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mattware49

Hard Brake Pedal & Airbag Light

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HI Guys,

In need of some help please.

I have a 55 plate Mk2 Focus 1.8tdci duratorq engine.

the problem i'm having is recently (past fortnight) every now and then the brake pedal becomes rock hard and doesn't appear to be effective at stopping hte car, this is only when pressing slowly to slow the car, when slamming on/emergency stopping/harsh braking it works fine. Any ideas where to start looking for a problem, i've heard possibly vacuum check valve or vac pipe maybe? if so any one know where i can order one and how much this would be?

 

Also the airbag light has appeared on the dash, doesn't show up anything using the f-super diagnostic tool, any suggestions.

Thanks in advance guys,

Matt

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5 hours ago, mattware49 said:

Also the airbag light has appeared on the dash, doesn't show up anything using the f-super diagnostic tool

Forscan, with an ELM327 can diagnose SRS systems (airbags etc), I am pretty sure.

If you need more info of Forscan, see

Re vacuum servo problem: As you probably know, failure of the vacuum servo system is the likely cause of hard but ineffective brakes.

There should be enough vacuum stored in the servo unit (*), for about 3 full applications of the brakes, even with the engine stopped. You can test this on the driveway: start engine, check normal brake pedal feel. Wait a few sec, stop engine, press brake fully a few times until it goes hard. If the pedal goes hard as soon as the engine stops, then the non-return valve is faulty, so the vacuum leaks away (*).

Diesels have an engine driven pump for servo vacuum. Check the hose from pump to servo. I once had a hose that collapsed internally (no visible external signs), so stopped the system from working on occasions.

Then check the vacuum pump. Probably needs a vacuum gauge, but I expect these can be got quite cheap now. Which cannot be said for the vacuum pump, I believe.

If pump, hose, valve all ok, it must be the servo unit itself.

Obviously this is a critical problem that needs pretty urgent attention!

Peter.

(*) yes I know vacuum is absence of gas, and so cannot really be stored, or leak away, but you know what I mean!

 

 

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8 hours ago, Tdci-Peter said:

Diesels have an engine driven pump for servo vacuum

Some modern petrols, too, I believe. I'm pretty sure my 1.0 EcoBoost has one.

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As for the air bag my light came on briefly it turns out there are connections under seats which in my case was knocked moving the drivers seat back and forth,have a fiddle n press them tight ! Think somebody had said do this after the engine has been stopped for at least half an hour 

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23 hours ago, MrRedman said:

somebody had said do this after the engine has been stopped for at least half an hour

I think it's advised to disconnect the battery for half an hour when working on any part of the airbag system.

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Hi Guys,

just been out looking at it, don't want to touch the vac pipe really until i get a new one with check valve as its pretty seized on so if something breaks i want to be able to replace it.

sussed out a better way to describe the issue if you guys can help any better..... when you have the engine off and pump the brakes and it goes hard, the car does the same with the engine on when lightly pumping the brake to come to a stop, almost identical as to when the engine is off.

If just braking quickly or in one press all is fine and car stops as should.

anyone have any more of an idea if this helps identify the problem any more,

Thank you appreciate the help.

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4 hours ago, mattware49 said:

when you have the engine off and pump the brakes and it goes hard, the car does the same with the engine on when lightly pumping the brake to come to a stop, almost identical as to when the engine is off.

Sounds like either the pipe to the servo is almost blocked, or the vacuum pump is performing badly.

So if you use the brake, wait a while (with engine running), & re-use it, then it is ok?. But if you use the brake multiple times too quickly, then the vacuum does not recover, and the pedal goes hard?

Does that sound about right?

Like you say, go for the pipe first. One other fairly simple possibility: The pump must exhaust its air to somewhere. It may be to inside the engine, or there may be a vent pipe somewhere. If this vent is partly blocked, it will stop the pump from working properly.

Peter.

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9 hours ago, Tdci-Peter said:

Sounds like either the pipe to the servo is almost blocked, or the vacuum pump is performing badly.

So if you use the brake, wait a while (with engine running), & re-use it, then it is ok?. But if you use the brake multiple times too quickly, then the vacuum does not recover, and the pedal goes hard?

Does that sound about right?

Like you say, go for the pipe first. One other fairly simple possibility: The pump must exhaust its air to somewhere. It may be to inside the engine, or there may be a vent pipe somewhere. If this vent is partly blocked, it will stop the pump from working properly.

Peter.

That's exactly what is happening. For the vac pipe. Can this be a silicone hose and is the check valve a universal part? And can any hose be attached to the pump attachment?

Thank you for your help. Really appreciate it.

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3 hours ago, mattware49 said:

vac pipe. Can this be a silicone hose

It must be designed for vacuum duty. A normal pipe will kink or collapse, it has to be reinforced with stiff rings or a coil.

I think the valve is part of the servo, I have never investigates to see if it is available separately. Some else my know?

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I'd suggest that from the symptoms you've described it probably isn't the valve. To test run the engine for a while then switch off and wait for ten minutes or so. Without restarting try the brake. If it is not immediately hard and you are able to pump a few times before it goes hard the valve is ok.

