What does this sensor on Toyota thermostat housing do?

Question

It screws into the thermostat housing on my 89' Cressida. I see it id'd as bi-metallic vacuum switch - has an AISIN p/n 90925-05068

Link to pics below. The hose nipples have deteriorated and broken. What does it do and what happens when it's not working? Car seems to run okay but obviously it's there for a reason.

Thanks.

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nm5k · Accepted Answer

I'm thinking it's for the EGR. But don't take that as gospel.. I don't have a manual to check. Normally you don't want EGR when the engine is cold, and I bet that is the device that controls it as far as temp. EGR is normally vacuum run..  I'd replace it. EGR problems can cause poor running when cold, and emissions problems.. I'm thinking the valve would be stuck closed with vacuum leaks in the lines. No EGR could cause high NOX scores, with the higher than normal combustion temps. If it were stuck closed, cold operation should seem normal.. It would need to be stuck open to cause cold run issues.

. · Answer

"This device is a heat-sensitive switch that remains closed until the engine's coolant reaches a certain temperature. The PVS screws into the intake manifold, thermostat housing or engine so the heat- sensing element is in contact with the engine's coolant. Inside the switch is a wax plug that pushes a sliding plunger to uncover or block vacuum ports in the switch. As the engine heats up, the wax expands and pushes the plunger up until it uncovers or blocks the vacuum port. At this point, vacuum to the device that the switch controls is either applied or blocked. Severe engine overheating can damage the switch, making replacement necessary."

Geoff Welsh · Answer

> Is the Emmissions Decal still on the underside of the hood?  It'll show  that vacuum switch and where the lines go. GW

Sanity Clause · Answer

"brassplyer" wrote According to Autozone's 89-90 Cressida diagram, your BVSV decides when the charcoal cannister is allowed to vent its vapors into the intake manifold.  or:

uncle_vito · Answer

> My wife wishes I had one of those.   I vent my vapors any time and anywhere  I want.

What does this sensor on Toyota thermostat housing do?

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