What does this sensor on Toyota thermostat housing do?

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Old 04 Mar 2013, 02:11 pm   #1 (permalink)
brassplyer
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Default What does this sensor on Toyota thermostat housing do?

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.

https://encrypted-tbn1.gstatic.com/i...xlRnfg3XQu8wFg



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Old 04 Mar 2013, 02:34 pm   #2 (permalink)
nm5k@wt.net
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Default Re: What does this sensor on Toyota thermostat housing do?

On Monday, March 4, 2013 2:11:36 PM UTC-6, brassplyer wrote:
> 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.
>
>
>
> https://encrypted-tbn1.gstatic.com/i...xlRnfg3XQu8wFg


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.



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Old 04 Mar 2013, 02:44 pm   #3 (permalink)
.
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Default Re: What does this sensor on Toyota thermostat housing do?

"brassplyer" <brassplyer@yahoo.com> wrote in message
news:8de64c36-7019-48ac-b477-1e3211a6b17a@c6g2000yqh.googlegroups.com...
> 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.
>
> https://encrypted-tbn1.gstatic.com/i...xlRnfg3XQu8wFg


"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."
http://autos.yahoo.com/maintain/repa...ques080_1.html




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Old 04 Mar 2013, 02:46 pm   #4 (permalink)
Geoff Welsh
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Default Re: What does this sensor on Toyota thermostat housing do?

nm5k@wt.net wrote:
> On Monday, March 4, 2013 2:11:36 PM UTC-6, brassplyer wrote:
>> 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.
>>
>>
>>
>> https://encrypted-tbn1.gstatic.com/i...xlRnfg3XQu8wFg

>
> 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.
>

Is the Emmissions Decal still on the underside of the hood? It'll show
that vacuum switch and where the lines go.
GW
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Old 05 Mar 2013, 01:32 am   #5 (permalink)
Sanity Clause
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Default Re: What does this sensor on Toyota thermostat housing do?


"brassplyer" wrote

> 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.


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.

http://tinyurl.com/agws2sj
or:
http://repairguide.autozone.com/znet...5280081681.gif



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Old 05 Mar 2013, 12:13 pm   #6 (permalink)
uncle_vito
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Default Re: What does this sensor on Toyota thermostat housing do?


"Sanity Clause" <Way.Up@The.North.Pole> wrote in message
news:kh46uv$vdq$1@dont-email.me...
>
> "brassplyer" wrote
>
>> 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.

>
> 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.
>
> http://tinyurl.com/agws2sj
> or:
> http://repairguide.autozone.com/znet...5280081681.gif
>
>
>


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


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