Another brake pedal to the floor type post.

[Mr Cull]

A short while a go I noticed that when coming to a sharp stop before a set of lights my brake pedal went to the floor and the Supe didn’t stop quite as fast as it usually did.

 

Quite concerned I crawled the short distance home and started trying to diagnose the problem.

 

Since then I have tried various things and read several postings on here.

Listed below are some of the ones I have found useful. I thought I would post them on here as they might help someone else out some day if they stumble across this thread...

 

Brake system manual

http://www.turbosupras.com/pdfs/JZA80%20TSRM/BR.pdf

 

Bench bleeding the master cylinder whilst still attached to the car

http://www.mkivsupra.net/vbb/showthread.php?119753-Bleeding-master-cylinder&highlight=master+cylinder

 

Bleeding brake issues and advice

http://www.mkivsupra.net/vbb/showthread.php?237994-cant-bleed-my-brakes-WHY&highlight=bleed

 

http://www.mkivsupra.net/vbb/showthread.php?169608-Bleeding-the-brake-system&highlight=brake

 

http://www.mkivsupra.net/vbb/showthread.php?196487-Brake-Bleeding&highlight=clamp+brake

 

Bleed nipple issues (don’t over tighten!)

http://www.mkivsupra.net/vbb/showthread.php?250422-Brake-bleed-nipple-woes!&highlight=bleed

 

New and old master cylinder innards compare

http://www.mkivsupra.net/vbb/showthread.php?118304-Master-Cylinder&highlight=master+cylinder

 

 

For my issue my first thought was seals in the master cylinder. I’d had the car several years and this brake issue happened overnight so I did not think it could be air in the system. No fluid was leaking either.

I spoke to keron about a refurb brake master cylinder kit but they were getting on for about £100 from Toyota (part number 04493-14150). But luckily for me he had a used spare Master Cylinder which I took.

 

Before fitting I bench bled the replacement master cylinder. Made sure there was no air left in it. Next bleed the callipers (with engine running as I have ABS).

 

To bleed the callipers first I tried the 2 man method of pumping and then opening and closing bleed nipple. I was pretty sure I got all the air out. But no joy, the pedal still went to the floor.

Next I purchased a one way valve bleed system off ebay (£4)

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260826474018#ht_1098wt_1139

This works really well and makes bleeding a one man job. The only issue I found was that getting the rubber tube over the end of the nipple sometimes was a bit fiddly. But after this I still the pedal still went to the floor.

I saw on here the post advising the “Gunsons Pressure Bleed Kit” at around £20 so got myself one of these.

http://www.amazon.co.uk/dp/B001KTFIWA/ref=asc_df_B001KTFIWA1856065?smid=A3P5ROKL5A1OLE&tag=googlecouk06-21&linkCode=asn&creative=22206&creativeASIN=B001KTFIWA

As mentioned the cap does not fit on a jsec NA reservoir. I had to fabricate and try and G-clamp a new cap on. After some trial and error I got this to work but it was a bit of a pain to do and also has the potential to spray, the not so paint friendly, brake fluid if you get it wrong.

But even after that still the pedal goes easily to the floor

 

 

The reservoir never went so low that air could have got back in the master cylinder.

 

So after putting 3lts of fluid through the system I was pretty confident that there was no air in there (could there still be some in the ABS unit???)

 

Still pretty sure there is no leak anywhere.

 

 

Next I thought maybe it wasn’t the MC in the first place so took one of the pistons out from the original. Couldn’t see anything wrong with the seals but not really sure what I’m looking for. Below are a couple of pics if anyone else knows what to look for.

www.photobucket.com/mkivMCpiston

 

 

So when I get some spare time again I’ll give it another go.

 

Next things to possibly try are:

- Clamping brake lines. Tbh im not too sure if I have braided ones. I assume not. Anyone got any advise on this. Have not really found any info on this.

- Stuck sliders in callipers. Could this really cause the brake pedal to go to the floor?

- Possibly find some things to screw into and block off the two outlets on the master cylinder. If I can do this I should be able to prove whether the MC has a fault or not(??)

- Someone has mentioned trying a vacuum bleed system. Maybe if there is still some air in there this would get it out.

 

Does anyone have any advice on which to try first or any other things I may have missed?

 

As per usually all comments/suggestions most welcome and thank you in advance for anyone that chips in

Edited August 15, 2011 by Mr Cull
corrected title (see edit history)

[Mr Cull]

Can any mods please remove the duplicate “to the floor” from the title.

[kjgreen3]

I would say that you definately have tried the best ways to get air out of your system. So thats not your problem. If the master cylinder and the brake cylinders are in good working order then next thing to check will be leaks in the actual brake lines itself. They do corrode over time especially near the rear wheels where they are protected from damage by plastic covers. These areas trap dirt and water tight against the brake lines so after a number of years they will corrode.

 

I would suggest you throughly clean the underside of the car, get it on a ramp with a friend in the car pumping the brakes whilst you inspect all brake lines for corrosion and/or leaks. I suspect if everything else in the braking system is fine then you have a tiny pinhole leak/or loose joint/connection. Not enough to cause catastrophic brake failure 'YET' but enough to degrade the braking performance and cause the pedal travel to maximise.

Edited August 15, 2011 by kjgreen3 (see edit history)

[kjgreen3]

Can any mods please remove the duplicate “to the floor” from the title.

 

You can edit your own post titles, click edit and go advanced. I know cos a mod told me when I wanted a thread title changing.

[kjgreen3]

- Clamping brake lines. Tbh im not too sure if I have braided ones. I assume not. Anyone got any advise on this. Have not really found any info on this.

 

Stolen from one of the threads you posted regarding brake clamping. Thanks go to Mr Wilson for this advise

 

"Clamp off a caliper hose and see what happens, try all 4 in turn. You may identify where the air is like this. Don't try clamping braided hoses, they don't like it, only OE type rubber ones..."