That sinking feeling...

[f1fascination]

Hi again, anyone has an experience with a sinking brake pedal while the car is idling at the lights?
It sounds a bit master cylinder-ish,but these look horrendously expensive to take a punt on, and I can't find a seal kit anywhere.
Is it possible for the servo's to bypass fluid? I have had a bit of fluid loss and can't see where it's going. I've bled the whole system twice, including the master cylinder.

[colcol]

It sounds like the master cylinder is leaking brake fluid back into the brake vacumn servo, and it is being sucked back into the manifold and being burnt.
Is your car puffing a bit of blue smoke?, have a look at the inside of your vacumn hose from the manifold to the brake booster and see if it is wet with brake fluid, Colin.

[Barry Edmunds]

Have you tried 105s alive, an Alfa parts supplier in Perth, for a seal kit. Have been told his prices are excellent and his service is first class. Check his web site.
I'd start with colcol's suggestions.
White or blue smoke from the exhaust could be a guide to the source of the problem. Try taking the vacuum hose off at the booster and blocking it. Could eliminate the booster as the problem of the sinking pedal. By-pass the booster to see if that stops fluid loss. Could indicate fluid build-up in the booster.

[LaStregaNera]

It'll be the remote booster most likely. Disconnecting from vacuum won't tell you anything, and bypassing the booster won't tell you much beyond giving you a really heavy pedal. It's pretty simple to put a kit through the remote booster, and if its a dual system, you'll be able to tell which unit needs kitting when you pull the vac hose off.

[colcol]

First of all you have to find where the master cylinder is leaking, and if it isn't leaking, look at your booster, sit in the car with the engine off, and pump the brake pedal until it goes hard, then, start the engine with your foot on the brake pedal, to see if the pedal sinks, to see if the servo is working.
If the rubber bellows is leaking, because it has a tear or is perished, it will be leaking air back into the manifold, upsetting the idle mixture, resulting in a rough idle, Colin.

[f1fascination]

Thanks for all of the responses guys, the idle is somewhat fluffy, but there is also some smoke from exhaust of a bluish nature.
I've pulled the hose from the rear-most servo and there is some staining on the inside, and I know it's fresh because I only replaced the hoses two weeks ago!
So a reseal is looking right for it.
Many thanks again, and Barry I'll check out 105's Alive for sure.

[LaStregaNera]

First of all you have to find where the master cylinder is leaking, and if it isn't leaking, look at your booster, sit in the car with the engine off, and pump the brake pedal until it goes hard, then, start the engine with your foot on the brake pedal, to see if the pedal sinks, to see if the servo is working.
If the rubber bellows is leaking, because it has a tear or is perished, it will be leaking air back into the manifold, upsetting the idle mixture, resulting in a rough idle, Colin.

It's a 105, the remote booster has a servo cylinder arrangement that commonly shits the bed and leaks brake fluid into the vacuum side of the booster. You're clearly used to the normal vac booster attached to the master cylinder that Alfetta onwards (and pretty much any normal car) has. Stick to what you actually know Colcol.

[f1fascination]

Hey thanks guys, but I hope I haven't started an argument!
I'm gonna start by rebuilding the booster and the cylinder attached to it, and go from there.
In regards to smoke, well, it was a bit smoky anyway so any reduction will be an improvement!

[f1fascination]

Good news and bad news folks, have stripped the offending booster, only to have brake fluid pour out of the vacuum port, not a good sign I'm sure, but the insides of the booster are quite rusty so I'm chasing a replacement or reconditioned booster if anyone knows where I could locate one at a reasonable rate.

[colcol]

I was chasing a booster for the 33, and all i came up with were boosters for 105's, so there are some out there, and there are reconditioning kits as well, i would see what a changeover one would cost, [around $300?], if i remember rightly, most are on ebay, because they are large, freight will be a killer, Colin.

[colcol]

In my search for a booster, i came across a company in Argentina, who make replacment rubbers for boosters of all different kinds, even Benditalia's for Alfa 33's, but i emailed them about 5 times, and they never got back to me, you might have more luck than me, Colin.

[LaStregaNera]

Good news and bad news folks, have stripped the offending booster, only to have brake fluid pour out of the vacuum port, not a good sign I'm sure, but the insides of the booster are quite rusty so I'm chasing a replacement or reconditioned booster if anyone knows where I could locate one at a reasonable rate.

The steel part of the booster can be cleaned up easily with a wire brush, and as long as it's air-tight, it's condition is not critical - give it a lick of vht caliper paint and bake it if you're keen to really clean it up.
The bore of the servo cylinder is the critical part - and anyone who sleeves master cylinders shouldbe able to sort it for you - Power brakes in Adelaide can certainly resleeve it for you if the bore is no good.
https://www.powerbrakes.com.au/

[f1fascination]

Thanks guys, I think I'll be going for a new booster from Alfaholics or Classic Alfa as they seem to be the most reasonably priced.