Bleeding brakes on Audi 100 Type 44 problem

nokia7799 · 05-03-15, 01:35 AM

HI,
I had to replace a couple of sections of steel brake pipes and a couple of flexible brake hoses for the NCT here in Ireland. Afterwards I couldnt bleed the brakes. I tried it the old fashioned way and then bought the air pressure type bleeder to pull the fluid through the lines to no avail. I have two spare master cylinders which i swapped also (checking the pedal on the cars i took them out of beforehand) but to no avail. Its a strange one. Both of these spare master cylinders appeared to be fine in the cars they were in before i took them out. I cant get brake fluid back to the rear calipers, only the front left wheel. has anyone come across this before? I would really appreciate some help.

Thanks

Barry

Hanuman · 05-03-15, 02:04 AM

There is a device called a brake force regulator, which is an alloy valve body, with a lever arm attached to the rear axle by a spring.
It frequently is a problem, due corrosion in both the arm and the valve.

The device works by reducing pressure to the rear circuit as the car 'dives', the rear end unloads a bit, causing the spring to pull on the arm, closing a plunger.

If memory serves, it's mounted on the left side. Just trace the brake line to the rear.
It was certainly a problem on one of my. V8s.

Pic. Courtesy of VagCat.

Item 14 is my bet as the culprit.

nokia7799 · 05-03-15, 02:14 AM

thanks very much. I know the regulator you're describing.... i replaced the two pipes going into this from the rear wheels.

On another note I tried to bleed the master cylinder itself, considering I have put two secondhand ones in along with the one that was in it.... all of these strangely wouldn't push out fluid when pressing the pedal only on the front left circuit so i put the air operated unit on them to try and encourage it to bleed. It is unlikely that three master cylinders are dodgy? particularly when the brakes were fine before i replaced the pipes! But if the master cylinder isnt pushing out fluid on all of the four outlets when pressing the pedal does this not mean it is fecked?

Thanks again for all your help

Hanuman · 05-03-15, 02:22 AM

ABS? There are some notes on this, which I've not run into problems with as yet, although I haven't replaced a master cylinder.
I'll dig them up later today, when if get a chance. They're notes from a V8 manual, but I expect a lot of commonality.

nokia7799 · 05-03-15, 07:21 PM

Hi. I disconnected the pipes going into the brake regulator from the master cylinder side and attached the vacuum type bleeder. I got brake fluid out there but when i run it through the regulator it wont suck it through it. I then changed the regulator with a second hand one i had in another car i have for parts. No Good. still cant get brake fluid through the brake regulator to the rear calipers. Its an 83 Audi 100 with calipers in the back and no ABS. What am I doing wrong? Is there a particular way to bleed these circuits? Could i bypass this regulator?

Hanuman · 05-03-15, 08:03 PM

Possibly, there is some commonality.

The V8 manual says that where the master cylinder has been replaced, the clutch slave cylinder needs to be bled first. I can't visualize why, though (no UK manual versions)

TeXerv · 07-03-15, 12:05 PM

A vacuum bleeder possibly won't work with this brake force regulator. I would try it in this way (forget about your bleeder tool): Three persons are required. Jack the car at the rear axle thoroughly and safely- engage the brake force regulator lever by hand to maximum vehicle load - bleed the system in the old fashioned way in the following order: RH rear, LH rear, RH front, LH front. Always mind the fluid level.
After successful bleeding adjust the regulator thoroughly.

nokia7799 · 08-03-15, 03:44 PM

Hi, Thanks for all your advice, I really appreciate it. One thing that I found strange is that to test the master cylinder itself I loosened the pipes on the master cylinder itself, one by one. I could only get fluid to come out of one of the four outlets when depressing the pedal. the front left if memory serves me correct. The fluid level was fine during this. I done this with the three secondhand master cylinders that I used and all of them appear to be doing this. Does this not suggest that the master cylinder is defective or is it a common thing? I thought that if u were not getting fluid at this point you wouldnt be getting it further back near the regulator.

TeXerv · 08-03-15, 04:14 PM

If you want to test your master cylinder (after replacing!) you need to proceed like this:
Replace all lines from the cylinder and fit bleeder screws instead.
Now bleed the master cylinder (similar to brake bleeding): Start with the first circuit (close to the brake booster) and bleed at both bleeders of this circuit simultaneously.
Then bleed the second circuit also at both bleeder screws simultaneously.
If this doesn't work check the reservoir for clogged fluid port.

