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sprinkles08
sprinkles08, ASE Certified Technician
Category: Toyota
Satisfied Customers: 22695
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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On my 2006 Scion Xb just recently the power assist seems to

Customer Question

On my 2006 Scion Xb just recently the power assist seems to have gone out. I have no codes or ABS light on or VSC light on. Everything seems normal except that I must press the brake pedal extremely hard to stop. Occasionally the brakes will seem normal but then the power assist fades away and I'm needing to almost stand on the brake pedal. Would this be the vacuum assist module or what?
Submitted: 1 year ago.
Category: Toyota
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to Justanswer!

You could have a master cylinder issue or fluid contamination can also cause a hard pedal but most likely you either have lost vacuum to the brake booster or the booster itself is the issue. Most likely you have a failed brake booster.

Have you checked for proper vacuum to the booster with the engine running?

Customer: replied 1 year ago.
I agreed that the booster was the most likely issue but it isn't. The vacuum is similar to my other scion's around 16 inches of mercury on my cheesy little vacuum gauge. This vehicle is just slightly lower than a working vehicle. I installed a new booster anyway but it made zero results. What is the possibility that the abs motor has gone out? It seems a little far fetched but could it possibly be limiting the pressure to the wheel cylinders? I also did a cursory check on the master cylinder while it was out and all is well, no leaks was easy enough to bleed no problems I could detect.
Expert:  sprinkles08 replied 1 year ago.

If you pump the brake pedal five times, press and hold it firmly and start the engine does the pedal drop?

Customer: replied 1 year ago.
No the pedal stays firm. I'm thinking there may be a small vacuum leak, however the engine runs fine. When I put a vacuum gauge on both the bad scion and a good scion the there was only 2 In Hg difference. I didn't think that was significant enough to worry about but I could be wrong. Anyway what are the possibilities of the ABS motor being a problem in this case?
Expert:  sprinkles08 replied 1 year ago.

Where did the booster come from?

Customer: replied 1 year ago.
The booster is a rebuilt Cardone from 'Auto Zone'.
Expert:  sprinkles08 replied 1 year ago.

Is it possible the fluid was contaminated with something such as power steering fluid?

Customer: replied 1 year ago.
Apparently my reply to your last question did not go. However, recent developments solved my problem. It was an odd problem to say the least. It was a clog in the vacuum tube that routes the hose to the booster from the air intake. The clog would actually allow some vacuum but as vacuum pressure increased it moved into the constricted part of the metal tube causing vacuum to drop off to an unusable pressure. I discovered this by using the vacuum from another scion xb I have that was working normally. I got an 8' length of hose and connected the booster to the known good vacuum source and the booster 'worked'! Then remeasured the vacuum and found it to be zero on the bad scion. I routed around the metal tube with the hose and the booster started working on the bad scion. I noticed when I routed through the metal tube there was little to no vacuum so I thought it was a crack I hadn't seen. I removed the metal tube expecting to find a crack but I found a bunch of crap that moved to clog the pipe when I applied air to one end. I removed the clog and my ordeal was solved.
Expert:  sprinkles08 replied 1 year ago.

I'm glad you got it fixed!

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