So I replaced the rad stat and sects and when the mother gets close to operating temp the low speed fans kick on and stay on, the stat never opens. If I take fan relay one out the stat will open and eventually the high speed fans kick on for a few seconds. If I plug the relay back in the low speed fans kick on and stay on until the stat closes and almost seems that they don't shut off. I changed out the ects thinking this was the issue and tested both the old and new in ambient temp and boiling water and they read the same. I am at a loss and am about ready to leave the low speed fan relay out. I know there is no air in the system. Any thoughts?

 

Sorry I'm on my tablet that's replaced ects And Motor

 

Did you install the t-stat backwards?

 

did you test to make sure the relay is working correctly and verify no other relay is out that may be used in conjunction with the fans?

 

if the t-stat was in backwards, then the fans would never kick on right?

 

Stat came preinstalled in the housing, appeared to be correct. I've also moved around relays from other things and have noted them to be good and not sticking, its almost like the ects is tripping too early keeping the stat closed

 

I have to admit that I don't fully understand what is going on from what you have said. Several things don't make any sense.

Just to make sure of one thing - the air conditioner is turned off when all this is happening. If the air conditioner is on, the radiator fans will constantly run at low speed.

Two things happen in the cooling system that are based on the engine coolant temperature. These 2 things are independent of each other and not connected in any way. But they both have to happen for the engine to cool properly.

1) The thermostat opens and closes based on the engine coolant temperature. It starts to open at 180 degrees and should be fully open at 203.

2) The radiator fans are turned on and off by the ECU based on the engine coolant temperature that is sent via the ECTS. The radiator fans come on at low speed when the engine coolant temperature reaches 200 degrees. Should the coolant temperature reach 212 degrees, then the fans will run at high speed.

So the sensor you replaced, was it the one with 2 wires on it?

You say that the thermostat doesn't open if the fans run at low speed. I seriously doubt that is happening. If the thermostat does not open, the engine coolant will not circulate through the radiator. If the engine coolant doesn't flow through the radiator, the engine will overheat. Doesn't matter what the fans are doing.

You never say that the engine is overheating. But you say that the fans will kick on at low speed when the engine approaches operation temperature. This part sounds normal.

You go on to say that the fans never turn off. This isn't right and is the part that needs to be checked out. In normal operating conditions, the fans will cycle on and off. This will happen when the car is sitting and idling and when the car is being driven at lower speeds.

Assuming you don't have any test equipment to monitor the engine coolant temperature (the output of the ECTS), I'm going to take some guesses and make a suggestion. You probably have a good ECTS, since you have replaced it.

My suggestion is based on that you don't have all the air out of the engine. Bleed the radiator with the car on an uphill incline, the steeper the better. Run the engine with the radiator cap off until the engine coolant starts to circulate in the radiator and continue to run for a couple of minutes more, allowing any trapped air to escape. Add coolant to radiator as necessary. Put on the radiator cap and turn off the engine. Allow to completely cool. Remove radiator cap and check the coolant level. The radiator should be completely full, no air.

if the fan problem still exsists, we'll discuss plan B.

 

Ac is off. Engine never overheats. I know the difference between ects and sending unit for gauge. Air has been bled like crazy and problem still exists. Top hose really hot bottom cold fans on low. Stop fans and bottom gets hot in less than a minute... gotta go to work now though

 

OK so at lunch today I ran the car and realized that both hoses when hot are hard as a rock, would this indicate a closed stat? I'm going bonkers here and appreciate the help. I don't have any good inclines around my area is there another way to do this without a jack?

 

When the fans are hooked up, is your dash gauge showing normal temperature or does it show the engine is running cool? Or does it go up and down between normal and cool?

The hoses being hard only indicates that the cooling system has pressurized. When you can feel that the lower radiator hose is hot, that means that the thermostat has opened and the coolant is circulating. Those are both good things.

As for an incline substitute, can you can drive the driver front wheel up on something, like a curb maybe, or some pieces of lumber or bricks? 4 inches or so high should do it. It doesn't have to be a super incline.

Trying to think things out... When the fans are on, this is cooling the water in the radiator which is then pulled back into the engine by the water pump to cool the engine. The system tries to regulate the coolant temperature at about 200 degrees. The coolant gets hot, the fans come on and the coolant temperature goes down and the fans are supposed to turn off. In both of my cars, I can watch the coolant temperature fluxuate between 197 and 202 degrees and the fans are turning on and off. If the fans do not turn off, I suppose that the coolant will be cooled below the 197 point. How much further, I don't know. Outside temperature plays a part in that as well as how quickly the engine can re-heat the coolant. The thermostat is "monitoring" the water coming from the radiator. If the coolant from the radiator is dropping below 200, the thermostat will begin to close. The cooler the water the more the thermostat closes. I suppose that could make the lower hose seem cool when the fans are staying on.

