Technical Uno Fire 1100 – correct order to bleed brakes

[DigitalNomad]

Hi folks,

My brakes have become dangerous. Before actually stopping I need to pump them about 5 times. Then at the next stop again!

The shoes and pads are all new and everything was working OK for quite a while (about 1500km) and then slowly got worse.

I understand that apparently there is a specific order in which I need to bleed the brakes. Could someone please let me know the correct order.

My Uno is the right hand drive one (driver seat on the right hand side and so is the reservoir).

I tried to bleed the thing by doing the two back wheels first and then the two front wheels using the two-man method in this order:

1st Back left hand side (passenger)
2nd Back right hand side (driver)
3rd Front left hand side (passenger)
4th Front right hand side (driver)

The problem I’m facing is that after bleeding, the pedal is nice and stiff, but after just a short drive I need to pump it a few shots again by the time I get to the second stop sign. So I’m hoping that it is simply a matter of doing it in the wrong order.

Also someone suggested I bleed the brakes with the engine running – this sounds a bit weird to me. Is the correct?

Any tips or hint on a quick test I can do on the master cylinder and servo would also be of great help.

Thanks in advance.

 

[DigitalNomad]

UPDATE:

I have just done the following test.

With the engine turned OFF, I pumped the pedal three times to make sure it is stiff and on the fourth push down, I kept it down. While keeping it down, I can feel and see the pedal slowly moving down under the pressure of my foot.

There appears to be no leaks anywhere in sight. Is this bad news? The calipers on the front was fitted with new rubber kits about 3000km ago. Is this something one can fix on your own? This car is costing me a freek'n fortune:bang:

 

[varesecrazy]

Hi,
there's a similar SA thread on poor UNO brakes,

also sounds like it may be a worn master cylinder - with the brake fluid leaking past the piston ( but still within the actual cylinder- so NO visible leaks),

EDIT - when you bled the brakes was there ANY air coming out with the fluid,
not too sure if your brakes are just SPONGY..??

trapped pockets of air can cause issues in "dual-circuit" systems,

Charlie

 

[Ziggy122]

Pumping pedal is a sign of low compressionbin the btaking circuit

Caused by
Air in the system
Expanding flexi brake lines
A worn master cylinder

Ziggy

 

[DigitalNomad]

Hi guys,

Just for those who follow after me, I mention these two links to some good info on brake trouble shooting.

I found the following nice summary of simple tests to be done at:
http://honda-tech.com/showthread.php?t=3007522

BRAKE BOOSTER INSPECTION

Functional test:
1. With the engine stopped, Depress the brake pedal several times, then depress the pedal hard and hold that pressure for 15 seconds. If the pedal sinks, the master cylinder, brake line or a brake caliper is faulty
2. Start the engine with the pedal depressed. If the pedal sinks slightly, the vacuum booster is working. If the pedal height does not vary, the booster or the check valve is faulty

Leak Test:
1. Depress the brake pedal with the engine running then stop the engine. If the pedal height does not vary while depressed for 30 seconds, the vacuum booster is OK. If the pedal rises, the booster is faulty
2. With the engine stopped, depress the brake pedal several times using normal pressure. When the pedal is first depressed, it should be low. On consecutive applications, the pedal height should gradually rise. If the pedal position does not vary, check the booster check valve.

Check valve test:
1. Disconnect the brake booster vacuum hose at the booster.
2. Start the engine and let it idle. There should be a vacuum available. If no vacuum is available, the check valve is not working correctly. Replace the check valve and retest.

END TEST

I also found some great stuff on breaks in general on this site:
http://cr4.globalspec.com/thread/22457

Anyhow, after a little close inspection I found some slight signs of oil leaking from the back of the master cylinder where it attaches to the servo, plus all the trouble shooting tips etc...also pointed to the MC being the culprit. It is still the original part from 1994 with the car having done over 200,000km already.

Our local Midas (parts store) was charging R630 for a new one so I got the repair kit for only R50. Dismanteling the MC was a bit diffferent than explained in the Haynes Manual. It just had a circlip on the side which fits onto the servo.

Long story short, I took it apart and replaced all the bits and pieces, reassembled and bled the system again. Just drove round town quit a bit as well as to the neighboring town and everything is 100% :slayer:

The most difficult part for me was getting the bottom brake line hose's nut loose - there is very little space to work down there and I almost stripped the nut. Took the vice-grip and got it loose. I first sprayed some Q20 on all of them too to help loosen them a bit.

Thank you to all who replied and offered advice.

Safe driving

 

[varesecrazy]

how did you refill / bleed the system.?,

manually of using pressure / vacuum??,
Charlie

 

[DigitalNomad]

Hi Charlie,

Just before reattaching the MC to the servo, I put a little break fluid into the reservoir and sort of bench bled the MC first until fluid came out of the holes where the lines connect by pushing the little hollow rod which usually attaches to the servo inwards a few shots (I'm now the proud owner of a nice yellowish bruise on the palm of my hand )

I then installed the MC and when done, filled the reservoir up to full. I then continued to bleed at each wheel in the order I mentioned in my original post. The method was simple. My fiance steps down on the brake and I would open the nipple briefly (uhm the nipple at the wheel that is, cough-cough, I never touched hers ) to allow the fluid to escape through a plastic tube (bought it at the pet shop) and into a bottle. Then I would tighten the nipple and she would release the brake pedal again. No air bubbles ever came though at any of the wheels.

I continued like this until we basically used up 500ml of fresh break fluid at which time I called it quits and accepted that all was well.

I checked this morning again and all is still working 100% and there are no leaks around the the areas where the lines bolt onto the MC either.

I'm still curious though as to whether there really is a correct order to bleed the system, so if anyone knows, I'm all ears

Safe driving!

 

[somyunguy]

The Haynes manual does'nt seem to spec an order to brake bleeding and i don't think it really makes any difference.

I usually start at the back though , and the Uno's have to be bled with a preload of 60kgs in the rear of the vehicle to get the brake balance correct to prevent rear wheel lock.

 

[varesecrazy]

The Haynes manual does'nt seem to spec an order to brake bleeding and i don't think it really makes any difference.

I usually start at the back though , and the Uno's have to be bled with a preload of 60kgs in the rear of the vehicle to get the brake balance correct to prevent rear wheel lock.

I don't think bleeding will upset the balance, full of clear fluid is all you can ask..!!, the weight is for the "proportioning valve spring".

BUT - as I said before doing an early 1990's tipo I had an air-lock I couldn't clear using "conventional" methods,
so I towed it to a local friends garage business - it took them 3 attempts with a "pressure bleeding set-up",
so that's why I'm a little wary.

 

[somyunguy]

I am aware of the proportioning valve spring and yes it does make a difference, they would'nt have spec'd it so if it did'nt.
Also have had the experience of missing that point when i replaced the rear cylinders and got rear wheel lockup under heavy braking.
This was also done using a pressure bleeder and a litre of fresh fluid so i am certain there was no air, redid it correctly the second time round and had no further issues.