Hello. My dad reported the brakes don't work when the car is cold. Well it feels like there is no brake booster. After driving for a while it works. Is this normal? Car has been running awfully weird as well. Only getting like 250km a tank. Could the power booster be creating a significant vacuum leak?? Help is well appreciated, thanks.

What year/model is the car? There was a recall on the brake boosters for failing in cold weather. I know my 99 was effected.

93 Legacy Wagon L N/A

I just did a few google searches and didnt find anything linking that recall to a 93.

93 doesnt usually have this issue, the 95-99 do. The first thing to do is clean the check valve in the brake booster vacum line. Usually thats the simple fix.

 

That valve gets frozen.

 

Next time its that cold, start the car and let it idle for 15 minutes. If you get brakes back, its the check valve.

 

A master cylinder that old would be flaky all the time if it was failing.

 

nipper

Can I clean the check valve with throttle body cleaner? Ill just spray it down the hose, and maybe some WD40 to prevent it from freezing? OR just replace the vacuum line? It is definitely the valve because after it warms up the brakes operate like normal.

I had a similar problem with our '02 OBW. It went on for 2 years(?) or so. I did what Nipper suggested, and cleaned out the check valve in the booster vacuum hose with parts cleaner (actually, I may have used carb cleaner, not sure). It's been fine ever since. Theory is that a little moisture in the line would freeze the check valve and prevent the vacuum from reaching the brake booster. Cleaning out the hose/valve removed the moisture.

 

I would try the simplest/cheapest fix first.

 

For more details, search this thread for "brakes not working when cold" or some similar terms.

Well sprayed some carb cleaner down the tube started it up ran fine, and was freezing outside -5C I believe. Brakes work, but is it normal for the idle to flucuate when I hit the brakes??

[...]Brakes work, but is it normal for the idle to flucuate when I hit the brakes??

Whether that's unusual or not depends on how badly the idle is affected. In addition to the use of intake manifold vacuum by the booster, stepping on the brake pedal of course actuates the stop lights; the current drawn by them puts a slight load on the electrical system. Those things will affect the idle a bit, perhaps more noticably when the engine is cold than when warm.

 

I once saw a car that had a very pronounced change in idle when stepping on the brake -- there were master cylinder and vacuum booster leaks, and the intake was sucking brake fluid. Fortunately, it got fixed before the brakes failed altogether!

Time for another test.

 

 

with the car off pump the brake pedal 10-20 times. Put your foot on the brake pedal, hold the brakes, and start the car (do this with the car warm so its not the check valve). When the car starts the brake pedal should move towards the floor. If it doesnt, then you have a leaking brake booster.

 

I think you may have two issues, not just one. Your idle shouldnt be affected if everything is ok.

 

 

nipper