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Problem with XC 4 wheel disc brakes 

 

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 Post subject: Problem with XC 4 wheel disc brakes
Posted: Tue Apr 28, 2009 12:02 pm 
Oompa Loompa
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Ok i'm lost for what else to do to improve my brakes so I have turned to the internet. Here's the situation- I have fitted the whole braking system from a 77 LTD to a 57 Customline. That includes everything, pedal, booster, master, pipes, calipers, falcon stub axles and 9inch diff. Master cylinder and rear calipers are reco exchange, front calipers have been kitted with seals only, all flexible hoses are new as are all pads and rotors. My problem is I have a slightly spongy pedal, too much braking in the rear and not enough in the front. If I stand on the brakes hard, the rear wheels lock up and front dont. Rear wheels are getting hot, handbrake is disconnected to rule that out. Tried clamping rear brake hose and I get a nice firm pedal but still cant lock up the front wheels no matter how hard I stand on the pedal. Have bled them to death and almost positive theres no more air in the system. Rear wheels have very slight brake drag when jacked up and spun round. As both rear wheels are getting hot, I'm assuming it's the master but there's no pressure there when I crack the bleeders. If you think you can help, please reply.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 1:01 pm 
Getting Side Ways
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Some things to check....brake pedal free-travel, should be about 1mm to 3mm.
Is the master cyl the right one????, if it is wrong, can cause the rear brakes to drag, because the drum brake rear type master cyl has a residual line pressure valve in it.
When you bled the brakes, did you bleed it at the flare nuts at the master cyl first????

 

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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 1:12 pm 
Getting Side Ways
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And, did you use Good Pads on the front, have they been bedded in Properly!. If not, you may have glazed them

Nigel
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 3:12 pm 
Getting Side Ways
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i remember the disc rear cars also had a brake proportioning valve fitted.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 9:29 pm 
Oompa Loompa
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Ride: 1957 Customline, 63 XL Falcon

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Brake pedal free travel is about 2mm. Used Bendix pads all round and DBA Rotors. XC/D/E master cylinders have the proportioning valve located internally in the master cylinder. The Brake Mast cylinder exchange bloke told me they are the same for disc/disc and disc/drum. Can anyone tell me if that is DEFINITELY incorrect, not an opinion but fact. I do know the rear proportioning valve is different for commercial vehicles. I have 2 options, iether buy a brand new master for an XC and hope I have the wrong one in there now, or change over to an XBGT master for 4 wheel discs and use an adjustable rear proportioning valve. I am suspecting the rear wheels are getting warm because they're working too hard but I could be wrong.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 9:37 pm 
Oompa Loompa
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Definitely bled them well too. Bled the master at the pipes first, then made a pressure bleeder that allows me to bleed fluid through at 20psi without any air. A whole bottle of fluid goes through in about 30 seconds. Pretty sure theres no more air in the system.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Thu Apr 30, 2009 10:41 pm 
Getting Side Ways
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On the XD/E the brake master was the same for both. - at least for mine.

20psi? - any chance thats too much, and you get forced air bubbles?
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Fri May 01, 2009 5:42 pm 
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henryman wrote:
My problem is I have a slightly spongy pedal, too much braking in the rear and not enough in the front. If I stand on the brakes hard, the rear wheels lock up and front dont. Rear wheels are getting hot, handbrake is disconnected to rule that out. Tried clamping rear brake hose and I get a nice firm pedal but still cant lock up the front wheels no matter how hard I stand on the pedal. .


