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[Road Hog Mad]

Not had much look over at vauxhall forums so decided to pop over here being an x mv6 owner

Right so I switched to the 1.7 DTI, as I like the 600 miles between fill ups and not the 200 lol.

Anyway, got a brake fault!

Will try and give you a quick line of events...

When braking the brake pedal goes hard, the car still stops but it is as if the rear brakes are only working.

If you pump the pedal with the car off and switch it on the pedal sinks to the bottom.

I have replaced the master cylinder as it was full of poo (genuine part) and its still the same.

Brake fluid change (when bleeding the pedal sinks nicely to the bottom as it should, when all nipped up the pedal goes hard again).

Prior to changing the master cylinder I had it brake checked at work and the front brakes where not working, after replacing the master cylinder the brakes worked (passed an m.o.t and random free kwik fit brake check) but the pedal is still hard, and by christ you have to stand on the pedal. Both the m.o.t'er and kwik fit man commented on the brake pedal but said it passed.

Prior to the pedal going hard it was an intermittent going hard fault but now it is permanently hard.

Someone has said that the front brakes have seized, but i find this hard to believe that they would both seize together.

Occasionally when slowing down on a slip road, i.e. gradual braking they feel like the want to grab and work properly.

Occasionally the abs light comes on but will reset if turned on and off (pedal hard either way).

Any suggestions?

[martin42]

Air in abs unit maybe

[Lazydocker]

Sounds like a servo (vacuum) issue from what you've described

[Andy B]

....
Someone has said that the front brakes have seized, but i find this hard to believe that they would both seize together.
 ......

Have you looked? Does the piston move when you apply the brake pedal ................... don't allow the piston to pop out of its bore though  Do the pads move/slide within the caliper?

[JimE]

Slave cylinder?

[Andy B]

Sounds like a servo (vacuum) issue from what you've described

The vacuum pump on my 1.7 diseasal was driven from the cam, but I think some others are driven from the alternator 

[Lazydocker]

Sounds like a servo (vacuum) issue from what you've described

The vacuum pump on my 1.7 diseasal was driven from the cam, but I think some others are driven from the alternator 

Some certainly are

[Marks DTM Calib]

Yep, check for vac from the vac pump.

The 1.7 diesel isuzu units (1.7 DTI Y17Dt engine at that era) have the vac pump on the alternator, the Vx units have it cam driven.

[Road Hog Mad]

If I pull the pipe off the alternator you can feel it sucking so that's working fine, I replaced the vacuum pipe as well from the servo to the alternator pump as that has a valve in it which was broke.

I am going to check the front brakes, but if you stand on the pedal hard for the front brakes to work does that mean they are still seized?

Someone has mentioned a brake compensator fault, any suggestions on this?

We have bled the brakes when we replaced the master cylinder (have I got this right? the master cylinder being that thing on the front of the servo?), so would this not bleed the abs unit?

Will strip down front brakes and see if they are working, but as mentioned they work when pedal pressed hard.

 

[Marks DTM Calib]

If I pull the pipe off the alternator you can feel it sucking so that's working fine, I replaced the vacuum pipe as well from the servo to the alternator pump as that has a valve in it which was broke.

Not a great check as there could be a leak elsewhere, needs a vac gauge fitting whilst running to see what is realy happening.

IS the valve you fitted installed the correct way round.

There is a load compensator on the Astra G near the rear torsion beam but, this would affect rear brakes and not the front ones.

[Road Hog Mad]

The valve fitted is the correct way.

When I have time I will do a full check on vacuum pump and see if its sucking enough, anyone know what it should suck? lol.

And if anyone else has any suggestions apart from buy another omega, post here

Thanks again!