Two radiator fans, three relays, thermostat, pump?

[robert]

Ahoy Eric and crew!

I have a bit of a puzzler to tackle, but have a limited amount of time. So hoping for some wisdom.

There are two radiator fans on my 2001 Nissan Maxima. They don’t run when it’s cold, but as the engine warms up, both of them kick in and stay on. Sounds like a small jet taking off.

This occurred shortly after I replace the radiator and thermostat. Coincidence?? Not sure.

Possible culprits, it seems, are three radiator fan relays, the temperature sensor, thermostat, and water pump.

The temperature gauge shows the coolant always in the sweet zone… not to hot, not too cold. Thank you Lord!

We’re taking a trip in a couple days and I’m trying to fix this puppy. Where would you begin? Thermostat, relays???? I’m guessing the temperature sensor is OK, as it seems to read OK on the dashboard gauges.

Also… is there a trick to pulling those relays out? They see to be in there pretty darn tight.

Thanks in advance for your thoughts and insights. Now,I need to go take out a membership. :-O

Topic

[Lorrin Barth]

For a DIYer leaving in two days I’d suggest the local Nissan dealership.

If time wasn’t a constraint I’d suggest obtaining a wiring diagram and studying it until you understand how the fans are supposed to work and that should cue you in to whats wrong.

[robert]

Thanks for the reply.

Not enough time to bring in the repair shops.

I started rotating the relays tonight … radiator 1 and radiator 3 relays, to see if that would shed any light on things.

My greatest concern is that the thermostat might not be working… However, the temp gauge registers in the low/sweet zone when I take it out and drive it 10 miles or so. Which leads me to think it should be OK. Not sure if there is an easy way to see if a thermostat is working correctly…

I want to think that if the thermostat wasn’t opening, the temperature would run waaaay hot. And, there’s no signs of that.

So, it seems like I’m back to the relays.

I’m beginning to think I might be expecting the fans to run quieter than they do. And, I’m not certain at what point both fans should be kicked into high.

Again, when I go out and drive it, the temperature gauge stands firm in the below middle zone. Never seems to fluctuate. (Temperatures outside here are at about 75 degrees.)

I wouldn’t be concerned so much, except I’ll be driving it 300 miles each way this weekend. Obviously, don’t want any surprises along the way.

Thanks for the thinks.

[Lorrin Barth]

If you question the thermostat the thing to do is replace it. The best test of a thermostat I know of is to put it in a pan of water on the stove with a new one and see if they both act the same.

On the other hand I hate to see you opening the cooling system right before a road trip unless you know you can purge it properly and have it cooling correctly immediately. Maybe buy a thermostat and take it with you on the trip. If the old one acts up find a shop that will replace it then.

As for the fans on all the time, that will reduce gas mileage but is maybe something that you can deal with when you return.

[Its me]

[quote=”thefranks5″ post=100628]Ahoy Eric and crew!

I have a bit of a puzzler to tackle, but have a limited amount of time. So hoping for some wisdom.

There are two radiator fans on my 2001 Nissan Maxima. They don’t run when it’s cold, but as the engine warms up, both of them kick in and stay on. Sounds like a small jet taking off.

This occurred shortly after I replace the radiator and thermostat. Coincidence?? Not sure.

Possible culprits, it seems, are three radiator fan relays, the temperature sensor, thermostat, and water pump.

The temperature gauge shows the coolant always in the sweet zone… not to hot, not too cold. Thank you Lord!

We’re taking a trip in a couple days and I’m trying to fix this puppy. Where would you begin? Thermostat, relays???? I’m guessing the temperature sensor is OK, as it seems to read OK on the dashboard gauges.

Also… is there a trick to pulling those relays out? They see to be in there pretty darn tight.

Thanks in advance for your thoughts and insights. Now,I need to go take out a membership. :-O[/quote]

I am trying to figure out your problem… Is it the noise or the fact they are continually running?

The fans should not kick on when it is cold (if they are electronic).. One is for the radiator, the other is for the condensor… They should cycle off and on when the car is moving and gets more air in to cool the system…

The needle on the temperature gauge is in the proper location, correct?

If it is noise, then possible you have a bearing going bad in one of the fans… You can inspect this by ensuring the engine is cool and then directly hooking up 12v to the fan and if it is too noisy, then you have your problem..

-Karl

[EricTheCarGuy]

For starters you’re making an awful lot of assumptions. This is a bad thing when it comes to diagnosis and repair. First, what is the actual problem? Are the fans staying on and not turning off? It sounds like they are operating normally otherwise.

That said, you MUST bleed the air out of the cooling system anytime you open it up for service. Also, anytime you perform a repair and have a problem afterward, YOU are the most likely cause of the problem. It’s a good idea to go back over your work to make sure everything is connected properly.

The info here may also be helpful to you.

http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems

http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats

Good luck and keep us posted.

[Andy]

I work on Nissans like these all the time so let me give my piece.
Eric is right about bleeding the cooling system and you should do that first.

now if the fans do not come on as soon as the engine is started or with the key in the on position but they do when the engine first gets hot then it is not the relays.

if all is well with the radiator and the cooling system then your next move should be to clean the coolant temperature sensor but do this with the key out before you set a code because you will have to unplug it.

if that doesnt work then it cud just mean that the fans are just flat wearing out and dont spin as fast as they used to.

so recheck your work with the cooling system and try these if that dont work.

[Author]

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