(OT) Car stuff, but not Ford or Toyota

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Old 01 Apr 2009, 02:04 pm   #1 (permalink)
Jeff Strickland
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Default (OT) Car stuff, but not Ford or Toyota

I have a '93 Mazda MPV that sprung a coolant leak from the housing that the
Lower Hose connects to. This housing has a small-diameter hose coming off of
if that goes to the housing where the Upper Hose is connected.

The Lower Hose Housing also has a passage, obviously, that lets coolant into
the engine.

The housing also has a theromostat inside of it. I've done my share of
engine work, but I'm not familiar with a thermostat in the housing where the
Lower Hose is connected. I know all about the housing where the Upper Hose
is, and the thermostat that goes there.

It looks like this housing diverts coolant during cold-temp operation
(initial warm up) to the intake, or other such system, to warm it faster
than might happen if the lower hose simply was connected to the block --
which is the method I'm familiar with.

What is the default state of the t-stat in the lower hose housing?
What does this t-stat do?
Since I'm scratching my head over this part, what are the symptoms
associated with its failure?
Does this t-state replace the one I expect to find in the upper hose
housing, or is this one in addition to that one?

FOR THE RECORD
It looks like my only problem here is that the mounting bolts were a bit on
the loose side, and the gasket gave out.



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Old 01 Apr 2009, 03:46 pm   #2 (permalink)
Hachiroku ハチロク
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Default Re: (OT) Car stuff, but not Ford or Toyota

On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:

> The Lower Hose Housing also has a passage, obviously, that lets coolant into
> the engine.
>
> The housing also has a theromostat inside of it. I've done my share of
> engine work, but I'm not familiar with a thermostat in the housing where the
> Lower Hose is connected. I know all about the housing where the Upper Hose
> is, and the thermostat that goes there.
>
> It looks like this housing diverts coolant during cold-temp operation
> (initial warm up) to the intake, or other such system, to warm it faster
> than might happen if the lower hose simply was connected to the block --
> which is the method I'm familiar with.
>
> What is the default state of the t-stat in the lower hose housing?
> What does this t-stat do?


Subaru does this too. It's a standard thermostat. I wonder why they do
that, because that means changing the thermostat means loosing a LOT of
coolant rather than...er, NONE!


I guess the logic is that if the thermostat is shot, so is the coolant...


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Old 01 Apr 2009, 04:06 pm   #3 (permalink)
N8N
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Default Re: (OT) Car stuff, but not Ford or Toyota

On Apr 1, 3:46 pm, Hachiroku ハチロク <Tru...@e86.GTS> wrote:
> On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:
> > The Lower Hose Housing also has a passage, obviously, that lets coolant into
> > the engine.

>
> > The housing also has a theromostat inside of it. I've done my share of
> > engine work, but I'm not familiar with a thermostat in the housing where the
> > Lower Hose is connected. I know all about the housing where the Upper Hose
> > is, and the thermostat that goes there.

>
> > It looks like this housing diverts coolant during cold-temp operation
> > (initial warm up) to the intake, or other such system, to warm it faster
> > than might happen if the lower hose simply was connected to the block --
> > which is the method I'm familiar with.

>
> > What is the default state of the t-stat in the lower hose housing?
> > What does this t-stat do?

>
> Subaru does this too. It's a standard thermostat. I wonder why they do
> that, because that means changing the thermostat means loosing a LOT of
> coolant rather than...er, NONE!
>
> I guess the logic is that if the thermostat is shot, so is the coolant...


Probably a reverse flow cooling system - as in, the reverse of the
"traditional" direction, where it entered the engine through the lower
hose and returned to the radiator through the upper hose, said layout
being determined by the fact that hot (whatever) rises, dating back to
the days before water pumps were used and coolant circulation was
solely done by the thermosyphon effect. Makes for more even
temperature distribution between the head(s) and block.

nate
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Old 01 Apr 2009, 04:11 pm   #4 (permalink)
Jeff Strickland
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Default Re: (OT) Car stuff, but not Ford or Toyota


"Hachiroku *" <Trueno@e86.GTS> wrote in message
newsan.2009.04.01.19.46.26.485863@e86.GTS...
> On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:
>
>> The Lower Hose Housing also has a passage, obviously, that lets coolant
>> into
>> the engine.
>>
>> The housing also has a theromostat inside of it. I've done my share of
>> engine work, but I'm not familiar with a thermostat in the housing where
>> the
>> Lower Hose is connected. I know all about the housing where the Upper
>> Hose
>> is, and the thermostat that goes there.
>>
>> It looks like this housing diverts coolant during cold-temp operation
>> (initial warm up) to the intake, or other such system, to warm it faster
>> than might happen if the lower hose simply was connected to the block --
>> which is the method I'm familiar with.
>>
>> What is the default state of the t-stat in the lower hose housing?
>> What does this t-stat do?