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On Wednesday, July 13, 2016 at 10:10 PM, Tdci-Peter said:

Sounds like either the pipe to the servo is almost blocked, or the vacuum pump is performing badly.

So if you use the brake, wait a while (with engine running), & re-use it, then it is ok?. But if you use the brake multiple times too quickly, then the vacuum does not recover, and the pedal goes hard?

Does that sound about right?

Like you say, go for the pipe first. One other fairly simple possibility: The pump must exhaust its air to somewhere. It may be to inside the engine, or there may be a vent pipe somewhere. If this vent is partly blocked, it will stop the pump from working properly.

Peter.

Ok. I've replaced the pipe and checked the outlet for the pump by completely disconnecting but still doing same trick. Still no luck.

Oil is dripping out the pump outlet though. Is this normal or is it likely a pump seal has gone hence poor performance and oil in pump.

Cheers

Matt

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7 minutes ago, mattware49 said:

Oil is dripping out the pump outlet though

What sort of oil?

Hydraulic fliud could be a failure in the servo.

A small amount of engine oil may be normal. The pump must surely be be piston operated, and the upper side of the piston will get oil from the camshaft area. Some will get past the piston in normal use, and will drain back to the engine via the vent. But too much oil, or if it continues dripping with the engine stopped, would show a worn pump that cannot deliver enough vacuum.

If you can hear of feel air being drawn back into the vent valve when the engine is turned off (after running), then that would indicate a faulty pump.

A leak in the diaphram/piston in the servo unit could also give a similar problem. Sucking air out of a tube connected to the servo might reveal this. (remember brake fluid can be a bit harmfull, though!)

 

 

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57 minutes ago, Tdci-Peter said:

What sort of oil?

Hydraulic fliud could be a failure in the servo.

A small amount of engine oil may be normal. The pump must surely be be piston operated, and the upper side of the piston will get oil from the camshaft area. Some will get past the piston in normal use, and will drain back to the engine via the vent. But too much oil, or if it continues dripping with the engine stopped, would show a worn pump that cannot deliver enough vacuum.

If you can hear of feel air being drawn back into the vent valve when the engine is turned off (after running), then that would indicate a faulty pump.

A leak in the diaphram/piston in the servo unit could also give a similar problem. Sucking air out of a tube connected to the servo might reveal this. (remember brake fluid can be a bit harmfull, though!)

 

 

It's engine oil. No loss in brake fluid at all. Must be from the cam area like you say.

Where to go from here is the question? 

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2 hours ago, mattware49 said:

It's engine oil. No loss in brake fluid at all. Must be from the cam area like you say.

Where to go from here is the question?

Looking at the design and position of the pump, with the vent joining the crankcase breather pipe back to the sump, it does suggest it is intended to be oil lubricated all through. And many vacuum pumps are oil lubricated.

I have a test procedure that might narrow it down a bit. Can you arrange the vent pipe so that it dips into a little pot or jar of engine oil? This may need an assistant, one to operate engine & brake, one to watch the vent.

Pump the brake a few times to ensure the servo has no vacuum, then start the engine, and just let it idle.

On a healthy system I would expect air to bubble out of the vent quite quickly, then slow down & stop.

Apply the footbrake quite hard, and release. Again, some air should bubble out and stop.

Stop engine, and wait. The oil level in the pot should not drop.

Faults detected:

Bubbles continue with engine on idle: Leak in servo, leak in pipe (eliminated now I hear). Leak within pump (eg past piston).

To eliminate servo, disconnect pipe to servo, plug it (airtight), and repeat test. If bubbles still continue, then fault is pump leak / wear.

Bubbles feeble and take a long time to subside, possibly quicker if engine rpm raised: Pump faulty, possibly vacuum side non-return valve.

Oil level in jar drops on engine stop: Faulty pump, vent side non-return valve. (This is why oil is suggested, not water, as it won't matter if it is sucked back into the pump.)

The main point of all this is to try to separate servo faults from pump faults. (I have seen new pumps advertised on Ebay for under £50, but not OEM.) I would guess the servo unit is more expensive.

The alternative is to let a garage try to determine or guess where the fault is, and hope they get it right 1st time!

Any use?

Peter.

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On 18/07/2016 at 8:03 PM, mattware49 said:

Where to go from here is the question? 

Any new or progress? It might me or others in the future.

Peter.

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On Monday, July 18, 2016 at 7:03 PM, Tdci-Peter said:
16 hours ago, Tdci-Peter said:

Any new or progress? It might me or others in the future.

Peter.

Ok. I've tried the test you suggested and here's the results

With servo still in loop the bubbles never 100%stop there is a very slow trickle. It takes a good 10+seconds to get to this stage.

With the servo out the loop (unplugged and bunged up (when removing the plug a loud pop was heard which leads me to believe that the servo is holding vacuum)). The bubbles don't stop at all and when turning the engine off approx 10mm "disappears" from your standard jam jar of oil.

Thus leads me to believe and I hope you can confirm it appears to be a pump issue? 