So why are the fans staying on? That is still the question that needs to be answered.

Either the ECTS is bad, the engine coolant is low or the ECU is bad. I've never hear of the ECU doing this but it is possible, as unlikely as it seems.

 

As much as I bled the sysyem before it appears that I still had air and the stat never did open. So I ran the car with no rad cap with both fans disconnected, then waited finally I could visually see the coolant stirring about in the radiator. This is when I knew the stat opened. Then thanks to another thread I took my old rad cap and removed the lower gasket and put that on and suspended the over low way high on the hood latch. Upon revving the motor to high rpm more air came out. After a bit I shut the car off and now I'm waiting for it to cool. I also plugged he fans in while running with that setup and they ran as they should. I'm going to give it another hour to cool and put it back and test again. This was done in my flat driveway. I'll post back in a bit with my results. I can't believe ho hard this motor is to bleed, are there any , mods that have been done to make this easy?

 

BTW thank you guys again, its nice to find a place where I can bounce ideas around

 

Well everything worked fine in the driveway, took for a test ride and same issue arose. I'm assuming I still have air in this thing. Thing I don't understand is why air would cause the stat to stay closed even after its open. Wouldn't the air stay at the highest point of the motor?

 

Did you get an OEM tstat? I think that is more likely your problem than air. It will bleed just fine on flat ground. Always a few air bubbles in there as it is not an easy system to bleed of air. If you got a tstat from the auto parts store then take it out, boil it to see if it opens and if it doesnt take it back. Or just take it back anyways and get an OEM one like you should have in the first place

 

I'll try bleeding again, if it don't work then I'll do that. Where about do I get an OEM BTW. I hope I don't have to go to the stealership.

 

OK so I bled it out again and it does as should sitting in the driveway if I drive around the block and check the bottom hose, again bone cold. I also noticed that I don't have any plastic covers under the front of the car. Is it possible that could cause the lower hose to cool off too much?

 

OK after watching the fans cycle on and off a few times and stat open eventually the fans stay on so I took off the low speed relay cover, put it back in and waited for the fans to get stuck. I thought maybe a bad relay even though I thought it was good. Ecu is keeping the relay on? Wtf so now I'm thinking the ects is giving a slightly lower reading than its supposed to. If I add a resistor in there what value? What is the resistance values on the ects hot?

 

The ECU telling the radiator fans to run is what I was thinking was happening.

Do you have or can you borrow an OBD reader/laptop program/smartphone app that can read live data? Coolant temperature is one of the pieces of data that you can monitor. This is what the ECU interprets from the ECTS.

The ECTS is a thermistor that has less resistance the hotter it gets. At 212 F (100C) it is about 100 ohms if I read the FSM correctly. Adding a resistor in the circuit (my guess would be 100 ohms) to make the reading about 10 to 15 degrees cooler might make the fans turn off, but it would also make the engine run 10 to 15 degrees hotter. I don't know if that would cause any problems or not.

Overall, I have to say that I don't like the idea. Something is wrong that needs to be fixed, not compensated for. But what the problem is eludes me.

But if you want to try the resistor thing, here are the specs on the ECTS from the FSM.

 

I think installing a Nissan thermostat is a simple first step. Was there something wrong with the old thermostat? You can reinstall the old thermostat to see what happens.

 

Im almost positive it is due to a faulty auto parts store thermostat. There is no telling how long, if at all, those will last. AN OEM at the dealership or courtesyparts.com is not expensive and you know it will last

 

Well as you suggested I pulled out the aftermarket stat and took both the original (Nissan) stat and boiled them both at the same time.it was really interesting, the both opened and closed at the same time but the distance they traveled was shocking.... wait more like disturbing. The aftermarket was almost triple the shaft movement compared to the original. 0.0 since I have that vacation tomorrow I put the old one back in. When I get back I'll order a brand new Nissan stat and install it. With all that being said, what other parts should be avoided when dealing with aftermarket stuff. I'm worried now because the ects is aftermarket also >.< in the meantime I'm waiting for the motor to cool from the bleeding to see if it all works like its supposed to.

Also stating that this board had opened my eyes for the better, thank you all much!

 

Problem fixed, it was the aftermarket thermostat. FYI the brand was motorad. I can't believe they can sell such junk.

 

 

Glad I could help, aftermarket is either hit or miss. Just do a quick search before you buy next time but as a rule of thumb never buy aftermarket mass air flow sensors, ignition coils, or fuel injectors. Of course these are the most expensive components but it makes sense a part at half the cost will not perform so well