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[Andy A]

My Sons friend wants me to look at her brakes for her. About a week ago she drove the car and found the brake pedal was spongy.

If the brakes are pumped a few times so they go firm the car will do a full journey and the brakes will feel normal. But after going shopping for the return journey the brakes have to be pumped again until firm and then they will be fine for the whole journey back.

Passenger side where the servo is there is a very notable load hiss from inside the car that disappears, once the brakes have been pumped and firm up before a journey. The hiss is not there throughout the journey. I have not had chance to test the car myself yet. 

What do you think the problem is, servo going bad?

Thanks

[Doctor Gollum]

Hiss is vacuum being expended... Your Omega does it too, albeit less noticeably due to the way the car is designed Once engine is running, there's a permanent vacuum, although diesels usually have a dedicated vacuum pump due to the different inlet manifold pressure compared to a petrol...

Spongy suggests a fluid leak rather than a vacuum one. This could be within the master cylinder, but don't forget to check inside the rear drums (if fitted)

[Andy A]

Hiss is vacuum being expended... Your Omega does it too, albeit less noticeably due to the way the car is designed Once engine is running, there's a permanent vacuum, although diesels usually have a dedicated vacuum pump due to the different inlet manifold pressure compared to a petrol...

Spongy suggests a fluid leak rather than a vacuum one. This could be within the master cylinder, but don't forget to check inside the rear drums (if fitted)

That was my first thought about a fluid leak. But wouldn't the brakes go spongy again through the journey? These stay firm.

[TheBoy]

If fluid level not going down, free up all calipers.  If drums at rear, check the adjuster is working.

[dave the builder]

If fluid level not going down, free up all calipers.  If drums at rear, check the adjuster is working.

good advice , and once you've checked for no leaks, also replace the brake fluid
and do a sustained test of the brakes under pressure after to make sure there is no further pedal creep .

[Andy A]

It is drum brakes on the back. I'll see if I can have a good look at her car this week.