C4: Brake bleed / hydraulic system bleed procedure
#18
Excellent! I was wondering how to bleed the "stuff" inside the trunk.
I did however find a method of bleeding the PDAS locks without the tool. Switching the 4WD-lock on/off (switch inside car) with a pressure bleeder attached seems to work. One person in car operating the switch, one person under the car operating the bleeder nipple. It is possible to do it alone as well, but you´ll have to jump in and out of the car and underneeth a few times for a complete bleed.
I did however find a method of bleeding the PDAS locks without the tool. Switching the 4WD-lock on/off (switch inside car) with a pressure bleeder attached seems to work. One person in car operating the switch, one person under the car operating the bleeder nipple. It is possible to do it alone as well, but you´ll have to jump in and out of the car and underneeth a few times for a complete bleed.
#21
Thanks for the terrific write up! And hats off to garett as well. Just a couple of highlight points that folks may have already encountered...
1) I cannot overstress the importance of having a 7mm wrench to put across the clutch slave nipple. I struggled with an adjustable wrench, and I won't make that mistake again.
2) The CLUTCH bleed needs to be conservative (around 50-100ml) in order to avoid sucking air into the system. In order to get a good flush, I reloaded the reservoir 4 times with 50ml bleeds. Interestingly, the fluid continued to look cloudy after the initial sludge flushed out. See the picture below. Perhaps it was due to infrequent flushes or something to do with the sludging that may occur in the slave. In retrospect, I may simply elect to add hydraulic fluid to the Motive bleeder and flush everything without removing & replacing the the bleeder after each bleed. At any rate, the clutch definitely seems softer and shifts seem smoother.
3) Three out of 4 calipers had slow draining from the outermost nipples. I'm assuming that this was due to sludging once again from infrequent changes. To overcome this, I unscrewed the nipple completely under pressure from the bleeder and stuck a 14 gauge copper wire down the channel to free up any loose sludge. If this still did not produce adequate flushing, I then gently stepped on the brake pedal (bleeder still pressurized) and that caused brake fluid to squirt out and produce a nice flow. Keep the opening covered with paper towels to avoid it squirting on the body. The nipple can then be screwed back on.
1) I cannot overstress the importance of having a 7mm wrench to put across the clutch slave nipple. I struggled with an adjustable wrench, and I won't make that mistake again.
2) The CLUTCH bleed needs to be conservative (around 50-100ml) in order to avoid sucking air into the system. In order to get a good flush, I reloaded the reservoir 4 times with 50ml bleeds. Interestingly, the fluid continued to look cloudy after the initial sludge flushed out. See the picture below. Perhaps it was due to infrequent flushes or something to do with the sludging that may occur in the slave. In retrospect, I may simply elect to add hydraulic fluid to the Motive bleeder and flush everything without removing & replacing the the bleeder after each bleed. At any rate, the clutch definitely seems softer and shifts seem smoother.
3) Three out of 4 calipers had slow draining from the outermost nipples. I'm assuming that this was due to sludging once again from infrequent changes. To overcome this, I unscrewed the nipple completely under pressure from the bleeder and stuck a 14 gauge copper wire down the channel to free up any loose sludge. If this still did not produce adequate flushing, I then gently stepped on the brake pedal (bleeder still pressurized) and that caused brake fluid to squirt out and produce a nice flow. Keep the opening covered with paper towels to avoid it squirting on the body. The nipple can then be screwed back on.
#23
I am doing my C2 Tip bleeds now. Its so much simpler. I actually tried to find the accumulator and then realized the C2 doesn't have one!
I love having to refer to my own posts to figure out how to do things.
Oh, and don't forget to get a 7mm flare nut wrench for the clutch bleed! I still don't have one. Its not common in the flare nut wrench sets.
I love having to refer to my own posts to figure out how to do things.
Oh, and don't forget to get a 7mm flare nut wrench for the clutch bleed! I still don't have one. Its not common in the flare nut wrench sets.
#24
Hello All. Please excuse my ignorance on this matter. I recently had removed all four brake calipers on my C4 to have them powder coated. When I had the calipers powder coated I left my brake lines open and they bled out into a cup on all four corners. Do I have to do all thirteen bleeds that were discussed here? If not, which ones are recommended?
Thanks so much in advance!
Thanks so much in advance!
#27
I got the PDT999 and bled the locks this weekend. Yes, simple procedure. I was expecting bats and monkeys to come flying out of the bleed, but was surprised to see that what came out wasn't too bad at all. Interesting. PO must have been keeping up with that. But it had been 8 years between.
Now that the $ to Euro is high, it's not a bad time to buy a PTD999...
Now that the $ to Euro is high, it's not a bad time to buy a PTD999...
#28
Hello All. Please excuse my ignorance on this matter. I recently had removed all four brake calipers on my C4 to have them powder coated. When I had the calipers powder coated I left my brake lines open and they bled out into a cup on all four corners. Do I have to do all thirteen bleeds that were discussed here? If not, which ones are recommended? Thanks so much in advance!
You should do the full bleed anyway. Twice per year, but at least once if you can't do twice...keeps all the water out of the system and from corroding the internals...
#29
Thanks!!
Just did the first 2 parts.. brakes and slave cylinder for the clutch.
The brakes must have been done before as they seemed very clean but I wanted new fluid in there.
The clutch on the other hand was a different story. It was disgusting. The clear bottle is the old brake fluid... the smaller dark one is from the slave cylinder. The third was a shot today while driving. Clutch seems easier but I will probably bleed again to ensure it's all out. I'm guessing it will be dirty again.
Question: Does anyone have a tool in Central Cal... I live in the Fresno area and would love to borrow on of those so I can do the lock cylinders for the diff's x2.
Thanks for a great write up. Brakes I knew.... everything else I didn't know the procedure.
The brakes must have been done before as they seemed very clean but I wanted new fluid in there.
The clutch on the other hand was a different story. It was disgusting. The clear bottle is the old brake fluid... the smaller dark one is from the slave cylinder. The third was a shot today while driving. Clutch seems easier but I will probably bleed again to ensure it's all out. I'm guessing it will be dirty again.
Question: Does anyone have a tool in Central Cal... I live in the Fresno area and would love to borrow on of those so I can do the lock cylinders for the diff's x2.
Thanks for a great write up. Brakes I knew.... everything else I didn't know the procedure.