CWBETB

UGH, I am having a crap time with this rear disc swap. I have installed G2 teg rear discs, and for a week I used my stock civic prop valve, car stopped ok, but pedal was lower no sinking. About a week after I found a Teg 4040 prop valve, installed, and after bleeding brakes "did the rear then fronts not criss cross" the pedal seems a little higher but if I sit at a light, the pedal slowly sinks. Also no leaks found near prop valve/lines

Is this the case of bad bleeding or a sign that my MC is crapping out?

Suggestions? Thanks!

4drEF

Yes, this is a sign that your MC is going bad.
When you replace it, you might as well take the time to do the 'criss-criss bleeding.

Ass$nyper

Imo, always bleed when doing a MC.

But it does sound like the MC is failing.

Tyson

you could have upset the seal in the MC when bleeding the brakes after all the installation. when you bleed, the stroke is typically much further than normal and where the seal is no longer nicely bedded over time.

but dont rule out any leaks until youve verified every connection visually. most likely tho a slowly sinking pedal is the MC.

now would be a good time to replace the MC anyway.

CWBETB

Thanks guys, Tyson I was hoping you would see this!

Tonight I went ahead and re-bled the brakes, criss cross kinda fashion. Did this 2 times over, brakes felt WAY better and no sinking pedal after I started the car in the driveway. Took it for a drive, and UGH started sinking again. Takes about 3 mins of pressure till the pedal hits the floor. Bummer. I noticed this only after I installed 4040 prop valve install btw. Tyson you mention this could have happened with bleeding the brakes which is possible. Not seeing any leaks around prop valve brake lines etc.

What would be the best upgraded MC I should go for 90-91 Civic EX? New/reman/salvage yard? Brake booster upgrade worth while? Could brake booster be issue or very slim?

Thanks again!

Spaceballsthelunchbox

Do not change the size of the MC, unless you are using larger brake pistons.
Stick with what was there, but new.
Going to a larger MC will only lower the pressure at the pistons and actually lower the braking power. It's a physics thing, I didn't make it up.

CWBETB

Intersting. Here is my setup now btw

Stock front brakes "DX"
G2 Teg rear Disc
4040 prop valve

So if anyone can recommend MC/Booster or stick with stock

4drEF

0_o

Ummm... pushing the pedal down the same distance with a large bore MC will result in more fluid dispensing into the calipers. Simple hydraulics.
It will not increase or decrease overall braking 'power', but pressure will be increased as more fluid will try to cram into the same volume in the caliper.
What it will do is require the driver to press the pedal down less to achieve the same braking 'power'.
Initially this sounds like a good thing - "Oh! I don't have to press the pedal down as far to stop the car", but in actuality it's typically bad.
To brake hard, you try to find the fine line where the tires are on the verge of losing grip.
(It literally sounds like frying bacon on most tires.)
This requires the driver to modulate the brakes to find that sweet spot.
With a larger than needed MC, the driver loses some pedal travel making it more difficult to find the sweet spot and increases the chance of skidding the tires.
Consider it like a 'dimmer switch' in comparison to a simple 'on-off'.
The properly sized MC will give you more control to achieving proper braking 'power'.




OP - when you bleed your brakes make sure you don't pump the pedal to the floor!
On a used MC, the piston often wears a lip inside the bore from regular use.
Pushing the rubber seal over this lip can tear it making it leak.

You basically have the same setup as an Si (rear disc).
7/8" MC as I recall rather than the DX/LX 13/16".
Civic EX and DA Integra have the larger front caliper and use a 15/16".
1/16" difference sounds like splitting hairs, but it is a difference.

I'mStock

So I'm having the same issue but it's been doing it since I bought the car.

It's a track car, so I don't drive it enough for it to bother me, hence why not really addressing the issue until now. It's a 90 Si, CRX rear discs, 40/40 prop and the stock 7/8" master.

Just purchased a 13/16" mater + booster on eBay, should I swap that on or just rebuild my 7/8"?

What's the difference in pedal feel/travel/pressure going to be like?

CWBETB

I just ordered a new OEM MC from Honda, ordered same one I had from the DX. Seems like mixed bag on the MC size, If stock up front being told to stick with stock MC unless I got larger up front. Researching found out older MC are more at risk of breaking the gasket while bleeding due to built up dirt. Prob what happened in my case. Hopefully

4drEF

I think I would have gone with the Si MC since your brakes resemble it better than the stock DX.
Shouldn't be that big of a deal though especially if it's a DD.

1/16" isn't significant, however a 2/16 (1/8) difference or greater I can personally attest to as noticeable (and annoying).
I ran a 1" ITR on stock for a very short time. NOT nice.
Changed to EX front calipers and it was nearly stock again - just a little touchy.
Rear discs clean it all up to a near stock feel again.
- Having stainless lines and a MC brace amplifies the differences a whole lot.

CWBETB

4dref thanks for your input! I have Russel SS lines also and slotted power slot rotors on as well.

I will let you guys know how this works out after I get the new parts

ApexiH22

Why can't somebody answer I'mStock's question??????!

I too wish to know!

Tyson

whats the question that hasnt been answered? sinking pedal means bad master cylinder. there is no mystery.

CWBETB

Good news! Got the new MC in and the brake pedal is no longer sinking! Actually feels better then ever now, very solid!!

waspcrx19

SO that is what is wrong with mine too!? :ff to autozone:: lol

KLeSe

Good to hear the problem is fixed. I'm having the same issue, what did the oem MC cost?

CWBETB

Yep, was hoping this might help people with the same issue.

I ordered one from Majestic Honda, came to my house shipped for about 170. New from Autozone is a little less new but I was afraid of aftermarket fitmint.

Very easy to install also,used a suction to take out the fluid of the old one, took off two bolts in back that hold it in place, took off brake lines. Bench bled new MC "suggest getting some brake lines from a junkyard to revert back into cup". Used some rubber caps to cap the holes, installed, bled and done!

I would suggest wrapping up your car in plastic/rags though, dont want brake fluid on your paint!

Thanks for the help all

Tyson

winning.

tonylovesjdmEF9

damn i have the same problem too and i was gonna upgrade to a da mc and booster thanks ppl

KLeSe

Thanks for the info. I also prefer oem over aftermarket parts anyday but u just can't beat Autozones axles for the price and warranty. Read the Haynes, installalation is simple like you said. Anyone know if the newer 92 up Civic mc will work/bolt up to the pre 92'?

spoon93

I also have a 91 civic si but but rear ls teg brakes and ls fronts and booster and 4040 valve so I'm gonna wanna run the ls mc rite I'm haven the smushy pedal thing rite now possibly cause of the stock mc?