Symptoms of a bad BVSV? - Toyota Nation Forum : Toyota Car and Truck Forums

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post #1 of 3 Old 12-18-2008, 10:56 PM Thread Starter
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Symptoms of a bad BVSV?

Looking at some vacuum line diagrams it seems like the BVSV could be causing a vacuum leak in my system. The engine (3VZE) idles with a lope and will eventually die. I can't get a real good look at the BVSV right now, its way too cold outside right now lol.

However when we got the engine running again there seemed to be a fluid/fuel leak in the area of the BVSV. It stands to my reason that the BVSV would be causing my vacuum leak as all the other areas seem okay but I have no idea if any fuel/fluid is associated with the part. What does the BVSV actually do, I'm always looking to learn more

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post #2 of 3 Old 12-29-2010, 11:42 AM
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BVSV = Bi-metal Vacuum Switching Valve. Its mounted on the water bypass outlet at the back of the intake. It sends gas fumes from the charcoal canister to the air intake chamber to be burned. Mine has part number 90925-05047 stamped on it. Since its on the water bypass outlet, maybe thats coolant leaking?
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post #3 of 3 Old 12-30-2010, 10:21 AM
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when the coolant gets hot enough it opens the valve to vent the charcoal canister. It's actually plumbed before the throttle blade so it won't be under enough vacuum to cause a problem at idle. When it's functioning properly, it's open any time the coolant is over roughly 100f so if it's stuck open, it's not going to cause much change in how the engine runs. Yes the system is very approximate, that's why there's an O2 sensor to correct things (albeit after the fact) and why newer cars use more control.

If there is liquid fuel from the BVSV your gas tank has been over-filled to the point of overflowing into the charcoal canister. When the BVSV opened it started sucking in liquid fuel instead of air with a few fuel vapors. I'd guess your lumpy-idle is from running rich.

Coolant is pretty distinguishable from fuel by smell or touch. the likelyhood of coolant leaking out through it is also very low because the threads and bulb that extend into the coolant are all one piece of metal.

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