p5 brake swap

[Justin2129]

I haven't looked at a p5, or mazda 6 for that matter, but the mazda 6 could use an electronic boost pump and not a vacuum booster, which could change pedal feel.

the pedal is so soft that it's undrivable, and people have done this mod before, so that shouldn't be the issue. I've never seen it mentioned on the p5 forum either...

After all things are bled, and you are running the car, is the first push of the pedal low, but if you quickly step a 2nd time on the pedal does it firm up? When I had my land rover shop a lot of the land rovers had that problem. Sadly uncureable.

it's always soft when the car is started, no matter how many times you push the pedal



anyone think it could be a bad master cylinder? Someone on the p5 forum suggested that

[villageidiot]

its possible it could be a bad master, but if the master was fine before the swap, i doubt it would be the problem

[Justin2129]

do you guys think it would be worth it to take it to a shop and have them bleed the brakes, and see if that works?

[crazyrog17]

The brake pedal is coming back up. It's just soft like there is air in the lines.
The tool we have is similar to and works like this.
http://shop.advanceautoparts.com/web..._T|GRP2007____

This tool pulls a vacuum through the lines, it doesn't push fluid up to the resevoir.

To use this tool:

Fill the master cylinder's resevoir

Fill the pump's jar to the lowest indicator line and slide it's tube onto the caliper's bleeder screw

Open the screw and pump away as it pulls the brake fluid through the lines and into the caliper

Stop when you see no more bubbles in the pump's catch jar and tighten the bleeder screw.

[ejp2fast]

paul, did you put a new master cylinder in? If so, was it bench bled? I had similiar issues when I was doing my hydraulic clutch on the porsche 944 a few months ago... and that air just DID NOT want to get out!

[neanderpaul]

No sir, stocker in place. It was working before the swap. Hasn't been moved.

[htchbck]

I'm not too familiar with the 6/P5 brake swap but did you have to use any of the hoses off the 6? Could be one of the hoses is breaking down on the inside and bulging, which will let the pedal drop. I doubt the P5 ones were bad since they were working before, but if these are JY parts its a possibility. Makes it very hard to get all the air out, and even if you do the pedal will be mushy.

Also, you had mentioned that with the car off the pedal would get very firm, if you pumped it up till it was firm and then stood on it for thirty seconds would it drop any?

[Dustin]

If you didn't replace the mc, and the masters are different bores it will behave as you describe. Even a 1/16th of an inch in bore diameter will make a significant difference. Just my $.02.

[neanderpaul]

I'm not too familiar with the 6/P5 brake swap but did you have to use any of the hoses off the 6? Could be one of the hoses is breaking down on the inside and bulging, which will let the pedal drop. I doubt the P5 ones were bad since they were working before, but if these are JY parts its a possibility. Makes it very hard to get all the air out, and even if you do the pedal will be mushy.

Also, you had mentioned that with the car off the pedal would get very firm, if you pumped it up till it was firm and then stood on it for thirty seconds would it drop any?

All the brake lines are from the P5. I will check tmrw on the "car off 30 second thing."
Thanks again.

[neanderpaul]

If you didn't replace the mc, and the masters are different bores it will behave as you describe. Even a 1/16th of an inch in bore diameter will make a significant difference. Just my $.02.

Good info./ Factoring it in. thanks

[neanderpaul]

This tool pulls a vacuum through the lines, it doesn't push fluid up to the resevoir.

To use this tool:

Fill the master cylinder's resevoir

Fill the pump's jar to the lowest indicator line and slide it's tube onto the caliper's bleeder screw

Open the screw and pump away as it pulls the brake fluid through the lines and into the caliper

Stop when you see no more bubbles in the pump's catch jar and tighten the bleeder screw.

This tool is designed for a number of jobs. It pushed very effectively. Thanks.

[Biff]

Try to confirm the master cylinder has all the air out. I have seen very stubborn M/C's.
Disconnect lines at M/C , maybe hook junk lines bent up above resevoir level and into a container to help contain the mess. Try to work the M/C to get any air out. My son has a hand held vaccum pump that I have not used but I could see it might be handy in a case like this.

[neanderpaul]

Thanks Biff. A hand held vacuum pump is what we're working with.

[Gomez]

buy a new p5 ha ha

I'm working the same issue on my brothers Festy. Constant flow of fluid, mixed with air, in the lines. Took cap off m/c res and see that is sucking air in when pedal is released. Tells me that one of the seals is bad even though it worked fine until the line went dry. Today I am going to try the brake line into the reservoir thing to bleed the m/c before I go any further.

If you see my issues on yours LMK and I will post my findings later today. A mechanic buddy told me today that even though it worked perfect before, running a m/c dry can easily tear a seal and make it useless even when trying to benchbleed it. Looks like I may be going to the jy too

[htchbck]

buy a new p5 ha ha

I'm working the same issue on my brothers Festy. Constant flow of fluid, mixed with air, in the lines. Took cap off m/c res and see that is sucking air in when pedal is released. Tells me that one of the seals is bad even though it worked fine until the line went dry. Today I am going to try the brake line into the reservoir thing to bleed the m/c before I go any further.

If you see my issues on yours LMK and I will post my findings later today. A mechanic buddy told me today that even though it worked perfect before, running a m/c dry can easily tear a seal and make it useless even when trying to benchbleed it. Looks like I may be going to the jy too

Yep, very very good point, as soon as I read that line that I bold-ed I started thinking about the very thing you wrote in the rest of your post. Good call! Which, BTW Paul makes it even more important to try and stand on the brakes once they are pumped up. You may have all the air out, but an internal leak in the MC that is allowing pressure to bleed off without actually losing fluid. In fact, I think Gomez may have just cracked this case wide open for us.