105 brakes sticking

[Craig H]

Hi all,

I have a 1750 berlina and I am having no end of trouble with the brakes sticking on. I have found that if I clamp off both of the power boosters and run just on the hydraulics then they don't stick (but they don't work particularly well either) however if I clamp off either one of the power boosters individually then they stick on. I suspect the problem is the valves but would they both go? Is there anything else in the pneumatics that it could be? I have been quoted about $800 ($400 each) to put new valves in the boosters but I have also been told that this may not cure the problem anyway as it could be any number of things that are wrong.  I suspect that the two boosters where fitted initially because one simply wasn't complicated enough, so with this in mind would it be simpler (cheaper/more reliable) to ditch the originals and go with a single booster set up from a later model car?  Or is there an aftermarket set up I could use?

Craig h

[Gary Pearce]

It sounds to me by clamping off the vacuum you have correctly diagnosed faulty power boosters. Of course the brakes seem poor because there is now no power assistance.
When sticking you could jack up the car and do a quick run around the wheels to see if there is any particular wheel cylinders sticking too.
Two power boosters were used to keep the 'Twin' circuits separate in R/H/D cars while still retaining the under floor twin master cylinder. One booster for front one for back. Commonly the valves in the booster, the alloy bit, corrode and jam.
You may find isolating the rear power booster (the one facing east/west) will still provide good braking performance IF the front one is working satisfactorily. I can't see you saving much more than overhauling the front booster and pulling off the vacuum pipe from the east/west one. Blocking the hose of course. Then see if you are still happy with the boosting to the front and foot pressure to the rear.

[Craig H]

Thanks Gary,
I have tried clamping the booster off individually but they still stick, suggesting that they are both faulty.  Unfortunately, I can't test each wheel by jacking it up because after a few seconds the pressure on each side of the diaphragms equals and they unstick.  Now I know which one does the rear brakes I'll clamp it off and see how it goes.  Can you still buy the valves new and how tough is it to put them in?

Craig

[Gary Pearce]

Out of my league now. I use ABS brakes after I pull em off the car. Too big a risk safety wise so I leave it to the experts.

[1750GTV]

I had the same problem with my twin booster GTV. The rear booster was jamming and the rear brakes were partially locking on resulting in worn pads and very hot hubs and rotors. For a while I drove with the rear booster disconnected with no real discernable, at least by me, decrease in braking efficiency - maybe the rear booster had been not functioning properly for a while. Eventually a rear caliper leak forced a complete overhaul - 2 new boosters, new master cylinder, rebuilt calipers, new rotors and new flexible hoses. After lots of dollars, I now have brilliant brakes.
The point of this story is that I've heard that it may have been cheaper for me to convert the system to a single booster, a'la earlier models. The master cylinder is much cheaper and in ready supply and you only have one booster to crap itself over time.
As to rebuilding the boosters, apparently some of the parts are available but not all, and even if so, they are tricky to get right as they are often badly corroded. I stripped both of my old (and original) boosters and found this to be the case - despite changing the hydraulic fluid regularly.
I guess the upside is that my original system lasted nearly 38 years, though the last couple were a bit tricky, and I'm hoping that the rebuilt hydraulics will last just as long - only time will tell.
I'd be interested to hear if anyone else has had similar problems or whether it was just my usual luck.
Sorry my story is so bleak,
Chris

[Tim Jobson]

Chris,

Having just bleed my 105gtv 2000 brakes iaw the hand book instructions there was no mention of the bleed screw nipples on the boosters and the brake master cylinder, so what are these nipples for and are they part of the brake hydraulic bleeding process?

Cheers tim

[1750GTV]

Tim,
My old Bonaldi tandem master cylinder did not have a bleed nipple, but the new replacement one does (see photos). Neither the old nor new Bonaldi boosters have nipples. The only bleed nipples I have are on the M/C and at each wheel caliper.
I use a pressure bleeder to get all of the air out - it works very well and takes all of the hassle out of trying to get a firm pedal.
Chris

[Tim Jobson]

Cris,

Your new Master cylinder looks like mine, so the question still remains, what is the bleed nipple on this used for in the brake bleeding process?

Any advice on how to turn the engine over by hand?

Tim

[1750GTV]

Tim,
I bleed the M/C first. Once no more air is present in the M/C I then move on to the wheel calipers. Traditionally you bleed the one furtherest from the M/C first (LHS rear) working your way through them until you get to the one nearest the M/C (RHS front), so on RHD cars it goes LHS rear, RHS rear, LHS front, RHS front. Having done this once, and particularly with 105 Alfas, I normally leave the car overnight, start it and run it the next morning to test the brakes and repeat the entire process. It always surprises me how much more air comes out second time around - particularly after the boosters have been activated by starting the engine and applying vacuum. Usually by the end of the second bleeding I've got a real firm pedal.
When I change the brake fluid (about annually) I only go through the process once, unless I've inadvertently let in some air.

As to turning the motor by hand, the easiest way is to remove the spark plugs, put it in neutral and gently rotate the fan. If you're concerned about snapping off a fan blade, put a socket (I think it's a 36mm but check) on the crank pulley and turn it using a T-bar or rachet.

Hope this helps,
Chris

[Tim Jobson]

Thanks Chris,

I will try your suggested bleeding routine and hope that fluid does come out of the M/C bleed nipple when I do it!

I have looked at trying to turn the engine over by hand using a socket however there does not seem enough room to get a socket and handle in there, the fan and cowling leave no room and the front beam supporting the radiator is very close to prevent doing it from under neath the car?

regards TIM

[1750GTV]

Tim,
I think the last time I turned the motor using a socket was when I had the radiator out - gives you a lot more room that way. Sorry, I probably should have mentioned that 
It is quite safe to do it using the fan particularly if you grip the blades close to the centre and tension the belt with your thumb.
Let me know how you get on,
Chris

[1750GT]

Guys thanks for a great read about brakes and turning over engines by hands (hope we are not calling Chris 1 finger in th enear future!). I recently had the same problem with the brakes, its just an issue in the use of pressure/hydaulics instead of the more modern system, but then with a properly operating system theres something special about the feel of the agricultural brakes dont you think.

Guys I do want to ask, do you ever drive your cars and speak about it?

1750GT

[Gary Pearce]

You are making a good point, as we all drive em and love em, but don't always tell of the exhilarating tactile experience that comes with driving such a great model which leaves a smile on your face every time you drive. The gear change, the steering and the brakes are all part of the package and given that the performance of a 105 in reasonable condition is equal too or better than a lot of current model cars I can't see much down side in driving a classic..... on week-ends anyway. Keep a look out in future editions of our club magazine 'Cross & Serpent', as I believe our editor plans to do road test drives on every model Alfa Romeo that he can get his hands on.