Spongy brakes

[Brianmoooore]

Does the car have ABS?

Not with rear drums.

[E30REDD]

Does either car have ABS? Can you even have ABS with rear drums?

ABS also makes it harder to successfully bleed air out of the brakes - it is best not to drain the fluid out completely letting air in & then bleed air back out again on an ABS equipped car.

The ABS valve unit is what makes it more difficult to get the air out - just flush through with lots of fresh fluid on an ABS car.

Brianmoooore is right, there is no ABS on the car.

[Fred555]

Well as neither car has ABS then they both have a very simple & reliable (and very easy to correctly bleed) braking system(s) that anyone can fix with ease - so if there is something wrong it is quite obvious that whatever it is has still been overlooked. Look closer.

[TheDutch]

It's the one thing on an E30 that you can guarantee needs adjustment after many years!
Several heavily loaded joints, all of which will have worn slightly over the years, times the leverage ratio of the brake pedal equals a pedal which has dropped considerably from where it was when it left the factory.
ALL RH drive E30s have either had this rod adjusted or need this rod adjusted, unless they have only covered an extraordinary low mileage .

Does making this adjustment merely remove free play from the action, or can it have an effect on the leverage/feel?

[E30REDD]

Well as neither car has ABS then they both have a very simple & reliable (and very easy to correctly bleed) braking system(s) that anyone can fix with ease - so if there is something wrong it is quite obvious that whatever it is has still been overlooked. Look closer.

What should I look for? I have inspected the outside of the whole brake system, lines, hoses, joints and shit. Can't find any leaks, therefore I am asking what to do next. Do I have to disassemble the whole brake cylinder and take a look at that? Can I not test for vacuum leaks or check if the sealings inside the master cylinder are bad without disassembling everything?

I mean are there no easy checks I can do before I start ripping it all apart?

[Brianmoooore]

I have inspected the outside of the whole brake system.... hoses,

With the engine running and someone pressing HARD on the brake pedal?

Pull rod (cross link) adjustment just removes free play before the brakes start to work.

[Fred555]

Get hold of a copy (haven't used mine for years so have lost my copies somewhere in the house - otherwise would give you scans of the relevant pages) of the American published Robert Bentley Publishing E30 Repair Manual & also a copy of the Haynes E30 Manual (Autodata also used to do one which is good in a different way to the other two) the Robert Bentley one has lots of great stuff on the brakes & also shows how to test the servo without a vacuum pump.

Basically following the Bentley manual take off each rear drum - check the drum is not worn beyond the maximum permitted diameter (use a cornflake packet box to make a piece of card exactly the maximum permitted size listed in the manual by an inch or so across & if it cannot touch the wear surface of the drums new drums are needed as they are too big) - make sure the self adjusting mechanisms are installed on the correct side of the car they are both different & only work correctly on the side of the car they are meant to be installed on - check the brake line connections (that have been disturbed since the factory) are tight enough - too tight they will snap off - too loose they will not leak but will let air in - Bentley lists a torque figure for them that you could use with a crows foot wrench on a torque wrench - then adjust the handbrake according to the manual.

Then following the manual go and take a very close look at the fronts.

Could be the brake fluid reservoir seals connecting it to the Master Cylinder have gone - that might let air into the master cylinder with the slight movement of fluid every time you brake - the air vent in brake fluid reservoir cap isn't blocked by any chance?

[E30REDD]

I have inspected the outside of the whole brake system.... hoses,

With the engine running and someone pressing HARD on the brake pedal?

Pull rod (cross link) adjustment just removes free play before the brakes start to work.

I noticed one big leak; I removed the dust cover from the rear drum caliper and pushed the brakes. It was literally squeezing out brake fluid from both sides of the cylinder.

This is most likely what is causing the mushy brakes, right?

[Speedtouch]

Yes, you don't want that to be happening!

[E30REDD]

Replaced the leaking brake cylinder with a good one, bled the line (not all 4, only the one I replaced). Brakes feels exactly as before...

[zd3bx]

Replaced the leaking brake cylinder with a good one, bled the line (not all 4, only the one I replaced). Brakes feels exactly as before...

What about the cylinder on the other side? It's not leaking fluid?

[E30REDD]

Replaced the leaking brake cylinder with a good one, bled the line (not all 4, only the one I replaced). Brakes feels exactly as before...

What about the cylinder on the other side? It's not leaking fluid?

Nope, checked it and it's fine.

[Speedtouch]

Try bleeding all the brakes again - one line leaking may have let air into the entire system, or at least the other side of the circuit it's operating from (assuming dual circuit brakes, which may be split diagonally).

[E30REDD]

Try bleeding all the brakes again - one line leaking may have let air into the entire system.

I am so tired of bleeding brakes by being two persons, one pump and hold pedal, other opens air nipple, closes air nipple, do this again 500 times.

So in order to bleed the system by just pumping the brakes without having to open/close the air nipple I am wondering if this idea would work:

Btw, on an E30 you bleed in this order: Rear right, rear left, front right, fron left?

