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wtf is up with my brakes
02GF74 - 5/9/06 at 07:29 PM

I removed the braided hoses to replace by rubber ones for SVA and the brake pedal is horrible!!

I press it and nothing seems to happen so I press hardere and harder and harder to slow down and stop. now maybe I have been softened by using PAS for many years now but that cannot be right.

They passed SVA & can lock the wheels so are safe; it is just that with so much less weight, I was expecting to stop on a button with next to no effort.

set up is cortina callipers, sireea master + escort 8 inch rear drums and cylinders.

now there may be a bit of air in the front n/s (even though I bled them twice!) but the pedal is spongy - but was not like that when I fitted the braided lines (I will get suaged briaded lines on and see then).

I cleaned the disc and the pads using sand paper but it made next to know difference - the srufaces are nice and clean now so I do not thing that is a reason - or some weird pads that do not grip until hight temp?

Just wondering if there is anyting obviously wrong with the set up.

t.j. - 5/9/06 at 07:34 PM

if it wasn't there with steel-braided it must be air.

Try to bled them better

stulad - 5/9/06 at 07:34 PM

this is not an answer to ur question.
but more a question.
am i right in assuming that braded hoses are a big no no for sva?
many thanks stu

nitram38 - 5/9/06 at 07:39 PM

Mine passed sva with braided.
It might be that your rubber hses are expanding so they feel different under foot. Braided hoses tend not to expand. The Atom brake pipes are entirely braided.
Yes, no copper brake pipes on them at all!

Hellfire - 5/9/06 at 07:39 PM

quote:
Originally posted by t.j.
if it wasn't there with steel-braided it must be air.

Try to bled them better


Ditto

02GF74 - 5/9/06 at 07:43 PM

quote:
Originally posted by stulad
this is not an answer to ur question.
but more a question.
am i right in assuming that braded hoses are a big no no for sva?
many thanks stu


depends.

I've been through all of this so this should be as good an snawer as you can get.


there are at least 3 different ways of construction; the swaged type (ggodrich see BP catalogue) and olive/nut assembled types; possibly with or without support inside. (I called SVA and BP about the inner support but don;lt really know but have a reasonable idea what that is so best to stay clear of that greay area.)

see also the SVA manual, 16.4 if memory serve me well.

in short, the ones you want are the ones that cannot be tampered or taken apart; the ones that can meet that criteria are the swaged/crimped fitting ones otherwise you would need to get letter from manufacture (BP will not do that nor will tell tell you who that manufacture is - honestly not worth the hassle gong that route).

I asked the SVA tester about the "abrasive" cover - he said no issues as long as they not bent into a tight corner - but others - do a search - say otherwise.

nitram38 - 5/9/06 at 07:49 PM

I got mine made by thinkautomotive.com.
I didn't supply any paperwork to the tester, but they passed and he didn't even mention anything.

02GF74 - 5/9/06 at 07:50 PM

quote:
Originally posted by t.j.
if it wasn't there with steel-braided it must be air.

Try to bled them better


I didn't drive it with the braided but know when I pressed the pedal. it went down by maybe 1 inch then was absolutely solid!

so if the set up (master dia/caliiper and cylinders are a resonable match) then it has to be bleeding to fix (even though I couldnlt see any bubbles will thry harder I guess.

caber - 5/9/06 at 08:58 PM

Could be you have a soft rubber hose that is expanding when you press the pedal, if you can get the car up in the air and have someone press the pedal while you look around and feel the flexis for any lumps or swellings you could find out if that is the problem. This is not usual for new hoss but can happen with old ones or ones that have been used with unsuitable fluid.

Caber

the_fbi - 5/9/06 at 09:08 PM

I don't know where the nipples are on the cortina calipers and they aren't visable on the pics in your archive, but ensure you've got the calipers on the correct side with the nipples at the top, else they won't bleed properly.

Also, if you're running a pressure based switch, worth undoing the switch till it leaks fluid then pressing the pedal in order to expel air from it too, as it gets stuck there. (if the switch is topmost).

