180f thermostat for the Chrysler 3.3l V6?

Does anyone know if there is a lower temp thermostat available for the
3.3l Chrysler V6? This is for a '95 Grand Caravan. So far every place
I have checked tells me that only a stock 195f one is available.

Responding with editoral comments about staying with the stock thermo-
stat is unnecessary.

 

I imagine they do.

So is helping you do something stupid, so I guess the part number for the
thermostat you seek will remain a mystery to you from me.

DS

 

Editorial comments may be unnecessary - but staying with the stock
'stat is NOT. Computerized engine controls are quite sensitive to
engine temperatures, and the engine will NOT run properly if it is
always seen as being cold.

 

Stay with the stock 195F thermostat. Your computer is set for that
and you will NOT HELP if you change.

 

I think the most common reason people go for the lower temp
thermostat is they have a problem with overheating. Most likely our
poster has a head gasket leaking combustion gasses into the cooling
system, this creates air pockets which impair the cooling ability of
the system and make it overheat.

These folks are somehow under the impression that their engine
will produce less heat when it is running a lower temp thermostat.

Ted

 

Is it true that under most normal running situations, the thermostat is
not fully open and modulates itself between full open and full closed as
part of closing the engine temperature regulation loop? If so, then it
could be argued that a lower temp thermostat would go more to the open
position (or perhaps peg to the full open position) and result in less
percentage on-time of the cooling fans to maintain the same engine
temperature (less wear on fans, which do wear out these days, less
average alternator load on engine).

However, if the factory thermostat typically goes to full open at normal
engine operation, then all the lower temp. thermostat would mean is that
it opens sooner and once the engine reaches full operating temperature,
there is no difference between having the 195 or 180° thermostat (i.e.,
engine would not operate any cooler, fans would duty cycle the same
amount).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

To be more thorough, "...if the factory thermostat typically goes to
full open at normal engine operation, then all the lower temp.
thermostat would mean is that it opens sooner and once the engine
reaches full operating temperature, there is no difference between
having the 195 or 180° thermostat (i.e., engine would not operate any
cooler, fans would duty cycle the same amount) - it would, however, take
longer to reach normal operating temperature.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

You all need to remember the thermostat does NOT limit the maximum
temperature of the engine - it regulates the minimum temperature. If
the cooling system is inadequate, or air flow is restricted, a 160 and
a 195 will run at the same temperature under load.
As for fan cycling, the fan ONLY comes on when the rad temp is above a
set point. The thermostat range will not affect this as the setpoint
is ALWAYS higher than the thermostat setting.. If it wasn't, the fan
would run when the rad was not yet up to temp.

 

On the highway the thermostat modulates to keep the temp up if the
wind blowing through the radiator is enugh to over cool the engine.
Same is true if outside temps are cold enough to cool the engine
around town. In warmer weather around town your thermostat opens at
195 but the coolant temp switch isn't going to kick on the fans until
around 220. Even if you totally removed the thermostat the fans still
wouldn't kick on until 220 and still would kick back off at 205
(numbers vary with make and manufacturer).

Another variable would be if the car has a/c then the fans will be on
if the a/c is on and could also cause the thermostat to have to
modulate enging temp if the engine was being overcooled.

Either way a different thermostat won't change the max temp or save
more than a few seconds wear on the fan.

Steve B.

 

The first part of what you're saying is not inconsistent with what I
said (or stated in the positive, is similar to what I said). In terms
of what I said, I think you are saying that under normal operating
conditions, the thermostat settles out at full open, rather than
modulating (in between full open and full closed)? If that's what you
are saying, I think some here would disagree with you, as I have
certainly seen posts in the past that claimed that thermostats are in
servo mode (i.e., modulating) to help regulate engine temperature. I
honestly don't know which is the case, but I covered both scenarios in
my explanation.

The last part of your post I disagree with.

