Spongy Brakes

[Maxmush]

My E30 comes with disc all round. The previous owner had it changed. However I find the brakes not responsive enough, lacking in braking power. What could be the cause?If it is the brake pads, ok I'll get it changed. My mechanic said there was a bit too much free play in the calipers, meaning some parts may have worn off. Does that have an effect on the performance of the brake. I am going to ask the mechanic to bleed the brakes, if that would help. Other than that what could cause the brake to feel spongy. Macam tak makan got to press the pedal harder to get the car to slow down. I think the car is using stock standard brake servo. Maybe I need to change the servo to something bigger or more effective perhaps. Yes, I'll have to check if the brakes are fitted with braided hose.Any advise you can throw my way would be greatly appreciated.

 

[fabianyee]

try searching the forum, there's been other thread on this E30 brake charateristic...

 

[Maxmush]

Well indeed there was quite a bit of posting on E30 braking problem and there was even notable postings on the mods undertaken and recommended to overcome this problem. My engine idling and tuning have been done, only just, and now its the brakes that I must attend to before considering further restortion works which I believe will take me months.

I had a discussion with my mechanic and he recomended a couple of options open to me. It would involve changing of the servo and master pump. I am not upgrading to ventilated disc upfront as yet. I will probably change the servo and pump to E32 or newer model of E30 servo.

Thanks fabianyee for pointing me to the right direction regardng this matter.

 

[cempaka]

Have you changed the brake fluid since you bought the car?

 

[saturation]

try changing the stock rubber hoses to braided brake hoses.

 

[yim1986]

Well indeed there was quite a bit of posting on E30 braking problem and there was even notable postings on the mods undertaken and recommended to overcome this problem. My engine idling and tuning have been done, only just, and now its the brakes that I must attend to before considering further restortion works which I believe will take me months.

I had a discussion with my mechanic and he recomended a couple of options open to me. It would involve changing of the servo and master pump. I am not upgrading to ventilated disc upfront as yet. I will probably change the servo and pump to E32 or newer model of E30 servo.

Thanks fabianyee for pointing me to the right direction regarding this matter.

first, check your brake fluid, it is one of the source of the problem, if the brake fluid is expired, it will start to absorb moist, the moist will vaporize in the system during increasing of the system temperature, creating air inside the system which caused the bad responsive of the system. when it comes to moist, it will involved rust inside the system which will damage the oil seal, clogged brake hose...etc

my personal opinion, changing a brake master cylinder when your brake is spongy but there is no leakage in the system, it will be your master cylinder piston oil seal could not stand the fluid pressure and cause internal leak. the brake servo is not necessary to replace if it is still working, a twin servo is just multiply the driver braking effort more than single servo, it will improve the response but not the braking performance, like the size of the brake caliper, provided if you change to bigger diameter brake disk and change to wider tires, the tire will be the first to improve if you want a better braking performance.

hope my opinion and explanation help...

cheers!

 

[virtualmystic]

if there is too much free play in your calipers then it might be that the floating mechanism (one caliper rides on pins) is sticky and needs to be taken out and cleaned. But since this is your braking system we are talking about, it would be a good idea to take it all out and refurbish the whole system instead of doing it piecemeal. You should:
1. bleed the whole system of it's fluid.
2. remove all calipers and inspect them as well as the discs (change if need be)
3. renew all brake pads.
4. renew all master and slave cylinder seals.
5. change brake hoses and also brake assist hoses (pneumatic)
6. restore everything, renew fluid and bleedby my estimate it should not cost more than RM1000 even if you have to change all those above mentioned items.

