[wlspn]

I was unfortunate enough that when I first got my 32 it had the front & rear single-piston calipers.
Then was lucky enough to pick up a 33 GTST for next to nothing so swapped brake calipers (& rotors) over.
They stopped the car fine but even when properly bled the pedal felt like it didnt start actually doing anything until it was about halfway down.

I figured the 33 m/c probably had a bigger bore size & even if it didnt, the 32 m/c has a weird design with fluid going to the end of the bore then doing a u-turn before getting pushed down the line, so figured even if same bore that the design was giving me the low pedal feeling.

So recently when I fitted the motor & gearbox from the 33 into my 32 I also swapped master cylinders, modifying a few lines along the way.
Also swapped boosters as my 32 m/c had been leaking all over (& into?) my old one.

However, now, even with the R33 master cylinder & booster that was originally matched to the calipers I have, I get the same low pedal feel.

I am going to re-bleed the brakes but dont think it is going to make much difference. Very confident there is no air in them...

Does anyone have any other suggestions or has anyone had this same problem?

Thoughts & advice would be great.

Cheers,
Brett

 

[wlspn]

Anyone? Any ideas/advice, even opinions?

 

[Dick_GTT]

Although it was not on a skyline I had a similar problem many years ago and it turned out to be a hose that had lost its strength and was turning into a balloon when the pedal was pressed. So it might be worthwhile getting someone to press the pedal whilst you check the hoses. I also found when I had my R33 I had to use a vacuum pump to get all the air out of the system to get rid of the spongy feel after changing to braided hoses.

 

[lammy426]

a warped/bent ill fitted disc can do it aswell,does the peddle come up if you pump it a second time

 

[wlspn]

Although it was not on a skyline I had a similar problem many years ago and it turned out to be a hose that had lost its strength and was turning into a balloon when the pedal was pressed. So it might be worthwhile getting someone to press the pedal whilst you check the hoses. I also found when I had my R33 I had to use a vacuum pump to get all the air out of the system to get rid of the spongy feel after changing to braided hoses.

Rear lines are braided, will check fronts as these are still rubber at the moment. Although as the pedal is so soft I assume no pressure is being built up until pedl is halfway down...

a warped/bent ill fitted disc can do it as well,does the peddle come up if you pump it a second time

Due to needing a tune, which I am getting in next few weeks I havent driven the car much. In the driveway pumping the pedal more than once builds pressure but as Ive only driven it twice (to shops) I havent had much of a play with pedal whilst driving... I just noticed when I used the brakes the pedal sank halfway before anything happened.
Also R33 discs were machined before fitting them & calipers to car

 

[Stusy]

Have you also bled the master cylinder? There is a bleed nipple on it.

 

[TriniGT]

Was the master cylinder bench bled before installation? If not then that may be your problem. A way to solve this would be to get two cut brakeline ends, what I did was to get about a 12" brakeline end and screw them into the master cylinder where the stock lines would be being careful to not spill any fluid and if you did quickly wash away. Have the lines bent up and into the fluid reservoir so as the end of the line is always submersed in the brake fluid. Have someone pump the brake pedal and watch bubbles come out of the lines being careful to not let the level drop below the bottom of the lines and keep topping up until there is no bubbles coming out of the hardlines. See here for more help and let me know how it goes, bench bleeding is to the bottom.
http://www.jull.co.uk/index.php?option=com_content&view=article&id=71&Itemid=76

 

[wlspn]

Didnt bench-bleed the master cylinder & because of that it took quite a while to getfluid through it & to the calipers but did end up doing so & bled the master...

But also as I mentioned, this was a problem right from when I first fitted R33 calipers & discs, retaining original master cylinder...

I may try your method of bleeding the master but am quite confident all air is out of system. Once halfway down pedal is firm where I imagine with air in the system (even in the master) it would slowly sink to the floor...

Thanks heaps for ideas though! Keep them coming...

 

[Stusy]

Ok last 2 ideas.....

pedal box bent

or

to much bulk head flex

 

[wlspn]

Please explain bulk head flex...
I possibly know what you mean but in different terminology.
Will check back tomorrow as its getting quite late here in oz.
12.30 already & I have to be up by 5.45!
Anyway whether you're right or wrong thanks for your help & advice...

 

[R33 GTSTEEHEE..]

same problem when I upgraded my brakes... had to bleed them a fair few times including master cylinder, kept topping up fluid and had one guy in the drivers seat pumping pedal.

Got there eventually...

 

[Dean33GTR]

Trick I used to do when bleeding awkward old Land rover brakes that were known to hold air in.
Jam suitable length of wood between pedal and drivers seat to hold pedal down overnight.Loosen reservoir cap.
It lets any air bubbles float up into the master reservoir and out to atmosphere. Worked many times for me. Might be worth a try