Ok this will be a little long but I'm stumped and wanted to see what others can tell me. It might be simple and I'm just dumb. Ok so from the beginning, bought an
90 ef d15b2. Ac worked, no over heating car was fine, only drove twice short distances pre maintenance stuff. Did tune up stuff, decided to replace radiator because it was a bit old and causing me issues when trying to refill rad fluid. Put new rad and fluid, hooked all plugs back up to fans and drove it. Ac wasn't working and when I checked I noticed the condenser wasn't kicking on or the fan for the condenser. Wasn't sure about the other fan at that time because I didn't check. Also noticed a hose on the iacv was leaking so I just put it on hold, didn't feel like dealing with all that at that time.

Fast forward some months and I'm back to it. Replaced the iacv hose and went to fill up rad fluid and bleed air again. When doing so I noticed the other fan (rad fan) wasn't kicking on either once up to temp. It was a good 20 minutes in idle and never kicked on. Top hose was hot, fluid dropped and bottom hose got hot as well, so I know the thermostat opened. But because the fan wasn't kicking on, the coolant wasn't cooling (bottom hose too hot for sure) so I had to stop. This is where it all started getting confusing. My temp gauge on the dash goes up to about middle and stays there, doesn't go higher, yet the coolant isn't cooling down because of the fan. Now today I jumped the rad fan with alligator clamps from battery to plug and the fan worked. I then went to the switch on the back of the block and paper clipped the plug for that sensor and not only the rad fan came on but so did the ac condenser fan at the same time. So I guess they are both wired together. But point is both fans work and paper clipping the switch did the job, which led me to think the sensor is bad. So I decided to see if I can just run the fans like that while I fill fluid and bleed air, but noticed that the rad fluid never went down and the bottom hose never got warm or even felt like there was anything flowing through it. And this was also after about 20 minutes idling, even with heater this time. Now it's acting like the thermo isn't opening. Or am I wrong and the bottom hose should be completely cool. Although it didn't feel like anything was moving in the bottom hose at all. Sooooooooo lol, I'm confused. General question, any idea? Question two, is sensor the problem as for the fans not kicking on? Question three, why does it seem like with the fans hook up to stay on, did the rad fluid not seem to be flowing through bottom hose into motor? Thermo not opening, fans cooling everything off too much, which doesn't make sense because fluid still would be getting hot and opening the thermostat and causing the fluid to start cycling though everything. When just yesterday it did do all that with out the fans on. Last question, shouldn't the temp gauge be going higher and overheating if all this is happening?

Anyways bought this car and had it transported from three states away because of condition and how hard it is to find them. And haven't even been able to drive it because I can't get inspection and so can't get title transfer and so can't get stickers and plates. It's pissing me off so just want to figure it out and get it done already. Any help would be extremely great.

Fans good, checkAll fuses good, checkThermostat is new and opening fine, checkWiring from sensor switch on back of block to the fans all good, checkSeems like sensor isn't good but not sure.

 

Impeller fins on the water pump may be corroded to the point they no longer move water.

How did you bleed the coolant system of air? You may have a large air pocket trapped.

20 minutes may not be long enough to let the car warm up enough for the fans to kick on, especially in the winter, and depending on what kind of climate you live in.

 

If the water pump was no good, wouldn't that keep it from circulating rad fluid? Because I didn't have a circulation issue. The first day the thermo opened and everything was circulating but the fans didn't kick on even after the bottom hose was very hot. The second day I pinned the switch to keep the fans on and waited same amount of time and the thermo didn't open.

I didn't get to the full bleeding at all so for sure I have air in the system. But I couldn't finish because I ran the chance of causing overheating issues if I kept going with the fans not on. But my system is, jack up the front, open rad cap and turn car on, let it reach temp and circulation can start in which I can see the fluid drop and start to flow in the rad, then top it off put cap on and bleed the rest from the bleeder valve. Maybe turn on the heat to red with fans off if it helps. But again, I couldn't get to all that.

And yeah I thought maybe 20 wasn't long enough the second time if I had the fans always on. So today I'm gonna try again with a different method and see if the thermo opens and everything circulates.

I'll update later today. I'm pretty sure the fan issue is just the sensor is either bad or maybe it was lose or something, gonna check the sensor more today. And I'm hoping there is no other issue and I just didn't give it long enough to heat up, to open the thermo, as I had the fans on from the start.

 

I recommend getting a Lisle funnel or something similar when bleeding the coolant. Jack the front of the car up, move climate control lever fully to heat (blower does not need to be on), attach funnel to the radiator, fill radiator until funnel remains about 1/3 full, fill coolant reservoir to full mark, crank and let it run until the fans come on. Once fans cycle once or twice, shut car off, plug and remove funnel, install radiator cap. After the car completely cools down, top off the coolant reservoir if needed. While it's running, you can monitor the temperature gauge, or if you have a thermometer, you can monitor the temperature of the coolant in the funnel. I think the fans come on above 194F. If you monitor the gauge, I wouldn't worry unless the gauge gets over 3/4 height. If you're using a thermometer and the fans don't come on by around 210F, shut it down and dive into the fan wiring.

I'm betting you didn't let the car warm up enough, though. At idle it likely will take longer than 20 minutes.

 

Well I just got done with the bleed, doesn't seem to be any air in the system. There was barely any at all, couple bubbles.
So I'm pretty sure after some testing, the fan issue is just the sensor, nothing else, easy fix. And after testing today with the fans not running, I'm positive the thermostat opened after about 17 minutes of idling. But now another question has come from that. After 17 minutes I saw the coolant drop in the radiator and could see it flowing. Telling me the thermo opened. But after about a minute the fluid started coming back up to the very top. Is this a bigger issue I should worry about or is it just because the fans weren't on to cool off the fluid and so it heated up and rose to the top? Or is the thermo closing again even though their was no fans to cool down the coolant that was going into the engine? And I let it run completely for almost 30 minutes, to the point of both hoses being too hot to touch and steam starting to come out of the rad cap, just slightly. So I'm pretty sure the fans not coming on, even with out knowing temp, is the sensor. I didn't want to let it run any longer and risk damage to anything else. And my gauge seems faulty too, considering it doesn't even reach full half way point. But that Im not sure. So I don't trust my temp gauge right now.

 

The radiator fan isn't triggered by a sensor, but a switch. If your gauge (which is based on a sensor) is sitting right in the middle it is actually possible that the system is not heating up enough that the fan will trip. I once had a hatch with a strange old double-depth rad and the fan hardly ever ran in the winter.

But I have also had massive stubborn air pockets that screwed with me for days before I finally managed to bleed them. Engine didn't seem to care, for what that's worth.

 

Yeah switch for the radiator fan, the back of the block one. Just a habit calling it a sensor. But yeah I figured it all out. Thermo is opening fine and I'm just replacing the switch for the rad fans and that's that. Or maybe just hook it up to run off a toggle switch to make it easier and never have to deal with the switch again. Pretty sure I got all the air out though. I'll find out soon enough once I start driving it more. As of now no air bubbles coming out, no over heating, thermo is good. And figured out the fans not kicking on issue, so yeah. But I appreciate the help though.

 

The fluid rising after the thermostat opens is normal - heated liquids expand. This is why the system pressurizes, and why you have a spring loaded radiator cap and expansion reservoir attached to the radiator. This is why I suggested using a funnel on the radiator to allow the expanding liquid somewhere to go while you are testing the system.

Before buying a switch, why not pull your old switch off and test it? Heat it in water and monitor the temperature until you get the switch to close.