>
> Subaru does this too. It's a standard thermostat. I wonder why they do
> that, because that means changing the thermostat means loosing a LOT of
> coolant rather than...er, NONE!
>
>
> I guess the logic is that if the thermostat is shot, so is the coolant...
>
>


So, in this configuration, the t-stat is moved away from the top hose to the
lower hose?

I am not familiar with this arrangement. I think I can understand how it
works, but I was thinking there was something with the smog equipment that
gave me two t-stats for some reason.






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Old 01 Apr 2009, 04:34 pm   #5 (permalink)
Hachiroku ハチロク
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Default Re: (OT) Car stuff, but not Ford or Toyota

On Wed, 01 Apr 2009 13:06:49 -0700, N8N wrote:

> On Apr 1, 3:46 pm, Hachiroku * <Tru...@e86.GTS> wrote:
>> On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:
>> > The Lower Hose Housing also has a passage, obviously, that lets coolant into
>> > the engine.

>>
>> > The housing also has a theromostat inside of it. I've done my share of
>> > engine work, but I'm not familiar with a thermostat in the housing where the
>> > Lower Hose is connected. I know all about the housing where the Upper Hose
>> > is, and the thermostat that goes there.

>>
>> > It looks like this housing diverts coolant during cold-temp operation
>> > (initial warm up) to the intake, or other such system, to warm it faster
>> > than might happen if the lower hose simply was connected to the block --
>> > which is the method I'm familiar with.

>>
>> > What is the default state of the t-stat in the lower hose housing?
>> > What does this t-stat do?

>>
>> Subaru does this too. It's a standard thermostat. I wonder why they do
>> that, because that means changing the thermostat means loosing a LOT of
>> coolant rather than...er, NONE!
>>
>> I guess the logic is that if the thermostat is shot, so is the coolant...

>
> Probably a reverse flow cooling system - as in, the reverse of the
> "traditional" direction, where it entered the engine through the lower
> hose and returned to the radiator through the upper hose, said layout
> being determined by the fact that hot (whatever) rises, dating back to
> the days before water pumps were used and coolant circulation was
> solely done by the thermosyphon effect. Makes for more even
> temperature distribution between the head(s) and block.
>
> nate



It DIDN'T work! I have a blown headgasket on that car!


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Old 01 Apr 2009, 05:47 pm   #6 (permalink)
Ray O
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Default Re: (OT) Car stuff, but not Ford or Toyota


"Jeff Strickland" <crwlr@verizon.net> wrote in message
news:gr0hpq$fap$1@news.motzarella.org...
>
> "Hachiroku ????" <Trueno@e86.GTS> wrote in message
> newsan.2009.04.01.19.46.26.485863@e86.GTS...
>> On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:
>>
>>> The Lower Hose Housing also has a passage, obviously, that lets coolant
>>> into
>>> the engine.
>>>
>>> The housing also has a theromostat inside of it. I've done my share of
>>> engine work, but I'm not familiar with a thermostat in the housing where
>>> the
>>> Lower Hose is connected. I know all about the housing where the Upper
>>> Hose
>>> is, and the thermostat that goes there.
>>>
>>> It looks like this housing diverts coolant during cold-temp operation
>>> (initial warm up) to the intake, or other such system, to warm it faster
>>> than might happen if the lower hose simply was connected to the block --
>>> which is the method I'm familiar with.
>>>
>>> What is the default state of the t-stat in the lower hose housing?
>>> What does this t-stat do?

>>
>> Subaru does this too. It's a standard thermostat. I wonder why they do
>> that, because that means changing the thermostat means loosing a LOT of
>> coolant rather than...er, NONE!
>>
>>
>> I guess the logic is that if the thermostat is shot, so is the coolant...
>>
>>

>
> So, in this configuration, the t-stat is moved away from the top hose to
> the lower hose?
>
> I am not familiar with this arrangement. I think I can understand how it
> works, but I was thinking there was something with the smog equipment that
> gave me two t-stats for some reason.
>
>

1 t-stat, moved from the top hose to the lower hose; reason as Nate
described.

