Hiya guys.

Just had a call from my girlfriends dad. He has just changed the servo and pads on his mondeo. Having bleed the system and pumped the pedal till it's rock hard. When he turns the key the pedal goes halfway to the floor (not normally a problem) but then stays there.

I've not looked at the car yet (going over tonight) but assuming there is a problem and he's not being paranoid any tips on where to start looking? Don't want to waste time searching if I don't have to.

Oh it's a 2ltr mondeo 97 reg. Doesn't have ABS (apparently)

If no ABS then bleed brakes with engine on.
May need to bleed all 4 from nearest to master cylinder to furthest then turn engine on, check, then try bleed with engine on.
If this does not work then you may need a pressure bleed system.
The other thing to try if all else fails is bleed nipples in the master cylinder, if you turn on the engine and the pedal goes down then the master cylinder is the problem

[Edited on 29/10/10 by snapper]

From Haynes Manual...hope i helps.

Vacuum servo unit-Testing.

1. To test the operation of the servo unit, depress the footbrake four or five times to dissipate the vacuum,
then start the engine while keeping the footbrake depressed.
As the engine starts, there should be noticeable 'give' in the brake pedal as vacuum builds up.
Allow the engine to run for at least two minutes, and then switch off.
If the brake pedal is now depressed again, it should be possible to hear a hiss from the servo when the pedal is depressed.
After four or five applicayions, no further hissing should be heard, and the pedal should feel harder.

2. Before assuming that a problem exists in the servo unit itself,
remove and inspect the Vacuum servo unit hose and non-return valve.
Examine the non-return valve for damage and signs of deterioration.
The valve maybe tested by blowing through its connection hoses in both directions.
It should only be possible to blow from the servo end towards the inlet manifold.

Update.

Have looked at the car and there is a definate problem. Pedal pumps up nice and hard but once the engine is on it is REALLY spongy. Apparently it's been bled twice, we are going to bleed it again so I know it's been done right. It's had a new servo, master cylinder, pads, disks and vacume hose. But with no change.

Where is the vacume hose valve? something in my mind says this could be the problem. Any other suggestions?

Well we have bled them again but still no joy. With the engine off the pedal pumps up fine and feels solid. With the engine on the pedal goes almost all the way to the floor with very little effort. It's almost like there is too much vacume if that makes sense?

One thing I did notice is that when you come off the pedal the pads seem to move (to my mind at least) a long way off the disks.

Any ideas people as my brain is starting to hurt.

For the record... new pads, disks, servo, master cylinder, vacume hose. System has been bled 3 times.

i had a problem recently when i fitted new calipers - the caliper seals were sticking to the pistons and pulling them back too far.
If it's this, remove caliper, force piston out a bit, lubricate the outside of the piston with some brake fluid and push them back in.

Try clamping the brake flexi hoses and then checking brakes with the engine running, if it is a caliper at fault it should show it up . Have had similar problems on a couple of Vectra's and a Volvo where the problem has been the ABS unit

Does it have rear discs? with handbrake operating on them?? Are the pistons screwed out (adjusted).
If the pistons are not screwed out the the seals could be pulling the piston back to far.

Mine were spongy after replacing them, the pedal would eventually go about 4/5 the way to the floor, but when moving the abs would cut in way before that.