Total brake fluid flush on C4
#31
I use a much larger motive than the one they sell at pelican. This way i never have to add fluid. I do use typically 5-6 in the motive. But i also very often end up pouring a bunch back into a can.
One correction from above- i never suggested to not have a bleed bottle connected to the bomb when releasing pressure. Always have a bleed bottle connected to the bomb if you are going to open the bleeder. ----just open the bleeder slowly, or you may blow the bladder.
Love this thread. I do so much bleeding now that i have the whole fluid flush on a c4 down to 1.5 hours working slow and talking and futzing around the entire time...can be a fairly quick thing without distractions and futzing...
One correction from above- i never suggested to not have a bleed bottle connected to the bomb when releasing pressure. Always have a bleed bottle connected to the bomb if you are going to open the bleeder. ----just open the bleeder slowly, or you may blow the bladder.
Love this thread. I do so much bleeding now that i have the whole fluid flush on a c4 down to 1.5 hours working slow and talking and futzing around the entire time...can be a fairly quick thing without distractions and futzing...
Also I never knew you could get a larger Motive. I got mine on Amazon and did not even see a larger one being offered.
I would be ashamed to reveal how long my bleeds took me. But one the bright side, I know I can be faster next time.
#33
I always start a brake fluid change with the bleed/flush of the accumulator and locks solenoid. These actions consume a large amount of fluid, thus doing an effective job of purging the large reservoir of old fluid, prior to doing the clutch and brake systems. For this same reason, I do the clutch slave bleed next, to purge the clutch chamber in the reservoir of old fluid. Somewhere there is a good diagram of the chambers in the reservoir and their respective volumes. Now, when you start the caliper bleed sequence, you are assured of a supply of fresh fluid to purge the master cylinder and lines to each caliper. I do the entire system every time I do a fluid change (1-2X per year, depending on how much track time I have). The accumulator bleed is very accessible and easy, and it only costs an extra liter of brake fluid, so why not do it? Take a look at how much the reservoir volume changes when you pump the pedal to release accumulated pressure, and then how much it drops when the pump runs through a full pressurization cycle. Why mix that much old and new fluid whenever the accumulator depressures? Our aging accumulators don't hold pressure like they did when new, when the car sits for a few days. Does your pump run for a couple seconds on startup, or take a couple minutes (and triggers the warning chime)? And, do you hear the locks activate when you first turn on the key before starting the engine?
It was great to see your deep dive into this procedure.
It was great to see your deep dive into this procedure.
You raise a good argument for changing the order of bleeds. In fact if you look at my post#1 the order of bleeds was the initial question. I researched this till the cows came home and was still in doubt so I sided as much as possible with the workshop manual figuring that would be the safest way to go. But clearly if your procedure works for you, it is worth considering. I did manage to suck at least 50% of the old fluid out of the reservoir with a turkey baster, but I do like your method better.
My accumulator is not too bad. It pumps up in just under one minute. No alarms. I don't think I have heard the locks activate when I turn the key, but I usually have the door open and door open alarm is dinging away and might mask the sound. Should I hear it?
#34
#35
Yes, you should hear both locks click - set/release. The controller must do a quick diagnostic when the power is turned on. Mine did not click, until I bled the locks (for likely the first time in 20 years) with 100cc of black ooze ejected.
And be sure to take the car out onto a nice slick wet pavement or gravel road and cycle the ABS a few times.
I can see no functional reason for a specific order of system bleeds.
Be sure to Not push the brake pedal when the reservoir is pressurized - will damage the MC.
Go have some fun with the car.
And be sure to take the car out onto a nice slick wet pavement or gravel road and cycle the ABS a few times.
I can see no functional reason for a specific order of system bleeds.
Be sure to Not push the brake pedal when the reservoir is pressurized - will damage the MC.
Go have some fun with the car.
#36
#37
A good detailed write-up. Thanks for using metric. I go cross-eyed when our US Rennlist friends write-up in Jugs, Quarts, Oz ???
Anyways here is a small tip, chop the 7mm wrench in half. You get a much better un-interrupted turn on the slave cylinder nipple…
Anyways here is a small tip, chop the 7mm wrench in half. You get a much better un-interrupted turn on the slave cylinder nipple…
Last edited by Spokes; 09-01-2021 at 08:51 PM.
#38
The shortened 7mm flare nut wrench is a great idea Spokes. I ended up having to use an open end wrench. But I have to say that I was shocked that I did not have to fight with a single bleed screw on the entire car. They all came free easily.
The only issue I had was when I opened the clutch bleeder screw, nothing came out. I had to insert a copper wire into the hole to clear the blockage. Of course when the blockage was cleared, the Motive pressurized fluid began to flow quite quickly.
I plugged the hole with my finger and yelled for my helper to release the Motive pressure. If I had not had a helper on that day, the flood would have been quite a bit worse.
The only issue I had was when I opened the clutch bleeder screw, nothing came out. I had to insert a copper wire into the hole to clear the blockage. Of course when the blockage was cleared, the Motive pressurized fluid began to flow quite quickly.
I plugged the hole with my finger and yelled for my helper to release the Motive pressure. If I had not had a helper on that day, the flood would have been quite a bit worse.