Well this is the 2nd consecutive day its been overheating. It happened once a couple weeks ago but I had the AC full blast waiting on an asphalt road in 100 degree weather, so I can see how it would then, but now its not hot outside and its doing it again.

It does it when I come to a stop and when I start moving it cools down again. I opened the cap and its topped off the reservoir is at the full line. Both fans work also

I checked both hoses and they are both hot. I pumped them both a little bit and it seems bubbles came out so I thought it was just air in the system. I started it and let it idle for a good 10mins and then drove around with the ac on full and parked in an asphalt parking lot and kept the revs about 2k and it stayed at normal temp the entire time I was doing it (5mins or so)

I'm at a loss...

 

Have you replaced the thermostat? Is the coolant spilling over into the reservour? Flush the system?

If that all is fine, I would replace your coolant temp sensor. It's cheap, about $15 I think, and it installs within 15 mins.

 

It might be. The hose going from the radiator to the reservoir was almost as hot as the radiator hoses to and from the engine. I dont think thats supposed to happen now that you mention it. I didnt check the temp of the coolant reservoir fluids temp though

I havent replaced the thermostat yet. I'm going to tonight along with flush the system. Tonight

Where is the coolant temp sensor located?

 

maybe your radiator cap isn't sealing all the way and you are losing fluid out from the cap when it gets hot and then when it cools down and the pressure drops you end up being low on fluid...

 

Is there any way to tell or test if the cap is faulty?

 

You could visually inspect it...

There is a rubber piece at the bottom that seals on top of the radiator which is on a spring so it can give way if there is really high pressure in the system. Look for pieces out of the rubber and exercise the spring to see that it doesn't stick anywhere

 

Are the fans coming on? I'm Houston, Tx and it's over 100 degrees Fahrenheit quite alot during the months of June, July, August!!! It should work regardless, unless there are problems. I would suggest you pressurize your system and look for leaks, test your thermostat for proper opening temp, maybe even reverse flush your cooling system! If all is good make an investment into a Nismo radiator cap( higher pressure cap) and some redline wet wetter! Good luck!!

 

If you see fluid in reservoir tank when the car is hot near the max level then there's no leaks in the system. If your radiator fans are spinning then it is definetly too hot and ECU tries to cool it down. This would eliminate the coolant temperature sensor for in cabin indicator as ECU uses its own sensor and it is not likely both of them went south simultaneously. Something prevents coolant from circulating through the radiator at the necessary rate. I'd start from thermostat. Unfortunately, I don't know an easy way to check it without taking it out and putting it in the bowl with water with thermometer and heating it up.

 

You don't have a leak....you would smell it. My radiator cap had a SMALL leak and I could smell the antifreeze everytiem I got out of the car.

 

sounds like you might want to start with changing or at least checking the thermostat, and the fluid i guess since you are going to have to drain a bunch to change it.

I lied to you about the price earlier today. I thought it would just be a generic round type but it is kind of an awkward polygon. The one for the 95-99 vq from courtesy nissan is about $19, probably about the same for your 01.

 

What is redline wet wetter?
Yeah, its still in there. The tube going to from the radiator to the reserviour is hot though. I'm doing a coolant flush tomorrow and I got a thermostat at Napa for $20 too so after tomorrow I guess we can troubleshoot some more

 

And there's no leak anywhere. Its still full and I can't smell any glycol

 

Human hands are poor thermometer around 82 C(180F) - the opening threshould for thermostat. You wan't be able to tell for sure if it's too hot or not just by the touch.

 

it might be the sign for engine oil low

 

also make sure your water gauge is not faulty and check your sensors... i had a faulty cluster gauge it would always go up and down never read properly.

 

I never thought of that. Do VQ30's burn oil a lot? I've read that VQ35's do
How can you check if a quage is bad?





Anyway, I put in a new radiator cap and drove it around for about half an hour tonight with the AC on full blast and it stayed at normal temp

 

fan/airflow issue

 

Partially clogged radiator. Change radiator, problem solved. Trust me, I know.

 

It is not - your radiator fans are also running to confirm it is hot.

I thought it was overheating when the car was stopped with engine running and AC on, this is the worst case for cooling system: no air flow, just from those fans and hot AC condenser heating air in front of the radiator, lowest coolant rate from pump with engine at idle. Usually cooling problems surface under these conditions first. When the car is moving the airflow is much better as well as water pump provides higher coolant flow.

I don't see how cap replacement could change anything; you were not loosing coolant anyway.

