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Discussion Starter #1 (Edited)
I am having a bear of a time bleeding the brake system on a 1969 GTV and I am wondering if anyone can post some experience with good bleeding technique. My main problem is that I cannot get a consistent pedal feel, and I think I still have air in the system...though I can't be sure what the actual problem is for sure. With the car not running (no boost) I have to pump the pedal a few times to get good pressure, but it will almost always bleed down and pedal goes to the floor. With the engine running (boost on) it does a similar thing.

The car has had quite a bit of brake work in the past few days:

New front calipers.
Newly rebuilt master cylinder.
New Boosters (from Classic Alfa).

Originally the car had a very sticky and inconsistent brake pedal feel. It also would on occasion get a lock up of the front brakes (after releasing the pedal). New front calipers and boosters seem to have gotten rid of those two issues but then I choose to rebuild the master because it had a slight seap. I found a high quality rebuild kit which I sourced from Jon Norman and the cylinder was in pretty nice shape internally. There are no leaks in the system anymore and I've tried all bleed methods:

Gravity bleed.
Power bleed at 15psi.
2-man bleeding
3-man bleeding
Vacuum bleeding at each caliper
Vacuum bleeding at the reservoir
Cracking open the lines at each booster (under pedal pressure)
Cracking open the lines at the master (under pedal pressure)
Tapping on all components

My only doubt is that I possibly still have a master cylinder issue because when I pump the brakes and build pressure, I can hear a "whishing" sound coming from inside the master.Maybe it is air returning to the reservoir? or maybe my rebuild failed?

NO luck! I am defeated. Help!

PS: I believe I have read every "1969" brake bleeding thread on here haha.
 

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I have a 70 model gtv which is right hand drive, but still dual circuit, I spent over a year trying to sort it, rebuilt the calipers, the car had had 2 new matser cylinders, rebuilt both boosters, 1 of them 3 times, turned out the shiny new looking bias valve at the rear had been badly overhauled. there were no leaks out but as you released the brakes it sucked air in. put a new one in and all was solved. but it sounds like your master cylinder is your problem. cheers Ian
 

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I have to pump the pedal a few times to get good pressure, but it will almost always bleed down and pedal goes to the floor. With the engine running (boost on) it does a similar thing.
If the pedal goes to the floor after you have built pressure and you are not losing fluid anywhere then it seems to me that it must be the master cylinder. There are about a half dozen seals in that cylinder that must be installed in the right direction. You might want to double check that. Also check for seals that may have gotten nicked during installation and scoring on the MC.
 

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Discussion Starter #4
Update, I bit the bullet, swallowed my pride and bought a new master cylinder for this car.

After a very strange bleeding procedure which consisted of:
Light and very slow pumping of brake pedal about 40 times to prime system.
Pressure bleed with 15psi at the reservoir.
2-man bleed: pump pedal until pressure builds, hold pressure and then open bleed screw (about 10 cycles per corner).
Start car to activate boosters and repeat the 2-man bleed.
Spirited drive with hard brake testing...

During the entire bleed procedure the pedal was inconsistent and took many pumps to build pressure and then all of a sudden brakes came in and started working amazing. I just test drove the car and the brakes are better then they've ever been..... Very strange. The funny part is that I hardly got any air coming through the bleed line after the first couple of bleed cycles, yet after enough wasting of nice good fluid, it just started working. I went through about 2 liters of fluid total.

To summarize:My rebuild of the master cylinder was no good. The "whishing" sound coming from the rebuild cylinder was not present once I swapped in the brand new unit......the one I rebuilt must have had an issue, or the seals were junk.....anyways dual circuit brake bleeding sucks, good luck.
 

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The 1969 cars are notoriously hard to bleed. In this case it seems a bad master cylinder was the problem but this is not always the case.

One thing we have had good luck with is bleeding the car with the front wheels on the ground and the back of the car on high jack stands. Sometimes, letting the car sit overnight with the rear raised like this also helps. This seems to get a good pedal much faster than simply bleeding multiple times with the car on flat ground.
 

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vespam5

Here are the Alfa service bulletin's for bleeding the brakes on the early dual systems.

I thought I had the tool bulletin for the brake bleeding tool. But I only have the updated on from 1973. But more then likely its the same from the floor pedal car. One interesting thing to note is the recommended pressure is around 42 psi.

