's only the brakes, on a HDI it's many
things.
yeah they dont stay on, from time to time they go stiff and unresponsive, will check all the vacuum pipes tomorrow and see if theres any splits or deterioration
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Post by panason1c »

Update?
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