2015 C4 Brakes

[DHallworth]

Well, they changed the brake fluid on the car and apparently one of the flexi pipes going into the drivers side front caliper was twisted so that’s been straightened up.

Cheryl reckons the brakes felt better but tonight the exact same fault has appeared which is irritating.

Looks like we’ll be having another interesting phone call tomorrow.

David.

[GiveMeABreak]

Frustrating isn't it.... I'm wondering if it the circuit now needs to be bled again - if that twisted pipe was restricting flow - it may mean the circuit has not been able to be properly bled and may still have a lock in there.

[DHallworth]

Well, after another 3 days in the dealership we have an update...

1. They found one of the springs on the rear pads wasn't fitted properly... That's funny as Arnold Clark put new rear discs and pads on it prior to us buying it.

2. They've found a broken vacuum pipe on the air box. They went quiet when I informed them that it was them who last serviced it and then said they only did an oil and filter change on it and are now telling me it needs a new air box as it's the spigot on the air box that's broken.

3. The front discs and pads are warped. I noticed this on Saturday evening when I drove it which is infuriating as they weren't warped when they had it in the last time. They apparently "bedded the discs in" last time they had it so I'm convinced that they've warped the discs which had only done 2k miles when they had it but I can't prove it.

I'm confused about the vacuum leak though. The car has a vacuum pump on the end of the camshaft. Why would a pipe not being fitted correctly on the air box cause the brakes to act up when the vacuum pump will be connected to the brake servo? There's no way the pump would be trying to pull a vacuum on the air box and it won't be generating a vacuum from the inlet manifold with it being a diesel. Well, not unless I'm thinking this through very wrong.

If it will indeed fix the issue I'll get a new air box for it but I'm not convinced.

Would appreciate anybody's thoughts on this as I'm loosing the will to live just now.

David.

[GiveMeABreak]

I'm not sure what is meant in this context by the 'Air Box' David.
This is my understanding of the cam driven vacuum pump:

(1) Vacuum pump. "c" Vacuum pump lubrication. "d" Flexible coupling. The vacuum pump is a vane pump driven directly at the end of the camshaft.	(1) Vacuum pump. "a" Outlet to the vacuum reserve for electrovalves. "b" Output to the brake servo unit. "e" Moving plate. "f" Venting. The rotation of the moving plate creates a vacuum in the vacuum pump.

Role: Vacuum Pump

"a" Outlet to the vacuum reserve for electrovalves.
"b" Output to the brake servo unit.

Supplier: BOSCH.
The vacuum pump supplies the vacuum required to control the following components:

• Control electrovalve for the EGR heat exchanger by-pass (*)
• Proportional electrovalve controlling the variable resistance turbocharger (*)
• Proportional electrovalve controlling the fixed geometry turbocharger (*)
• Exhaust heat saver electrovalve (*)
• Brake servo

I have the checking procedure for the vacuum circuit if you need this, but will need the VIN David as there are differences between engines.

[DHallworth]

Hi Marc,

From what they’ve told me, there’s a spigot that sticks out of the air filter housing that takes a plastic vacuum tube and the spigot has broken.

I’m that fed up with them trying to fob me off now so any troubleshooting advice would be welcomed. The VIN on the car is VF7**************[VIN obfuscated, can be read by forum staff].

David.

[GiveMeABreak]

Ok, so unfortunately I don't have detailed info on this engine - it's the 1.6 HDi 100 FAP (DV6FD)

Do you think this is the bit they are referring to? If it is (1) it's about £163.

[DHallworth]

I’m not entirely sure, Marc. I’m due to be picking it up tomorrow and will find out for sure.

You don’t have a diagram of the vacuum system on the car by any chance, do you?

Thanks,
David.

[GiveMeABreak]

That's what I was looking for and unfortunately don't have for this engine David.

[DHallworth]

Thanks for looking Marc.

[Paul-R]

Is it the small spigot that's broken? Sounds similar to the problem I had viewtopic.php?t=65782

[DHallworth]

I believe that's the one.

If the vacuum pump is directly connected to the brake servo though, I don't see how it'll be affecting the problem that the car is in the dealer for - on the first application of the brakes on the 1st journey after it's been parked up for hours, there is a second or two delay in the brakes doing anything and then they snatch. It happens first thing in the morning after being parked over night, or after it's been parked outside Cheryl's work from 8.30am - 6pm.

Anyway, I've ordered another set of front discs and pads. I got genuine ones off Ebay this time as I'm sick of them blaming aftermarket brakes for their lack of ability to fault find. I refused to pay them £130 for an air filter housing and found a brand new one on Ebay for 55 quid so I've ordered that too.

When neither of these cure the fault they can have it back again. If I could find something suitable to replace it, I'd trade the bloody thing in at the moment.

[DHallworth]

It almost sounds to me as if something is sticking and is coming unstuck when you apply the brakes which would explain the slightly delay and the snatching that we're experiencing. I don't know if it could be something in the master cylinder or the servo though.

[KennyW]

David,

Could it be a sticky piston on the calipers

Kenny

[DHallworth]

I did wonder about that, Kenny.

However, when you drive it for the first time of that day and slam on it pulls up in a perfectly straight line. I'd have thought if it was a caliper sticking then it would have dived off to one side.

[KennyW]

The reason I'm suggesting this, when F/O/S caliper piston started to play up it would appear then disappear until it gradually got worse and really started to bind.

This happened over several weeks.

As you said above first drive hit the brakes hard and it would run fine for several days then come back.

It just a thought and if you replacing the front discs and pads you will soon notice a sticky piston when you wind it back. If I remember the piston kit was £15 -£20 pounds from Brake international for the C5.

Hopefully you'll identify the problem soon'

Kenny