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2.5 Tdi vacuum specification


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Hello all.

My old Superb has developed a hard brake pedal (again, after 6 years, but this time no flooding of battery compartment).

It also sounds like possibly a major vacuum leak as even the characteristic "whoosh" sound on turning the engine off (anti judder inlet valve) is not audible.  Or my vac pump has packed up.  So, I intend on buying a vac tester, does anyone have the specification of what I should be able to read at what engine speed?

Or whatever the specification may be?

 

Also, I have no teen able to locate a vacuum reservoir, as found on many / all variants of the 1.9 tdi.  Is there one?  If there is one, I'd check for any cracks.

 

Many thanks!

 

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  • 4 weeks later...

Just to let everyone know the outcome.

Purchased a hand held vacuum pump / gauge and systematically checked all parts of vac system with it. Everything held vac except the brake servo. Bought a new one, got a good deal on Amazon cost me £85 delivered. It is branded TRW. I noted the original master cylinder was also branded TRW but forgot to check the old brake servo as after 6 hours of battling with it it went straight in the bin! It was satisfying. A note if you do this yourself. You need a T45 torx and a rathet 8mm spanner to fit onto the T45 bit (mine is 3/8 drive and the hex on it fits a 8 mm spanner. You will need to drive the lower long bolt going through the servo due to limited space with the ratchet or normal (slower) spanner fitted into the T45 bit, a bit at a time. Fiddly but possible. You will also need a 22 mm spanner for the two bolts holding the master cyl onto the servo. I didn't have a 22 mm (I have all of them up to 21 but as this discovery was made just after Halfords closed I had I improvise with an adjustable plumbers wrench which did the job all right but took time to undo.

There is also a cross brace between the left and right struts. This is held in with 2 T45 capscrews on each side and one right in the middle. It is just behind the turbo on the V6 in fron of the battery. Pull this cross brace out otherwise there will be access issues for the lower servo screw.

I advise against pulling the plastic clip with the ball joint at the end of the servo rod out of the pedal box. Instead just undo the threaded section of the servo actuator rod from the ball ending, and then just screw the new rod/ servo assembly into the old ball joint bit that is left dangling loose on the pedal box. Ensure you have the correct number of threads as the length is important. from the hex nut to the forward part of rod was 16 thread pitches. Full 4 corner brake bleed was a must which used te best part of a liter of DOT4 and the car is now as good as new.

Edited by oh_superb
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Are you satisfied all the air is out of the braking system?

 

I only ask because I changed a brake pipe on a golf last year and while I was having a brew the bung I was using in the pipe fell out and drained all the fluid. I went round in the correct order bleeding all the brakes twice but my pedal was still a bit soft. A quick look at a Haynes manual suggested the back and front should be bled in tandem first before going round and doing each one and to my delight, it worked. I think there must have been some trapped air in the ABS and the tandem pumping is meant to help.

Edited by SuperbTWM
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I know that air getting stuck in the ABS unit

Can be a bit of a problem to get out. But I am confident it was ok. Initially the squirts were not powerful as the air inside the pipes is compressible. Then I got a lot of spits as the air was getting expelled. The final stage was a good solid pressurised squirt and a hard pedal. This obviously required regular master reservoir topping up. I just made a mistake once when I underestimated the brake fluid consumption when the pressure was solid towards the end of the purging / bleeding process so didn't top up enough and pulled air through. Pedal went spongy again and oh bummer had to re-bleed. But very happy with end result. Just need some new disks, pads, auto tranny oil filter change, new CV boots and timing belt water pump thermostat and ancillary belts :-)

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