Cosworth Brake help needed!!
27-12-2010, 06:44 PM
#1
Cosworth Brake help needed!!
Ok here's a problem for you.
Earlier in the week the brake "servo" assistance died leaving me having the brake the old fashioned way with lots of force on the pedal.
As cossie peeps will know, its not a vacuum type set up but uses a pump to pressurise a hydraulic accumulator to offer brake assistance.
Checked the obvious fuses, wiring etc and all fine there.
Pump makes noises....
so stripped down the unit and removed it all from the car for an inspection.
There are no blocks in the low pressure pipework from resevoir.
You cant see much of the pump internals but it turns freely and smoothly and no bits of metal in the pump outlet filter.
bench tested the pump motor and pressure switch. pump motor turns fine and pressure switch is working.
So this leaves me with a dilema.
the only things i can think could not be working is:
Impellor blades in pump broken off
Accumulator bag broken so holds no pressure
leak in master cylinder unit.
Car has no ABS system. There are no external leaks on the brake lines/system and the fluid level hadnt dropped. Have not been experiencing brake fade or any other abnormal symptoms, the servo assistance just suddenly died.
I dont think theres an internal link within the master cylinder as if there was I would expect pressure to build, then "bleed" away as it leaks into other chambers of the master cylinder. Plus without servo assistance the brakes hold fine and dont fade away either.
So im thinking its the first two.
Anyone had similar problem?? any ideas??
Earlier in the week the brake "servo" assistance died leaving me having the brake the old fashioned way with lots of force on the pedal.
As cossie peeps will know, its not a vacuum type set up but uses a pump to pressurise a hydraulic accumulator to offer brake assistance.
Checked the obvious fuses, wiring etc and all fine there.
Pump makes noises....
so stripped down the unit and removed it all from the car for an inspection.
There are no blocks in the low pressure pipework from resevoir.
You cant see much of the pump internals but it turns freely and smoothly and no bits of metal in the pump outlet filter.
bench tested the pump motor and pressure switch. pump motor turns fine and pressure switch is working.
So this leaves me with a dilema.
the only things i can think could not be working is:
Impellor blades in pump broken off
Accumulator bag broken so holds no pressure
leak in master cylinder unit.
Car has no ABS system. There are no external leaks on the brake lines/system and the fluid level hadnt dropped. Have not been experiencing brake fade or any other abnormal symptoms, the servo assistance just suddenly died.
I dont think theres an internal link within the master cylinder as if there was I would expect pressure to build, then "bleed" away as it leaks into other chambers of the master cylinder. Plus without servo assistance the brakes hold fine and dont fade away either.
So im thinking its the first two.
Anyone had similar problem?? any ideas??
27-12-2010, 06:48 PM
#2
I've found that life I needed.. It's HERE!!
how is the pump powered?
via an abs ecu(i know it has no abs but this can still be used to power the pump)
or just fed via ign +(relay etc)
had probs with an ecu before where the pedal kept losing pressure,
but if its fed via ign live then it aint that
you said pumps makin a noise, i'm fairly sure the 1 i had done that but wouldn't built any pressure
via an abs ecu(i know it has no abs but this can still be used to power the pump)
or just fed via ign +(relay etc)
had probs with an ecu before where the pedal kept losing pressure,
but if its fed via ign live then it aint that
you said pumps makin a noise, i'm fairly sure the 1 i had done that but wouldn't built any pressure
27-12-2010, 06:57 PM
#6
I've found that life I needed.. It's HERE!!
ah well its not tht then
only prob i've ever had with any the 1's i've bult,
i have heard of the pumps going faulty several times but never dealt with 1 myself,
so cant realy guess as to what was wrong with it
i've got spare everything lying here, but theres already a few offers above closer than me
if your stuck for anything let me know anyhow
only prob i've ever had with any the 1's i've bult,
i have heard of the pumps going faulty several times but never dealt with 1 myself,
so cant realy guess as to what was wrong with it
i've got spare everything lying here, but theres already a few offers above closer than me
if your stuck for anything let me know anyhow
Last edited by jamie's; 27-12-2010 at 06:58 PM.
27-12-2010, 07:11 PM
#7
ive got a complete replacement unit here, so thats not the problem, i need to find the problem to work out what to replace first if you get me. All my pipework is custom so swapping the whole thing is a pain in the ass so i only want to swap the broken bit, once i know what it is!
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27-12-2010, 07:27 PM
#9
I've found that life I needed.. It's HERE!!
i've had the plug on the pump is loose,
this can give a bad connection,
dont sound like what you've described realy but just a thought
this can give a bad connection,
dont sound like what you've described realy but just a thought
27-12-2010, 09:02 PM
#13
well tried again. motor turning, nothing squirting out.
Will prime the pump manually in a min with fluid to make sure its not airlocked and if that dont work i know its the pump impeller that's broken so replace the complete pump assembly which will need some more copper pipe knocking up.
Can you bend copper brake pipe gently without a pipe bending tool or does it close up inside????
