No Power Brakes with cold engine
Thread Starter
Instructor
Joined: Jul 2007
Posts: 106
Likes: 0
From: Hudson Ohio
No Power Brakes with cold engine
Hi All,
In the AM with a cold engine, I don't have power assist when braking--very hard. Once the engine gets up to temp, I have power assist. Am I loosing vacuum over night?
Thanks!!
In the AM with a cold engine, I don't have power assist when braking--very hard. Once the engine gets up to temp, I have power assist. Am I loosing vacuum over night?
Thanks!!
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
My guess is you have a vacuum booster that has a leak or crack in it and as the engine warms up the booster warms up and seals the leak.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
It doesn’t quite work like that. You have vacuum immediately when starting the engine and all should work normal.
Start out checking the vacuum to the check valve in the morning when its cold. Pull off the line and put your thumb on it and see if it sucks good. If you take you thumb off it should stall or at lest run real bad. This will check the vacuum and to see if there is a kink in the line.
Another possible problem is a bad check valve. It can also leak around the edges of it. And of course the booster might be defective. Listen for a hiss from it, that will be a sign it may be internally leaking.
A good booster will hold vacuum at least for several minutes which you should be able to get 3 good pumps from the brake pedal before it gets hard.
Also wondering if the booster is a metal or plastic unit,. Possibly when the engine compartment heats up if it is plastic there could be some expansion causing it to seal when hot (just a thought).
You can start there and see if you can find anything. I would not think master cylinder as of yet. If you have a vacuum gauge you could use that to check the actual vacuum.
Start out checking the vacuum to the check valve in the morning when its cold. Pull off the line and put your thumb on it and see if it sucks good. If you take you thumb off it should stall or at lest run real bad. This will check the vacuum and to see if there is a kink in the line.
Another possible problem is a bad check valve. It can also leak around the edges of it. And of course the booster might be defective. Listen for a hiss from it, that will be a sign it may be internally leaking.
A good booster will hold vacuum at least for several minutes which you should be able to get 3 good pumps from the brake pedal before it gets hard.
Also wondering if the booster is a metal or plastic unit,. Possibly when the engine compartment heats up if it is plastic there could be some expansion causing it to seal when hot (just a thought).
You can start there and see if you can find anything. I would not think master cylinder as of yet. If you have a vacuum gauge you could use that to check the actual vacuum.
Thread Starter
Instructor
Joined: Jul 2007
Posts: 106
Likes: 0
From: Hudson Ohio
I got good vacuum at the check valve in both instances. I will seal the edges and try again.
I am not getting a hiss from the metal booster. I am thinking that the heat has something to do with this. Expanding the seals when hot to restrict a vacuum leak?
Thanks again
I am not getting a hiss from the metal booster. I am thinking that the heat has something to do with this. Expanding the seals when hot to restrict a vacuum leak?
Thanks again
