Rennlist - Porsche Discussion Forums

Notices
924/931/944/951/968 Forum Porsche 924, 924S, 931, 944, 944S, 944S2, 951, and 968 discussion, how-to guides, and technical help. (1976-1995)
Sponsored by:
Sponsored by:

Turbo brake issues

Thread Tools
 
Search this Thread
 
Old 01-07-2019, 02:22 PM
  #16  
Jfrahm
Addict
Rennlist Member
 
Jfrahm's Avatar
 
Join Date: Mar 2002
Location: Boulder, CO
Posts: 6,402
Likes: 0
Received 104 Likes on 92 Posts
Default
Wedging the brake pedal down for a while helps, makes the bubbles really small and easy to dislodge. You can use scrap wood between the seat frame and the brake pedal. Wedge the pedal down, wait 30 min or so, bleed one corner (or I suppose one inner) then lift the pedal, wedge it down again, wait, repeat on the outer, and continue around. I am not sure if waiting helps, on bikes I always let them sit a while with the brake pressure on as I had been instructed.

You want the pressure up way higher than the Motive can safely apply to get the bubbles mashed down small and a strong jet of fluid to come out under high pressure, hopefully carrying the bubble out or to somewhere where it can get flushed out more easily.
Jfrahm is offline  
Reply Like
Old 01-07-2019, 02:53 PM
  #17  
mj951
Rennlist Member
 
mj951's Avatar
 
Join Date: Jan 2006
Location: Midwest
Posts: 1,854
Received 121 Likes on 98 Posts
Default
Originally Posted by Jfrahm
Wedging the brake pedal down for a while helps, makes the bubbles really small and easy to dislodge. You can use scrap wood between the seat frame and the brake pedal. Wedge the pedal down, wait 30 min or so, bleed one corner (or I suppose one inner) then lift the pedal, wedge it down again, wait, repeat on the outer, and continue around. I am not sure if waiting helps, on bikes I always let them sit a while with the brake pressure on as I had been instructed.

You want the pressure up way higher than the Motive can safely apply to get the bubbles mashed down small and a strong jet of fluid to come out under high pressure, hopefully carrying the bubble out or to somewhere where it can get flushed out more easily.
Good tip.

One warning with the Motive Bleeder, if you've owned it for a few years do yourself a favor and replace the plastic tubing.
Brake fluid degrades the plastic and it will eventually fail or split creating quite the mess.
mj951 is offline  
Reply Like
Old 01-07-2019, 03:45 PM
  #18  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by GPA951s
Buck "the system" I just put some dye in mine anyhow.. much easier to change fluid..
1. open bleeder
2. pick up beer and drink
3. Put beer down when color changes close bleeder
4 Repeat 7 more times
Ya know, there's a post somewhere here from a guy that knew exactly which dye to use to get ATE blue, If you search under my "handle" along with "brake fluid" you should find it.

I'm going to print your procedure and hang it on the wall of my shop! .
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 03:50 PM
  #19  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by mytrplseven
Yeah, I know. We're the DOT.....were here to help.
Why is it these people who're "helping" never seem to be around while I'm bleeding my hydraulics?
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 03:58 PM
  #20  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by mj951
Don't forget to bleed the clutch.
Truer words have rarely been spoken.
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 05:12 PM
  #21  
mj951
Rennlist Member
 
mj951's Avatar
 
Join Date: Jan 2006
Location: Midwest
Posts: 1,854
Received 121 Likes on 98 Posts
Default
Originally Posted by Otto Mechanic
Truer words have rarely been spoken.
Ha, it's easy to be lazy.
mj951 is offline  
Reply Like
Old 01-07-2019, 05:27 PM
  #22  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by GPA951s
I Sort of had the same problem with My Turbo-S … I used to have to STAND on the pedal, and that is not a comfortable feeling at Watkins Glen, and It really will mess with any heel-toe Downshifting..
I can imagine. I lost my brakes in the 928 S3 driving it back to back with my son at Laguna Seca; two different run groups but not spaced far apart enough to cool anything down, that's when we melted the pads.

I often call it "a religious experience".
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 05:51 PM
  #23  
mytrplseven
Drifting
Thread Starter
 
mytrplseven's Avatar
 
Join Date: Aug 2010
Location: Orlando area
Posts: 2,654
Received 20 Likes on 15 Posts
Default
Originally Posted by GPA951s
I Sort of had the same problem with My Turbo-S … I used to have to STAND on the pedal, and that is not a comfortable feeling at Watkins Glen, and It really will mess with any heel-toe Downshifting.. Anyhow, I ended up getting a Caliper rebuild Kit, I did all 4 calipers.... 16 pistons.. Took my time and was very detailed in the cleaning all new o-rings, got 30 years of junk and varnish out of the calipers. Put it all back together... Took it for a rip on the street and was a TOTALLY different car at the track.. It was amazing the difference the rebuild made... they work awesome now.
Look on YouTube, Van has a great Video on how to rebuild/clean them...I got my rebuild kit from Racers Edge. I took my time and it was about an 8 hour job. FYI You Don't need the scraper rings.. just the seals..
I've been wondering about rebuilding the calipers. I believe they've been redone by someone professional like Rennlist because the red paint quality is perfect. That being said, this was a barn find and there's no telling how long the car sat before I rescued it. I know the front pads are dragging when I turn the wheels and that doesn't seem kosher to me. By the way, I love how good your car looks. Here's what I've been building:



