Mk1 Mx5 Brakes!!!

Technical Area Wheels, Tyres & Brakes
2

Hi Guys 

My Name is Henry 

 

I have recently bought a mk1 mx5 1991, and i had to replace the brakes. 

I decided to change them for the 1.8 disc and callipers, which was pretty straight forward. or so i thought…

 

I didn’t have a problem with fitting them. and I’ve had plenty of experience bleeding brakes on my minis and land rover. 

However i can’t seem to get a break pedal. When i undo the bleed nipple good fluid comes out i.e. no air bubbles 

i think it could be the master cylinder rubbers? as the fluid is a dark brown. i don’t know and would like some help and suggestions

 

Thanks Guys

 

Henry

3

Were the 1.8 calipers in working order before you fitted them? It appears to me that as you are only having this problem after changing the brake discs and the calipers it must be something to do with them.
The dark brown fluid suggests some contamination or rust from some where.
I guess you got the calipers very cheap and were not from MX5PARTS.
I suppose you could put the original calipers back on to see if they were working OK, that would eliminate the master cylinder.

4

Are the bleed nipples at the top of the calipers. If not change them from side to side.

5

As above but you need to swop over the brackets to suit.ie LH to RH and visa versa.(They go on upside down when fitted to opposite side but thats ok)

6

Brown brake fluid is water contaminated and well overdue for a complete change.  As mentioned, make sure the bleed nipples are at the tops of the calipers.  There’s another possible master cylinder issue.  I’ve heard of master cylinder seal failure after brake system work that requires bleeding.  My personal theory is that the old fluid which has collected water allows the master cylinder bore to corrode.  In normal use only a small part of the cylinder is used and that section stays ‘clean’.  When bleeding the system the full pedal travel pushes the seal over the corroded section which is not normally used, resulting in it being damaged.  May be worth a check if nothing else works.

Apart from brake cylinder corrosion, fluid changes can save the ABS unit from corrosion. 

JS