brake trouble

[lost4good2009]

ok so when i got my mx3 only the front brakes worked, when i got my loan for the swap, i replaced, rotors f&b, pads f&b, calipers f&b, the brake hoses on the back calipers, and the mastercylinder, well now i can only get fluid out of the front right and the back left... i have tried bleeding the brakes a few times now for hours at a time, and even tried gravity bleeding it, so im up for suggestions im hoping its not the proportioning valve but thats what i think it could be

[umcamara]

I'd say proportioning valve. Why are you hoping that's not it? It's not difficult to change, just spray all the brake lines that connect to it a day in advance with PB Blaster or whatever penetrant you prefer.

[lost4good2009]

yeah but idk where its at either... and i cant find one at any parts store...

[umcamara]

You replaced all those parts and you don't know where the proportioning valve is? It's on the middle of the firewall, closer to the passenger side. If you follow the hard brake-lines from the master cylinder, you'll find it. It can be slightly awkward to get to because of the size of the engine in the bay, but it's not that bad.

As far as a replacement, try an auto-wrecker or dealership. But determine if that's for sure your issue before visiting the dealership.

[lost4good2009]

yeah i replaced the master cylinder but dont remember coming across the proportioning valve, or i might have seen it but idk what it looks like, ill have it looked at and im doing my klze swap in the next couple weeks so that would be a great time to replace it lol

[mazdags94]

If it's anything like mine, it'll be covered in rust!

Mine is attached to the firewall near the top of the engine bay, in the middle. There will be hard lines going in and hard lines coming out. It's hard to miss if you take a look behind the engine (and maybe a flashlight).

[lost4good2009]

alright ill be looking tonight, thanks. but i heard these almost never go out... think i am one of the lucky... well, UN lucky ones?

[davmac]

I highly doubt the proportioning valve is bad. It is more likely that you have not bench bled the master cylinder. I can't remember how the MX3 master looks when installed, but if the cylinder body is pointing up it will be nearly impossible to bleed when mounted in the car. Therefore one of the brake circuits will have air at the master cylinder and will never be able to move fluid to the wheel hydraulics on that circuit.

To bleed the master cylinder you have to get the cylinder body level. Your choice is to raise the rear of the car or remove the master and clamp it in a vise. A master cylinder bleeding kit is cheap from auto parts store and will come with some directions. Make sure you have no air in both the master outlets.

[wytbishop]

I have had a proportioning valve that would not pass fluid tot he rear. Changing it was an absolute wh...er..umm...it was not fun.

[lost4good2009]

yeah it was my first time installing a master cylinder so i very well may have installed it wrong. when i got the car the front breakes were the only thing that worked, then i replaced all those parts and now diagnolly, right front and back left work, and i figured since it was diagnol split it was the proportioning valve rather than the master cylinder because if i remember right the master cylinder is split front and back? correct me if im wrong plz

[Daninski]

When you bleed it in a vise watch out. the fluid could spray out and screw your paint job. Ya, happened to me.

[davmac]

The proportioning valve controls fluid between front and rear. Its purpose is to provide more power to the front brakes. The master brake cylinder splits outputs to 2 brake circuits for safety. On most fwd cars the split is cross linked so one circuit is rear right and front left and the second circuit is rear left and front right. That is why I think the problem is in the master not the prop valve. Another possibility is that you have a bad leak in one of your circuits prior to wheels - but i'd guess you would have seen that.

I have never changed a proportioning valve, but it looks like an evil job due to location and condition of the brake lines. You'd spend most of the time wondering if you should remove the engine for access. I'd consider replacing or revising the hard lines and mounting a new prop valve in a more accessible spot. I do know I'd get my brake lines here.

[lost4good2009]

hmmm... i didnt know the master cylinder had it split diagnol... i was thinkin prop. valve was diagnol and master cylinder was front and back. So ill prolly try to bench bleed it again on a vise, and lucky my vise is in our tool shed so i wont spray it on my car =P thanks for the heads up