Finn's KA24DET

[okayfine]

Sounds like a classic your-BMC-pushrod-is-adjusted-too-long condition. Doesn't take much to keep the port in the BMC covered, not fully releasing brake pressure.

Some KAs need to have the VSS signal patched into the ECU, else there is some sort of top-end limit. But I thought that was only the KA24E. What year KA do you have, again?

[Uber Deaf One]

Sounds like a classic your-BMC-pushrod-is-adjusted-too-long condition. Doesn't take much to keep the port in the BMC covered, not fully releasing brake pressure.

Some KAs need to have the VSS signal patched into the ECU, else there is some sort of top-end limit. But I thought that was only the KA24E. What year KA do you have, again?

IIRC the manual ECU requires the VSS signal.

[okayfine]

My '95 KA (OBD-1) did not. VSS went to an electronic speedo for signal, but not to the ECU.

The cutout would have to be revs in gear, obviously not MPH since the ECU doesn't know speed.

[finn]

i'm going to have to get under my car again... i don't remember the transmission being plugged into the harness. i know there's several pig tails but none of them were installed IIRC. i know the crankshaft position indicator isn't installed but i think that for self diagnostics not indicated speed.
the ECU is actually from an S13 KA ('95 and less) that's adapted to the S14 harness.

the brake pedal pushrod feels rather loose.. but what would it hurt to thread it in a little and see what happens.

[okayfine]

VSS goes to the instrument cluster in the 240SX, IIRC, which is then patched internally to the ECU. CPS is an emissions thing (detect misfires) for OBD-II cars.

Any chance the looseness you feel in the brake pedal is clevis slop or ovalized pedal arm? 'Cause what you experience sounds like a mis-adjusted pushrod.

[finn]

well I was hoping Julian was right and I just screwed up the pedal/push rod mounting but no dice I disconnected the push rod and jacked the front and the wheel still had some resistance. perhaps there's some springs missing off the calipers I'm not aware of... I need to do some research. just venting here..

I know the pic of the wheel doesn't help but man, is that a hot rim or what?

[finn]

oops


Master Cylinders have a Residual Check Valve which preloads the drum brakes with about 10 psi pressure. Only the portion of the M/C for the drums has a residual valve. This is sometimes called RLPV (residual line pressure valve), or RPCV (residual pressure check valve).

Disk brakes must not use a Residual Valve, but only need a weak pressure which naturally results from the M/C being mounted high on the firewall.

So, no, in stock form it won't work correctly -- the brakes will still work OK, but will wear faster than normal if the RV is left in place.

You should do either:
* swap in an all-discs Master Cylinder
OR
* remove the Residual Valve(s) from the master cylinder.

good ole ratsun. silly me

[okayfine]

I'm still confused then, since stock 510s had discs in the front. Unless I misread your post, I thought your front discs were the issue (hot, resistance).

In any case, you're saying you fixed it?

[finn]

i never removed the valves before installing it. i get what you mean by the fact the 510 came with front disc so it shouldn't matter so i'm a little confused as well. when i get home i'm going to take them out and jack the front again and see if the bleed back fully releases the rotors. perhaps the bigger front disc of the 280zx requires it removed but the smaller stock calipers didn't. i'd read more but swamped at work

[finn]

I pulled the brakes apart and inspected them. everything looked fine there despite the heat they've been subject to lately.. pulled the master cylinder and took out those residual valves. after bleeding the BMC I jacked it up and spun the wheels. they'll go over a full rotation before the brake rub slows them down so those valves ended up being the culprit. should have done some research before installing that new BMC. unfortunately, the lines going to the BMC were on their last leg and now I can't get them tight. even with vise grips I got it to a very small leak so I took it up and down the alley to see if I could feel a stick and check the rotors. the roll out is noticeable and the rotors were cold when I got back so that's a success but the pedal is soft and I'm blaming that on the leak.

[okayfine]

Stock 3/4BMC with ZX front discs will also give a softer pedal. Even the TO Pep Boys has brake line with 10x1.0 fittings, so you shouldn't have trouble finding new stuff in Cam. Is the foreign auto parts place still there in the K-mart shopping center?

[finn]

Kmart?.. I havent seen one around. There's an asian auto place off rose that might have some. I'll shop around tomorrow. Pep boys huh?... so your telling me theres a chance!

[okayfine]

Napa by the Post Office in Cam, if nothing else.

[finn]

Napa only had domestic but the O'Reilly s down the street had some lines. Went home, bent em up and threw them in. The front brake line leaked I took it out and checked the threads and what not. Everything seemed normal. Tried again with no luck so pulled the line again and inspected the mating surface of the inside BMC. The cone had a ridge to it.. pulled it out and sanded it flat and tried it all AGAIN. I had to tighten it something serious but it actually stopped leaking so I went on to bleed the brakes and took it on a test drive. I must have left some air in the system cause that pedal is still real soft. Im sure the 3/4 BMC has it work cut out pushing those 280zx pads but It seems too excessive. I'll try again tomorrow on my base because their hobby shop has a lift and we can pull tires and what not.

[finn]

Bleed the brakes again and got a little stiffer pedal. I installed an inline water temp adapter I got from summit as well so I truely know what my temp is. Took it out for a nice long drive this morning and it ran great. water temp stayed around 150 so that big ass ebay radiator is doing its job... brakes are a little soft but very manageable. I'll just have to get used to that. I stopped by the dyno place to see what power im pushing but their closed:( so next time I suppose.. just need to get that sway bar from david and ill be all set.