How much is a T-stat supposed to open?

[1997Ranger]

I am having overheating problems in my 1997 ford ranger. What seems to be happening is after putting water in the radiator and running the truck, the engine overheats and a lot of steam and hot water is forced out of the radiatior into the resivoir leaving nothing but steam in the cooling system.

The t-stat was changed and the problem still persists. I was wondering if this was due to a faulty new t-stat so I put it in a pot of boiling water and I notice it opens about 1/4". I am wondering if this is normal or if it should be opening farther than this? It looks like the spring is not very compressed at 1/4".

Another thing I was suspecting was maybe the radiator cap is not holding the coolant in so it is going out of the system into the resivoir?

At this point should suspect a faulty new t-stat and get another one or should I look into the radiator cap?

Thanks for any replies in advance..

 

[Pensa]

Water boils at 180 degrees, most thermostats are rated higher than that, so the thermostat is probably OK. The cap could be a problem and you may need to flush out your system. Is your coolant rusty looking? If it is you need to flush the system.

 

[1997Ranger]

well, we did put in that stop leak stuff before because we thoguht we had a leak. do you think that could have clogged up some passageways?

as far as flushing - is there a pro way to flush it like pressure or something or do i just buy those bottles of prestone flush?

see, the problem is we had changed the radiator before this problem started happening, so, i don't think it is because of rusty coolant. the coolant was changed when the radiator was changed.

could there be anything else that's causing the problem? everyone who looked at it seems to think that the water pump is still working.

if it is not the tstat and not the water pump and not rusty coolant, what else could it be besides the cap?

 

[steventadams]

Water boils at 180 degrees

212 degrees?

 

[Hurricane]

sure you didnt have it in backwards? is radiator plugged internally or externally? fan clutch working correctly? whats the temp gauge read? 50/50 mixture of coolant or just straight water?




Mechanical Test

The thermostat should be replaced only after the following tests have been performed:

1. Heat Test 89°C (192°F) Thermostat Immerse the removed thermostat in a 89°C (192°F) solution of antifreeze and water mixture. An 89°C (192°F) thermostat should open to 0.08 mm (0.0003 inch) . When immersed in a 100°C (212°F) solution, the thermostat should open to 3.2 mm (1/8 inch) . 92°C (197°F) Thermostat A 92°C (197°F) thermostat immersed in a 92°C (197°F) solution of antifreeze and water should open to O.O8 mm (0.0003 inch) , when immersed in the 100°C (212°F) solution, the thermostat should open 3.2 mm (1/8 inch) .
2. Visual Test

1. If heat is not available, the thermostat should be checked for leakage. This is done by holding the thermostat up to a lighted background. Leakage of light around the thermostat valve (thermostat at room temperature) indicates that the thermostat should be replaced with an original equipment, approved thermostat. Some thermostats have a small leakage notch at one location on the perimeter of the thermostat valve which is considered normal.

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Electrical Test

CAUTION : Always vent the exhaust to the outside when performing this test.

NOTE: Procedure is most accurate if performed indoors at less than 37.8°C (100°F) ambient air. This test may be performed with or without the hood open and with the engine warm.

1. Check coolant level in radiator and engine coolant recovery reservoir. Fill as needed.
2. With the key OFF, remove the Engine Coolant Temperature ECT sensor harness connector and attach the Rotunda Service Coolant Temperature Monitor Harness 007-00064 or equivalent as a jumper between the Powertrain Control Module PCM and the ECT. Attach a Rotunda 73 Digital Multimeter 1005-R0051 or equivalent to the thermostat monitor harness. Voltage values (0 to 5 V) may now be monitored while the sensor retains its connection to the wiring harness.
3. Place transmission in PARK (P) or NEUTRAL (N). NOTE : Running this test with the vehicle in gear or with the A/C compressor clutch engaged (running) will cause improper diagnosis.
4. Start the engine and allow it to idle throughout this test. Allow engine to run for 2 minutes, then record the ECT voltage. Record ECT voltage every 60 seconds. When ECT voltage trend changes direction or changes only slightly (0.03 volts or less) from the previous reading, record this as the thermostat opening voltage. Use the voltage and temperature chart that follows:

Coolant Temperature ECT Volts
22°C (71°F) 3.00 volts
43°C (109°F) 2.01 volts
71°C (159°F) 1.01 volts
82°C (180°F) 0.75 volts
91°C (195°F) 0.59 volts
97°C (206°F) 0.50 volts
105°C (221°F) 0.40 volts

5. If the thermostat opening voltage is greater than 0.75 volts and less than 82°C (180°F) , replace the water thermostat.
6. If the thermostat opening voltage is less than 0.75 volts and greater than 82°C (180°F) , water thermostat is good and should not be replaced.

 

[Ranger Al]

bad radiator???

 

[nmpdk1]

1997 Ranger

The radiator cap may be the problem. I've seen aftermarket caps boil over and not send the fluid to the overflow tank because the spring and seat are different from OEM and actualy blocks the overflow tube. It may also be the water pump, or a combination of the pump and the cap. I've seem it quite a bit on vehicles I work on.