 

I'm just telling it how I saw it. A good 15 minutes in a parking lot with AC on full blast with constant revving and it stayed the same

I'm going over to my friends to change the coolant in about an hour or two and I'll report back. I might as well take out the radiator and the fins out and check flowage through it

 

OK, if it helped under same conditions then it helped. The clean test would be to put the old cap back and see if the problem comes back. This is of course if you're curious. I wouldn't mess with radiator as of now: if it ain't broke ... If you haven't put anything in the coolant in the past I don't see a reason for it to be clogged with anything. Not at the age of your car anyway.

 

Keep us updated on the fix. I followed the same path as you (t-stat, flush, cap) and it turned out to be the radiator. It had flow, just not enough.

I think Soonerfan had the same problem on his old 5 gen.

Good luck

 

How often are you guys flushing and changing your coolant? I can't believe all these ppl with radiator replacements on cars that are still so young! My original D21 radiator was finally replaced this year after 22 yrs of service!
I think changing your coolant/flushing once a year or once every other year is a good practice!

 

I flushed the coolant out of the system until the water came out nearly clear. I also changed the thermostat, but..............

It turns out it was the radiator. There were enough fruit flies/mosquitoes(sp) in the fins to make it so I could barely see through it holding it up to the sun. I took it out and took it to a self service car wash and sprayed it on the pressure wash setting. It took about 10-15 minutes, but it's almost all the way cleared out now.

I'm happy to report no issues anymore. And its running a slight bit cooler than it was before the problems had even arisen

 

No issues today either and I drove around all day today

 

Good deal!

 

sweet, good to hear!

 

The basic troubleshooting lesson learned here is........check the simple things first, unless you know for sure that the problem lies elsewhere.

 

I'm happy for you! You didn't need to spend any big $$$!!!!

 

Having the same problem with my 2004 maxima. When I am moving the temp is fine and if I stop at a long light the temp starts to rise. Never pegged just about 3/4 up. started with the easy and wash all the bugs off the radiator, however that did not solve the problem. both fans seem to work and no leaks. any sugestions???

 

If you read the OP messages you might notice that he changed thermostat as well but chose to attribute his resolution to the clogged radiator fins. If your coolant level is fine I'd start from thermostat as it seems closest to the problem and is kind of classic reason for this. When you're moving your water pump provides higher rate of coollant which becomes satisfactory for the amount of heat engine produces even on partially open thermostat.
Last summer with 30 C (86 F) outside I lost coolant from my car due to crack in the hose. Long story short - 1/3 of radiator filled with water was enough to keep temperature around normal level. I didn't have AC running though. This was 93 SE with new thermostat.

 

I had to take my radiator out and spray it. It was really clogged up with bugs. You might as well just take it out and flush the system and get a new thermostat since they are pretty cheap anyway

 

Fush it and add some Redline (Wet Wetter), it aids in the transfer of thermal energy out of your engine into the airstream!

 

Hey Guys, thanks for the advice, I had the thermostat replaced and problem went away.

Thanks Again

 

You're welcome .

 

I think that if the problem happened on and off it would be the fan assembly. On my 4th gen I had overheating issues. The first thing I replaced was the thremostat followed by the radiator. The issue went away for a while. I was driving back home from school one day and lo and behold the car tries to overheat again a couple of months after we fixed the problem? Uh oh.

Upon inspecting the engine bay I found that only one of my fans were running. Now, one fan in the 4th gens stays on as long as the AC is on. The other one will only come on when a certian level of heat is generated. Surely if my car is on the verge of running hot that the limit was already reached.

When I noticed that one of the fans wasn't running, I did something that was very logical. I poked it with a stick. The fan came on. My temp returned to normal very quickly. I eventually had to replace the entire fan assembly and I never had another problem with overheating. If your car overheats again check to see if both fans are running because that could of been your problem.

 

I checked the fans probably 20 times a day and they had no problems turning on at any point. It was definitely the clogged radiator core

And I siphoned out some coolant last night and put in some Water Wetter just for some added measure. She's running beautiful right now. I can't wait for the mods in the next two months

 

So is it true the VQ30 has 2 thermostats?
My Haynes book says it does but it don't specify where.

 

one is called a thermostat and the other one is called a water control valve although they are both heat activated. From looking at the FSM it looks like it is on the driver side just above where the starter is.

 

I had to buy two new fans. Both fans need to come on one is for A/C and the other to cool the engine.