Here are two things that it appears that you have negelected to take
into account:
(1) When you talk about a 195° thermostat, it does not stay closed below
195° and then suddenly slam full open at 196° (for simplicity, I'm
ignoring any tolerance variations - I'm using nominal numbers). It may
start opening at 195°, and proportion itself until it's fully open at,
say 205 or 210°F (I don't know what the actual numbers are, but I think
they're in the ball park).
(2) If my '99 Concorde has a typical cooling system (and I think it
probably does), according to the FSM, the temp. sensor that is the main
input to the PCM for determining when the radiator fans come on is
located in a coolant line just as it comes out of the engine going into
the upper radiator hose (carries hotter coolant from the engine into the
radiator), while the mechanical thermostat is at the point that the
lower radiator hose joins the engine on the side of the block (coolant
that is the coolest point in the entire system that is returning from
the radiator to the engine). Certainly there is a difference of at
least a few degrees between what the temp. sensor sees coming out of the
engine just before it goes into the radiator and what the thermostat is
looking at coming out of the radiator (that temp. difference would in
effect be the temperature drop that the coolant sees as it goes thru the
radiator).

With the combination of (1) and (2), above, it is likely that the
thermostat is normally in modulating mode, and that putting a lower
temp. thermostat will have some effects (if not in actual lower
operating temperature, then certainly in lower fan duty cycle). This
lower-temp. thermostat will modulate closer to the full open position
(allowing coolant to flow faster), or may actually peg full open most of
the time, whereas the original factory thermostat was probably varying
constantly between full open and full closed (and if so, further from
full open than the lower temp. thermostat).

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Starts to crack open at 195° (nominal) - probably doesn't hit the full
open stop until, what, 205°? 210°? 215°. (I don't know the answer, but I
suspect there's somtehing on the order of an 8 to 10° range full close
to full open.

As I wrote in another recent post, if my Concorde is a good example, the
temp. sensor (that is the major determinant on when the fans come on
(when a.c. is not running), sees the hottest coolant coming out of the
engine just before it goes into the radiator, and the termostat sees the
coolant at its lowest temperature right out of the radiator before it
goes back into the engine. What's the typical drop in temperature thru
a properly functioning radiator? That has to be factored in.

Certainly true.

I'm thinking it would make more of a difference than that, but that is
pure conjecture on my part.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Bill:
The thermostat should be full open well before the fan cut on point
and still full open before the fan cut off point. 195 themostat
should be all the way open by 205. Engine fan doesnt cut on until
atleast 220 and off again at 210. So in a high heat load situation
the thermostat is always open.

A/C causes the fans to run all the time and can cause the thermostat
to modulate the engine temp in milder weather.

Steve B.

 

It's all conjecture on my part as well. I also am assuming a 10
degree split between full off and full on.

Most of the cars that I am familiar with have the thermostat at the
top of the engine as the coolant exits the engine and enters the top
radiator hose. The fan switch is also in this same general area.

Maybe a Chrysler expert will pipe up and tell us how it works out when
the thermostat is at the bottom of the engine.

BTW,, I've answered several of your posts tonight. I'm not trying to
argue with you, just find your ideas interesting and enjoying
discussing the issues with you.

Steve B.

 

I seriously doubt this. I suspect that engines that have the thermostat
at the bottom hose are "reverse flow" cooling systems. Traditionally,
the coolant flows from the head(s), to the top of the radiator, is
cooled, then goes from the bottom of the radiator back to the water pump
and into the water jackets of the block. This is something of a
holdover from when engines didn't have water pumps at all but relied on
thermosyphoning to move the coolant around (as the cold water/coolant
would be denser than the hot) Today most radiators are crossflow type
so that wouldn't work as well anyhow and you get more even temperatures
throughout the engine if you cool the hottest part (head) with the
coolest coolant (directly from the radiator) then allow the coolant to
flow through the rest of the engine.

The thermostat opening temp won't change max temp if it tends to be full
open all the time - but if there's a lot of reserve capacity built into
the radiator the engine will pretty much always run at a temp close to
the opening temp of the thermostat. I personally like a setup like
that, as with careful selection of thermostat and thermoswitch values,
you can keep the engine running at almost the exact same temp all the
time (+/- 10 degrees or so) no matter what the ambient temp. I have no
hard numbers to back up my claim that that's desirable, but it certainly
makes tuning more consistent and I can't help but think that that would
help engine longevity as well.

nate

 

The LH engines are not like that. The fan switch (actually analog temp.
sensor sending its signal to the ECM as one input to its algorithm to
determine when to turn the fans on) is, as you say, at the up-stream
side of the upper hose as the coolant leaves the engine on its way to
the radiator. But the thermostat is at the engine side of the lower
hose, i.e., as the coolant leaves the radiator returning to the engine.
That was my point about the difference in temperature (i.e., radiator
drop) narrowing the gap between when the fans come on and when the
thermostat is less than fully open, and possibly those two events
overlapping, at least in certain operating environments. And I think
you got that - just though I'd reiterate.