Will prime the pump manually in a min with fluid to make sure its not airlocked and if that dont work i know its the pump impeller that's broken so replace the complete pump assembly which will need some more copper pipe knocking up.
Can you bend copper brake pipe gently without a pipe bending tool or does it close up inside????
27-12-2010, 11:46 PM
#16
well put the working motor into the new pump housing with new accumulator and new pressure switch plumbed it all in, and guess what, still no servo assistance 
not bled them yet but despite that i would expect the pedal to go to the floor if there was a lot of air in it and its still rock hard!!
fuck knows whats wrong now.
not bled them yet but despite that i would expect the pedal to go to the floor if there was a lot of air in it and its still rock hard!!fuck knows whats wrong now.
30-12-2010, 09:20 PM
#22
the pump charges up to 180 bar before it switches off
so it may be the pressure switch not alowing it to pump up, the green thing, as it may be sensing an issue
have you got it set up to simply provide the assistance without the abs ecu?
so it may be the pressure switch not alowing it to pump up, the green thing, as it may be sensing an issue
have you got it set up to simply provide the assistance without the abs ecu?
30-12-2010, 09:23 PM
#23
dojj ive replaced the pressure switch. I can hear the pump running so the pressure switch must be working fine.
Yep dojj its set up to provide simple servo assistance without ABS. Even with ABS, the hydraulic actuation of the pump is the same, ie off the pressure switch when the pressure drops.
Yep dojj its set up to provide simple servo assistance without ABS. Even with ABS, the hydraulic actuation of the pump is the same, ie off the pressure switch when the pressure drops.
30-12-2010, 09:34 PM
#24
i would then assume there is a blockage in the system somewhere that is stopping the fluid from getting through, there is a filter somewhere in the system but i can't remember where it would be know
it may be that cloch pipe that goes from one end to the other with that funny r clip holding it on one side
it may be that cloch pipe that goes from one end to the other with that funny r clip holding it on one side
30-12-2010, 09:43 PM
#25
theres 2 pipes to the system, the "low pressure" pipe from the resevior and the high pressure pipe from the outlet of the of the pump going into the master cylinder.
The low pressure pipe has free flow and no blockages all the way into the pump.
if the high pressure pipe had a blockage then it expect the pump to pressurise still and the pump to switch off once the pressure on the pressure switch side of the circuit is high enough.
its an odd one for sure.
does anyone know how the fluid is distributed inside the master cylinder to achieve brake assistance?? is there some pressure disc that could be leaking past??
The low pressure pipe has free flow and no blockages all the way into the pump.
if the high pressure pipe had a blockage then it expect the pump to pressurise still and the pump to switch off once the pressure on the pressure switch side of the circuit is high enough.
its an odd one for sure.
does anyone know how the fluid is distributed inside the master cylinder to achieve brake assistance?? is there some pressure disc that could be leaking past??
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31-12-2010, 01:20 AM
#26
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Have you got a good heatsheild warren? Often on cars running no/ poor heatsheilds the pump unit cooks, and either kills the wiring or the internal seals. Might be worth throwing another servo block on, if its the bit I am thinking about.
25-07-2012, 09:34 PM
#29
Use these wiring diagrams to make your own loom:
This is how the pressure switch works:
At 140 bar system pressure it closes 2 contacts to run the pump motor (brown/black to brown), and opens these contacts when system presure is 180 bar.
At 105 bar it closes 2 contacts to illuminate the ABS warning light (brown/yellow to brown), and opens 2 contacts to disable the ABS system (brown/green and brown/white). These 2 sets of contacts open and close respectively at 134 bar.
(wiring colours in this case are for a saff)
This is how the pressure switch works:
At 140 bar system pressure it closes 2 contacts to run the pump motor (brown/black to brown), and opens these contacts when system presure is 180 bar.
At 105 bar it closes 2 contacts to illuminate the ABS warning light (brown/yellow to brown), and opens 2 contacts to disable the ABS system (brown/green and brown/white). These 2 sets of contacts open and close respectively at 134 bar.
(wiring colours in this case are for a saff)
25-07-2012, 09:49 PM
#30
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I dont have an abs/servo loom in my car & am looking to make a complete loom to just run the servo pump with pressure switch.
Any idear what these pins are on the servo?
Obv the pump is live/earth but needs to be triggered. Ia the pressure switch but am unsure the locstions if the pins to turn on/off
Cheers
Any idear what these pins are on the servo?
Obv the pump is live/earth but needs to be triggered. Ia the pressure switch but am unsure the locstions if the pins to turn on/off
Cheers
29-07-2012, 06:44 AM
#34
Ok nOt sure if this will help but a friend had a similar issue on his Sapph it turned out the fault was a dodgy relay in the passenger side near where the radio is tucked up under there , I think it's a yellow relay there's 2 I think can't remember exactly. He was actually driving the car and the brake pedal just went rock hard!
Hope this helps mate.
Hope this helps mate.
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