MonzaPhil
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Right, bit of an odd one which I hope someone can help me with. We have a non ABS, Diesel Corsa commuting machine.
The brake pedal is rock solid but very little or no brake effort possible, all the components in the brake system are new or proved to be working. This has happened before just the once (hence all the replaced bits) and Mrs MonzaPhil said it was after driving through some water. This sounds a bit odd to me but it seems to be the only common thing.
Any ideas please?
The handbrake is poo and I'm told that the adjustment of the rear brakes is quite critical on these.
(none of this would happen on a seventies Vauxhall....)
Thanks all.
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Rear brakes drums then?
If so, they must be adjusted correctly
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taurus
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Rear brake balance valve?
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Dec 14, 2012 10:30:59 GMT
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Servo, or the vacuum pump what drives it. I can't think of anything else that would leave you with a rock hard pedal but still some braking effort.
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bl1300
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Dec 14, 2012 11:59:36 GMT
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Got to be power assistance related for those symptoms my bet is servo or the pump as jrevillug says. Poor adjustment on the shoes will introduce play into the pedal normally.
Try disconected the vacuum line from the servo and see if this makes any difference, then use a vacuum gauge and see if there is a vacuum registering from the same line. If there is a vacuum then the servo is at fault if there isn't you need to be looking at why, so split pipes or dodgy pump.
edit to add.
These checks need to be done with the engine running.
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Last Edit: Dec 14, 2012 12:00:18 GMT by bl1300
Current fleet.
1967 DAF 44
1974 VW Beetle 1303s
1975 Triumph Spitfire MkIV
1988 VW LT45 Beavertail
1998 Volvo V70 2.5
1959 Fordson Dexta
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taurus
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Dec 14, 2012 12:19:24 GMT
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Maybe I am reading it wrong, but I read the original post as saying the pedal is hard with no braking effect. A dud servo would make the pedal harder, but the brakes would still operate.
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bl1300
Posted a lot
Posts: 1,678
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Dec 14, 2012 12:54:01 GMT
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Maybe I am reading it wrong, but I read the original post as saying the pedal is hard with no braking effect. A dud servo would make the pedal harder, but the brakes would still operate. Yes but they would not be power assisted. The purpose of the servo is to magnify the force applied to the pedal. As such if its not working and you press the pedal with the same force you would with the servo working you will get some braking effort but no where near as much as if the servo was working. If you are getting no brake effort at all at the wheels have you checked there is nothing jamming the pedal, such as rubbish from the footwell kicked up behind the pedal and stopping it from moving? |
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Current fleet.
1967 DAF 44
1974 VW Beetle 1303s
1975 Triumph Spitfire MkIV
1988 VW LT45 Beavertail
1998 Volvo V70 2.5
1959 Fordson Dexta
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Dec 14, 2012 13:17:12 GMT
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Maybe I am reading it wrong, but I read the original post as saying the pedal is hard with no braking effect. A dud servo would make the pedal harder, but the brakes would still operate. It's quite astonishing how hard you need to mash the pedal to get some stopping power with a heavily servo-assisted modern that's lost it's servo - both feet required in my experience. |
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Last Edit: Dec 14, 2012 13:17:44 GMT by jrevillug
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bortaf
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Posts: 4,549
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Dec 14, 2012 13:42:51 GMT
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Maybe I am reading it wrong, but I read the original post as saying the pedal is hard with no braking effect. A dud servo would make the pedal harder, but the brakes would still operate. It's quite astonishing how hard you need to mash the pedal to get some stopping power with a heavily servo-assisted modern that's lost it's servo - both feet required in my experience. so true way way harder than a set up designed for no servo, lost the vac pump on my old lucida and bent the steering wheel levering against it to stop the dam thing, "usually" it the vacume pump but servos are known to split the diasphram as well ? |
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R.I.P photobucket
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v8ian
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Dec 14, 2012 17:59:12 GMT
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don't vauxhall use a vacuum pump on the back of the alternator, I seem to remember they are not as reliable as they could be,
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style.