[Speedtouch]

Yes, this is the traditional way of bleeding the brakes. Start with the brake furthest away from the master cylinder (offside rear on a RHD E30) and end up with the one nearest (nearside front on a RHD E30).

I generally just undo the nipple and pump the pedal hard up and down at least 10 times on each brake to ensure fresh fluid gets through, holding the pedal down on the last stroke before tightening the nipple.

[E30REDD]

Okay, I have bled the brakes really well now and there are no improvements whatsoever. The brake pedal has been pumped a few houndred times and there are no visible leaks.

My brake pedal is getting rock hard when it's close to the bottom. There is no way I can floor it. But when I release the pedal it's very mooshy on its way back up.

Sometimes it bubbles in the brake fluid reservoir when the brakes are pumped.

Is the next thing to do just to remove the master cylinder and inspect it?

[Brianmoooore]

The master cylinder push rod seal is goosed. New cylinder required.

[E30REDD]

The master cylinder push rod seal is goosed. New cylinder required.

New cylinder needed? Can I not just replace the sealing on the push rod?

If not, if I go to a car scrap, is there any way to check if that master cylinder is in good condition except from just pumping the brake and see how it feels?

[Brianmoooore]

It's somewhat vital part of the car! A new one's not expensive. That should have read push rod end - the seal doesn't actually fit around the rod.

[Brianmoooore]

Correction! There £110 odd from CP4L now - I'm sure I've never paid anything like that amount.
Seals can be replaced if you can get hold of them, but I don't know of a source.
A second hand cylinder can be used, although I don't know of a way of checking them, other than checking for fluid around the push rod when you unbolt it from the servo.

[E30REDD]

It's somewhat vital part of the car! A new one's not expensive. That should have read push rod end - the seal doesn't actually fit around the rod.

Well, this one doesn't seem to be too expensive. Damn, just noticed that it has been used, but buyer claims it's in good condition and he has good feedback.

Okay, is it as easy to replace it as it sounds?

1. Buy this
2. Disconnect brake lines from master cylinder
3. Unscrew the two bolts that holds master cylinder
4. Swap brake fluid reservoir from old cylinder to new one
5. Screw everything back in place
6. Bleed brakes

Is there no vacuum shit that I have to take in consideration when doing this?

[Altrezia]

Just to stay in the loop - I decided to do the MC on my car, too, as I couldn't find anything else wrong. Hopefully it'll fix both of our issues.

[Brianmoooore]

That's about all there is to it. Press the brake pedal a few times after the engine is stopped to get rid of any residual vacuum in the servo, although I can't see that it would cause problems changing the cylinder anyway.

[jas025]

A spongy brake pedal on an E30 - i.e one with too much travel as opposed one that goes to the floor and then pumps up - is caused by a bit of wear in the cross linkage. It's easily rectified by dropping the column undertray and glovebox, slackening the 17mm locknuts on the crosslinkage and turning the crosslink bap with long nosed grips to raise the brake pedal around an inch - this transforms the feel of the brakes but don't overdo it.

Going back to the comment on adjusting the cross linkage - is this item 11 on the OEM diagram below or does anyone have a handy picture?

http://www.realoem.com/bmw/showparts.do ... g=35&fg=05

Cheers in advance.

[Brianmoooore]

Part #11. There are flats on the rod near the RH end to enable you to turn the rod with a 7mm (?) open ended spanner.

[jas025]

Part #11. There are flats on the rod near the RH end to enable you to turn the rod with a 7mm (?) open ended spanner.

Cheers - added this to the list of things to do when the weather improves.

[kangman]

My car is currently making a hissing noise when the brake pedal is applied, google tells me its the brake booster?

My car has an e34 servo

It was making this noise prior to my conversion (before the servo was swapped for an e34 setup)

[AardHawk]

Buy and use one of these http://www.ebay.co.uk/itm/CLASSIC-CAR-B ... 3a65513ed1

Be brutal, dont pussy foot about. Shock the system to get any last bubbles out.

[E30REDD]

My car is currently making a hissing noise when the brake pedal is applied, google tells me its the brake booster?

My car has an e34 servo

It was making this noise prior to my conversion (before the servo was swapped for an e34 setup)

Mine does also make that hissing noise. You can hear it when you press the brakes when engine is off.

[Brianmoooore]

It's supposed to! All cars with normal vacuum operated brake servos do.

[Fred555]

As Brian says, the hissing is normal

If you think the servo diaphragm is damaged, start the car and then spray some "start ya bastard" or similar at the servo push rod behind the glove box. If the engine RPM increases, the servo is faulty.

Used to have a can of "start ya bastard" can you buy it in London UK?

[Brianmoooore]

Used to have a can of "start ya bastard" can you buy it in London UK?

A can went for £20 on ebay last year, so I doubt if it's readily available! Bradex Easy Start is the UK equivalent.
Alternatively, use a propane blow torch with the jet removed. It's possible to get a car to start, run and drive (no petrol) with one of these directed into the air intake.

[Speedtouch]

My local garage mechanic uses brake or clutch cleaner aerosol sprayed into the intake, which seems to work well.

[BenHar]

Fag lighter gas is good for this, too.

Ben