Stingraynut

My 1988 auto coupe has been converted to right hand drive for Australia. I discovered that the line to the FRONT brakes is the REAR line at the master cylinder - is this normal?

The reason I ask the question is that 3 years ago I fitted a brake bias spring and could feel no difference and I am about to fit a new master brake cyclinder, so this is the time to swap them back if they are not in the original position.

My question is - does the hydraulic line coming from the front position on the master brake cyclinder go to the FRONT or REAR brakes?

redrose

checking

Stingraynut

Hi redrose - I got your original reply via email notification BUT - I just had a close look at the new MC and it clearly has an F and a R for front and rear and they are R at the back and F at the front- so I would really like to hear from any vette owner that KNOW the answer - especially if they have an 88.

I took a pic of the new MC to show the F and R markings - I bought it from Ecklers and it is for an 88 Corvette -


Thanks for the PM Qiken, I bought the MC from Ecklers in November last year, I forget the cost- it would probably be same, or close to what Ecklers are showing now.

Iroc57

Just based on your pic you have the answer. Regardless of your current config it clearly tells you how to pipe it

Slalom4me

On my '89 and on instances of member's '88 & '91 master cylinders,
the OEM tube for the FRONT circuit has the smaller (M10 x 1) tube
nut and assembles to the FRONT port on the OEM master cylinder.

(The OEM tube for the REAR circuit has an M12 x 1 tube nut.)



However, since your system has likely been modified as part of the
RHD conversion, ...

Does the M/C installed on the car now look like the replacement
from Ecklers?

PBR makes other master cylinders which have the ports reversed
(front port for rear circuit, rear for front). However, IIRC, these
do not have the integral proportioning valve housing cast into the
body like my OEM '89 C4 unit.

.

Slalom4me

I also have reason to believe that the later C4 models received M/Cs
that have the small port for the front line cast at the rear of the cylinder.

It looks as though the change may have occured for '92 when the
switch from dual to single reservoir occured.

.

Stingraynut

I've checked the MC and the front hole IS smaller than the rear.

I know for sure that the rear reservoir is for the front brakes on the old MC, so if this MC is the same then the internal plumbing must cross over ?

Anyway, both Mc look identical and because of the different sizes, there's only one way to fit the lines, so it must be correct as it is.

How come the front brakes get less hydraulic pressure, limited by the smaller outlet at the front? That seems all wrong

redrose

four minutes after that reply (check times),memories of recent brake massacres surfaced , forcing declaration of time-out , started looking at parts in my garage , different years Service Manuals...here's what weirdness has appeared:

1) looked at the m/c and piping that we pulled off my 84 vette a couple months ago, that has TWO lines at the front of the m/c that serve the front brakes...THIRD line serves from rear of m/c to rear brakes...absolutely no question on routing (no anti-lock obscures view)
2) my 86 vette has only two lines, m/c is labeled F and R, both lines are same size but fitting at R port is larger (port labeled R is at rear of m/c)...86 Service Manual sez front m/c piston is 'primary' and serves front brakes...(nest of snakes at anti-lock unit prevents observation)
3)both 94 and 96 vette Service Manuals claim rear piston is 'primary' and rear piston serves front brakes... (opposite from 84/86)
4) 88 Service Manual sez the front piston is primary and serves the front brakes ...(same as 84/86)
5)looked at a half dozen other m/c's, all GM, none vette, none port labelled, all have one fitting and pipe bigger than other, big one at front of m/c.

hope you can make some sense of this nonsense

rodj

Anything can happen down here as far as conversions go. Generally everthing is just moved to the RH side.
However as PBR is a local co , the convertor may have used a similar PBR MC with the ports inverted or someone in the past my not have been able to get a OEM MC.
In any case the new one you have is correct.

Stingraynut

Thanks Slamone4me and redrose - I've saved the pic of the two pipes and M10/M12 nuts, and taken on board all the info - I'm certain now, because of the different size connectors that there's only one way to connect. Thanks very much for your help, the forum always comes up with the answer!!

I've made a new post about trying to remove the combination piston from the new MC, it won't come out, I've taken a picture looking into the bore where the piston is - maybe you can help me out with this too?

Here's the url for the post http://forums.corvetteforum.com/c4-t...post1569277562

redrose

we do have the fancy test gauges that screw in place of the caliper bleed screws, but s.o.p. before racing is quick/dirty brake check:

jack all four wheels off ground...engine off, trans in neutral...one person at LF wheel, second person at LR, driver in seat...'wheel guys' (or gals) slowly spin wheels in forward direction while driver gently presses brake pedal...when each wheel is stopped by its caliper, respective wheel guy shouts 'yes'...front 'yes' should always be heard BEFORE rear wheel shout...spin/holler is then repeated at LF vs RF, shouts should be nearly simultaneous (never are 100%) if RF prop valve is not used, delayed RF shout if prop valve in that side (circle racers trick only)...rear end is locked, no brake test side/side.

technically there are probly 87.5 reasons why this test is not valid, but it has found problems before they grew big teeth, bit the wall.