180f thermostat for the Chrysler 3.3l V6?

Discussion in 'General Motoring' started by Paul Middlestat, May 4, 2004.

  1. Paul Middlestat

    Bill Putney Guest

    Kind of hard to discuss differences of a few degrees though with such a
    method. Not criticising - just a comment.
    Yes - I know that feeling about engineers all too well (and I won't say
    that it isn't oftentimes deserved). Sometimes, however, it is an excuse
    to avoid something necessary being done (not accusing you of that at
    all). Two quick examples: I was in charge of some process batch ovens
    in a factory one time. It was a 2 man-day job to replace the heater
    elements in an oven when they burnt out, and the heaters in each oven
    typically failed every 2 to 4 weeks of normal usage, so the equipmant
    down-time as well as tangible expense (labor and heating elements at
    several hundred dollars a pop) was considerable. I observed that the
    obsolete process controllers could not be properly tuned, and as a
    result, they would drastically overshoot temperature while trying to
    keep up with the profile, and to keep the duty cycle required to
    maintain the temperature profile, the heaters would go from 100% on for
    5 and 7 minutes (literally red hot) at a time to full off for comparable
    periods of time. I know the solution was to use self-tuning
    (proportional tuning) controllers (under $400 each) that would optimize
    the duty cycle algorithm to the time consant of the oven (system) to
    prevent the wild swings and abuse of the heater elements. The
    maintenance supervisor, knowing how "impractical" and ridiculous
    "college boys" are, refused to invest the man hours to replace the
    controllers even though they were sitting on the shelf waiting to go in,
    and I assured him that the payback would be a matter of a couple of
    months when he didn't have to replace the heaters nearly as often (he
    didn't believe me). Finally I raised enough sand (actually contracted
    it out to an outside vender since he refused to do his job and follow
    orders and there were no consequences for that) and got it done. The
    heater elements lasted on average well over a year each after that (plus
    I found a third party vendor to supply heating elements at $300 a pop
    rather than the $800 that the oven manufacturer had been charging).

    This same maintenance supervisor also refused to repair a 100% hydrogen
    fitting leak on a gas mixer (100% nitrogen and 100% hydrogen in, 93/7
    out) going to the same ovens. Again, he was allowed to do that without
    consequence to himself. Technically I could (and really should) have
    declared a safety hazard and shut the area down until it was fixed, but
    that would have come down on me - "over-reacting", you know. Anyway,
    after six weeks of my submitting several work orders to fix it that were
    ignored, he had an outside contractor welding above the mixer where the
    leak was - the mixer was draped with a canvas tarp for "safety". I
    happened to be walking thru the area with sparks falling onto the tarp,
    and all of a sudden, a 3 foot flame shot out of the leaking fitting.
    Keep in mind that this was about 5 years after one of those ovens had
    exploded due to over-ridden hydrogen safety interlocks (before I was
    hired) almost killing one guy, and Factory Mutual threatening to refuse
    to cover the plant until the safety interlocks were restored and
    upgraded. Fortunately nothing more happened, and we were able to
    evacuate the area and shut the hydrogen off. Even so, I was accused of
    over-reacting. Even another engineer told me that there was no danger -
    after all there had to be just the right mixture of hydrogen and air to
    be explosive, and the chances of that happening were "minimal". I said
    - yeah - I guess that's how that oven exploded a few years ago, and
    maybe we ought to move his desk over next to the mixer and let it run
    and a welder be overhead until the leak could be fixed. He still didn't
    get it. IOW - I see both sides of that "engineers are anal" coin.
    No problem.

    However, what Ted described is, by definition *hysteresis*, so on that
    point either there is hysteresis and he's right, or there isn't
    hysteresis and he's not right (on that particular point of observation
    of a shift in going from hot to cold/open to closed vs. gfoing from cold
    to hot/closed to open). Perhaps what you meant was that you are not
    denying that the hysteresis is there, but are making the point that it
    just doesn't have significant effect on the end result. I still can't
    help but wonder if what was also a time soak phenomenon giving the false
    impression of the hysteresis that Ted thought he was observing.

