A4 - No brakes, spongy pedal

partyatmygaff

I've a B5 A4 that's been left unused for the past 2 years. The engine's running perfectly fine (Considering it was replaced only 1 month before being left unused that's not too surprising) but it looks as if the car's brakes have an issue.

The pedal has little to no pressure and the resistance doesn't increase even if I keep pumping the pedal. Looking at each wheel, there's no movement whatsoever in any part of the system when someone pushes the pedal. The brake fluid reservoir is at MAX but strangely whenever someone pushes the pedal I can hear what sounds like a small rush of air.

I've bled the brakes and the symptoms haven't changed at all. That said, i'm not sure if I bled the brakes enough as I only removed about 50ML of fluid from the calipers (Which are covered in rust if that matters).

Anyone have any ideas?

Ferris

Vacuum hose from the vac generator on a diesel or the inlet manifold to the brake servo could be split. Happened on a golf I had.

Mar4ix

could be seized calipers, have to remove, clean from rust, make sure cylinder working. could be master cylinder gone, ... God know what would happen , if car 2 years parked.

Edit: also caliper guides could be seized.

partyatmygaff

Ferris wrote: »

Vacuum hose from the vac generator on a diesel or the inlet manifold to the brake servo could be split. Happened on a golf I had.

Had a look just a few minutes ago. No obvious cracking or leaks but considering how it runs right next to the battery (Which has been installed and uninstalled over the past two years a fair few times) it could well be cracked.

Is there a proper way to diagnose it? A spray or something?

biko

It could be several things. I'd take off and lube the calipers and at the same time bleed/flush again, just in case there's air in there still. Also you want to keep bleeding until all you get out is fresh fluid (flush). Refer to manual to know how much fluid is in your system.
What method did you use to bleed? What order do you bleed in? No offence but it can be tricky to get it right unless you know what to do.

Ferris

I just remember finding an obvious leak, you could feel air being sucked in. It was on a diesel with a vacuum generator so it was easy to detect.

Just thinking if the car has sat for some time defo look at siezed calipers and old brake fluid. When you brake hard does the car move to one side, this could indicate a duff caliper. Brake fluid absorbs water too and gets contaminated over time which can cause unresponsive brakes.

partyatmygaff

biko wrote: »

It could be several things. I'd take off and lube the calipers and at the same time bleed/flush again, just in case there's air in there still. Also you want to keep bleeding until all you get out is fresh fluid (flush). Refer to manual to know how much fluid is in your system.
What method did you use to bleed? What order do you bleed in? No offence but it can be tricky to get it right unless you know what to do.

I'll take off and lube the calipers tomorrow and bleed them again. As for the method I used:

1. Removed the rear left wheel (Master cylinder is in the front right) and removed the cover from the bleed screw.
2. Opened the fluid reservoir
3. Attached the rubber tubing to the bleed screw.
4. Had someone pump the brakes five times and hold, repeated four times over.
5. With the rubber tubing still attached I tightened the bleeder screw again.
6. Removed the tubing and repeated for the other three corners (Rear right, front left, front right in that order).

What's odd is almost no fluid came through the tube on the front right brake. When I opened the screw, the fluid started dripping out from the base of the bleeder screw, off the caliper and down on to the ground.

Ferris wrote: »

Just thinking if the car has sat for some time defo look at siezed calipers and old brake fluid. When you brake hard does the car move to one side, this could indicate a duff caliper. Brake fluid absorbs water too and gets contaminated over time which can cause unresponsive brakes.

The car doesn't brake at all. Even with the pedal down to the floor there's no visible response in the brake system.

Mar4ix

i assume car has ABS. could be abs unit stuck. Any warning lights when started ? unbolt front right brake line from ABS unit, see, if fluid goes from there, if it not, then abs unit stuck..... if it does leak, then as i said, brake caliper guides seized. happens to number cars, suggest get recon kit.

aujopimur

On a car laid up for 2yrs. I'd seriously consider replacing the timing belt.

partyatmygaff

aujopimur wrote: »

On a car laid up for 2yrs. I'd seriously consider replacing the timing belt.

The engine was replaced only a month before it was left unused and i've been running it for about ten minutes every few weeks ever since to keep the battery from going flat. I'd say it's been run less than 1000 miles since the swap, is a timing belt change really necessary? It'd almost be uneconomical on a car this old.

aujopimur

partyatmygaff wrote: »

The engine was replaced only a month before it was left unused and i've been running it for about ten minutes every few weeks ever since to keep the battery from going flat. I'd say it's been run less than 1000 miles since the swap, is a timing belt change really necessary? It'd almost be uneconomical on a car this old.

