Hard braking causes car to force stall

[huss]

As per title, under normal braking conditions the car acts normally, under above normal - hard the rev's drop and it sometimes stalls, Any idea why? Car rev's at about 800-900 rpm, I'll lift raise the rev's to see if it makes a difference.

I replaced the old carb with a much better one. Was hoping this would fix the problem, but it still exists.

I upgraded the brake system, Audi 80 front, Mk3 rear, seat ibiza booster, corrado MC.

Really want to get the car on the road but too dangerous with this problem.

Any tips????

[Stan]

some things to check mate:

Because of vacuum etc, a leaky brake booster might do this, it might be blocked, damged hose or diaphragm.
Check you master cylinder for leaks also
Brake line obstuctions, snagged/kinked lines etc, also air in the fluid.
Vacuum leaks in an ABS system
Check clutch as well, and if the transmission is contaminated.
Check for any loose or leaking connections - hoses, earths, battery

[chesymoon]

i had the same problem and It was the brake booster.

I checked the all the vacuum lines and there was no leak.

But Brake booster was stuffed and I replaced with good second hand one and problem solved.

hope this might help.

[huss]

None of my lines are kinked, pretty sure there is no air in the brake lines, no brake fluid leaking anywhere, transmission could be contaminated but doubt it.

My gut instinct is telling me that it is my brake booster. Guess there's only one way to find out.

[ross_m]

Sounds like an air leak through your rubber carb mount. Its common for the carb to flop forward when braking hard opening a crack in the rubber. This lets air in and stalls the car. Ive had it with two mk1's and had to replace the rubber mounts. The fact you have replaced the carb tells me there may be a leak after desturbing it. Mightnot be sealing properly... Hope that helps.

Let usknow how youget on

What carb/engine is it?

[huss]

Unfortunately I also had this problem on the other carb when I redone the braking system. So im pretty sure its not the carb. Its a 32/36 weber running on a 1.6l. Jetted for a 1.6l. And runs MUCH better than the original.

Ill be getting another (second hand) brake booster in it this weekend. So ill let you guys know if that was the problem.

[chesymoon]

there is a certain test for the brake booster.. take off the vacuum hose to to booster and try to blow and suck the hole on the booster with your mouth.. I don't know how it turns out but my mechanic did it and told me booster failure, haha.
(I reckon you could feel the diaphragm somehow..)

If the second hand one is no good you can also get it reconditioned by a specialist.

[huss]

I done a brake booster test which I found in the link below. It passed the first and half failed the second and failed the third. Guess it is the brake booster

Will hopefully get another one on during the weekend, will keep you guys updated

http://www.autoshop101.com/forms/brake05.pdf

[mikinoz]

there is a certain test for the brake booster.. take off the vacuum hose to to booster and try to blow and suck the hole on the booster with your mouth.. I don't know how it turns out but my mechanic did it and told me booster failure, haha.
(I reckon you could feel the diaphragm somehow..)

This is true. It is also valid for vacuum diaphragms on distributors!

[kaanage]

You could have just disconnected the vacuum line at the brake booster and plugged it to see if the problem went away - of course you have to be aware that you will need to press on the brake pedal a LOT harder to slow/stop the car when testing this.

[chesymoon]

of course you have to be aware that you will need to press on the brake pedal a LOT harder to slow/stop the car when testing this.

you can just test it on stationary.

[kaanage]

.............

[huss]

So when doing this what should I look out for?

[kaanage]

chesymoon is pointing out that the leaky booster should have an effect on the car when it's just idling if you stamp on the brakes so you could disconnect and plug the vacuum line and stamp on the brakes to see if the car just idles with no change.

[huss]

OK so I pulled the vacuum line end where it connect to the manifold, plugged it up, tried to start the car and the car could barely idle.

Then I unplugged it and connected it up again and the car started normally.

Thoughts??