First, make doubly sure you havent got the master cylinder connected a*** about. If you have the front brake outlet connected to the rears, they will lock up for sure.
Secondly, the master cylinder on an XC is defiately different for 4 wheel discs. Make sure you have the correct one.
If the above is all correct, maybe an aftermarket proportioning valve would be the way to go.
If all else fails, try a good brake specialist, like Custom Brakes & Automotive at Moorooka.
Good luck,
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:D :D :D

 

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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Fri May 01, 2009 6:11 pm 
Oompa Loompa
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Pipes are definitely on correct, front wheels come from 2 outlets at front of master and rear is single pipe from back of master, splits into 2 at the diff. 20psi is nothing compared to the pressure you can deliver with the pedal I wouldn't think, The bleeder I made is a sealed cylinder pressurised from the top and forces the fluid out the bottom, 99.999% sure there's no air in there. May be just the dual diaphragm booster giving a spongy feel. I can live with that. As for the master cylinder, brake shops are saying there's not a different part number for different master cylinders and the manual doesnt show any difference iether. Might give Custom Brakes & Automotive at Moorooka a try then. Feels to me like wrong master cylinder but cant tell just by looking and it's the second one I've had in there, same as the first.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Sat May 02, 2009 12:05 pm 
Getting Side Ways
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henryman wrote:
The Brake Mast cylinder exchange bloke told me they are the same for disc/disc and disc/drum. Can anyone tell me if that is DEFINITELY incorrect, not an opinion but fact..


There is your problem...they are not the same...have seen this problem before.
As I mentioned before, the drum rear master cyl has a " Residual line pressure valve"
Get a new XD/XE/XF 4 wheel disc brake master cyl.

 

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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Sat May 02, 2009 5:07 pm 
Oompa Loompa
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Yeah mate I think you're right but I cant get anyone who sells them to agree. They are all telling me its the same part number and theres no difference on this model. Can someone give me the name of a place who can sell me a master cylinder that is definitely for 4 wheel discs or can the residual valve be removed??? Haven't tried Moorooka bloke yet.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Sat May 02, 2009 6:32 pm 
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I had a similar problem with a 91XF ute.

Installed a EA Ex ambo rear end with disc's was informed masters were the same, made up imperial to metric lines and it worked.

No proportioning valve to correct, its been about 5 years now with no drama's

 

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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Sat May 02, 2009 6:32 pm 
Getting Side Ways
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Location: Rockhampton
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henryman wrote:
Yeah mate I think you're right but I cant get anyone who sells them to agree. They are all telling me its the same part number and theres no difference on this model. Can someone give me the name of a place who can sell me a master cylinder that is definitely for 4 wheel discs or can the residual valve be removed??? Haven't tried Moorooka bloke yet.


Try BRAMAC, Rockhampton, phone (07) 49 224 020.
They are good blokes there, have been dealing with them for over 20 yrs.

 

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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Wed May 06, 2009 3:08 pm 
Oompa Loompa
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Ride: 1957 Customline, 63 XL Falcon

Location: Brisbane
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Bit the bullet and had a professional look at it. Masters are definitely the same for disc and drum rear on this model and there is no external proportioning valve, it's inside the master cylinder. Showed me a cross cut cylinder. It allows a certain amount of pressure to the rear and no more, then the front keeps working depending how hard you stand on the pedal. This is done with a pressure differential valve. This pressure is determined by different size springs. I am having the master cylinder "Tuned", to give less pressure to the rear. Also an adjustable rod fitted to the booster to bring the piston seal up as close to the reservoir fluid port as possible. At the moment, I have about a quarter inch of piston movement in the master cylinder before it goes past the reservoir fluid port and starts pressurising the system - hence the crappy pedal and all my braking is in the rear. The front isnt getting enough pressure - or piston travel past the reservoir fluid port. Seems to make sense to me. Picking it up today, will put it back together in the next few days and see how it goes.
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 Post subject: Re: Problem with XC 4 wheel disc brakes
Posted: Fri May 08, 2009 12:43 am 
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I worked for a ford dealer about 15 years ago, the drum/disc master cylinder was the same part number. However the V8 and 6cyl had different differential valve pressures. These valves were a small green annodized valve which did their stuff. (All XC V8's had discs fitted from the factory.)

But, we seen on more than one occasion where someone had fitted a 6 cyl master cyl to a V8 and sure enough the rears will lock every time. This is because V8's are much heavier over the front end.
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