    There's also the observation of others of a temp spread in transitioning
    from full closed to full open - probably a thermostat manufacturer spec.
    sheet would clear all of that up (i.e., hysteresis as well as temp.
    spec. from full open to full closed). I do not have first-hand
    observations on this - only have the (obviously sometimes conflicting)
    statements of others to work from.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 7, 2004
    #21
  2. Paul Middlestat

    Bill Putney Guest

    According to the diagrams and descriptions in my '99 LH (2nd gen) FSM,
    it is true of all their engines (2.7, 3.2, and 3.5L).

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 7, 2004
    #22
  3. Paul Middlestat

    Bill Putney Guest

    Take a look at this coolant system schematic and flow daigram right out
    of the '99 LH FSM:
    http://images5.fotki.com/v63/photos/4/42816/143201/radiatorflowinLHcars-vi.gi

    I have verified that the diagram and flow directions shown in it are
    accurate per my '99 Concorde and exactly as I described (the thermal
    sensor for fan control is not shown in that diagram, but does physically
    reside at the upstream end of the upper rad. hose).
    100% agreed. However I believe that the design intent on the modern car
    is that the fans are the dominant factor in controlling the engine
    temperature, with the thermostat playing at best a secondary role.
    Again, I think the design intent is for the fans to be the main
    determining factor, not the thermostat.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 7, 2004
    #23
  4. Link's NG


     
    Jim Shulthiess, May 8, 2004
    #24
  5. Paul Middlestat

    Bill Putney Guest

    Bill Putney, May 8, 2004
    #25
  6. > Oops - Thanks Jim! I used the URL that works for
    externally linking
    Seems like rather an odd setup to me. Water doesn't flow until the radiator
    cooled fluid reaches a predetermined temp. I guess it makes sense to assure
    engine temp rises to an efficient level asap, but it sure is backwards to
    this old phart's recollection. Emissions control?

    Gramps
     
    Jim Shulthiess, May 8, 2004
    #26
  7. Paul Middlestat

    Bill Putney Guest

    I had not thought of that, but you're right.

    OK - after a little more study of the diagram that I linked, and seeing
    how the thermostat housing is constructed (from another figure/sketch in
    the FSM that I did not post), that heater return tube ports to the
    engine side (temperature sensing side) of the thermostat, so the heater
    circuit (which also feeds the pressure bottle) acts as a thermostat
    bypass during warmup - that's what initially opens the thermostat.

    You had me going for a minute there, because without that heater circuit
    bypass, that thermostat might never open on warmup. That also would get
    the passenger compartment heat operating as quickly as possible.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 9, 2004
    #27
  8. Paul Middlestat

    Steve Guest

    Jim Shulthiess wrote:

    If that is really the layout, the bypass flow must come back directly
    across the thermostat element or it would never open.
     
    Steve, May 10, 2004
    #28
  9. Paul Middlestat

    Guest Guest


    That is not even close to what I said.
    What part of "the thermostat does NOT limit the maximum
    temperature of the engine - it regulates the minimum temperature" do
    you not understand???
    You are way off of the ball park - out in left field. The stat starts
    to open roughly 3 degrees before the rated temp, and is fully open at
    about 20 degrees over rated.. It us far enough open to provide
    appreciable coolant flow at the rated temp. IF the rad sheds enough
    heat from the coolant to maintain 190F ( with a 190 stat) with this
    opening, it will not open any farther than this - and if it sheds no
    more heat than is required, it will not re-close or "modulate"
    The "typical" coolant system has the thermostat at the "engine outlet"
    or "radiator inlet". It prevents coolant flow into the rad untill the
    operating temp of the engine reaches the set point.. The fan control
    sensor is usually at the bottom of the rad - but can also be at the
    top., particularly on a crossflow rad, where it is on the outlet side
    (generally).
    The fan only comes on when ambient airflow through the rad is not
    sufficient to keep the return temp cool enough to avoid overheating
    the engine after the "cooling load" is pumped back into the coolant
    from the engine.

