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So when i got the P38 the brake system was broken. The pedal was spongey and brakes were barely effective, one press of the pedal had the pump running and the lights on the dashboard flashing up. It did stop, but the travel was long and the brakes were really weak.

I replaced the brake accumulator, and did a full system bleed, and the problems seemed fixed.

However when driving the brakes dont seem all that powerful.

I've noticed that on startup, the brake pump runs for quite a while, then once driving, every 2 or 3 applications of the brake you hear it start up and run for a few seconds.

Once driving the pedal seems firm, but theres not a huge amount of power unless you really lean on it. Maybe its just an old car thing, and i'm more used to modern stuff. I dont remember my old trooper being quite as bad though.

Any thoughts?

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The pump running every 2 or 3 applications is normal, it's topping up the pressure as you are using it. The brakes work well but the pedal is heavy (on mine anyway) and can feel a bit 'dead' until you get used to it. There's two totally separate circuits too. The conventional hydrostatic circuit only works on the front brakes and the powered circuit (which is simply opening a valve to allow pressure from the accumulator to the calipers) works on all 4 wheels.

With no pressure in the power circuit the pedal should still be firm and not spongy unless there is still some air in there, although it needs an awful lot of pressure on the pedal (like, both feet) to stop the car. Air in the power circuit will give a very slight delay between hitting the pedal and the brakes coming on.

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Worth checking your brake pads in case someone's fitted Sh!tpart or something in the past. Fitted Mintex pads to the blue one and got a great pedal and plenty of feel without having to push too hard.
Fitted Mintex to the black one and at the moment the pedal is heavier than the blue one as pads haven't bedded in fully yet.

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yeh i guess at some point i'll have the calipers off and clean everything up, grease all the sliders and make sure pistons are all free and check the pads while i'm in there. Its not went far in 5 or 6 years so might be a bit siezed.

They dont feel spongey any more, the pedal feels fine, it just requires a lot of pedal effort to generate good retardation.

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I find them powerful and progressive, with good feel. Good feel is, of course, subjective and the pedal is stiffer than modern overservoed shopping trolleys.

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i think it might well just be the old-car vs new car thing.

My A4's brakes used to be fine, but since driving the 330d and B250e they now feel pretty poor. The P38 is worse than the A4 though.

A good hard shove on the pedal and it certainly seems to stop, and the MOT tester had no issues with it. I'll try some vigorous braking at higher speeds next time i have it out and about.

Is it normal for the brake pump to run for ages at first startup?

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Aragorn wrote:

Is it normal for the brake pump to run for ages at first startup?


Define ages!
From standing for a while cold, both of mine run the brake pump for around 8s, the TC light goes out after around 5s

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If the pressure bleeds down out of the system (eg overnight) it can take up to 45 seconds for it to pump the pressure back up and charge the accumulator.

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My pump runs for several seconds on startup. My brakes work well and stop the car nice and quick but I've got bugger all feel through the pedal.

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yeh it took a good 20-30 seconds for the TC light to go out and the pump kept running for a bit longer.

Had it out on the motorway today and they're definately lacking. Will have to strip things down and investigate!

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If it's only been stood for a couple of hours it shouldn't take that long to get up to pressure, but it isn't unusual if it's stood overnight,

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That was overnight. I guess as long as its not indicative of a fault i can ignore it. Other more important issues to concentrate on!

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Stripped the front brakes today and had a look. Everything was clean and free. Pistons all moved easily, silders free and pads moved easily in the carrier. Pads are Mintex brand. Disks look pretty good as well, no pitting or corrosion.

Will check the rears as well maybe tomorrow.

I did notice the ball joint on the drivers side track rod was fubar, boot has split and its all rusty inside, so that needs sorted!

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Pulled the rears apart tonight.

Again the disks look new, pads are TRW brand so no crap been used. The NSR caliper is new, but the bottom slider pin was siezed quite badly. managed to free it off, got it all lubed up and working and rebuilt.

Offside caliper wasnt new but piston did move with some persuasion. again disks and pads all good, and again the bottom slider pin was a bit stiff though not as bad as the other side. Oddly when i took that one apart it was seriously pitted and corroded, so i'll get a new slider for that side.

Is there any forum members local to me (fife, scotland)? Be useful to have a go in another P38 to compare!

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I think Mace and Gordon are in Scotland, so they must be near you. It's only a little place isn't it?!
:)

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I could probably swing by on my way up to Dundee at some point?

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That might be handy, i'm right on the A92 in Glenrothes, so literally driving right past me if you take the scenic route to dundee.

Where about are you based? I work in Loanhead which might be closer?

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I'm a bit outside Glasgow but I work in Hamilton, neither of which are especially close to Loanhead. I do need to go through there at some point and visit a friend's parents at some point though...

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Well if your passing by can always ping me a message and see if it happens to line up. If i'm over glasgow way i can always give you a shout! :)