I have a 1992 Honda Civic CX with a D16Y8 motor/tranny swap.

On my way home from work today the brake pedal started to sink to the floor.

At first, the car had no signs of problems. Then about half way home, one time I pushed the brakes I thought I felt the brake pedal sink a little. So I started paying attention to it. With every time I pushed the brakes the brake pedal sank further and faster. But if I pumped the brake I would get a little pressure and then it would sink again while I was moving. But at a stop light if I let go of the brake and then pushed again, it would hold pressure. By the time I got home I got barely any pressure. Keep in mind this all happened relatively quick seeing as I only have a 18 mile drive home from work. So I got it home by down shifting and pulling the e-brake while pressing the brake pedal. When I got home I opened the hood and my fluid is right at the Max line, looked under the car at the front calipers and there wasn't any visible signs of any fluid leaking.

So from what I've read in the forum before and what I just described it seems to me that my problem is the brake master cylinder. Or could it be the brake booster? I'm not sure what problems the brake booster causes when it goes. Is there a way of testing either of these parts to make sure what the problem is?

 

???

 

Look around your brake pedal area and see if you see any liquid. Try bleeding your brakes as well.

 

It sounds like a bad master cylinder to me. The piston seal leaks, letting fluid back to the reservoir. (That's why it doesn't leak OUT.) If the piston rod seal were leaking out, that fluid would go into the vacuum booster, not necessarily thru the firewall to the pedal area. You might not see the leak until the booster is all full of fluid & ruined, but you'd see the reservoir inventory dropping.

Bleeding might help, but usually only temporary. I was stubborn when this happened to my '95 GSR. Bleeding it was OK for a week or 2, but it would come back (especially with higher temperatures). Never REALLY fixed until I got a new master cylinder.

Take old & new master cylinders and compare the length of the piston rod sticking out of the MC. It has to be EXACTLY the same. If not, there's a funny tool for measuring & adjusting the pushrod at the brake pedal.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Luserkid &raquo;</TD></TR><TR><TD CLASS="quote">Look around your brake pedal area and see if you see any liquid. Try bleeding your brakes as well. </TD></TR></TABLE>

I'll take a look when I get home, didn't think to look there, but I don't think it is.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">but it would come back (especially with higher temperatures).</TD></TR></TABLE>

it's funny you meantion that because it was pretty hot yesterday, I think it go to 91 or something.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">Take old & new master cylinders and compare the length of the piston rod sticking out of the MC. It has to be EXACTLY the same. If not, there's a funny tool for measuring & adjusting the pushrod at the brake pedal.
</TD></TR></TABLE>

So if it's not the same, where would I find this "funny tool" to measure and adjust it at the pedal?

I'm going to order a new MC from Majestic. Decided I might as well do a timing belt/water pump on this car as well and since the MC on Majestic is only slightly more than at local parts stores for aftermarket units, so since I was going to order the MC I figured I would order the timing belt/water parts.

 

does anyone have any tips for bleeding the MC?

just get some lines to run from the openings to the reservoir so as I push the rod it'll just pump fluid back into the reservoir until all air is bleed out?

Any other tips?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TouringAccord &raquo;</TD></TR><TR><TD CLASS="quote">does anyone have any tips for bleeding the MC?

just get some lines to run from the openings to the reservoir so as I push the rod it'll just pump fluid back into the reservoir until all air is bleed out?

Any other tips?</TD></TR></TABLE>That's basically it. How those tubes fit into the MC is sorta sketchy, so it might make a mess. Have some rags ready...

I've replaced MC before I knew about bench-bleeding. It takes a long time bleeding before you work all the air bubbles out of the MC. But it CAN be done.

 

so would some brake lines an fittings (flare the ends and bend the tubes) be my best bet or is there some other kind of tubing that can be used for this?

 

The tool for measuring the pushrod is pictured in the Helm manual. Check it out (downloads?) for ANY honda, it seems like it's the same tool across the board.

Here's the main idea...
The MC piston rod has a particular position where it needs to be when you're NOT pressing on the brake pedal. Same for the vacuum booster. If the new & old MC pushrods are exactly the same length, then you're good. That was the case with my Integra, so I never had to get that tool.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TouringAccord &raquo;</TD></TR><TR><TD CLASS="quote">so would some brake lines an fittings (flare the ends and bend the tubes) be my best bet or is there some other kind of tubing that can be used for this?

</TD></TR></TABLE>If you can handle the mess with a pile of rags, then you can use 50 cents worth of rubber tubing just stuffed into the threaded holes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">The tool for measuring the pushrod is pictured in the Helm manual. Check it out (downloads?) for ANY honda, it seems like it's the same tool across the board.</TD></TR></TABLE>

ah, ok. I'll check my manual when I get home.

hopefully the rods end up being the same length and I don't have to worry about it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">If you can handle the mess with a pile of rags, then you can use 50 cents worth of rubber tubing just stuffed into the threaded holes.
</TD></TR></TABLE>

I guess it'll depend on the cost difference of the supplies required

 

well, I got all my parts in yesterday

Brake Master Cylinder
Timing Belt
Tensioner Assembly
Water Pump
Valve Cover Gasket Set
Cam Seal
Crank Seal
PCV Valve
PCV Valve Grommet
Thermostat
IACV Gasket (cleaning IACV)

I'll start tearing things apart today after work.

I plan to take pictures of the processes for the brake master cylinder and for the timing belt job, then do write-ups for them.

I couldn't find out what the thread size of the ports on the MC were so I didn't buy any tubing or fittings. The new MC came with rubber cupped plugs in the holes so I'm going to cut the cupped plugs open at the bottom and silicon some rubber hose into them and use that during the bench bleeding process. Hopefully it won't get too messy

The MC in the car is a 13/16 Nissin and the new one I got from Honda is marked 13/16 Nissin as well so I'm hoping the push rods will be the same length and wont need adjusting.

 

so what exactly is "bench bleeding"? simply bleeding the MC without the lines hooked up?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 03akkord5spd &raquo;</TD></TR><TR><TD CLASS="quote">so what exactly is "bench bleeding"? simply bleeding the MC without the lines hooked up?</TD></TR></TABLE>When it's all installed, it's difficult to work all the air bubbles out of the MC itself. So before installing it, insert some random tubes where the brake lines are supposed to go, put them so they squirt back into the reservoir. Fill the reservoir, & pump away by pushing the MC pushrod.

The MC will have fluid when you install it into the car, so it'll be messy. Otherwise you'll bleed forever (it seems) before all the air is out.

 

Just make sure to rinse off any spilled brake fluid IMMEDIATELY. That stuff can dissolve your paint very quickly. Especially if the paint is kinda dull...