Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 924/944/968 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
Power brake question

My turbo has the brakes rebuilt, new lines and new master cylinder. I've flushed the system and bled it numerous times but even when I stand on it, the brakes won't lock up. It will stop after it slows down but I'm not sure if it's the booster or not. I'm asking the forum if they can tell me how much the brake pedal goes down when you start the engine? Mine doesn't seem to move noticeability when the engine is started. I've put 10inches of vacuum on the booster line and it holds it until I push the brake pedal which I determined as normal. I did install the Lindsey Racing venturi elimination hose package and I'm generating about 12 inches of vacuum on the booster line.

__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 10-17-2020, 10:25 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered
 
Join Date: Mar 2008
Location: Nashville, TN
Posts: 3,826
Pedal doesn't move on 944 when engine starts.
That vacuum reading sounds low?
Old 10-17-2020, 02:35 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered
 
Join Date: Oct 2006
Location: va
Posts: 2,371
Garage
First I would make sure the brakes are bled properly. Booster or not, if bled properly, you should be able to lock up all 4.

Longer story: The best way to bleed brakes was shown to me buy a guy who's father raced at Indianapolis. Two persons are required. One pumps and holds down the pedal to force the air to the end of the line. The second person cracks the bleeder screw to let out the air, and then closes it quickly. Once this is done a few times, the pedal will be rock hard. No flushing or Motive or other bleeder equipment is needed to achieve a rock hard pedal. Just get the air out by pressing down the pedal firmly and cracking the bleeder screw for a instant.

For some vehicles the engine needs to be running and for others not. It has something to do with the brake booster obviously.
Old 10-17-2020, 02:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
That's the procedure my friend and I performed and then went back to make sure no air got backed up into the lines. When I stand on the brakes, the pedal is firm and the car slows dramatically to a full stop but I can't lock the wheels. I had heard that power brakes booster causes the brake pedal to move inward a small amount when the engine is started. V2rocket says it doesn't on the 944. I'm going to an autocross tomorrow and will talk to other racers about what they think after they drive my car.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 10-17-2020, 04:38 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
To V2Rocket: what kind of vacuum should I see from one of the vacuum taps on the turbo intake manifold? I can't seem to find anything written that defines it.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 10-17-2020, 04:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered
 
Join Date: Mar 2008
Location: Nashville, TN
Posts: 3,826
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/64960-what-is-an-average-vacuum-reading-2.html
Old 10-18-2020, 06:35 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
vacuum readings

Bought a quality vacuum gauge today and after hooking it up I had around 18 inches of vacuum at cold idle and 21 inches at cold 2000 rpm. I guess I'm in the market for a new brake booster. I really look forward to this project....not.:


IDLE



2000 RPM
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 10-18-2020, 10:33 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered
 
Join Date: Oct 2006
Location: va
Posts: 2,371
Garage
Quote:
Originally Posted by djnolan View Post
if bled properly, you should be able to lock up all 4.
Actually I have never locked up all 4 on a 944. I think with the 50/50 weight balance it may not be possible! Should we start a poll?
Old 10-18-2020, 11:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
You may have a point there. All I know is I had to virtually stand up on the brake pedal to get it to stop. With no booster, it's very noticeable. New booster coming in this week.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 10-18-2020, 06:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered
 
Stoneguy's Avatar
 
Join Date: Apr 2020
Location: Boston Area
Posts: 117
Garage
Mytrplseven,
At the beginning of the summer I did, basically what you did on my brakes. I converted a standard 944 to the Brembo Porsche calipers and setup that is on the turbo. After the work, calipers, rotors, pads, master cylinder bias valve addition struts and spindles, I was a little disappointed with the feel. I replaced the booster. I had checked it out and it SEEMED ok, but a 34 year old booster it was. After the booster change, my brakes are wonderful. Just my experience.
__________________
1986 944 NA
2009 Cayenne
Old 10-19-2020, 05:56 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
Thanks for the supportive comments. I'm right in the middle of removing everything under the hood so I can pull the booster out. On a 951, it's a complicated process in confined spaces.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.

