Slotted booster- brakes incredibly sensitive and locking up

[E30stan]

Just put my s52 swap on its wheels!
The problem im having is the brakes were locking up slightly, as in i dump the clutch and it doesnt coast for long.
I bled both front brakes and it gets better, but then after ten minutes they begin to slightly drag again.

Another thing i noticed it while bleeding the brakes, theres a popping sound from the brake booster when releasing the valve.

Im just wondering what this bench bleeding talk is all about?

Any ideas what could be the issue?

[Roysneon]

Did you modify the clevis at all or just slot the firewall and move it over? If you don't do something about the connection point it will bind and not want to fully release or engage smoothly.

[E30stan]

Did you modify the clevis at all or just slot the firewall and move it over? If you don't do something about the connection point it will bind and not want to fully release or engage smoothly.

thats the strange thing, i did modify the clevis, so everything should be in the right place, im thinking of trying to adjust the rod length on the clevis but it doesnt make sense to me if everything should be in its proper place.

After doing some research, cjdontthink was having similar issues, im thinking i must have bolted the MC crooked.

I don't have any check valve between the booster and manifold, could that be the problem?

[36brua]

re adjust the brake linkage? sounds like there may be pressure on the back side of the master cylinder not allowing it to fully return/bleed pressure off, which may keep pressure applied to the brakes. Is the brake pedal hard up on the brake light switch ? to give more clearance turn the clevis clock wise to 'shorten the rod/clevis length you have to hold the rod from the booster while doing this. and you have to be a contortionist

[36brua]

thats the strange thing, i did modify the clevis, so everything should be in the right place, im thinking of trying to adjust the rod length on the clevis but it doesnt make sense to me if everything should be in its proper place.

After doing some research, cjdontthink was having similar issues, im thinking i must have bolted the MC crooked.

I don't have any check valve between the booster and manifold, could that be the problem?

possible but you should install one for safety

[E30stan]

I just installed the valve from the 318is hose, because the hose I had from the m3 didn't have the valve, and it still begins to drag the brakes after 10 minutes.

I then removed the vacuum line, and it's giving me the same drag even without any brake assist. Later I disconnected the clevis from the pedal and the booster would not extend the quarter inch it needs to press the brake light switch. I think I might have to take out the booster Tommorrow and make sure the pushrod and diaphragm are ok.

Anyone else have experience with slotting over the booster on a 24v swap?

[hooken m]

i bought a modified e21 booster from robert k and an e32 7 series booster from another member and the brakes were just stiff as fuck. and i bled them twice with no bubbles. i then switched to a 22mm MC and the brakes works, but i believe i have the same problem as you do with a shitty brake feel? idk i wish i had a better feeling brake and slightly more assisted i guess. idk i'd like someone who knows their 24v swaps/brakes to let me know whats wrong

[Todd Black 88]

E21 booster is probably the worst feeling booster option for 24v swaps

[Jand3rson]

E21 booster is probably the worst feeling booster option for 24v swaps

This. While I haven't used or experienced any others, I stand by the Porsche 944 booster.

I encountered a similar situation to the OP's when I first got my car driving, the brakes would lock up to a standstill within several minutes of driving. Turns out I had the clevis adjusted too far out, and it wasn't allowing the pushrod to return all the way, and was building up pressure in the booster to the point of the brakes slowing locking up completely.

[7pilot]

Adjust the clevis. It needs to be adjusted further away from the booster, i.e., towards the driver.

m

[E30stan]

Thats the one thing i was hoping i dont have to do since it was all fine before, the nut was welded together with the clevis extension, so now i have to take the whole darn thing out if i want to adjust it

[Mr.SWISS]

E21 booster is probably the worst feeling booster option for 24v swaps

This should be sticky.

I like the E32 booster/ix booster with the 25mm master. Brakes are easily modulated and I can engage ABS with ease. But not touchy/grabby like my Hondah.

I have heard good things about the Audi booster, but haven't got around to installing mine yet. Maybe whenever the M52 comes out and the S52 goes back in....

[E30stan]

re adjust the brake linkage? sounds like there may be pressure on the back side of the master cylinder not allowing it to fully return/bleed pressure off, which may keep pressure applied to the brakes. Is the brake pedal hard up on the brake light switch ? to give more clearance turn the clevis clock wise to 'shorten the rod/clevis length you have to hold the rod from the booster while doing this. and you have to be a contortionist

you were spot on, after adjusting the rod to engage the brake light switch the brakes are normal now. It's just weird that i needed to adjust them at all.

[Danny]

I like my E21 booster. You guys are all just pansies with sticks for legs.

[Jand3rson]

Thats the one thing i was hoping i dont have to do since it was all fine before, the nut was welded together with the clevis extension, so now i have to take the whole darn thing out if i want to adjust it

Well, that was pretty darn silly.