Vacuum booster

Hi All - Apologies for the long post here,. I’ve been to six shops that replace/fix brakes all with mostly a different diagnosis. Each morning for the past three months I start my V-6 engine keyless by stepping on both the brake pedal and gas pedal (as required with the keyless option) at the same time. The brake pedal is hard with very little if any slack, the engine starts, the brake pedal retracts to a more normal “feel” but is not spongy. I drive away, park, and when I restart with the same brake/pedal combination, the hard brake isn’t there, the motor starts again OK.

No warning lights on the instrument panel, no “wooshing” or squeeking sounds, there’s play in the brake pedal but is now not “spongy” like I remember brakes to be when I drove my other cars and when I first bought this new '09 Venza. Definitely not a confident situation but there’s no Toyota tech service or recall bulletins on this symptom…

Stopping the car at any speed is by pushing a metal-feeling, (not “spongy”) hard brake pedal (it’s not the same “hard pedal” after leaving the car overnight) and the ride seems to be more rumbling on the roadway. Brake inspections measuring wear shows 70% front and 80% rear - brake fluid is OK - mileage is 35,000. Transmission front differential and rear differential need to be flushed is the only maintenance issue to be done.

One diagnosis is there is a leaking valve in the vacuum booster and probably inside that keeps leaking air incrementally overnight. No active leaking observed on the spot inspections. The morning hard start pedal does not seem to be getting worse, I start the motor every morning but my question to the group is… will it? and does it pose a significant risk of not stopping the car when I least expect it? I’m concerned about the risk of safe stopping!

Would anyone advise to start repairing with smaller issues like the leaking valve to determine source, or replace part-by-part of the vacuum booster and/or the ABS brake? BTW, my six shop visits to get diagnosis opinions did not include the Toyota dealer/service manager. When I contacted a dealer by phone initially, the immediate reply was “bring it in, ya gotta replace the whole vacuum booster" but he didn’t say with or without a master cylinder, or is it a new or remanufactured product or any other option to resolve the brake issue at the dealership. Total replacement cost with labor is very high for my budget, so I’m reaching out to this list for some feedback, please. I’ve read all of the discussion posts so far, and I’d appreciate your responses to this long post of mine. Thanks!

Maybe there is nothing wrong with your brakes, @Arby. For the next few days, whenever you wish to start the engine and expect the brake pedal to be “not the hard pedal like being parked overnight” press and release the brake pedal 3 times and then start the engine and if the pedal has become “high and hard” the peculiar situation you describe is not peculiar at all. The booster valves are bleeding off vacuum overnight and that’s no big deal.

+1 to Rod’s post.

Expect that after pumping the pedal, making the feel hard and high, and then starting the engine while pressing the pedal, you’ll feel exactly the sink-a-bit-and-soften feel that you’ve described. This procedure Rod describes is actually ised as a quicktest to see that the booster is working properly, the vacuum pulling on the diaphragm when the engine is running.

And I wholeheartedly agree with Rod that bleeding out overnight is no big deal. It sounds like the booster is holding vacuum except when let sit overnight, and that’s a good sign. It means the leak is tiny, and not likely to suddenly fail. Even if it did, you’d still have brakes, they’d just feel hard and require more oomph on your part. You won’t lose youyr brakes.

Thanks, Rod. I’ll give it a try to see the results. Glad to know that my brakes are not at risk
and, hopefully, you’ve saved me a ton of $$$ to repair / replace the master cylinder and / or
the vacuum booster-thingy. I’ll report back to the list, and if others have another suggestion,
please let me know. Thanks again.

Mountainbike - I appreciate your confirmation and comforting words that the brakes will
still work. Is the fix for the small leak a real $$$ in a brake specialist shop (not the Toy
dealer)? I’m told the valve could be inside the booster or master cylinder in this V-6
Venza 2009 which would most likely result in everything pulled apart to fix the leak.
Also, is the ABS system involved in any of this? Thanks.

Last month a Lexus ES350 (related to the Venza, Highlander and RX350 in the Toyota family) was towed in for a no start condition. The vehicle started and drove fine, the only problem was the brake booster would leak down after a few hours and the vehicle owner did not push the brake pedal hard enough to trigger the switch and illuminate the green light in the start switch.

The vacuum check valve should be tested but it is likely that the brake booster is leaking. I have noticed on a few customers cars that the brake booster leaks after shut down but most people don’t compain about it. It may take a very long time (years) before braking perfomace is affected by the vacuum leak.

Unfortunately, boosters aren’t cheap. Figure upwards of $300 just for the part. There is, however, a possibility that the chamber forward of the diaphragm that holds the vacuum is bleeding via the check valve. Check valves are cheap, in your case less than $20 from Auto Parts Warehouse.
And the check valve is really easy to replace. There’ll be a line from the engine to the booster canister, and the check valve will be where the two connect. If it were me, I’d try changing it and see if the problem disappears.

I hope I never live long enough where I have to buy one of these ridiculous cars…Dozens of high-dollar service and maintenance nightmares built in at the factory…Who needs it??? What’s the benefit of “keyless ignition” that has fifteen no-start conditions built in?? The consumer is left with only one option: Tow the car to the dealer…No thanks…

Thanks to all who have replied. to my post. I’ll give your suggestions a good try
to see what I can find out. I may come back for more help from this great source at
Car Talk. You folks know your automotive info and I appreciate your kind responses.