When you say "default" state of the thermostat, there is no "default" state
of a t-stat. The "state" or position of the t-stat depends on temperature
of the medium it resides in. Below its opening temperature, it will be
closed, and above its opening temperature, it will be open.
--

Ray O
(correct punctuation to reply)


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Old 01 Apr 2009, 07:34 pm   #7 (permalink)
Ulysses
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Default Re: (OT) Car stuff, but not Ford or Toyota


"Jeff Strickland" <crwlr@verizon.net> wrote in message
news:gr0abn$tp3$1@news.motzarella.org...
> I have a '93 Mazda MPV that sprung a coolant leak from the housing that

the
> Lower Hose connects to. This housing has a small-diameter hose coming off

of
> if that goes to the housing where the Upper Hose is connected.


I don't see much difference between a Ford and a Mazda so to me it's on
topic.

I don't know anything about your lower thermostat but my guess would also be
some kind of emissions control to heat up the engine more quickly but I
don't see how it would help. If it opened at a lower temp the engine would
run cooler and if it opened at a higher temp then it would be pointless.



>
> The Lower Hose Housing also has a passage, obviously, that lets coolant

into
> the engine.
>
> The housing also has a theromostat inside of it. I've done my share of
> engine work, but I'm not familiar with a thermostat in the housing where

the
> Lower Hose is connected. I know all about the housing where the Upper Hose
> is, and the thermostat that goes there.
>
> It looks like this housing diverts coolant during cold-temp operation
> (initial warm up) to the intake, or other such system, to warm it faster
> than might happen if the lower hose simply was connected to the block --
> which is the method I'm familiar with.
>
> What is the default state of the t-stat in the lower hose housing?
> What does this t-stat do?
> Since I'm scratching my head over this part, what are the symptoms
> associated with its failure?
> Does this t-state replace the one I expect to find in the upper hose
> housing, or is this one in addition to that one?
>
> FOR THE RECORD
> It looks like my only problem here is that the mounting bolts were a bit

on
> the loose side, and the gasket gave out.
>
>
>



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Old 01 Apr 2009, 08:06 pm   #8 (permalink)
Jeff Strickland
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Default Re: (OT) Car stuff, but not Ford or Toyota


"Ray O" <rokigawa@NOSPAMtristarassociates.com> wrote in message
news:gr0nhu$4dj$2@news.motzarella.org...
>
> "Jeff Strickland" <crwlr@verizon.net> wrote in message
> news:gr0hpq$fap$1@news.motzarella.org...
>>
>> "Hachiroku ????" <Trueno@e86.GTS> wrote in message
>> newsan.2009.04.01.19.46.26.485863@e86.GTS...
>>> On Wed, 01 Apr 2009 11:04:40 -0700, Jeff Strickland wrote:
>>>
>>>> The Lower Hose Housing also has a passage, obviously, that lets coolant
>>>> into
>>>> the engine.
>>>>
>>>> The housing also has a theromostat inside of it. I've done my share of
>>>> engine work, but I'm not familiar with a thermostat in the housing
>>>> where the
>>>> Lower Hose is connected. I know all about the housing where the Upper
>>>> Hose
>>>> is, and the thermostat that goes there.
>>>>
>>>> It looks like this housing diverts coolant during cold-temp operation
>>>> (initial warm up) to the intake, or other such system, to warm it
>>>> faster
>>>> than might happen if the lower hose simply was connected to the
>>>> block --
>>>> which is the method I'm familiar with.
>>>>
>>>> What is the default state of the t-stat in the lower hose housing?
>>>> What does this t-stat do?
>>>
>>> Subaru does this too. It's a standard thermostat. I wonder why they do
>>> that, because that means changing the thermostat means loosing a LOT of
>>> coolant rather than...er, NONE!
>>>
>>>
>>> I guess the logic is that if the thermostat is shot, so is the
>>> coolant...
>>>
>>>

>>
>> So, in this configuration, the t-stat is moved away from the top hose to
>> the lower hose?
>>
>> I am not familiar with this arrangement. I think I can understand how it
>> works, but I was thinking there was something with the smog equipment
>> that gave me two t-stats for some reason.
>>
>>

> 1 t-stat, moved from the top hose to the lower hose; reason as Nate
> described.
>
> When you say "default" state of the thermostat, there is no "default"
> state of a t-stat. The "state" or position of the t-stat depends on
> temperature of the medium it resides in. Below its opening temperature,
> it will be closed, and above its opening temperature, it will be open.
> --


I shoulda said "cold state"

I can see what I have cold. Of course, this does not tell me what happens
when it gets hot.

I'm not sure I understand what Nate said about the reverse flow.