If it's been run on a regular basis the belt might be ok, the problem is that timing belts degrade when not used, much the same as tyres and other rubber bits like hoses and window rubbers etc..

partyatmygaff

I think I may have found the culprit. Looks like one of the vacuum hoses (I think) has been chewed through. Anyone have any idea how I'd go about replacing it

healyboi

b5??? get it scraped not worth a ****

mickdw

If its a vacuum problem, you should have brakes just like when the car is turned off. They would need alot of pressure on the pedal to do anything but the pedal should be pretty solid regardless so perhaps you have more than one problem.

partyatmygaff

https://www.youtube.com/watch?v=Jj6ze8QCT_4

Ferris

Wrap tape around it and see if it makes a difference. If it does then go to a scrappy to get one.

partyatmygaff

Ferris wrote: »

Wrap tape around it and see if it makes a difference. If it does then go to a scrappy to get one.

Made a small but significant difference. The brakes marginally stiffen up a bit after the pedal is pumped but it's still very far from normal.

Plan of action is to replace that hose and re-bleed the brakes. The only problem is I have no idea where the broken hose came off from. If anyone is familiar with the 1.8E and its vacuum system, where would be the best place to look. I removed the intake pipe to have a look and there's no obvious place for the hose to have come from.

partyatmygaff

Another thing I noticed is that the brake pedal makes a hissing noise when the engine is running (But is silent otherwise). Sounds like something a lot closer than the master cylinder or vacuum. Anyone have any ideas?

https://www.youtube.com/watch?v=UkWfZSom-7E

partyatmygaff

Tried another brake bleed today. At the furthest brake caliper from the master cylinder, there's little to no pressure. The fluid just barely drips out even with the bleeder screw completely open and the pedal being pumped.

I'm also nearly certain the servo isn't the problem as there's a definite decrease in resistance with the engine running. Without the engine running the brake pedal is almost just like the clutch pedal. Not a lot of resistance and it returns almost instantly without any noise. With the engine running, the pedal softens under your foot and feels spongy and recoils slowly.

Would bench bleeding the master cylinder be worth a shot?

partyatmygaff

I forgot to mention. The engine takes a tiny bit of throttle to start. When it does it's perfectly smooth but if I brake within the first ten seconds, the car starts sputtering, the idle drops and it cuts out. Sounds like the brake servo/booster is having some effect on the vacuum which drops the idle speed and causes the engine to cut out. After about 30 seconds, I can push the pedal down as much as I like with no effect on the idle speed. To my mind, that's evidence that there's no issue with the servo.

dieseljohnny

partyatmygaff wrote: »

Tried another brake bleed today. At the furthest brake caliper from the master cylinder, there's little to no pressure. The fluid just barely drips out even with the bleeder screw completely open and the pedal being pumped.

I'm also nearly certain the servo isn't the problem as there's a definite decrease in resistance with the engine running. Without the engine running the brake pedal is almost just like the clutch pedal. Not a lot of resistance and it returns almost instantly without any noise. With the engine running, the pedal softens under your foot and feels spongy and recoils slowly.

Would bench bleeding the master cylinder be worth a shot?

While bleeding the brakes are you blocking the bleed nipple or closing it in between pumps??

With the pedal pressed to to floor you should close the bleeder before pulling it back up then press again,hold open or unblock bleed nipple,close then repeat

partyatmygaff

Got a replacement brake servo, master brake cylinder and fluid reservoir today (They're already attached together as one unit).

Is it as simple as bolt off the old system and bolt on the new one or will I need to bench bleed the master brake cylinder? Or are there any other steps i'm missing?

partyatmygaff

Installed a new master cylinder and reservoir (The old one was cracked at the top and the brake fluid was a murky green emulsion) and bled all four corners again yesterday. Little to no change in the pedal feel and the calipers still aren't compressing. There seems to be little to no pressure reaching any of the four calipers.

I'm stuck for ideas. Could it possibly be air in the ABS pump?

Mar4ix

did you check brake cylinders which in caliper separately ? unbolt from hub, someone press brake pedal couple times. , does it move ? handy to have a tool like this , does brake fluid goes out from ABS (if it have) , when detach pipe which goes from abs to hub. ?

sheehan12

not to be smart but i think it time to take it to a garages by now

partyatmygaff

sheehan12 wrote: »

not to be smart but i think it time to take it to a garages by now

How exactly am I meant to take a car with no brakes anywhere?

