RWCreative

I have a 1998 Maxima. My cooling fans both come on when I turn on the heater fan to 4, but I do not have to push in the AC button to get them to turn on, they just turn on when I turn the fan switch all the way to 4. I start the car and let it warm up for 20 minutes and I never hear the low fan speed turn on.

I am also experiencing other issues (maybe related) with my temp gauge. It goes all the way hot, but the car is not over heating. Radiator is full. No leaks anywhere. What is really strange to me is that I can tap the gauge near the bottom of the gauge and the needle comes back down to normal operation, but when I stop tapping, it goes back up to top. Sometimes I slightly smell that hot antifreeze smell when I park and open the door, but it is so very faint, and then it goes away.

I purchased a temp sensor (the one with the single wire) that goes directly to the gauge and will be putting it on, but i am suspecting it is also the coolant temp gauge that sits right next to it.

I have no way of checking the temperature of the engine (not the coolant), but it seems like it may be running more on the high side, because it just overall has started to smell warm when parking (kind of a mix of hot oil and coolant, but niether one is more dominant than the other. Could this also be a faulty thermostat?

I would appreciate any help in diagnosing these issues - I suspect they are all related. Thanks much!

RW

SupaMaxima

If I were you, I'd replace the thermostat. It's a pretty cheap part and takes minutes to replace. It may be that the thermostat is stuck slightly open. It still ciculates just enough coolant to prevent overheating, but not enough to bring the engine to optimal operating temps. Have you seen water boil into the overflow tank? This may cause the coolant smell.

I had a car in the past where the thermostat was stuck fully open so when I drove downhill the temperature needle would go down to cold and then back up to normal temps on flat or uphills.

RWCreative

Well, have never experienced boiling water in the overflow at all. But today I replaced the thermostat and both coolant temp sensor and temperature gauge sensor. Now the gauge goes from normal to high, stays 5 or so minutes, then goes back down to normal. (there is no set amount of time, just does it randomly) This continues to happen throughout driving. (Only went to store and back so far).

One good thing is that the rad fans turn on the low speed now after car is warmed up and idling. But I haven't heard them cycle off and then back on as they regulate the water temp while sitting in driveway, they just stay on low. And now, the high speed rad fans turn on just by turning on inside fan switch position 1, 2, 3 and 4, with the air conditioning button Off. I use to have to put the inside fan switch on 4 (high) to get the high rad fans to come on.

Inside Heater: One other thing is that the heater fan inside the car only actually turns on in the 4th (high) position (it was that way when I bought the car). Haven't had the car long so I am not sure if it is the inside fan switch, or if the fan switch has a fan resistor that is bad. But I am very happy with the improvements now and will continue to tweak. At least i feel more assured on the road knowing the car isn't actually Over-heating.

Should I discount the battery and reconnect to reset the computer to adjust to the new sensors? What do you think? Also, bad fans relays?

Thanks so much for replying!

FYI: I like this 98 Maxima alot! Got it at an auction for $1200. A great strong and quiet runner. Gutted the interior, laid new carpet throughout and shampoo'd the hell out of the seats front and back, headliner, doors and dashboard. Look, feels and smells like brand new inside.

231k miles and counting here.

Roger

DennisMik

iTrader: (2)

Either I don't understand the your problem or you have a really weird problem.

Here is the way the radiator fans should work.

When you start the car (engine cold) and the a/c is off, the radiator fans should not run. When engine coolant temperature reaches 203º F, the fans should come on at low speed. When engine coolant temperature reaches 221º F, the radiator fans should start running at high speed. When the engine coolant temperature drops down to 180/185º F, the fans will shut off.

When you turn on the a/c, the radiator fans should turn on immediately, at low speed, regardless of the engine coolant temperature. This is required in order to cool the a/c condenser coil that is mounted in front of the radiator. When engine coolant temperature reaches 203º F, the cooling fans should start running at high speed. The fans should never shut off while the a/c is turned on.

The radiator cooling fans are controlled by the ECU. The Engine Coolant Temperature Sensor (ECTS, the one with the 2 wires) sends a signal to the ECU and the ECU determines when and at what speed to run the radiator fans. As a FYI, both radiator fans always work as a pair. They are either both running or both off, never one on and one off.

Turning the heater control fan switch to ANY position will not cause the radiator fans to run. The heater control fan switch only controls the interior blower motor fan for blowing air out the ducts.

If the blower motor inside the car only runs on #4 high speed, then the blower motor resistor is no good. Fan speeds 1 through 3 go through the blower motor resistor, while #4 speed bypasses the resistor and goes directly to the motor. The blower motor resistor is located in the air duct near the blower motor, not in/by the switch.

