Need advice from experience for an M42 rebuild

[JonsE30]

update: went to put back the slave cylinder back in the transmission but decided to try again. it look like the reservoir was not at the max line. i topped it off and tried hand bleeding it and i got fluid!. i bolted the slave cylinder back in and then got in the car and got pedal back pressure!. i was able to go in an out of the garage! hahaha. but i left a trail of brake fluid so i think i didn't tighten the bleeder enough. i am so relieved! i love this forum! i could not have done anything without you all!

[roguetoaster]

You won't know until you open the line unions. I'd guess that you just have a bubble/air lock situation somewhere that can't quite pass. Worst case you have a failed slave or master, but you'll know soon.

[JonsE30]

gotcha, i will test for fluid first since the slave cylinder is now separate from the transmission. if there is no fluid where is it ? haha. does that mean there is a block or obstruction within the lines or an issue with the master cylinder since from the reservoir it has to go through the master cylinder first before pushing fluid to the lines that go to the slave?

[roguetoaster]

Just as if you were parked facing up a hill with the car in a forward gear and no hand brake engaged. Press the clutch and you'd roll back.

A worse test would be to start the car wherever, press the clutch pedal and select a gear. If you hear a grind the clutch is not working.

[JonsE30]

Oh i see. So the test is if the clutch engages when pedal is pressed, it should be able roll like if its in neutral, but if it doesn’t roll then the transmission stays in gear which mean the clutch is not engaging when i press the pedal?

[roguetoaster]

Put the car where it would roll or have a helper push against it with the car in gear and try both clutch engaged & disengaged.

You can start with cracking the line there and then move to the junction of 19/10. You may end up having to both crack the line at the location in the pic and bleed the slave by hand to encourage fluid movement.

[JonsE30]

how do i test if the clutch engaging/disengaging without the pedal? which line fitting up stream to do you mean? do you mean this part?

[roguetoaster]

Uncheck, uncheck.

Could be a hydraulic system failure, but it does not sound like a component being backwards in the clutch assy. Suggest that you try to crack the next line fitting upstream and see if you get fluid. Bleeding the slave by hand is usually NBD.

Is the clutch engaging/disengaging?

[JonsE30]

actually i think something might have come back to haunt me. as of now i was planning to bleed the clutch slave cylinder. the pedal comes back to its resting positing after being depressed, but there is no pedal back-pressure. i tried bleeding it but i get no fluid when pumping/holding the the pedal and cracking/closing the bleeder valve. i've read where you can take out the slave cylinder out of the transmission and just "bench" bleed or "hand" bleed but i still could not get any fluid. have i not pumped enough or is something else wrong?

i read it could be a bad master cylinder and it would be leaking fluid all over the floor, but it's dry. i dont recall messing with the clutch master cyclinder during the engine rebuild.

could it be like an issue if i installed the clutch fork and pressure plate? but would this even be a factor if it is out of the transmission trying to bench/hand bleed?

[roguetoaster]

Check, check.

[JonsE30]

seems fine 2500 RPM and up. i think at this point i can end the thread since all the issues i will encounter now are non rebuild related right? i can now go down the checklist haha.

[roguetoaster]

It's worth remembering that vacuum leaks will appear to clear up above 2500 or so RPM, whereas an electronic issue will probably not. Both types of issues can cause poor transition on and off throttle.

[bmwman91]

Yeah the black on the plugs is normal if you have only run it cold. The warm-up enrichments are fairly significant.

The M42 is definitely not the smoothest idling 4 cylinder out there, but if it does not feel like it is running right then there's probably another leak somewhere. Contrary to popular belief, it will at least have a stable idle when everything is working properly, so if the RPM dips or hunts it is likely that there is a clogged ICV, vacuum leak or worn sensor somewhere.

[roguetoaster]

Probable vac leak from the ICV. Black on the plugs is probably a result of that and a few attempts at starting during the timing work, just clean them and reinstall.

[JonsE30]

Crank damper pulley looks good. No tears, no wobble, everything looks aligned. AFM and TP sensors were plugged and no sign of any damage on the wires. I cleaned out the ICV and it’s bottom hose was loose so maybe it was a vacuum leak? No more CEL but still kinda rough. I can’t remember if that is just normal. What I did notice was the spark plugs were black on the tips, this could lead to a rough idle right? Temp started rising so I turned her off cuz I don’t have my cooling system in yet.