GQ Brakes & Clutch

[feet in 2 camps]

Hello, We have a 4.2l diesel GQ which, when first started, feels like there is no power assistance for the brakes, a mechanic told me that the brakes rely on vacuum from the alternator. Does anyone know if this is true, if so what is the remedy?
Also, the clutch master cylinder was replaced some time ago & since then the pressure required to depress the cluth varies, the Slave cylinder was not done at the time. Can anyone shed light on this & what needs to be done? The clutch still works well but my missus doesn't like driving it now. Cheers.

[Peter @ Aawen4x4]

Do you have the Vacuum assisted Clutch? If you DO, that could account for the variable action, 'cos what you are describing for the brakes is an unwell master cylinder, OR a LACK of VACUUM!! And since the mechanic was absolutely right when he told you that the brakes rely on vacuum from the alternator, well, from the vacuum pump on the back of the alternator!! Low vacuum for the brakes also means low vacuum for the clutch!! Vehicles after about 1995 had a difrnt vacuum pump, down the bottom of the engine on the Driver's side.

[Patrolling Paddy]

Yes you will have the vacuum pump on the Alt (or post 95 see above) and you will find that there is a loss of vacuum somwhere (so long as that IS the prob). It could be a pump not creating enough, it could be a leak in the hoses or 'tank', it may even be a faulty one way valve, it could be leaking through the brake/clutch booster.
Does it only happen on startup after being left for awhile or is it all the time? If it is only on startup it is probably a minor leak and will be harder to find, but if it is all the time then it should be alot easier to find and presents a higher safety risk as no vacuum means huge loss in brake ability (very difficult to operate with no vacuum).

[feet in 2 camps]

Thanks Blokes. The brakes have assistance after a little while so I have been able to use the vehicle. My Auto Electrician tells me the alternator is as good as buggered if the vacuum is shot so I shall investigate the other choices before I replace it. He does suggest a 2nd hand alternator as being much cheaper than a new one. Thanks again, cheers.

[sudso]

I took my GQ (89 model) for a drive tonight, hasnt been started for a week, and it took about 10 seconds for the vacuum to build up for the clutch!
Usually it's instantaneous when I drive it everyday.
Wonder if the vacuum hoses are perishing and need replacing?
The brakes have always been ok though:confused:

The alternator is about 2 years old.

[Patrolling Paddy]

The system is not a perfect seal and will have some leakage over time. If the only time it is present is on initial startup then the loss would be very difficult to find as it would be very minor, however if you have a loss while the engine is running or between starts (daily driving stop start type stuff) then the leak is more substantial and potentially dangerous as the brakes may be very hard to operate one time when your not expecting it.

Sudso if yours is an 89 then 18 years is a good run out of a rubber hose and changing hoses is probably a fair call even if just for preventative measures.

[sudso]

Yeah thanks for that. Glad this thread popped up again, has reminded me to put it on the growing "to do list" again lol.

[Patrolling Paddy]

There might be a few threads that pop up again as I am going through looking for stuff for the BIBLE.

PP