Thanks in advance

Matt

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1 hour ago, mattware49 said:

With the servo out the loop (unplugged and bunged up (when removing the plug a loud pop was heard which leads me to believe that the servo is holding vacuum)). The bubbles don't stop at all and when turning the engine off approx 10mm "disappears" from your standard jam jar of oil.

My description of the test was a bit un-clear, my fault. Did you block the pipe leading to the pump, or the one to the servo? If it was the one to the pump, I have difficulty understanding why the bubbles were more continuous with the servo disconnected, and the pump inlet pipe blocked.

Also I should have added another test while the servo was connected: Apply constant brake pedal pressure. This will test the servo diaphragm for leaks. Normally this diaphragm has vacuum on both sides, pressing the brake allows some air into one side, which pushes the diaphragm over, and gives the desired braking assistance.

As your main symptom seems to be poor or slow recovery of vacuum between brake actuations, and oil was sucked rapidly back into the pump, it does point to the pump being faulty. If bubbles continued at a similar rate with servo connected, or disconnected with pump inlet blocked, then I think this would confirm it.

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On 28/07/2016 at 5:55 PM, Tdci-Peter said:

Any new or progress? It might me or others in the future.

Peter.

Ok so i took the jump and replaced the pump, no difference. i have noticed however that when you press the pedal in the car there is quite a loud hiss from in the footwell, this tends to correlate with it stiffing up so if you do one quick press its fine and stops adequately with 1 hiss. however if you put your foot lightly on the brake e.g. to creep to a roundabout you hear a slight hiss when you touch the pedal and then another hiss then it goes hard.

I'm presuming this can only be the servo now, is this a bugger of a job and best paying a garage rather than fight with it?

Cheers

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On 02/08/2016 at 6:34 PM, mattware49 said:

is this a bugger of a job and best paying a garage rather than fight with it?

Yessad.pngsad.png

Haynes says the a/c has to be drained & disconnected. Just looked at my car, & I can see why. So that would probably mean two visits to a garage or a/c specialist. It looks fairly awkward to get at, part inside the car, part in the engine bay. Then getting air out of the hydraulics, it is likely to get into the ABS, not sure how good that is at self bleeding.

One little point, have you verified the pump is properly driven by the camshaft? Nothing worn or missing in there?

The symptoms you describe do not really match most of the likely servo faults I can think of, but I have not seen a detailed diagram of the inner workings. They are quite complex, so if all else is ruled out, it must be that. But do double check things like the pump drive.

One other query: I assume the pedal is not slowly sinking while applied. That would indicate a master cylinder leak, and pedal would go hard when servo runs out of travel. But that would be quite a long way, so you would have noticed it. I am pretty sure you would have said if this was the case.

 

 

Edited by Tdci-Peter
Add Query

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18 hours ago, Tdci-Peter said:

Yessad.pngsad.png

Haynes says the a/c has to be drained & disconnected. Just looked at my car, & I can see why. So that would probably mean two visits to a garage or a/c specialist. It looks fairly awkward to get at, part inside the car, part in the engine bay. Then getting air out of the hydraulics, it is likely to get into the ABS, not sure how good that is at self bleeding.

One little point, have you verified the pump is properly driven by the camshaft? Nothing worn or missing in there?

The symptoms you describe do not really match most of the likely servo faults I can think of, but I have not seen a detailed diagram of the inner workings. They are quite complex, so if all else is ruled out, it must be that. But do double check things like the pump drive.

One other query: I assume the pedal is not slowly sinking while applied. That would indicate a master cylinder leak, and pedal would go hard when servo runs out of travel. But that would be quite a long way, so you would have noticed it. I am pretty sure you would have said if this was the case.

 

 

What should the pump drive pin look like. It looked like a massive nail head in the engine head and smooth ended on the pump side. Once pump was removed it was very easy to move up and down.

When pressing the pedal down I can hear a slight hiss whilst foot is on the pedal

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4 hours ago, mattware49 said:

When pressing the pedal down I can hear a slight hiss whilst foot is on the pedal

A hiss with a steady pressure on the pedal does indicate a servo problem to me. It should not require any flow of air to hold a steady position. Assuming the pedal is not slowly sinking, which would be a master cylinder leak.

To check pump drive, I would jack up a front wheel, remove the cam cover, put it in 5th gear, and turn the engine over by turning the roadwheel (use a wrench on wheel nuts if needed), to see if the pump was being fully actuated as the camshaft turned.

But a hiss with steady pressure AND position is almost certainly servo.

 

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Hi, Did you get this sorted, I had a very similar problem, changed the servo, bit of a bugger, but got it done, Servo works fine no hissing etc. Only problem now is I cant seem to get rid of the air from the system. 

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11 hours ago, grajack said:

Only problem now is I cant seem to get rid of the air from the system.

If your car has ABS (most have), then a special procedure is needed to bleed air from the ABS system. Changing master cylinder or servo will allow air into the ABS.

It uses a computer connected to the diagnostic socket. Garages with Ford IDS can do it, but Forscan can also do it on most Fords. You can get Forscan for £16 or less, if you have access to a Windows laptop.

For more info on Forscan, look around this site, or just ask here!

(What engine is it, so I can try to check if Forscan implements ABS Bleed for that engine.)

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