Austin A35van, very different------- but still doing it in style, going to be a funmoble
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MonzaPhil
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Think like a man of action, act like a man of thought
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Dec 14, 2012 18:10:27 GMT
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Yep, pump is on the alternator. It's been suggested the servo may be filling up with water, as this has only happened in very wet conditions, then draining out and not showing any further signs of malfunction. I reckon the pedal will snap before the brakes do anything to slow the car. I've driven some scary things and this is now #2 on the list behind the Mk2 Cortina without any brake fluid in it. Will take everything apart tomorrow and report back. Thanks folks  |
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Dec 15, 2012 21:47:31 GMT
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Is the bulk head full of water under the scuttle panel? The drain holes may be blocked and filling the "bulkhead up" - where the servo is situated. Seen this happen on Audis before and I know the Vectra Cs suffer from blocked bulkhead drain holes.
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taurus
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Personally - my experience of cars with failed servos is that it is just as easy to lock the wheels under braking, you just need to press the pedal harder. So it depends how hard the OP is pressing the pedal. A reasonably fit person pressing a pedal with a failed servo ought to be able to lock the wheels no problem. If they ain't locking at all then I suspect it's something other than just the servo - unless they are just not pressing the pedal very hard.
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MonzaPhil
Posted a lot
Think like a man of action, act like a man of thought
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Dec 16, 2012 14:25:14 GMT
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I was pressing the pedal as hard as you would if you were heading for the side of a building and the brakes weren't working..... Had to postpone my investigation as MonzaNikki tried to seperate my head from my body on Saturday morning and I'm still not feeling quite right. Silly modern cars. |
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taurus
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Dec 16, 2012 16:17:24 GMT
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I was pressing the pedal as hard as you would if you were heading for the side of a building and the brakes weren't working..... Had to postpone my investigation as MonzaNikki tried to seperate my head from my body on Saturday morning and I'm still not feeling quite right. Silly modern cars. Oh dear - doesn't sound good. Well coming back to the issue re. the brakes. Even with a dud servo if you're pushing the pedal that hard the brakes ought to lock the wheels. So I'm not convinced this is just a servo issue. |
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MonzaPhil
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No, me neither, but given the possibility of it sucking in water and hydraulic-ing I'll start with that. Vacuum pump at the ready too but I doubt it's that. Has had fluid change and master cylinder out, that is fine, no sign of corrosion on the pushrod, no contamination in the fluid, no loss of fluid. Front discs and pads renewed a few months ago, calipers looked fine, pistons moved in and out fine, rear drums and shoes were a pain in the rear to get to give any effort. Any thoughts and suggestions still gratefully received. Have a big, cool truck.  |
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RobinJI
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"Driven by the irony that only being shackled to the road could ever I be free"
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Dec 17, 2012 15:58:52 GMT
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How the brakes work without the servo will come down to how much assistance the servo's actually giving. My Scirocco's pretty ok without the servo, hard but no big deal, you can still stop the car fine. My old A4 on the other hand, after a few presses to use up the remaining vacuum in the servo the brakes did very little, hard to slow the car to a stop at all and no hope of locking the wheels.
I'd agree with it being a servo issue, simply because it sounds like all the hydraulics are in good order.
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bl1300
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Dec 17, 2012 18:15:47 GMT
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I second what RobinJI said there. When I was been towed home after the l200 lunched its engine the brakes where scarily bad I don't think I could have locked the brakes up if I tried and was glad to be on a bar. Just rolling it into the workshop on gravity I had to press rather harder than I would have liked to stop it from about 5mph. However when it was back together again with power to feed its servo it registered 92% efficient on a calibrated brake tester.
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Current fleet.
1967 DAF 44
1974 VW Beetle 1303s
1975 Triumph Spitfire MkIV
1988 VW LT45 Beavertail
1998 Volvo V70 2.5
1959 Fordson Dexta
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MonzaPhil
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Think like a man of action, act like a man of thought
Posts: 2,456
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Dec 17, 2012 20:14:33 GMT
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Success!
After much head-scratching, testing, driving about, dismantling and re-assembling we found a tide mark in the servo. It seems it's been sucking in water and hydraulic-ing absolutely solid.
Couldn't see it before but with the servo out of the car it is quite obvious.
Replacement on its way.
Thanks for the combined efforts everyone.
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Dec 17, 2012 21:29:13 GMT
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Yea tyhats what I said further up in the post, the drain plugs fill up
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