A kit from this company will do the same as the Alfa power bleeder.

https://www.motiveproducts.com/collections/import-power-bleeder-kits
 

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I've had a very similar issue to this but its slightly different, the car is a 1971, 1750 spider Kammtail, it has dual circuit system, the car has been completely restored but I'll give a potted history of the problem.

If the brakes are bled it performs perfectly, the car doesn't get used all the time but when left it loses pedal feel to the point the pedal will travel to the floor and it does this quite quickly say 2 - 3 weeks, if the car is being used it does the same thing but its a bit more gradual.
I've had some health issues and I now can't do this myself but a good many specialist (Alfa) have had a go at the car but the results are the same, this is over a period of 4 years, I've replaced the following:
calipers, all new
Servos, refurbished then replaced with new
Master cylinder, New modern pattern part fitted, replaced with another modern pattern item then recently replaced with a new old stock Benalfa unit
all new disks
all new hoses and brake pipes
Can't tell you how many times this car has had its brakes bled, its breaking my heart, there are no leaks at all anywhere (never find fluid anywhere except where it should be), I can't say they have ever been bled to the above proceedure, I haven't used that method but I reckon that if the brakes where bled and I parked the car in the garage for 3 weeks the pedal would have gone soft.
I'm literally at my whits end with it, the car is lovely, the rest of it was a long road but got there eventually, has anyone got any suggestions on what to look at next PLEASE.

Andrew
 

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Discussion Starter #8
Andrew, try what Joe said above about angling the car, or maybe try (with help) to crack the hard lines at each booster whilst it is under "pressure". If you've ever seen a late model GT or Giulia Saloon, they introduced bleed valves at the boosters at some point in the early 70's maybe to help with this!
 

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I've had a very similar issue to this but its slightly different, the car is a 1971, 1750 spider Kammtail, it has dual circuit system, the car has been completely restored but I'll give a potted history of the problem.

If the brakes are bled it performs perfectly, the car doesn't get used all the time but when left it loses pedal feel to the point the pedal will travel to the floor and it does this quite quickly say 2 - 3 weeks, if the car is being used it does the same thing but its a bit more gradual.
I've had some health issues and I now can't do this myself but a good many specialist (Alfa) have had a go at the car but the results are the same, this is over a period of 4 years, I've replaced the following:
calipers, all new
Servos, refurbished then replaced with new
Master cylinder, New modern pattern part fitted, replaced with another modern pattern item then recently replaced with a new old stock Benalfa unit
all new disks
all new hoses and brake pipes
Can't tell you how many times this car has had its brakes bled, its breaking my heart, there are no leaks at all anywhere (never find fluid anywhere except where it should be), I can't say they have ever been bled to the above proceedure, I haven't used that method but I reckon that if the brakes where bled and I parked the car in the garage for 3 weeks the pedal would have gone soft.
I'm literally at my whits end with it, the car is lovely, the rest of it was a long road but got there eventually, has anyone got any suggestions on what to look at next PLEASE.

Andrew
Hi Andrew, these are the exact symptoms that I had as mentioned above. I must have gone thru about 6 litres of fluid. as I said above the brake bias valve at the rear was faulty. it looked brand new and the PO had replaced it with reconditioned unit. It's hard to explain but when you pull it apart you can see when under pressure the seal wont leak but when the pressure is released it lets air suck past the seal. I rebuilt the booster that supplied the rears 3 times thinking it was leaking. I cant guarantee this is it but it solved it for me. the previous owner had put 2 new master cylinders in trying to solve it. I think he sold it in frustration.

cheers ian
 

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Hi Ian,
I ordered a bias on reading your post, for the cost its not worth not trying, I'll let you know how I get on.

Andy
 

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I thought I had the tool bulletin for the brake bleeding tool. But I only have the updated on from 1973. But more then likely its the same from the floor pedal car. One interesting thing to note is the recommended pressure is around 42 psi.
Great googly-moogly! That's a lot of pressure. For a typical brake system you'd use like 15 psi, and even on my other car where you need to push fluid through the ABS system it only needs 29 psi. I wonder why it's spec'd so high?
 

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VW recommends bleeding one front and rear at a time on Buses with dual circuit. That is, bleed left front and rear togehter, then bleed right front and rear together. Use to hoses and containers, etc. I've done this and it works. I've also done dual circuits one wheel at a time, RR, LR, RF, LF, and had it work fine too.

Andrew
 

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A problem I had was air getting in around the outside of the bleed valve during bleeding the procedure with a one-man bleed kit.
I wrap the bleed valves with plumbers tape and that resolved the issue.
 
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