Focus 06 1.8 TDCI Brake Fade/Assist Problem - Servo?

[H22A]

Hi

I have a problem with my brakes fading/just not stopping sharply The problem has been around for a few weeks (starting literally 3 days before my MOT) and in that time the car actually passed its mot with nothing said about the brakes. Tbh I was expecting it to fail due to the brakes, but it didn't. I had the MOT and service done at a main Ford dealer, all I got back on the job sheet was "brake fluid boiling temperature too low" and a cost to replace the brake fluid.

So here's the problem. Normal driving pootling around town the brakes feel fine. I wouldn't say 100% but 95%. However, if you have to brake heavily or unexpectedly, for the first second or so the brakes stop sharply, but after that they just fade off and the car comes gradually to a halt, this could be anything up to about 5 seconds to actually completely stop. The brake pedal feels ok to start with, but then very hard after about an inch of pedal depression. In fact it's probably too hard to push any further after that. It's not spongy at all, but if you repeatedly stamp on the brake pedal hard you do get more stopping effort.

The day before the MOT, the car had 4 new tyres fitted and the fitter said that the pads were low, and the discs below manufacturer recommended limit. When I explained the "brake fade" problem I had been experiencing for the previous couple of days they said that the brakes were getting too hot, and that I should have new discs and pads all round, which I did. However, the problem was exactly the same after the new pads and discs were installed but there was no more time to investigate, so I put the car in for its MOT expecting it to fail. As mentioned above it didn't.

So I have now replaced the brake fluid with 5.1 as the "boiling point" issue mentioned after the service seemed to make sense with the brakes fading and also replaced the 2 rear calipers as the nipple stripped the thread on one and wouldn't re-tighten sufficiently on the other! The brakes were bled properly but the problem persists.

I am now left wondering what else it could be.

The master cylinder seems fine, there's no classic symptom of the pedal creeping to the floor. So I can only assume it's vacuum related. I've checked the pump and that's sucking fine, and the non return valve only works in one direction as it should. This now leads me all the way back to the servo unit. I suspect that it's not holding it's vacuum. However I am getting no sound of a breach as I can't hear any hissing of air ingress spoiling the vacuum and if have the engine running and then switch the ignition off and push the brake pedal down, I do get (only) one "whoosh" as the pedal is depressed but then the pedal is rock hard again. According to the Haynes manually it should be 4 or 5 pushes with accompanying whooshes until the vacuum is depleted. Also, if I pull the vacuum tube off I do get a little whoosh so there must be some vacuum in there, right?

I'd really be grateful to get some advice on this. Has anyone had the same experience? Basically I've started at the wheel to diagnose the problem and now got all the way back to the servo, so the problem can only be on this side, can't it? The car has cost me around £900 in the last month (4 tyres, discs, pads, full alignment, calipers, service, MOT etc) and I just need it sorted now!!!

Thanks :-)

 

[Tdci-Peter]

On 16/07/2016 at 10:54 PM, H22A said:

if you have to brake heavily or unexpectedly, for the first second or so the brakes stop sharply, but after that they just fade off and the car comes gradually to a halt, this could be anything up to about 5 seconds to actually completely stop. The brake pedal feels ok to start with, but then very hard

Almost got to be a leak in the servo diaphragm.

I am surprised the fitter did not recognise the hard pedal symptom straight off. The "hot brakes" comment by him was utter nonsense, for fade after just a couple of seconds use of the brake!

With the brake pedal released, there is vacuum on both sides of the servo diaphragm. On braking, air is admitted on one side, pushing the diaphragm and its piston over until hydraulic pressure balance stops further air entry. Thus the servo gives accurate proportional aid to braking.

If there is a leak in the diaphragm, then during braking, air from the high pressure side will pass to the vacuum side, and if the pump can not cope with the flow, vacuum will be lost, and servo assistance will be lost. Result is a very hard pedal, that requires massive effort to get much brake force.

A couple of tests:

On repeated brief brake applications just to the point of hard pedal, how long does it take for the vacuum to recover?

On turning the engine off, how long is it before vacuum (for the "one whoosh") to be lost (ie wait a while between engine off and applying the brake)?

Vacuum recovery should be quick, if not pump or hose may be suspect.

Vacuum should hold after engine off for a few minutes, if not, a leak may be in the pump, hose, or servo casing.

If those two tests pass, then I think there is no choice but to remove & test or replace the servo.

(If you can access the vent pipe from the pump (usually back into the crankcase), then it may be possible to test if there is a continuous air flow while constant pressure is applied to the brake pedal. This would pretty much confirm the diaphragm leak)

I suspect that may not be the news you wanted, but I can not see any real alternative!

Peter.

 

[Tdci-Peter]

On 16/07/2016 at 10:54 PM, H22A said:

Basically I've started at the wheel to diagnose the problem and now got all the way back to the servo

Any news or progress? Might help me or others in the future.

[Dave84]

Hi all,

 

I'm encountering Hard Brake problems with my Ford Focus mk2 1.8TDCI 2006, the problem started after having some pads replaced, as it was very difficult in applying the brakes and at first I could manage reving the engine to restore a bit of vacuum? but now after replacing first the Vacuum Pump, and now master cylinder could it actually been the Servo all along as apparently they are rare to fail? 

 

If someone could help that would be great

[adecashmoney]

On 07/01/2017 at 6:02 PM, Dave84 said:

Hi all,

 

I'm encountering Hard Brake problems with my Ford Focus mk2 1.8TDCI 2006, the problem started after having some pads replaced, as it was very difficult in applying the brakes and at first I could manage reving the engine to restore a bit of vacuum? but now after replacing first the Vacuum Pump, and now master cylinder could it actually been the Servo all along as apparently they are rare to fail? 

 

If someone could help that would be great

Any update as regards this issue . I have same problem with a car I have just won on eBay. Thanks 

[sully83]

Hey guys hope you dont mind me piggy backing on this post im after a name of a part on my engine its a 2005 1.6tdci Ford Focus it think it called the vaccum pump not sure but had to change the breather pipe as in picture because of an oil leak and is now sorted but once cleaned the oil off i noticed a leak on what look like a seal where the arrow is pointing does any body know the name of this part please

thanks

sullydnb5@gmail.com

[Tdci-Peter]

2 hours ago, sully83 said:

i noticed a leak on what look like a seal where the arrow is pointing

Looks like the vacuum pump to me.

If engine oil is leaking out of a seal up in the camshaft area, I would first check the crankcase breather system is working ok, no blocked or kinked pipes. With the engine on idle, remove the oil filler cap, and hold a thin piece of card over it (too big to get sucked in!), it should be drawn towards the hole, though it may shudder a bit. If blown away, there is a problem with the breather system. Pressure in the crankcase will cause oil leaks.

Also see:

https://workshop-manuals.com/ford/c-max_2003.75_06.2003/mechanical_repairs/2_chassis/206_brake_system/206-07_power_brake_actuation/diagnosis_and_testing/removal_and_installation/brake_vacuum_pump_1.6l_duratorq-tdci_(dv)_diesel/

[Chris wheeler]

Hi this definitely your servo I have the same problem garages will tell you its the vacuum pump I had mine replaced and it changed nothing.. Its almost as if garages avoid replacing servos as its such a big job. You can get a servo from a breakers yard for about £30 but then your problem lies with getting someone to fit it. You will need to have your aircon system bled and regased after your servo has been done. I hope this helps and if you need anymore info get back to me.