Last edited by mytrplseven; 10-19-2020 at 03:07 PM..
Old 10-19-2020, 02:51 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
After a lot of work I finally have the booster installed, bled the brakes and did a road test. NO CHANGE. I still don't have boosted brakes!! When I start the engine, the pedal does droop a little like most other cars when they are started with foot on the brake. I simply do not have a clue where to go next. Another question about the Brembo calipers: Since they have two bleed nipples, is there a proper procedure for thoroughly bleeding the calipers? I've only been doing the outside bleeder nipples. The un-boosted brake pedal is solid, though and the car will stop by standing on the pedal, just not like a power brake system.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 11-04-2020, 03:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
In the Fires of Hell.....
 
kdjones2000's Avatar
 
Join Date: Oct 2007
Location: Phoenix, AZ
Posts: 3,327
Garage
Bleed them both.
__________________
NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 11-04-2020, 08:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
Is there a recommended order, i.e. inner-outer or outer-inner?
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 11-05-2020, 07:00 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered
 
Join Date: Oct 2010
Location: Connecticut
Posts: 2,019
Garage
777, does anyone in your area have a similar car which you could compare (driving/braking sensation) to yours?

I suppose that begs the question, did the car always feel
like this or has it deteriorated over time?

John
Old 11-05-2020, 09:09 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
In the Fires of Hell.....
 
kdjones2000's Avatar
 
Join Date: Oct 2007
Location: Phoenix, AZ
Posts: 3,327
Garage
Quote:
Originally Posted by mytrplseven View Post
Is there a recommended order, i.e. inner-outer or outer-inner?
Not that important, although I would start inside first then outside. You need to bleed both halves of the calipers of all air. The fluid goes from one half to the other via that "U" tube at the bottom.
__________________
NASA/PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost
1987 924S 944 SPEC racecar - '88 pistons/DME, short 5th
1987 944S - Restored salvage title, ready to live again
I can fix your late 944 Cruise Control module - PM for details
Old 11-05-2020, 10:26 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
Jeffries: Initially it worked fine but during the 5 year restoration process the brake system was completely overhauled with new lines, master cylinder, brake booster, check valve, rubber lines and rebuilt Brembo brake calipers, Zimmerman rotors and Hawk pads. Vacuum readings into the Booster were well within spec and the pads were not glazed. A Lindsey Racing venturi delete system was also installed.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 11-05-2020, 02:05 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered
 
Join Date: Jun 2014
Posts: 785
bleed both sides but air in the system is a spongy pedal.

have you confirmed movement of all the caliper pistons?

does the master bore match the caliper upgrade(s)?

are you getting the pads up to temperature?
Old 11-05-2020, 07:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
944 addict
 
mytrplseven's Avatar
 
Join Date: Sep 2010
Location: Orlando area
Posts: 2,672
Garage
Send a message via AIM to mytrplseven
Quote:
Originally Posted by thomasryan View Post
bleed both sides but air in the system is a spongy pedal.

have you confirmed movement of all the caliper pistons?

does the master bore match the caliper upgrade(s)?

are you getting the pads up to temperature?
I wouldn't say the pedal is spongy. When we manually bled the brakes the pedal was firm afterwards. The master cylinder was replaced new and the proper one for the car. I don't know what "upgrade" you're referring to as I just cleaned up the pucks and replaced the seals and cleaned the bores. I ensured the pistons and pads moved freely after rebuilding the calipers. The pads aren't competition variety so having them needing pre-heating isn't an issue. that said, I did ride the brakes and used them hard during the road test so I don't feel that's an issue. Also after a temperature test of the rear rotors, they were about 25% cooler than the fronts so the proportioning valve is doing it's thing.
__________________
3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.

Last edited by mytrplseven; 11-06-2020 at 09:50 AM..
Old 11-06-2020, 09:44 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
Registered
 
Join Date: Oct 2006
Location: va
Posts: 2,371
Garage
Definitely make sure both sides are bled completely. I had a spongy pedal problem once that turned out to be a clogged bleeder screw on the rear. There was soo much air build up from oxidation in the rear lines that the only braking that was occurring was in the front. The car was really diving when I hit the brakes.

Old 11-06-2020, 01:10 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 12:56 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.