allmazda

95 just replaced the motor so the system was open everywhere. Car runs fine but the fan will remain on and prevent the Tstat from opening. Parked up hill to bleed the air. Not sure I have it all out. This is what is happening...

Fans will cycle sometimes. Lower hose gets hot so tstat is open. Take for a drive and park car. Fans will be running and lower hose is cold. If left to itself fans will not shut off at idle. Lower hose is cold. Race the engine fans go off after 20-30 seconds. Then half the time the tstat will open and cycle just fine. If engine is not raced fan will run and temp gauge does not move from normal...half way.

All parts are new and temp sensor has been swapped. Each temp sensor acts the same.

DennisMik

iTrader: (2)

When the a/c is on, the fans will run all the time, regardless of the engine temperature, so I hope you are not trying to figure this out with the a/c being on.

The thermostat has its own temperature sensor built into it to tell it when to open and close based on the water temperature. There is no connection between the thermostat and the cooling fans, other than the fans cause water cooling. The ECU tells the fans to run based on the coolant temperature reported by the ECTS (Engine Coolant Temperature Sensor).

If you connect an OBD code reader (one that reports live data), it will show you the water temperature according to the ECTS. At idle, the coolant temperature will fluctuate between 180º F and 203º F once the engine has warmed up. And while you replaced the sensor, I hope you replaced the one that has 2 wires on it, not the one with 1 wire.

I'm thinking you have a bad thermostat or that it is installed backwards.

allmazda

Thanks for the reply. No, the ac is off. The thermostat comes in the housing so there is no way to install it backwards. Also I replaced mine on the engine that died a few months before. Originally had this one on and had the problem. Put a new one in and it is still the same problem.

Yes, I replaced the 2 wire ECTS and not the one for the gauge.

allmazda

Fixed. Air...! I parked on steep hill and jacked up front of car several times. No air.

I then decided to jack the drivers side up. Got both driver's side wheels off the ground. Air started to bubble out almost immediately.

Since the air would have to travel to the water pipe to be removed jacking the car up this way would allow all the air to move in that direction.

I can't say where the air lock was but in 5 minutes I added more than 16 ozs of water using this method

DennisMik

iTrader: (2)

Good to hear that you solved it and that it wasn't anything major. Congrats.

allmazda

It was not overheating but running too cool...the fan would not cycle after driving and would if heated up parked. I would take it for a drive and when I would return fan would be running and never cycle and lower hose would be cold.

It seems like the ECTS would turn the fan on when driving before the tsat would open. This it appears kept the tsat closed and the bypass apparently kept the ECTS hot enough to keep the fans on.

DennisMik

iTrader: (2)

The temps you report for the fan turning on and off is not good. The turning on is correct but the turning off is not. The spread between the fan on temp and the off temp should be greater. I said 180º for the off but others have reported as high as 190º.

The thermostat should open at around 180º and close again at around 170º. The only way to verify this that I know of is to remove the thermostat and put it in water with a thermometer and heat the water and watch it. That is what is in the service manual.
See page 13 in this link - http://boredmder.com/FSMs/Nissan/Maxima/1995/LC.pdf

You have me pretty much convinced that the thermostat & ECTS are good, but I never bet my life on stuff like that. If this is true, this points to a water circulation problem. If it were a plugged radiator, you would have a constant, consistent problem. That doesn't seem to be the case.

That makes me wonder if there is some piece of crap floating around in the engine. It happens more times that you might think when an engine has been disassembled, swapped, etc. This is also very hard to prove.

I don't have any definite answer. Remove the thermostat and drive the car for a few days and see what happens. Depending on where you live and how warm the temperature gets, the engine might not get up to operating temperature.

The only thing I don't have any idea about is the radiator fans on and off temperature. This is determined by the ECU. Never heard of an ECU screwing that up.

allmazda

The fan off temperature was adjusted with the scan tool. I forget the exact temp but I adjusted the temp so the fan would go to high. The fan did turn to high. I also lowered the temp with the scan tool and it always would turn off at 198.

So for my 95 auto the fan on temp is 203 which is what the FSM says. The fan off is 198 but I could not find a value for this in the FSM.

I would agree about trash but if the car is not moved it will cycle just fine.

If the car is not stopped when driving.... given a chance to heat to 203... the temps stay under 203 and the tsat will open and close. This is seen by a hot lower hose. But if the car does reach 203 and the fans come on after driving for 3-5 miles the lower hose is cold.

allmazda

Finally Fixed!!!!

I went to pull-a-part and got 4 nissan thermostats. I had thermostat soup cooking in the kitchen for lunch. I picked the most tender (opened soonest of the lot) and cleaned it and installed. The fans cycle when parked and when driving.

Moral of the story.... This engine likes old oem thermostats more than new Beck Arnley or Advance Brand.

Also ECU likes ECTS to be oem and not aftermarket.

I also got 2 used ECTS at the yard as well and 4 pigtails to make testing with a multimeter easier. I tested all 5 that I had by placing in sun and measuring resistance. The 3 oems were close... the non oem was way off.

DennisMik

iTrader: (2)

Good show. You have learned that sometimes factory parts are best. There are many members of the org that will tell you that you should never use an aftermarket thermostat. Too bad I didn't mention it.

The ECTS is not like the thermostat. Many have used aftermarket ones with no problems. Where did you get yours?

Happy driving