Bleeding brakes or find a leak

[neilbardsley]

On Saturday I bleed the brakes. Firstly trying to have my son press down while released air out of the system. I completely failed using that method so I attached a pressure tool to the master cylinder. This worked much better and the brake pedal became higher and firmer. However, during my drive yesterday it changed to how it was before. Which is just a little too soft for my liking. I guess this means that have a leak in the system somewhere?

However, before I look for the leak I used DOT 4 and I don't know what was in before so should I push all the old brake fluid out? If so how much brake fluid, approximately, is there in the system of a 356?

To find the leak I was thinking that I would repeat the bleeding process and if a particular wheel has air bubble then replace the soft brake/line check the connectors. If all 4 do it's the after the master cylinder or pedal?

[Nine One One]

Does this help?

viewtopic.php?f=2&t=62821&hilit=BRAKES+BLEED

[neilbardsley]

Does this help?

viewtopic.php?f=2&t=62821&hilit=BRAKES+BLEED

It's does but I thought to mention the issue is on my 356 so a drum car.

[Lightweight_911]

Neil - how did the air get into your braking system in the first place ?

More times than not, you don't get all of the air out of the system the first time you bleed them - now that you driven the car a bit it would be worth bleeding them again.

I suggest getting a few bottles of brake fluid & bleed each corner until you get a constant stream of clear/fresh fluid coming out of each bleed nipple.

I've recently been through this process on my '59 Alfa Giulietta Sprint after a complete overhaul of the braking system including changing all of the drums/shoes/wheel cylinders, etc - I bought the DOT 4 brake fluid from Euro Car Parts (via ebay).

[neilbardsley]

Thank you Andy

Neil - how did the air get into your braking system in the first place ?

I think I introduced air into the system by having my son pump the brakes while I have the bleed nut open on a wheel. I thought that I was pushing brake fluid through the system. I appears that I was but sucking air in too. This process made the brakes disappear completely.

More times than not, you don't get all of the air out of the system the first time you bleed them - now that you driven the car a bit it would be worth bleeding them again.

I then got a 5l bottle of DOT 4 and bleed the brakes using the pressure thing attached to the master cylinder. No pump of the brake this time. Just the pressure from the spare wheel pushing fluid through the system. I did this on each until I got no bubbles. The brakes were much firmer and I took for a 200m test drive.

I suggest getting a few bottles of brake fluid & bleed each corner until you get a constant stream of clear/fresh fluid coming out of each bleed nipple.

I've recently been through this process on my '59 Alfa Giulietta Sprint after a complete overhaul of the braking system including changing all of the drums/shoes/wheel cylinders, etc - I bought the DOT 4 brake fluid from Euro Car Parts (via ebay).

I will have another go this weekend with the pressure bleeder, take for a longer drive and report back.

[neilbardsley]

I bleed the brakes again this weekend and the firmness of the pedal improved. I only had time for a quick test drive so it will need a longer drive.

[neilbardsley]

Longer test drive and the brakes where soft again. While at the Greatwork morning I got the car up on a ramp and we found a leak from the front right flexible hose. New hoses ordered so I will try to fix next weekend.

[neilbardsley]

I replaced a flexible hose. Took for a short test drive but need to take for a longer drive.

[sladey]

Once you’re doing the bleeding that’s the worst part of the whole thing so I would say replace ALL the hoses - they don’t cost much and you know you’re dealing with new throughout.

[smallspeed]

I’m bleeding brakes on the track car 2-3 times per year, and recently brought a set of Goodrich speed bleeders from jjc / demon tweeks .. definitely worth investing in - I can’t pressure bleed due to the type of brakes and these have been invaluable allowing me to do the job on my own vs using the wife and a second assistant!

[neilbardsley]

4 hours in the 356 today but brakes still not sorted. I will Jack up the car tomorrow and have another look

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[neilbardsley]

I replaced the back soft hoses and junction. Bleed the system using a new pressure bleeder. I had clear liquid coming out of each brake with no air bubbles. I tried using the vacuum one too but kept getting lots of air. In the end I figured that maybe I was getting air from beside the nipple and tube? However, as I said when I bleed the brakes using the pressure tool I get clear liquid and no air bubbles.

Still the same issue. Brake firm at start of the drive and then it travels down during the pedal but still is firm but with more travel. Maybe it's time to replace the master cylinder?

[PeterK]

Neil
Before you start spending serious money, are you sure you have an issue ?. Was it better before, and it is now poor ?

If the pedal goes firm and the brakes work, good. If you pump the brake pedal and the 'bite' point comes up, then you may have air in the system, but you may just need to adjust the brakes.

If you press hard and the pedal slowly sinks to the floor, then this is not good.
Peter

[911hillclimber]

Imho Peter is dead right.
I have a lot of trouble bleeding my 911s brakes, a real pain, some have no problems.
The vac pump system can and will draw air in via the nipple thread when the nipple is slack, also air can be sucked in so you just go round and round and round.
Wife in the seat doing the work works best for me.

As you must have changed everything else by now, that there are no leaks, then the master is the final step.

[neilbardsley]

If the pedal goes firm and the brakes work, good. If you pump the brake pedal and the 'bite' point comes up, then you may have air in the system, but you may just need to adjust the brakes.

Peter. This exactly describes the behaviour. However, now I have tried 3 methods

-> Wife in the seat. There is a lot of moaning associated with this method!
-> Pressure pusher
-> Vacuum on nipple

I don't know what I'm going wrong.
Perhaps as you said it's not air in the system but I need to adjust my brakes again. A while ago I adjusted them so that no noise was made when I span each wheel. As for how bad it is! The car will stop in a straight line and lock all 4 wheels (if I'm not careful). I just want the bite to be in the same place every time.

I'm enjoying learning at the moment. I'm not enjoying working under the car when it's on jacks but each time I'm learning. If I had a flat floor in my garage and proper lift the job would be easier.