05-03-15, 02:04 AM	#2
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Bleeding brakes on Audi 100 Type 44 problem There is a device called a brake force regulator, which is an alloy valve body, with a lever arm attached to the rear axle by a spring. It frequently is a problem, due corrosion in both the arm and the valve. The device works by reducing pressure to the rear circuit as the car 'dives', the rear end unloads a bit, causing the spring to pull on the arm, closing a plunger. If memory serves, it's mounted on the left side. Just trace the brake line to the rear. It was certainly a problem on one of my. V8s. Pic. Courtesy of VagCat. Item 14 is my bet as the culprit. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor Last edited by Hanuman; 05-03-15 at 02:14 AM.

05-03-15, 02:14 AM	#3
nokia7799 Grown up member Join Date: Jul 2011 Location: Mayo, Ireland Posts: 56	AUDI 100 brake bleeding nightmare thanks very much. I know the regulator you're describing.... i replaced the two pipes going into this from the rear wheels. On another note I tried to bleed the master cylinder itself, considering I have put two secondhand ones in along with the one that was in it.... all of these strangely wouldn't push out fluid when pressing the pedal only on the front left circuit so i put the air operated unit on them to try and encourage it to bleed. It is unlikely that three master cylinders are dodgy? particularly when the brakes were fine before i replaced the pipes! But if the master cylinder isnt pushing out fluid on all of the four outlets when pressing the pedal does this not mean it is fecked? Thanks again for all your help

05-03-15, 02:22 AM	#4
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	ABS? There are some notes on this, which I've not run into problems with as yet, although I haven't replaced a master cylinder. I'll dig them up later today, when if get a chance. They're notes from a V8 manual, but I expect a lot of commonality. __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

05-03-15, 08:03 PM	#6
Hanuman Trickster Classic Audi Club Member Join Date: May 2009 Location: Heckling from the cheap seats, Phnom Penh, KoW Posts: 7,006	Possibly, there is some commonality. The V8 manual says that where the master cylinder has been replaced, the clutch slave cylinder needs to be bled first. I can't visualize why, though (no UK manual versions) __________________ I wish they would keep the damned Chinese away now that I can go home, so that I can enjoy Fish amok and a draught Angkor

05-03-15, 07:21 PM	#5
nokia7799 Grown up member Join Date: Jul 2011 Location: Mayo, Ireland Posts: 56	Hi. I disconnected the pipes going into the brake regulator from the master cylinder side and attached the vacuum type bleeder. I got brake fluid out there but when i run it through the regulator it wont suck it through it. I then changed the regulator with a second hand one i had in another car i have for parts. No Good. still cant get brake fluid through the brake regulator to the rear calipers. Its an 83 Audi 100 with calipers in the back and no ABS. What am I doing wrong? Is there a particular way to bleed these circuits? Could i bypass this regulator?

07-03-15, 12:05 PM	#7
TeXerv Grown up member Join Date: Oct 2011 Location: Northern Krautland Posts: 241	A vacuum bleeder possibly won't work with this brake force regulator. I would try it in this way (forget about your bleeder tool): Three persons are required. Jack the car at the rear axle thoroughly and safely- engage the brake force regulator lever by hand to maximum vehicle load - bleed the system in the old fashioned way in the following order: RH rear, LH rear, RH front, LH front. Always mind the fluid level. After successful bleeding adjust the regulator thoroughly.

08-03-15, 03:44 PM	#8
nokia7799 Grown up member Join Date: Jul 2011 Location: Mayo, Ireland Posts: 56	Hi, Thanks for all your advice, I really appreciate it. One thing that I found strange is that to test the master cylinder itself I loosened the pipes on the master cylinder itself, one by one. I could only get fluid to come out of one of the four outlets when depressing the pedal. the front left if memory serves me correct. The fluid level was fine during this. I done this with the three secondhand master cylinders that I used and all of them appear to be doing this. Does this not suggest that the master cylinder is defective or is it a common thing? I thought that if u were not getting fluid at this point you wouldnt be getting it further back near the regulator.

08-03-15, 04:14 PM	#9
TeXerv Grown up member Join Date: Oct 2011 Location: Northern Krautland Posts: 241	If you want to test your master cylinder (after replacing!) you need to proceed like this: Replace all lines from the cylinder and fit bleeder screws instead. Now bleed the master cylinder (similar to brake bleeding): Start with the first circuit (close to the brake booster) and bleed at both bleeders of this circuit simultaneously. Then bleed the second circuit also at both bleeder screws simultaneously. If this doesn't work check the reservoir for clogged fluid port.