Soft brake pedal and air noise

[Danteval1]

My brake pedal is soft. When I step on the pedal, I hear a hissing noise. It sounds like air leaking. Has anyone had a similar issue? There is a 1988 Reatta in my local junk yard and I'm thinking about taking the ABS motor/pump. 

[Ronnie]

There is a vacuum switch (valve) under the dash that releases vacuum going to the cruise control servo when you press the brake pedal. It is a safety feature to disengage the cruise control in the event the cruise didn't disengage electrically. Maybe that valve, or the hose going to it, is defective and causing the hissing noise you hear. It is #4 in the photo below.

 

[Ronnie]

5 hours ago, Danteval1 said:

There is a 1988 Reatta in my local junk yard and I'm thinking about taking the ABS motor/pump. 

Be sure it is the later model pump with the steel pressure line going to the master cylinder. There were some early '88 models that had a pressure hose that will not fit your '89 model.

[Danteval1]

Would that be under the dash? Do you happen to have a picture of it. I tried my cruise control, it works great and I was actually surprised with how aggressive it is in acceleration. 

 

Just to make it clear on what my brake issue is:

My breaks make a hissing noise when I step on the breaks.

Ill get 2-3 break pumps then I hear the motor engage. I am going to drain all the fluid and add new fluid. I keep hearing that air in the pump will cause the pump not to operate accurately. 

I need to find regular brake fluid. Every time I check Auto zone, they only have synthetic. 

 

[Jim]

Ronnie,

Good thought on the leaking vacuum from the cruise hose.

You are also right on the pump being different on the '88s. Dante's car is an '89 so he cannot use the pump/motor from an '88 on and '89-90 but he can put on the whole system. I have seen this done a few times.

Dante-----

The pumps will run even with a pump or two as the pressure drops and even though the red and yellow lights might not come on the pressure drops and the pump brings it back up to about 2600 pounds.

These pumps are fluid pumps and will not work if there is air in them. This is why when replacing a pump it will need to be bled before it will work.

It is recommended that the brake fluid be changed about every five years but at this point it will not solve your problems. i would hold off changing the fluid until you find the solution to your problems as you may end up changing the fluid a second time.

Wal Mart fluid is cheap and the correct fluid.

 

[DAVES89]

Thanks for the confirmation on swapping the entire unit Jim. I have an early '88 with the early pump. I will be parting two '89s this spring and both throw no codes. This one throws a valve code and I did check the leads and they are good. So the entire pump gets swapped as well as the EBCM in the trunk. Hopefully that will correct my code/ABS Anti lock warning light.

[Jim]

The'89 that was my winter driver last winter unfortunately I had to quit driving it at 398,400 miles because a brake line rusted out and wasn't worth fixing to try and make 400K since I had a red '89 ready to go for this winter. 

Anywaaaaaaay, That car the ABS worked almost all the time but sometimes would bring in a main valve code. I could have changed the main valve easily as it it right on the front of the master cylinder but never did. If the yellow light was on when I left my driveway, I would go a mile to the next stop sign and shut off the key, pump the brakes about 6 times and then restart the engine and be on my way. The yellow and red lights would be on and a few hundred feet down the road they would go off and I had ABS.

[DAVES89]

I thought about doing that also Jim, but I have 3 complete '89-90 units and three '89-90 pump/motors, but no back up '88 units or pump/motors. So I will swap out the entire unit, keep the pump/motor and sell it to anyone needing an early '88. 

 This makes sense to me...

[Danteval1]

Thank you everyone for the suggestions. I just got the car and i'm continuing to work on it. I did an emergency brake stop and the front wheels locked up, the rear didn't. My parking brake also doesn't work, i'm thinking it may be seized. I bought new brake pads for the rear to see if that engages the brakes. They were $15 wagers, so no harm. Ill see what I need to do in order to test the pump. Ill first bleed the fluid in the pump itself. Ill keep everyone posted and I appreciate the support.