Paying for a flatbed and a mechanic's fees for a 98 doesn't make any sense. I'd much prefer the challenge of fixing it myself.

sheehan12

partyatmygaff wrote: »

How exactly am I meant to take a car with no brakes anywhere?

Paying for a flatbed and a mechanic's fees for a 98 doesn't make any sense. I'd much prefer the challenge of fixing it myself.

the problem with that you don t know how to fix it . it could be a easy fix for a mechanic. i guess by the time you will have it fix you will be able to tax it as a classic

partyatmygaff

sheehan12 wrote: »

the probable with that you don t know how to fix it . it could be a easy fix for a mechanic. i guess by the time you will have it fix you will be able to tax it as a classic car;)

I posted this on the DIY Car Maintenance, Repair and Detailing forum so I could get a few ideas on where to look for problems.

Telling me that I should head off to a mechanic with a smart-assed comment about how long it will take to fix isn't helpful.

In other news... i'm pretty certain the issue isn't with the master cylinder and must be something downstream of that. I'll check the lines around the ABS pump first. Considering all four calipers have no pressure and how unlikely it is for all four to fail at the same time, the ABS pump seems to be a good place to start looking for problems.

sheehan12

partyatmygaff wrote: »

I posted this on the DIY Car Maintenance, Repair and Detailing forum so I could get a few ideas on where to look for problems.

Telling me that I should head off to a mechanic with a smart-assed comment about how long it will take to fix isn't helpful.

In other news... i'm pretty certain the issue isn't with the master cylinder and must be something downstream of that. I'll check the lines around the ABS pump first. Considering all four calipers have no pressure and how unlikely it is for all four to fail at the same time, the ABS pump seems to be a good place to start looking for problems.

it might be a smart-assed comment but at least i know when i need to call a mechanic :pac:

partyatmygaff

sheehan12 wrote: »

it might be a smart-assed comment but at least i know when i need to call a mechanic :pac:

When you can't bother yourself learning how to do something and just get someone to do it for you?

Seriously, surely it's not that hard to believe that some people like a challenge? Give it a rest.

dp639

partyatmygaff wrote: »

I posted this on the DIY Car Maintenance, Repair and Detailing forum so I could get a few ideas on where to look for problems.

Telling me that I should head off to a mechanic with a smart-assed comment about how long it will take to fix isn't helpful.

Well said fella, if this was posted in the main Motors forum you would expect to get told to go to a mechanic. But this is a DIY forum after all, its obvious from the earlier posts that the car is old, you don't want to spend money on it and that you want to fix it yourself.

Alot of people have helped and the thread has been in the spirit of a DIY thread, so fair play to them. You'll always get someone being a smart arse.

Mar4ix

have you split calipers ?
if it is difficult for you, you shall ask somebody else to do the work, some nixer mechanics , or bring car to some indie garage. wouldnt cost to you too much to get it sorted right.
you done quiet big job already, so i assume you will manage it.

Ronnie Beck

http://elsaweb.spaghetticoder.org/nav/EN/Audi/A4-80/

This might help you. You'll find info here about all the braking systems. Select your model and follow the menu under running gear. If your 100% the brake are mechanically fine with no leaks etc. your probably looking at the abs systems. Sounds to me like your abs might be always on. If there is no OBD scan fault I don't envy you.

coppercat

could be a problem in the abs unit , try loosening a pipe at the master cylinder , give the pedal a pump and see if you have fluid pressure there if so tighten it up again and loosen pipe where it enters the abs unit check for pressure again , next open a pipe coming out of the abs and check for pressure . this should allow you to see where the pressure loss is eg blocked pie or faulty abs unit etc. basically start at the master cylinder and work towards the calipers . good luck

partyatmygaff

coppercat wrote: »

could be a problem in the abs unit , try loosening a pipe at the master cylinder , give the pedal a pump and see if you have fluid pressure there if so tighten it up again and loosen pipe where it enters the abs unit check for pressure again , next open a pipe coming out of the abs and check for pressure . this should allow you to see where the pressure loss is eg blocked pie or faulty abs unit etc. basically start at the master cylinder and work towards the calipers . good luck

I did that yesterday. There's new, clean fluid reaching as far the two lines exiting the ABS pump. There were about 4-5 bubbles that came through the fluid when I loosened one of two brake lines leaving the ABS pump but after about two seconds on the brake pedal all that was coming out was fluid.

I've also tried out the brakes (Not just the brake pedal feel as I usually do) for the first time since changing the master cylinder. In a small breakthrough, there seems to be some pressure back in the system. I can reverse the car up a small incline and the brakes can hold the car providing I keep the pedal all the way down. With a bit of experimentation, I found that the brakes seem to start engaging about halfway down.