My top hose is the return from the engine. Coolant gets picked up at the
bottom by the pump, circulates through the motor and comes out the top. All
cooling systems work that way as far as I know.


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Old 01 Apr 2009, 09:08 pm   #9 (permalink)
Tegger
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Default Re: (OT) Car stuff, but not Ford or Toyota

"Jeff Strickland" <crwlr@verizon.net> wrote in
news:gr0vih$87c$1@news.motzarella.org:


>
> My top hose is the return from the engine. Coolant gets picked up at
> the bottom by the pump, circulates through the motor and comes out the
> top. All cooling systems work that way as far as I know.
>
>
>




Indeed they do. Heat rises. Coolant is pumped in the direction the heat
wants to go anyway, so the upper house is always the outlet.

As for the thermostat being in the lower hose, Honda has done this since
about 1990 (on all injected engines). Toyota may have gone to this about
that same time.

In this arrangement, the water pump is at the opposite end of the block
from the thermostat, with (often) a large tube running behind the block
from t-stat housing to water pump. The pump sucks fluid through the t-stat
housing, through the tube, then pushes it into the water jacket in the
block. From there it rises through the head gasket and out the upper rad
hose. It's a "straight-through" system.

There are a couple of small bypass hoses (or channels in the various
housings) that recirculate coolant between block and t-stat housing bulb.
When the thermostat is closed, flow through the bypass hoses allows the
thermostat to "see" the heat being generated in the block. As the heat
builds up and the thermostat opens, the bypass is slowly closed off,
diverting /some/ flow through the water pump, until eventually /all/ the
flow is through the water pump.

My personal belief is that this arrangement was adopted in order to ensure
better thermal control of the block and head, and the lower emissions that
would be made possible through this control.

An older setup, for contrast: My '82 Corolla had the thermostat in the
traditional location at the upper rad hose. Both thermostat and water pump
were located at the front of the engine. Coolant traveled a longer,
U-shaped path, with some of the coolant passing through the head gasket
before the rear of the engine. I imagine the rear cylinders ran hotter than
the others.


--
Tegger

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Old 01 Apr 2009, 09:30 pm   #10 (permalink)
Jeff Strickland
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Default Re: (OT) Car stuff, but not Ford or Toyota


"Tegger" <invalid@invalid.inv> wrote in message
news:Xns9BE0D70C9E1E3tegger@208.90.168.18...
> "Jeff Strickland" <crwlr@verizon.net> wrote in
> news:gr0vih$87c$1@news.motzarella.org:
>
>
>>
>> My top hose is the return from the engine. Coolant gets picked up at
>> the bottom by the pump, circulates through the motor and comes out the
>> top. All cooling systems work that way as far as I know.
>>
>>
>>

>
>
>
> Indeed they do. Heat rises. Coolant is pumped in the direction the heat
> wants to go anyway, so the upper house is always the outlet.
>
> As for the thermostat being in the lower hose, Honda has done this since
> about 1990 (on all injected engines). Toyota may have gone to this about
> that same time.
>
> In this arrangement, the water pump is at the opposite end of the block
> from the thermostat, with (often) a large tube running behind the block
> from t-stat housing to water pump. The pump sucks fluid through the t-stat
> housing, through the tube, then pushes it into the water jacket in the
> block. From there it rises through the head gasket and out the upper rad
> hose. It's a "straight-through" system.
>


My motor is a V6, and the water pump is adjacent, perhaps even adjoining, to
the water pump. Clearly it is not at the opposite end.

I get the bypass hoses you speak of, but it is right in front, and connects
the lower and upper housing. I was thinking it helped heat the intake
quicker, but now that I've spent the day messing around with all of this
stuff, I think it just feeds the heater core. I know from past experience
that the heater is itself a bypass system from the main waterflow that
passes through the block. The idea is, you would want hot water at the
heater core even if the t-stat was closed. It appears the heater circuit
works by the effect of hot water rising and this creates a water flow all by
itself.




> There are a couple of small bypass hoses (or channels in the various
> housings) that recirculate coolant between block and t-stat housing bulb.
> When the thermostat is closed, flow through the bypass hoses allows the
> thermostat to "see" the heat being generated in the block. As the heat
> builds up and the thermostat opens, the bypass is slowly closed off,
> diverting /some/ flow through the water pump, until eventually /all/ the
> flow is through the water pump.
>
> My personal belief is that this arrangement was adopted in order to ensure
> better thermal control of the block and head, and the lower emissions that
> would be made possible through this control.
>


That was the theory I was working with as well.








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