soyjer
NAXJA Forum User
- Location
- California
Connected OBDII reader, and monitored radiator flow, temp, and rpm while warming up engine from 50 degree air temp and 50 degree engine temp:
Took a full 7 minutes of fairly linear change to stabilize at 195 degrees and ~720 rpm, at which point the thermostat finally did open and the radiator hose began to warm up a little (heater hose was already warm by then). Water in radiator cap opening never visibly moved at all during the entire test, including after the thermostat had opened, but since radiator hose became warm I am assuming that any coolant movement just wasn't visibly detectable.
The fact that two independent temperature measuring devices (the 195 degree thermostat, AND the Engine Coolant Temperature Sensor) both agree as to when the engine coolant is at 195 degrees, leads me to believe that my engine coolant is, indeed, taking 7 minutes to rise from 50 degrees to 195 degrees.
The radiator and coolant reservoir are both at the proper levels, and the heater hose does heat up, so the thermostat and Engine Coolant Temperature Sensor should be measuring coolant, not air.
And the PCM seems to be doing exactly what it is supposed to with regard to maintaining the idle rpm at the correct rpm level for the Engine Coolant Temperature Sensor reading that it is receiving. At 50 degrees, it starts it out at about 1150 rpm, and then gradually lowers the rpm level to ~720 rpm at 195 degrees.
So I'm still at a loss to explain why my particular 4.0L engine would take much longer to warm up and idle down than anyone else's 4.0L engine. If the problem were the opposite, and my engine was heating up too quickly, THAT I could understand (anything that restricts coolant flow could cause THAT), but in this case the only thing that I can think of that would allow my engine to warm up much slower than others' engines would be if my thermostat were stuck in the open position, which definitely does NOT seem to be the case.
If anyone out there has the time to try the above and let me know how long it takes YOUR 4.0 to reach 195 degrees and ~720 rpm (from ~50 degree starting point), I would appreciate it.
Took a full 7 minutes of fairly linear change to stabilize at 195 degrees and ~720 rpm, at which point the thermostat finally did open and the radiator hose began to warm up a little (heater hose was already warm by then). Water in radiator cap opening never visibly moved at all during the entire test, including after the thermostat had opened, but since radiator hose became warm I am assuming that any coolant movement just wasn't visibly detectable.
The fact that two independent temperature measuring devices (the 195 degree thermostat, AND the Engine Coolant Temperature Sensor) both agree as to when the engine coolant is at 195 degrees, leads me to believe that my engine coolant is, indeed, taking 7 minutes to rise from 50 degrees to 195 degrees.
The radiator and coolant reservoir are both at the proper levels, and the heater hose does heat up, so the thermostat and Engine Coolant Temperature Sensor should be measuring coolant, not air.
And the PCM seems to be doing exactly what it is supposed to with regard to maintaining the idle rpm at the correct rpm level for the Engine Coolant Temperature Sensor reading that it is receiving. At 50 degrees, it starts it out at about 1150 rpm, and then gradually lowers the rpm level to ~720 rpm at 195 degrees.
So I'm still at a loss to explain why my particular 4.0L engine would take much longer to warm up and idle down than anyone else's 4.0L engine. If the problem were the opposite, and my engine was heating up too quickly, THAT I could understand (anything that restricts coolant flow could cause THAT), but in this case the only thing that I can think of that would allow my engine to warm up much slower than others' engines would be if my thermostat were stuck in the open position, which definitely does NOT seem to be the case.
If anyone out there has the time to try the above and let me know how long it takes YOUR 4.0 to reach 195 degrees and ~720 rpm (from ~50 degree starting point), I would appreciate it.