Word of caution: If you are replacing the blower motor resistor, DO NOT EVER (that means NEVER NEVER) turn on the blower motor with the resistor out of the air duct and hanging by its wires. It needs the air blowing on it to cool it. If you want to try what I just said not to, buy two resistors when you go to the store and save yourself the second trip.

The temperature gauge going to high and then dropping down sounds like a bad thermostat. This is fairly common with a non-Nissan thermostat. The only brand of thermostat that seems to work on these cars is the one Nissan sells.

Disconnecting the battery won't have any effect on the cooling system temperature sensors or fan operation. What might be helpful for diagnosing problems (both current and future) is get an OBD II code scanner. Don't get the cheapest one, get one that can display live data. Among that live data is the engine coolant temperature.

The Wizard

iTrader: (43)

You have air in the system and/or a bad radiator cap.

RWCreative

How do I burp the system? I'll buy a new cap, any brand suggestions?

I Just installed an aftermarket thermostat along with the temp gauge sensor, and water temp sensor. These 3 things corrected the rad fan behavior, and seemed to reduce the occasional faint hot antifreeze, but it hasn't gone completely away.

The heat gauge in the dash still rides back and forth from normal (in the middle) to the top (hot), but the car is not visibly overheating or smoking, and water is not boiling in the overflow container.

I will have the computer scanned and get the live data on the engine and water temps as Dennis has suggested.

I guess it is possible that the new aftermarket thermostats do not perform adequately on these Maxima's.

Is it possible that the water pump is under-performing, causing the occasional hot smell which would then be reflected in the erratic behavior of the temp gauge?

The Wizard

iTrader: (43)

To burp the system of air, remove the radiator cap. Then, either park on a steep incline or use a jack and lift the front end up as high as you can. Make sure your heater is on full blast. Run the car for a bit, making sure the fans kick on high, then off for a few cycles. You should see air bubbles come out of the radiator. I like to rev the engine to 2000 rpms or so and hold it there for 10 to 15 seconds at a time during the process to assist with purging the air. Hopefully after you burp the air, the car will behave as it should. Re install the rad cap and monitor the behavior of the car. If the problem persists, replace the cap too.

I have one of these funnels linked below, and love it. It screws onto the radiator and allows all the coolant/water to bubble up/splash around inside while it purging and makes it easy to do and you don't lose valuable coolant.

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

It could be the aftermarket thermostat, but let's start with the free and easy stuff first. The radiator cap will run you about $15 to $20 at the dealer, where as an aftermarket radiator cap will run you about $10 at your local parts store. Go OEM if you can.

RWCreative

Ok, I haven't been driving my 1998 Maxima but recently got back to the temperature gauge issues I was having with the car. I have never had a check engine light come on to date, but I took it to emissions to get new tabs and it failed emissions and gave me a read out of P0110 Intake Air Temperature Circuit AND P0325 Knock sensor 1 Circuit (Bank 1 or Single Sensor). So I'm good on knowing how to replace these 2 sensors and I can troubleshoot if it is the wire shorting out, but I am wondering if either of these 2 codes (PO110 & PO325) have any affect with my ongoing problem of my temperature gauge going up and down, but the car never actually overheating?

Also I have purchased a Nissan OEM thermostat and will be putting that in as others here on the Nissan board have suggested that I take out the recent aftermarket thermostat i put in, and use the Nissan OEM because the Maxima is finicky that way.

Thanks for any insight on the IAT Sensor and Knock Sensor as it may affect the temperature gauge reading.

RW

Dave20

That's the same thing that happens to mine changed everything from term,to radiator, to water pump nothing will work so I just drive to for like 2 weeks and now it's ok.

asand1

iTrader: (1)

Sounds like you just need a heater fan resistor now, and the cluster may have som loose connections or cold solder joints.

Dave20

Did that to but did the same for a little but the cluster was bad .....

Shock_and_Awe

RWCreative...did you ever get this resolved?

I am having the exact same problem except my 99 is throwing P1706 (Park Neutral Position Switch) & P0325 (Knock Sensor Bank 1). My temperature gauge is going up and down with no overheating. It just started doing this yesterday. It will sit on the H for 15-20 minutes while driving...fluctuate a bit and then back to the center where it stays. I also wonder if there is a connection with Knock Sensor. My CEL goes off every 3-6 weeks or so with the same 2 codes reporting. The light just went off this past weekend after being on for about 1.5 weeks. I will replace the Neutral Switch this weekend, clear the codes and see if that works.