Brake pedal to the floor

[boycer]

Hi, the other day the accelerator cable snapped whilst out on the motorway on my 70 Westy. The van was recovered, but when I got back home I noticed the brake pedal was going flat to the floor. If I pump it once it works ok.

It has Porsche discs up front & drums at the back. There is no obvious sign of leaks from anywhere, the only thing I did was check the fluid in the master cylinder which was at the correct level, before I set off.

It may just be coincidence, but any ideas before I dive in would be appreciated!

Cheers.

 

[StuF]

Just bleed the brakes again - furthest away first, must have introduced air into the system somewhere and youll need to get it out.
Always good to get fresh fluid into the system too

 

[boycer]

Thank Stuf, I thought I might have to do this.What is the best fluid for my set up, is it Dot4? Thanks again

 

[KateLovesPurple]

If you're brake pedal is going to the floor and then goes solid and not spongey when you pump it once I'd be inclined to think you may need to adjust your rear drum brakes. The first press brings them closer to the drum, the second press makes them work. If that makes sense.

 

[boycer]

Hi Madman, no it is still spongy & gets harder the more I pump it. If I'm going to bleed the brakes I might as well add new fluid, so do you know what fluid I should use dot 3 or dot 4? cheers.

 

[Moseley]

Normally, the symptoms you’re describing would be of a failing master cylinder. To confirm, once you pump up the pedal to make it harder, does it sink slowly if you keep your foot on it after the last pump?

If it stays up, it’s probably just air in the system as others have suggested. If it slowly sinks, you need some new MC seals, or a new MC.


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[KateLovesPurple]

Yep, if it is spongey, then definitely air in the system. As Moseley said, if it slowly sinks to the floor with your foot kept on it, then MC seals, if not then just bleed the brakes and check the adjustment of the rear drums. DOT4 is fine.

 

[boycer]

Thanks for the responses. I tested the brake pedal and it didnt go to the floor, so assume was/is air in the system. Anyway, just started to bleed the brakes, using a Gunson kit & the master cylinder has just spilled its guts under the van. The pressure I used was 11PSI. I realise a seal has probably gone on the a master cylinder and it looks like the one that joins it to a/the reservoir? Any help or advice would be appreciated...

Thanks

 

[Moseley]

One of the reasons that I’m not a fan of pressure bleeders... you’ve probably blown the hose off that feeds the MC from the top reservoir or possibly the MC reservoir from the MC itself. Neither of these parts / their respective seals are designed to see pressure. The MC internal seals are probably good as these will withstand a pretty high pressure, as would normally be generated by your foot.

Re-attach whatever has come detached, and personally, I’d stick to bleeding the old fashioned way using 2 people.


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[sparkywig]

As Moseley says above, the low pressure side of the brake system from reservoir to master cylinder is not designed to cope with the force of a pressure bleeder.

 

[boycer]

Thanks for the help. I’ll look at it tonight & hopefully it will be a straight forward fix.

 

[boycer]

Update - I can see that the pipe from the upper reservoir to the lower reservoir has come off. There is a rubber seal between the pipe & the lower reservoir, that is damaged. Looking on a couple of websites I cant see any seal for that part of the system. There is a seal from the pipe to the upper reservoir, but nothing from the pipe to the lower reservoir. I could just leave the seal out, but the existing clamp is not strong enough to clamp the pipe to the reservoir without the seal, so I could use a jubilee clip(?)
Again any help/advice would be much appreciated...

 

[KateLovesPurple]

If you have the original semi rigid plastic type pipe from the upper reservoir to the master cylinder, chances are it is too hard now to work without a decent seal. What a lot of people have done now is to replace the pipe with a length of 12.5mm id EPDM hose. You can get it from here:

https://www.hoseworld.com/12-5mm-i-d-epdm-rubber-tubing-epdm-12-5.html

These old threads talk about it.

http://forum.earlybay.com/viewtopic.php?f=4&t=55570]
http://forum.earlybay.com/viewtopic.php?f=4&t=36654

Edit: Don't know why the links didn't go in right!