That said, odd it was OK with the braided, unless you were just lucky.

Dingz - 5/9/06 at 10:06 PM

Steel overbraided hoses will not really expand but the normal rubber ones will and also vary from make to make so the pedal will feel softer. You mentioned the pads, just use standard ones, performance ones do not work until they get very hot and on a light car with very well ventilated brakes they won't in normal use.

mcerd1 - 6/9/06 at 08:26 AM

Just one other thing to check - what brake fluid are you using ? and how old is it ? (ie has it been sitting on the shelf for years)

MikeRJ - 6/9/06 at 08:32 AM

If the pedal is spongy, and the rubber brake pipes are new, then it's almost certainly some air trapped in the system. You are using that useless silicon brake fluid are you?

However, you can't expect the braking system to feel anything like modern over-assisted cars. With no servo you are going to need to get used to a higher pedal pressure.

02GF74 - 6/9/06 at 08:58 AM

re "That said, odd it was OK with the braided, unless you were just lucky."

all I can say is the pedal felt much better; as I did not get it up to speed - I tested the brakes maybe rolling a few metres in the garag - so cannot say if braking would have been better.

an update + some answers.

bleed screws are on the inside, at the top - can rule that one out.

kit is one I have finished after having been started almost 10 years ago. I do not know at what point the brakes were fitted but would assume the hoses would be 5 or more years easily; when I bought it there was no fluid in the system as the rear backplate were missing.

I am using new fluid, locost from wilkinson but it is DOT 4 so although not yer top notch £ 10 a bottle stuff, I doubt that is the problem.

So maybe hoses have aged - they look fine though. I do notice them moving when I apply pressure (not expanding - at least not the one I can see which is the drivers one - but movement occurs anyway as I see that on my mountain bikes, both cable and hydraulic systems so not sure why I mentiopned it now...)

I would guess, judging by the rest of the components used, the brake pads are standard issue - black friction material but that probably won't identify them. They are not contaminated so that one can be ruled out. Disc, even rusty ones, should grip - I cleaned up the surface so that can be ruled out.

I am wondering if the pistons are operating properly - on the night before SVA I took out all the pads to give them a sanding and the inner one on the passenger side was really hard to remove so maybe piston problem in there? Again these will have been sitting unused for the same length of time.

there are no leaks - I cheked myself as did SVA man - I will look at reservoir level soon & pedal does not sink so that can be ruled out.


to get the kit in, I need to move a volvo (PAS and a landrover, servo with drums all the way round) - pressing on the LR pedal is a lot more effective than the kit despite having 3 or more times the weight so there is somethig wrong for deffo.

thanks for taking time to answer & keep suggestions coming.

[Edited on 6/9/06 by 02GF74]

DarrenW - 6/9/06 at 10:23 AM

My first thoughts were air in the system. Might be worth bleeding through again. After that id check the pistons are moving freely. Its possible that they may be corroded or seals about shot. Id imagine they wont like being stood for so long with no fluid. Assuming they were second hand when originally fitted they could be ready for re-build. I fitted recon Sierra calipers to mine, cost about £28 a side and work very well.

As you say even with std road pads and old discs in theory they should still give some braking efficiency. You say it passed SVA on brakes. I wonder if its a combination of air, old parts and the fact they would have recently just been used in anger up to temp that has caused some form of failure. If new recon calipers are cheap enough it might be worth replacing them as a starting point. Brakes are one thing that you need confidence of. Even if they start to work again with no intervention id be concerned over long term reliability.

Peteff - 6/9/06 at 11:02 AM

You might have been better letting the pads clean the disks up. What is your pedal pivot ratio like? If it's not 4 to 1 or higher you will have to press hard to operate the brakes and if the pads were new they take a few miles to bed in. The pressing harder and harder is what gives non servo brakes their feel, once you get used to it it improves your control of the vehicle unlike power assisted brakes (not PAS) which are often like a switch, on or off and work on how long you apply them for and not how hard you are pressing.

JamJah - 6/9/06 at 12:44 PM

Did you say you passed your SVA with them? if so have you tried to swap them back to braids?

