Testarossa Brake Booster and One way Valve

Paul,
I had a problem similar to this, I had the master redone with fresh caskets. Its far far cheaper if you need to get that booster done. I think the machine shop charge me $100 for it...it was well worth it.

 

Always possible that it's just something wrong in the Master Cylinder Booster itself, but another item you should check is the small auxillary vacuum pump mounted to the rear of the 7/12 exhaust cam. If this item fails, it appears as a vacuum leak (rather than a vacuum help) to the system (since it's connected between the Master Cylinder Booster and the Check Valve). As a quicky test you can just remove and the vacuum line and check if it's sucking in air or not when the engine is running.

However, the best "test" would be to put a vacuum gauge on the line going to the Master and measure the vacuum level/behavior.

 

My 86 TR has this issue, so I have the same question. The brakes just do not seem to be very poiwerful. The pads and rotors are in great condition, the brake fluid has been recently changed, and the pedal is very very firm. When removing the vacuum hose from the booster while the engine is running, there appears to be a lot of suction from the hose using the thumb test, although I did not put a gauge on it to measure just how much vacuum there is. I have always suspected that the booster is malfunctioning. Can there be something else to consider with these symptoms?

 

Paul, I will check the one-way valve, thanks. Doug

 

PV908, Paul, I took out the check valve and cleaned it best I could. Mine let zero through in the check direction and seemed to be very restrictive in the flow direction. However, I noticed that the valve's internal check is spring loaded and will move about 1/16 inch when pressed in. In the pressed in position the valve full flows. Paul, can you tell me if your valve did the same. Also, do you know the manufacturer of the original Ferrari part? Thanks. E. Doug.

 

Sorry to revive an old thread - my 91 TR seems to be having some brake issues, possibly related to the booster.

The symptoms are that the pedal throw is long, the brakes lack power, especially initial bite.

The vacuum pump produces vacuum, the one way valve holds a vacuum for some time after the car is turned off - I shut the car off, waited a bit and then disconnected the vacuum hose at the booster. Significant vacuum remained in the system.

That suggests no vacuum leaks to me (including from the booster diaphragm), but when I put my foot on the brake pedal after 3 pumps and turn the car on, the pedal does not go down any further, as if the booster is not helping. I always thought that was the way to test the booster.

Driving the car also suggests the booster is not helping, because the pedal throw is long and only gets firm at the end of travel when the brakes begin to bite.

Only thoughts I have are a defect in the master, or air still trapped in the system (I just finished an engine out and bled the brakes afterwards).

Car received braided steel lines, caliper rebuilds and new pads about 4 years and 10,000 km ago (and the brakes worked great after that).

 

A long pedal seems more master cylinder/air-in-system problem to me than a bad booster/vacuum problem (i.e., the pedal travel distance should be unrelated to whether the booster is working or not -- the booster just affects the force required). Maybe something like the seal in the MC feeding the front brakes has gone and you only have rear brakes working? Just a thought...

Does your brake warning light self-test work at engine start up, and, if so, it is not illuminated when applying the brakes during normal driving?

Does the pedal ever "pump up" to having a shorter travel, or is it just always a long travel?

 

The light only comes on when the fluid is low. Fluid is fresh and full. Self test works too.

The pedal does pump up after 2-3 pumps, the travel reduces.

One thought may be an air bubble in the m/c or front calipers. I spent most of my time bleeding the rear calipers.

M/c was replaced with a Ferrari original replacement about 7-u years ago; I flush the fluid every year with fresh fluid.

 

Then sounds like you need to focus on bleeding.