spongy brakes

[Hash_ra23]

hey guys.

I've got spongy brakes in my car after i replaced the motor. I don't think its air in the brake lines as they became spongy right after the engine change, they were normal beforehand. I'm thinking maybe its a vacuum leak but i can't find any leaks.

The brakes feel normal if i give it a pump at idle. But if i leave it for a few seconds they become spongy again. Also the idle increases a bit when i press the brakes.

I've checked the vacuum line that goes to the booster and can't see anything wrong with it.

cheers.

[Z2TT]

Did you use the same vacuum line for the brake booster after you did the conversion?

[oldcorollas]

is there a one way valve in the line? is it facing the correct way? (so air only goes toward the engine)

if you pump the pedal, then hold.. does it go down? can you push brake normally once or twice after engine is turned off? or it goes hard straight away?

[o_man_ra23]

What motor did you start with, and what motor did you finish with??

[Cuzzo]

To test if you vaccum setup is working correctly.

With engine off pump up the brakes to get them hard.
With your foot hard on the brakes start the car. If the pedal falls slighlty the vaccum assistance is working.

[maurice c]

Check to see if theres any damage to the brake lines near the firewall or to the brake bias valve, they are easy to knock when taking an engine in or out of a car. A hole of tiny proportions could be giving you problems.