I've got a theory that I need to test out. Back when I changed the cylinder/reservoir, the old fluid that came out was this murky green liquid with a lot of loose sediment floating around. Unless i'm mistaken, that sediment could have travelled all the way down to the calipers and is the reason for the calipers not bleeding properly and being so weak.

Would one of those power brake bleeders generate enough vacuum to remove sediments?

coppercat

partyatmygaff wrote: »

Would one of those power brake bleeders generate enough vacuum to remove sediments?

possibly , its worth a try if you have access to one , or you could try diconnecting the pipes at the abs unit and the caliper an blow them through with an airline. do you have a good flow of fluid at the caliper now or not ?

partyatmygaff

Finally got the brakes sorted today! I modified an old reservoir cap to attach it to an air compressor and used it to pressurize the system and force the fluid out. I opened up the four bleeder valves and removed nearly 200ml of nasty-looking green brake fluid and a *huge* amount of air to boot. Brake pedal is firm and feels as good as new now.

On a slightly less happy note, the engine decided to stop working. It was running fine last week until the fuel ran out and the engine conked out. Recharging the battery now and will give it another shot before the end of the day but is there anything obvious that may need to be checked?

partyatmygaff

I've checked the fuel pump and I can hear it whirr when I turn on the car's electrical system. I've checked for spark and i've checked the line feeding the fuel rail as well (Slightly loosened a nut and fuel came gushing out so I assume there's no issues there)and there's definitely spark and fuel reaching the engine.

Could it have something to do with the ripped vacuum hose I mentioned earlier? I don't see why it would prevent the engine from starting as it's been working fine the past few weeks but I just don't know what else could possibly be wrong.

icjzfmq7ewon1t

If it ran out of diesel it will be airlocked and needs to be bled. Sorry just reread your last post you appear to have bled it already.

Ronnie Beck

Kenneth Moldy Cocoon wrote: »

If it ran out of diesel it will be airlocked and needs to be bled. Sorry just reread your last post you appear to have bled it already.

It's a petrol if he's checkin for spark.
I'd would put a new filter in if you ran it dry after sitting up for two years. Hopefully you didn't clog or burn out the pump. Are sure it wasn't just a bit of fuel sittin in the fuel rail.

mickdw

Are these fussy about fuel pressure. Ive seen a few cars with fuel being fed fairly rapidly to the engine but just not quite enough pressure resulting in a non start.
I would fit new filter first anyway.

partyatmygaff

Ronnie Beck wrote: »

It's a petrol if he's checkin for spark.
I'd would put a new filter in if you ran it dry after sitting up for two years. Hopefully you didn't clog or burn out the pump. Are sure it wasn't just a bit of fuel sittin in the fuel rail.

I can't say for certain but I really don't think there's an issue with the fuel supply. I turned the electrical system on a couple of times to cycle the pump, loosened a nut on the fuel line to check for pressure and fuel gushed out with just 1/2 of a turn.

I know there's good reason to think the fuel filter's clogged but for the time being there's pressure and fuel in the fuel rail so I think I can safely rule out a problem with the pump or filter?

The funny thing is the engine sounds almost as if it's going to start.

https://www.youtube.com/watch?v=NQH-65a-KTE

(Turn down the sound, the video's very loud)

The past few weeks, it would sound exactly like that on the first attempt but always started perfectly fine on the second attempt. From what I can tell, i've got fuel, spark and what sounds like compression (It doesn't sound like this anyway) but strangely the engine refuses to start.

Ronnie Beck

Did you put the spark leads back on in the right order?

Sounds like it want's to start but it's not getting enough of something. Mick's theory sounds right. A new air and fuel filter and fuel system/injector cleaner and a throttle body clean should sort it out.

partyatmygaff

Ronnie Beck wrote: »

Did you put the spark leads back on in the right order?

I tested each one separately so yeah they're definitely on in the right order.

Do you think the engine sounds as if the spark is mistimed?

Ronnie Beck

partyatmygaff wrote: »

I tested each one separately so yeah they're definitely on in the right order.

Do you think the engine sounds as if the spark is mistimed?

I posted that bit while the video was loading. It's just a mistake I've made before.

Did you just put a can of petrol in? Might want a bit more. It just sounds like it's not getting enough fuel to me.

partyatmygaff

Tried it again today, still nada.

Could it possibly be a lack of fuel? I refilled it with a 5L can of petrol that I had around which brought it up to just over the red line. When I go to start the engine, the gauge goes all the way down to its resting position (The position it's in when the car is completely turned off).