Home
About Us
Calendar
Fiero Documents
Merchandise
Tips
Links
Members
Message Board
Other Fiero Clubs
VIN Decoder
Speed Calculator
GFC Facebook Page
 
« previous next »
Pages: 1 [2] 3 4

Author Topic: Overheat?  (Read 16732 times)

0 Members and 1 Guest are viewing this topic.

Fierofool

  • Global Moderator
  • *****
  • Posts: 10,578
    • View Profile
    • Georgia Fiero Club
Re: Overheat?
« Reply #15 on: September 12, 2020, 08:16:47 am »
The CTS is in the neck of the thermostat housing.  The gauge/light temperature sending unit is in the left front corner of the cylinder head, just in front of the thermostat housing.  It's possible to swap places with them if the wiring harness has been messed with enough that the wires can be extended. 

First, verify that your gauge is calibrated correctly.  With no power applied, the needle sits on the bulb of the thermometer symbol.  With engine cold and ignition ON, the needle should move to the 100 mark.  Testing temperature with an IR thermometer, focus the beam on the brass base of the sending unit.  It should be very close to the correct temperature.  Verify your gauge agrees. 
Logged
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #16 on: September 12, 2020, 08:26:01 am »
Well, the gauge was about 90 degrees lower.  The gauge has been calibrated.

I wanted to verify the coolant path, relative to the sensors.  Basically, is the CTS at the coolant exit from the engine, and the temp sensor while the coolant is in the engine?
Logged

Fierofool

  • Global Moderator
  • *****
  • Posts: 10,578
    • View Profile
    • Georgia Fiero Club
Re: Overheat?
« Reply #17 on: September 12, 2020, 10:11:18 pm »
My reply above is incorrect for the V6 engine.  I was thinking of the L4.  Sorry.

The coolant temperature sensor is in the outflow path of the cooling system.  It's in the lower manifold which is receiving water direct from the cooling jacket around the cylinders and in the heads.  The coolant passes over the CTS and exits up through the thermostat housing.  The gauge sending unit is in the flow as coolant comes up from the block on it's path through the head and into the lower intake.  Probably because the flow is so fast, the temperatures are equal. 
Logged
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #18 on: September 13, 2020, 04:06:28 am »
Therein lays the problem.  My temperatures aren't equal, which probably means that the flow is not fast.
Logged

Fierofool

  • Global Moderator
  • *****
  • Posts: 10,578
    • View Profile
    • Georgia Fiero Club
Re: Overheat?
« Reply #19 on: September 13, 2020, 07:21:15 am »
 Probably because the flow is so fast, the temperatures are equal.    That was my theory.  The fan switch is set in the intake also and it may not come on at the prescribed temperature when compared to the other two temp sensors.  They aren't precise instruments and they can be made by a wide variety of different manufacturers.  Because of it's proximity to the combution chamber, I could see the gauge sending unit reading or displaying a higher temperature.
Logged
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #20 on: September 13, 2020, 07:05:02 pm »
Still need to know if it actually overheats.
Logged

TopNotch

  • The Duke of URL
  • Global Moderator
  • *****
  • Posts: 3,977
    • View Profile
Re: Overheat?
« Reply #21 on: September 13, 2020, 08:25:16 pm »
Quote from: GTRS Fiero on September 13, 2020, 07:05:02 pm
Still need to know if it actually overheats.
Does it ever boil over, or dump an excess amount of coolant into the overflow bottle? That's one sign of overheating.
Another, if it's due to air pockets, is a popping noise while the temp is high.
Logged
The more complex the mind, the greater the need for the simplicity of play.

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #22 on: September 13, 2020, 08:34:06 pm »
Neither of those things.
Logged

Fierofool

  • Global Moderator
  • *****
  • Posts: 10,578
    • View Profile
    • Georgia Fiero Club
Re: Overheat?
« Reply #23 on: September 13, 2020, 08:47:06 pm »
Is your ECM programmed to control the coolant fan or does it still operate off the fan switch?  If off the ECM, what is the upper and lower settings?  If off the switch, what is the on and off for the switch. 

Knowing these values, you can let the car sit and idle after a warm up drive, and see if the fan comes on at a gauge temperature that agrees with your controlling device. 
Logged
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #24 on: September 13, 2020, 08:55:35 pm »
By the ECU.  I don't recall the set temps, but they are set for a 180-degree thermostat.  I did the idle test.  The fan comes on when the CTS (via the ECU) hits about 190.  The gauge shows whatever.  It sometimes agrees with the CTS.
Logged

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #25 on: September 24, 2020, 06:27:34 pm »
There appears to be a short.  Does anyone know the physical path for this wiring?
Logged

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #26 on: September 26, 2020, 01:55:57 pm »
The gauge needle can move half an inch at a time, up or down.  There must be something happening.  The gauge readings are now much worse.  The gauge indicates past the red very often, now.  In fact, the gauge almost always shows overheating.
« Last Edit: September 27, 2020, 04:37:49 pm by GTRS Fiero »
Logged

TopNotch

  • The Duke of URL
  • Global Moderator
  • *****
  • Posts: 3,977
    • View Profile
Re: Overheat?
« Reply #27 on: September 27, 2020, 04:37:30 pm »
Could be bad wiring somewhere. Since the temp gauge is a resistance operated device, any additional resistance in the circuit, such as caused by a bad connection somewhere, will throw it off.
Logged
The more complex the mind, the greater the need for the simplicity of play.

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #28 on: September 27, 2020, 04:39:57 pm »
In this case, less resistsnce.  To me, that means a short.  My theory is bad wiring, since it got worse after the temp gauge pigtail was replaced.  It almost seems to be right there in that harness.
Logged

GTRS Fiero

  • Hero Member
  • *****
  • Posts: 12,510
  • It is what it is.
    • View Profile
Re: Overheat?
« Reply #29 on: October 03, 2020, 04:47:27 pm »
My Fiero is not overheating.  That hsving been stated, last night, I drove 238 miles on the first tank, with the temp gauge a bit higher than the black mark above the red.  Rometimes, the needle would move as much as half an inch higher than that.  8.39 gallons of gas.

I drove 254 miles on the next tank, and the needle stayed mostly below the red.  8.03 gallons of gas.

Running 80 MPH does not improve fuel economy.

Frustrating.
Logged
Pages: 1 [2] 3 4
« previous next »