mytrplseven is offline  
Reply Like
Old 01-07-2019, 05:57 PM
  #24  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by mytrplseven
Here's what I've been building:
What a beautiful car! Well done sir! Now I have one more great looking Martini car to worry about. Sigh... .
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 06:00 PM
  #25  
mytrplseven
Drifting
Thread Starter
 
mytrplseven's Avatar
 
Join Date: Aug 2010
Location: Orlando area
Posts: 2,654
Received 20 Likes on 15 Posts
Default
Originally Posted by T&T Racing
DOT4 for autox is a good choice. if you mean higher stuff as synthetic or silicone, DO NOT use. These brake fluids entrap air bubbles when vibrated and the air bubbles do not escape back to the reservoir
I was referring to ATE 200 (supposedly higher temp capability) vs some generic DOT 4.
mytrplseven is offline  
Reply Like
Old 01-07-2019, 06:14 PM
  #26  
mytrplseven
Drifting
Thread Starter
 
mytrplseven's Avatar
 
Join Date: Aug 2010
Location: Orlando area
Posts: 2,654
Received 20 Likes on 15 Posts
Default
Originally Posted by mj951
Good tip.

One warning with the Motive Bleeder, if you've owned it for a few years do yourself a favor and replace the plastic tubing.
Brake fluid degrades the plastic and it will eventually fail or split creating quite the mess.
I was using 15 psi and starting with the OUTSIDE of the caliper first. Is that a problem?
mytrplseven is offline  
Reply Like
Old 01-07-2019, 06:21 PM
  #27  
mytrplseven
Drifting
Thread Starter
 
mytrplseven's Avatar
 
Join Date: Aug 2010
Location: Orlando area
Posts: 2,654
Received 20 Likes on 15 Posts
Default
Originally Posted by Otto Mechanic
Ya know, there's a post somewhere here from a guy that knew exactly which dye to use to get ATE blue, If you search under my "handle" along with "brake fluid" you should find it.

I'm going to print your procedure and hang it on the wall of my shop! .
I wasn't able to find your post about the blue dye. would you mind sending me the info?
mytrplseven is offline  
Reply Like
Old 01-07-2019, 07:50 PM
  #28  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by mytrplseven
I wasn't able to find your post about the blue dye. would you mind sending me the info?
I have to apologize, I can't find it either. I thought it was here, I was complaining about it maybe 2 or 3 years ago when ATE stopped shipping blue fluid. A fellow chimed in and sent pictures of the dye they use. I haven't bought it so I don't have receipts. I just figured it was there and it would be there when I needed it.

Guess I was wrong. Sorry,
Otto Mechanic is offline  
Reply Like
Old 01-07-2019, 09:46 PM
  #29  
mj951
Rennlist Member
 
mj951's Avatar
 
Join Date: Jan 2006
Location: Midwest
Posts: 1,854
Received 121 Likes on 98 Posts
Default
Originally Posted by mytrplseven
I was using 15 psi and starting with the OUTSIDE of the caliper first. Is that a problem?
I've always kept the pressure at 10 psi and is what most around here recommend.
The plastic tubing cracks from years of exposure to brake fluid not necessarily from psi exceeding 10.

I bleed the inside bleeder first to limit pushing dirty brake fluid through the caliper.
But doubt it matters, as long as they're both flowing clean, air free fluid.
mj951 is offline  
Reply Like
Old 01-07-2019, 10:38 PM
  #30  
Otto Mechanic
Rennlist Member
 
Otto Mechanic's Avatar
 
Join Date: Jan 2015
Location: Paso Robles, CA (Under the lift)
Posts: 2,936
Received 14 Likes on 14 Posts
Default
Originally Posted by mytrplseven
I wasn't able to find your post about the blue dye. would you mind sending me the info?
OK. Found it on a different site:

https://www.miataturbo.net/suspensio...er-blue-97675/

It's a video, the dye comes from McMaster Carr. You will have to put up with the video blogger expressing his justifiably irritated attitude. I was particularly enamored of "F**** the NTHSA". It defies logic and common sense we actually pay for and put up with this unsanity.
Last edited by Otto Mechanic; 01-08-2019 at 09:02 PM.
Otto Mechanic is offline  
Reply Like



Advanced Search
Quick Reply: Turbo brake issues


Reply Closed Thread Share
Forum Jump

All times are GMT -3. The time now is 07:38 AM.