Hey Honda guys, need some help with a brakes upgrade. Heres what I did:

91 honda civic hatchback DX:

Parts:
SI Master Cylinder 7/8 (With Stock DX Booster)
SI Proportioning valve (4030)
Scarebird Rear conversion plates
97 Integra rear calipers, brake lines, etc.
New front calipers/rotors/pads

Steps
swap rears via scarebird.
replace fronts
Bench bleed the MC
install Proportioning valve
Install MC
Bleed all 4 corners

Now, i have brakes. (E brake works too) but theres a lot of push in the pedal, almost to the floor, say... last 3 inches or so. Its consistent, no fade, just takes all the pedal to stop. It doesnt seem to 'build' with repeated pumps either. Not sure how to diagnose.

I checked all the lines, nothing seems to be leaking. Not sure what else to check.

thanks,
-zoloz

 

digging around, it could be one of two things?

1. Vacuum leak of some kind, read an article about 'wooshing' sound and stalling when pressing the brakes. I did notice the car stumble when pressing the brakes, but didnt think anything of it at the time.
2. Bad Brake Booster

guess ill be poking around vacuum lines this week some time. The stock booster is 7"? May be worth the effort to get the SI one, which i think is 8.5 or something. Anyone have thoughts on this?

 

The booster is going to effect pedal feel, but travel is up to the MC. Not sure about the "stumble", in my experience pumping the breaks brings up idle a little on cars I've owned, but with some research it sounds like this means its leaking? The brakes on those cars have always felt good.

On a 7/8 MC, mine did the same - it stopped but took a lot of travel to do so. Once I put in my 15/16 MC it felt great.

Thats with the scarebird rear setup as well, but the fronts were upgraded to DC2 calipers. Not sure what fronts you have (assuming stock). Without larger fronts the 15/16 MC may be too big for your setup.

 

Thanks for the response, If I go up to 15/16, can I use the same 8" brake booster?

 

This procedure may be helpful before you commit to more parts.
https://honda-tech.com/forums/honda-.../#post17932495
Though I wouldn't advise 15/16 MC if you're keeping the stock DX front brakes. 7/8 should be more than enough.

 

I am pretty sure the DX and SI both use the 205mm booster. I am running my old DX booster with the 7/8" MC and SI prop valve and with Hawk HPS pads I have no issues what so ever. Between my car and an actual SI with the same pads the brakes feel exactly the same.

I would also not recommend using a larger MC without changing the pedal throw. Increasing the size of the MC without increasing the caliper size will only make the brakes harder to modulate.

If the pedal is going to the floor, you either have an internal leak in the MC, external leak somewhere or air in the lines. The MC can leak into the booster and no visible leak will be seen as the vacuum line will suck it into the engine. If you sit and pump the brakes with the car off, eventually the booster will start leaking as it fills up with brake fluid. However, the pedal would bleed down to the floor if this was the case.

I would push another bottle of fluid through the car. When I did my conversion, it took two full bottles before all the air was out of the system.

 

no sink.

pedal sinks, a fair amount actually.

pedal doesnt vary

Pedal does rise slightly. every so slightly.

Not sure where this leaves me, i'll try bleeding them again, but, if the MC controls pedal depth, then... Its down to the last 2 or 3 inches off the floor from full height when depressed, is there something else i may be missing?

 

Thanks, ill give the 'more fluid' a try too, perhaps thats all it is, air.

 

How did you do your bench bleed? If it wasn't bench bled properly you won't be able to get the air out of it through normal bleed procedures.

 

finally got back to this today, and, found the driver front hose was/is leaking... didnt notice it, but, today i was pressing down and the pedal just sunk to the floor, saw a puddle under the driver side front. Cracked at the edge of the mounting bracket, looks like it was leaking there, but i didnt notice/see it until it fully failed. oh well. Guess i should have changed those along with everything else, not sure how i thought 30yo rubber hoses were going to work, lol.

thanks for the suggestions/help.
-zoloz

 

Take no chances, replace it all