Pushing BRAKES causes engine to STALL

brakes
alfaromeo

#1

Hi there,

My first post on here. A bought an 1988 Alfa 75 3.0 V6 last year and having recently encountered an issue where by pushing the brake pedal causes the engine to run rough. I pressed the pedal 3 times repeatedly and the engine cut out. Now every time I start the engine, it cuts out after a few seconds. Any ideas?

[I]INFO:
The brakes are [B]stiff[/B] (after a few pumps) when the engine is [B]off[/B], however [B]sink [/B]all the way to the floor when the engine is [B]started[/B]. I bled the brakes last week in the correct order, however no luck.

When the car is at low RPM and about to stall, there is a loud clunking noise coming from the rear left of the car (underneath).This doesn’t happen when we the clutch is pushed down.

The car hasn’t been driven for a couple of years, however has been running fine since this happened[/I]

Thanks for your help!


#2

I am not at all familiar with that 1988 Alfa but I assume it has a vacuum brake booster. The vacuum brake booster has failed. These are fairly classic signs of this. Replace the booster and check the master cylinder seal at the booster side as is may be the type open to the vacuum signal. If so, a small leak with make you brake fluid “disappear” - it ends up IN the booster. Considering the car’s age, replacing booster and master cylinder plus the lines from the engine and the check valve at the booster would be in order.


#3

Pressing on the brake pedal activates the brake power booster. That device is powered by engine vacuum. If the rubber diaphragm inside it tears – not an uncommon thing – that created an unwanted air path into the engine and can cause the engine to run poorly and stall. In some cases it can cause brake fluid to be sucked into the engine too, not a good thing. So have that checked. Folks here often report they hear a whistling or buzzing or hissing sound when that happens, but not always. If the car hasn’t been driven for 2 years, it would make a lot of sense to have a thorough inspection of the brake components in all four wheels done as part of this. Once you get the brakes under control, if you still have that clunking sound, come back here for more advice. I expect you’ll find several more issues to attend to on your car. Car’s aren’t designed to sit unused for long periods of time, and all sorts of problems can crop up. Best of luck.


#4

MustangMan,

Thanks for the quick reply! I also thought it would be the booster failing, or a leaking causing an imbalance of fuel/ air mixture in the engine. However, why would the brakes soften up when the engine is started if the booster is not working? It appears to be doing the job?
I have not yet been able to check for leaks.

Jack


#5

George,

Thanks for your advice. All brakes seem to be in a fair condition upon initial inspection. Once we’ve got this booster back working, I’ll strip down all the calipers. Thanks for your reply.

Jack


#6

It is still providing some boost but the leak is enough stall the engine. The booster is supposed to hold 2-3 boost assisted stops with the engine off so there is some margin if it stalls. The leak may not be a big one but enough to cause problems. If you have a vacuum gauge you can plumb under the check valve, turn off the engine and the booster should hold vacuum as long as you don’t apply the brake, if there is no leak.


#7

I think you’re right, as when we turn off the engine, we don’t get 2 or 3 full pumps of the pedal before it stiffens. Thanks for your help. I’ll be in touch soon


#8

You can rebuild a booster if you are so inclined, and a kit is available. I did one on my 1979 Jag XJ6. The spring is a monster. I made a cage out of nylon rope to catch things when I opened it up. I had to make a lever from 2X4’s and bolts to get it back together.

If a rebuilt unit is available, get it .


#9

Sounds like quite a job, but we’re struggling to find a replacement part, so might have to have a look into this. What do you mean a kit is available?

Jack


#10

Are you a member of the various Alfa forums? They’ll have lots of suggestions on how to fix this.

Where are you located?


#11

A Google search found several Alfa parts suppliers in the United Kingdom. Texas has a good idea about looking for Alfa forums.


#12

I’ve posted a new thread in 2 alfa forums. No replies. I’m based in North Wales, UK. Close to Chester. I have a found a few alfa breakers so think I’ll get in touch with them if we find the servo is dodgy


#13

One could hope it might be a cracked or broken hose, check that first1


#14

That’s what I’m hoping for! Broken hose or dodgy seal. I keep the car a few miles away, so haven’t been over to check yet