On a side note, the funny thing is that the people who wrote the FSM are
also used to thinking that the thermostat is where you said, because
they, several times, erroneously refer to the engine outlet as the
thermostat housing - it looks like one, but it ain't one - it's simply
an empty housing with an air bleeder valve built into it. I've had to
correct that misconception a few times for LH owners here and on LH
forums. The actual thermostat is on the drivers side of the block
(accessible from underneath) - which the FSM mentions correctly in
several other places. Hmmm - what does it mean when you're a DIY'er and
you spot errors like that in the FSM? 8^)

I won't flatter myself as an expert, but the FSM does have a flow
diagram, and it's clear that the thermostat sees the coolant at its
coolest point (right out of the radiator), and the temp. sensor sees it
at the hottest point. As I pointed out, that's got to narrow the gap,
and possibly overlap it. I guess that's the detail that you're thinking
we need the true expert on - I agree.

Heh heh! Not to worry. I too was concerned that you would take my
comments as argumentative, rather than thinking my way thru these things
as a learning process and an attempt at converging on the approximate
truth. I seriously thought about putting a comment similar to yours in
one of my earlier posts so you would know I was being matter of fact and
not emotional. I think we both can tell the difference between (a)
someone discussing some grey area and wanting to learn while at the same
time adding to the knowledge base, and (b) someone being argumentative
just for the heck of it or because they just want to prove you wrong (I
won't mention any names). 8^)

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

I don't think these thermostats modulate anyway. What I have observed
when testing them in boiling water (we all test our new thermostats before
going to the trouble of installing them, right?) is that they open at the
desired
temperature, but they do not immediately close when the temperature goes
down.

In short, a 195 degree thermostat opens at 195, but as the temp drops past
195 to 185 to 175 and so on, the thermostat remains open. When it gets
cool enough it then closes.

You can try this for yourself with a pan of water and a stovetop. See if
you
can get the water to a temp where the thermostat stays "half-open" I don't
think you will be able to do so.

The engine temp is modulated far more by the thermostat that the cooling
fans
are run off of.

Ted

 

FWIW, that is called hysteresis (probably due to internal friction -
possibly intentionally designed in?). *Or* it could be a false
observation due to the temperature change taking time to "soak" into the
sensing element (would have to be tested by very precise and very slow
changes in temperature to find out).

Will take your word for it. Not sure you can control the temperature
accurately and stabley (sp?) enough to know for sure in a pan of water
on the stove (due to that possible "soak" phenomenon that I mentioned).
Would be nice to have a PLC controlled oven and set it at various
temperatures to let it settle out for a time at each temperature.

Thanks!

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

Have to go with Ted on this one.. ... ... too much engineer in you Mr.
Putney !!

I have done the same thing many times to check thermostats,, new, and those
I have removed "just to be sure".. In the application I don't think
"hysteresis" plays much of a part in the operation... IOW I think the pan of
water on the burner, coffee maker etc...... pretty closely duplicates the
application..

That said, I certainly understand your viewpoint,,, I was the shop
engineering laison for many many years... Actually grew a pretty healthy
respect for engineers and the what I considered the "pointless" crap they
worried about,, they called what I had tunnel vision, but my job was to get
the stuff out the door to their specs, as cheaply and quickly as possible,
not much else.

Different frame of reference is all..

Ted

 

Uh, what LH car is that? Second-generation with a 2.7 or something?

I can assure you that the 3.5 and 3.3 in the first-generation most
definitely DO carry their thermostats at the usual location on the top
front of the intake manifold, in the housing that feeds the upper
radiator hose.

 

Who knew such a simple question would generate this kind of response.
In spite of the rigid orthodoxy of the self-appointed, several individuals
were kind enough to send me emails with the answer I had sought.

Speculation as to why I requested such information will remain as such.
As I was seeking neither guidance nor advice.