 

[Maxmush]

Well what happen today caught me completely by surprise. I went to my regular shop to check out a set of rubber for my E30. I could not decide on it so I got the mechanic to remove my front right wheel to fix the new tyre I intended to buy. I wanted to see how it looked on the car before proceeding with the purchase. To my horror the mechanic told me that my brake have no brake pad. Told me "sudah putus boss"! I was shocked and I said "nolah cannot be". Checked it myself and horror upon horror when he removed the front right pad, the pad materials dropped macam biskut kering. The inner pad was still intact attached to the base metal but the outer pad was completely broken in pieces and no longer attached to the base. I was saying to myself "no wonder the brakes felt so spongy and ineffective". For the first time after buying the car in 2 weeks time, I had a close look at my front brake system. The front disc is ventilated, braided brake hose and the calipers seemed good. However notice that the disc was slightly scorched, guess it would require skimming, I wonder if this is advisable. Immediately instructed the mechanic to check the brakes on all four wheels. Front left had the same problem as the right but the back with solid disc was good.

Changed all pads to ATE and sucked all brake fluid and bled the system using Shell brake fluid. (The mechanic shop is at the Shell Station). I could not wait to get the disc skimmed, postponed it to a later date. Need to check with the sifus of E30 as to whether this is advisable. I do know that disc have a certain thickness of hardened steel to take the braking abration but beyond the harden surface it is not advisable. Please correct me if I am wrong.

Now the brakes are more responsive but a bit low. I now wonder what could be the cause. I have that bit more confidence when driving now. Well good thing I asked the forumers about the brake, god knows what would happened if I had not decided to check out the tyres. I now know, thanks to everyone here with your very helpful help and tips, what I need to do. Only 2 questions remained.

1. Can or should I skim my scorched front ventilated disc.

1. My brakes pedal is a bit low, after changing pad and fluid, what could be the cause.

Thanks everyone.

 

[Maxmush]

Oh yes another thing, I will change my master and slave cylinder seals. Thanks virtualmystic. I am not taking chances on my brakes now. Not after what I saw.

 

[virtualmystic]

Get your brakes checked out as soon as possible! The reason the brake pads have worn unevenly is because the floating mechanism that i mentioned is sticky.....therefore one pad wears out before the other. The non floating pad now has to move too much (taking up too much fluid in the cylinder) before it makes contact with the disc.

For ventilated front disc, the minimum disc thickness is 20mm. The minimum thickness AFTER skimming is 20.4mm. So absolute minimum is 20mm. I suggest you replace the disc and pads together. PM me if you wish for me to assess your brakes.

 

[Maxmush]

Thanks Virtualmystic for this very valuable tip and advise. I have the brakes done but not exactly the way you have described it. I'll have the brakes reopened again next week and to be on the safe side I'll get the mechanic cleaned the brakes and replaced any faulty parts. As to the thickness of the front ventilated disc I shall get the mechanic to take a guage reading of the thickness. Should I need to change the disc do you think it is advisable to get a good used disc or go for a new one. How much is it if new, any idea?

 

[virtualmystic]

I bought my rear discs new for RM100 each. The fronts discs should cost a little more. With brake parts it is best practice to buy new. I suspect that if your disc have been scored, then the thickness will not be enough to warant a skimming.
What have you done to your brakes so far? If you did not lubricate the floating mechanism the brake pads will stick again and wear out in no time.

 

[3er]

Maybe you need to change your old rubber hoses to stainless steel brake lines. What? You havent changed them since 30 years ago? Rubber doesnt last forever in this heat....

 

[Maxmush]

Hi virtualmystic,

Sorry I have not log in for quite a while. After changing my brake pads and reading your posting on the brakes I did not want to take chances on the same problem recurring again. I got Optimum Auto to open up my brakes this time, cleaned it and change the rubber kit. The front left caliper bracket was faulty and I changed it. The floating mechanism checked and everything is ok now. However I had to skim the disc slightly and I reckon after this last skim I'll have to get a new disc the next time I have my pads changed. So, glad to inform that my brakes are working fine and what I am going to do in the near future is to change the servo to perhaps a newer model of the E30 maybe a 1991 make. I was informed that this would help.

3er......my brake hoses are all steel braided so there is no problem there. After draining the brake fluid again this time around the brakes feels a lot better.
Thanks for you kind advise virtualmystic. Its been a great help.