02GF74 - 6/9/06 at 01:04 PM

quote:
Originally posted by JamJah
Did you say you passed your SVA with them? if so have you tried to swap them back to braids?


yes they passed.

I did the pedal force test i.e. pressure transducer around foot, then press brakes at different pressures until they lock; I have a print out of the figures. (I can post them for comment).

It seem to me that I am having to press much harder than I expect; despite the comments about PAS, I am convinced something is not right.

MikeRJ - 6/9/06 at 03:56 PM

PAS is power steering!

Does the car brake straight, i,e, no pulling to one side or the other?

A single sticking caliper will cause the car to pull, though it's possible that both calipers are bad I suppose.

the_fbi - 6/9/06 at 06:41 PM

If they passed SVA (sorry I missed that part) then its probably just a case of getting them up to temperature and bedded in properly.

Do a few 60mph to 10mph braking's (not stupidly sharp, fast road rather than boy racer) taking care not to overheat them (ie. do 20 seconds of driving between) and by the 10th time I think you'll have noticed a massive difference.

If not, then summits up.

britishtrident - 6/9/06 at 07:04 PM

Usually load of boswellox getting talked about flex brake hoses expanding --- they do but not by a noticeable ammount. The problem is something I would a 2nd year apprentice mechanic to spot.

Very simple --- you have a tiny fluid leak at a union or bleed nipple -- dry off each union and very carfully examine each in turn with helper keeping pressure on the pedal. Using a good torch to illuminate the unions while examnining them helps.

Only takes a very very tiny leak -- don't expect it to show up as a wetness unless you have pressure on the pedal.

[Edited on 6/9/06 by britishtrident]

roadboy - 6/9/06 at 07:13 PM

It has to be either air in the system or a master cyl problem. If the pedal is spongy is is definitely not sticking calipers as this would make the pedal firmer. Try bleeding with an easy-bleed which pressures the system. If the master cyl is old sometimes using the full travel to bleed the brakes can cause a miss seating of the seals. Depending on the type of cyl there is also a seal in the end which closes the suction port, this could be suspct on an old master cyl.
regds
Ian

britishtrident - 6/9/06 at 07:16 PM

quote:
Originally posted by Dingz
Steel overbraided hoses will not really expand but the normal rubber ones will and also vary from make to make so the pedal will feel softer. You mentioned the pads, just use standard ones, performance ones do not work until they get very hot and on a light car with very well ventilated brakes they won't in normal use.



Try a very simple experiment -- take any car without a servo and a reasonably ridgid pedal box and cap off the wheel end of each flex brake hose and bleed properly -

Now jump up on down on the pedal has hard as you can provided the pedal box and pedal are stiff enough and the system bled properly the pedal won't budge it will be rock solid.

The difference in stiffness between textile-rubber hose and ptfe steel braided flex hose is so small it is swamped by all the other causes of lost motion in the system.

The Doc - 7/9/06 at 06:41 AM

Hi,
Two things:
You might be better with a master cylinder which was designed to be non-servo assisted

Also I have had a situation where fluid has leaked past the internal seals in the MC and not escaped out of the unit but remained in the system

02GF74 - 7/9/06 at 06:46 AM

... just to get this back on track as it is veering off discussing m/.c.

the master cylinder is brand new; I had braided hoses on and very firm pedal.

it all is pointing to air in fluid, a leak or duff hoses, in that order.

unless the m/c is incompatible with the callipers/cylinders.

how can I tell if the master should have a servo?
It is sierra one, bore 22 m.
front calipers coritina, 8 in mk2 escort drums.

new master
new master

[Edited on 7/9/06 by 02GF74]

britishtrident - 7/9/06 at 05:22 PM

Really basic stuff that is taught to first year apprentice mechanics if you can't get a solid pedal after changing a brake pipe or hose first check for a FLUID LEAK from a union.


Believe me I have about 40 years experience of fitting brake pipes and hoses and have only ever seen one faulty new hose and that was a Goodridge in which one of the end fittings wasn't drilled through properly.