    On many of today's engines, there is ONLY ONE COOLANT TEMP SENSOR, and
    it is in the water outlet or the cyl head. The computer is programmed
    to turn on the fan when a set max temperature is exceded. That max
    temp is usually significantly higher than the thermostat rating (
    aprox 20 degrees IIRC))
    Boiling point is somewhere above 230F

    The switches on engines that use a separate fan control have
    hysteresis built in. As an example, one used by Ford turns the fan on
    at between 216 and 232, and keeps the fan running until the temp
    drops to 201. Another turns on between 202 ans 228, and turns off at
    between 198 and 218. Another turns on between 207 and 217, and turns
    off at 192.

    One GM switch turns on between 224 and 236, and turns back off at 121.

    One used on the Chevy Geo turns on between 184 and 196, and turns off
    at 181.

    One used by Chrysler turns on at 193-207 and shuts off at 175

    A 10 degree hysteresis seems to be pretty close to standard.
     
    Guest, May 10, 2004
    #29
  10. Paul Middlestat

    Guest Guest

    Nope - totally different system That sucker has a bypass thermostat.
    The water circulates through the block bypass untill it reaches
    operating temperature - then it allows a bit of cold water in from the
    rad. This system DOES modulate, and controls the temperature to a
    closer tolerance for emission control. Even worse system to install a
    colder thermostat in.
     
    Guest, May 10, 2004
    #30
  11. Paul Middlestat

    Bill Putney Guest

    Yes - as I said - the heater loop return ports to the block side
    (sensing element side) of the thermostat. Heater loop acts as a bypass.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 10, 2004
    #31
  12. Paul Middlestat

    Bill Putney Guest

    Heater loop is the bypass - returns to the sensing element side of the
    thermostat. See the diagram I posted the link to.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 10, 2004
    #32
  13. Paul Middlestat

    Bill Putney Guest

    In my earlier post I said: "...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".

    Is that not what you are saying??? (That's for the scenario in which
    the thermostat normaly goes to full open at normal engine operating
    temperature, which I though is what you are claiming).
    That is one scenario that I covered. I said I did not know which to be
    the case for that vehicle - I covered both scenarios for discussion:
    Full open at normal operating temps., and a modulating thermostat, which
    you yourself covered in another post this afternoon (from your post:
    "This system DOES modulate, and controls the temperature to a closer
    tolerance for emission control."). We are both saying that there are
    both types of systems. We just need to be clear about which we are
    describing at any one time.
    Yes - two different systems.
    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 10, 2004
    #33
  14. Paul Middlestat

    Bill Putney Guest

    OK - so this is the second type in which the thermostat would modulate
    (rather than running full open under most normal operating conditions),
    correct? In that case, the thermostat *is* in the loop of controling
    the engine temperature, would you agree?

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 10, 2004
    #34
  15. Paul Middlestat

    Nate Nagel Guest

    huh. never woulda thunkit, but looks like you're right. thanks for the
    education. Wonder why they did it that way?

    nate
     
    Nate Nagel, May 11, 2004
    #35
  16. Paul Middlestat

    Steve Guest

    Nate Nagel wrote:


    More precise temperature control. With the configuration Bill posted, it
    looks like the fans keep the reservoir of water in the radiator BELOW
    the engine's optimum operating temperature, and the thermostat can blend
    water from a "cool" reservoir (the radiator) and a "hot" reservoir
    (recirculation from the engine block) to get an optimized stable engine
    temperature under a pretty wide range of driving conditions. The system
    like my '93 has probably 5-10 degrees of variability because the
    thermostat sets the minimum temperature and regulates it on the highway,
    but the electric fan control sensor regulates the temperature in traffic
    with the thermostat wide open.
     
    Steve, May 11, 2004
    #36
  17. Paul Middlestat

    Guest Guest

    Yes TO A POINT.
    That point is reached when the stat reaches full open and the cooling
    system can not shed all the heat.
    Doesn't matter if you have a 140 or a 215 stat - if the system wants
    to run at 235 IT WILL.
     
    Guest, May 11, 2004
    #37
  18. Paul Middlestat

    Bill Putney Guest

    Understood (from the beginning) and agreed.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, May 12, 2004
    #38
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