maxinout93

03 I 35 recently started to slightly overheat after driving down the freeway for about 35/40 minutes at speed between 70-85 mph. It only does it on the highway at high speeds. I can drive all over town and it will not overheat. Coolant seems to be full and dont think im loosing any, radiator is full. Never had any issues before with the cooling system except last year original radiator went out and was replaced by aftermarket. When the car does slightly overheat if i let off the gas and slow down it returns to normal. Oil is full, before it overheats it seems like it hard to accelerate, then when it goes back to normal, everything seems normal and it wont overheat anymore, but it never goes to the top of the guage.

TallTom

How does the front of the radiator look?

ukmastermind

Are you going by the gauge on the dash or do you have an OBD connector for actual temps?

I was always pushing 213-216 on the highway when pulling hills. Changing the radiator didn't help much, but when I put in new cooling fans, it dropped down to 200 (hills & hwy) and maintained 190-195 cruising (flat hwy). The cooling fans also helped my very average AC cool down drastically.

- I use a Scangauge to monitor actual Coolant Temps as I drive... amazing tool.
- I feel like this engine generates a lot more heat than the VQ30's (95-99) and even the VQ37's (370z).

TallTom

If the radiator is clear on the front, I would do a full radiator and engine flush.

I just drove from NYC to Florida and with the outside temps being 90*, my temp gauge didn't rise above about 1/3 way up the gauge while driving above the posted speed limit for hours on end.

if it was a stuck thermostat, it would be hot all the time. If it was a bad water pump, it would be warm to hot all the time.

Hot only when pushing the engine while there is air circulating around the engine meanings that coolant isn't pumping well.

For a temp fix, you can remove the two front engine shrouds that are attached to the bottom of the bumper. My temps went down further when one was dangling and I removed it until I got new clips.

maxinout93

thanks for the replies guys, yes im going by the guage cluster for reading temps. Everything seems to be normal as far as coolant goes. Ive swapped radiator caps to rule that out. Sometimes if i go up a steep hill at 85mph the transmission will drop a gear. So im assuming sumthing is causing a bit of overheating plus its been like 100 degree weather down here. Also both of my top radiator mounts broke off due to rust so ive tied it up with shoe lace. But i dont think that has anything to do with it. Im gonna try the coolant sensor first.

maxinout93

idk but this is first time ive had any issues with the guage moving up slightly. Im wondering if i need to do a coolant pressure test if its only happening under load. I kno i did do some off roading with the car and my bottom oil cooler small hose is saturated with oil from the pressure sender unit leaking.
Wow you drove from New york to Florida!! Man thats how you know you have a good car!

ukmastermind

Are your cooling fans very loud and noticeable or is it more of a hum?

TallTom

I love southern drivers. Everything from NC and south was a joy to drive with much better drivers than what I am used to. I was humming along at a speed 20mph above the posted speed limit and was getting passed on a regular basis.

Maxima's are solid cars. Hopefully you get your coolant issue sorted. The pressure test or engine flush would probably help since your issue seems to be under load only.

TallTom

I would think that at highway speeds that fans wouldn't be necessary with winds pushing through the open grill and radiator at 60+mph.

ukmastermind

That's what I thought until I put in new fans. Drastic Temperature Drop on and off the hwy
New Radiator, Thermostat, Cap, and Coolant made no real difference for me.

maxinout93

the fans at idle are more of a hum unless i turn the ac on then they kick on high speed, then low speed once the car gets cool enough inside. I dont know why the bottom of the floor on the driver side feels hot though. Or if ive driven the car shut it off, and restart it, the fans are high speed with no a/c for about a minute, then they stay on low speed. Im thinking a plugged cat, as i can hear the material inside rattling around. Coolant is full everyday when checking radiator and i get instant hot heat if i turn the temp to hot or 90 degrees.

DougR

You have the same symptom as presented in this thread, https://maxima.org/forums/5th-genera...peeding-2.html Lots of good suggestions offered there.

ukmastermind

Any updates on the cooling system?

maxinout93

I did get around to changing the coolant temp sensor on the engine today. Drove around for about 2 hours driving it hard and going 100mph down the freeway(short bursts of speed). So far the needle has not moved during the driving today. But I did see drops of coolant near the top of the radiator so I will keep an eye on that. Heat still blows hot, But I will probaly take it on a small trip once i replace the converter thats rattling.

Prophecy99

iTrader: (1)

sweet ! good to hear !

TallTom

the radiators are known to crack at the top, usually around 100K mile mark (but not always the case). Keep an eye out. Replacement radiators are cheap for what they do (under $100). The TYC from Amazon or Rock Auto seems to be a forum favorite.

$62 on amazon at the moment: https://smile.amazon.com/TYC-2329-Al...7159387&sr=8-3

scotty64

when i changed my engine temp sensor i also changed the larger one that feeds the info to the ECU. i had to do a radiator change later on and used new 2002 model radiator due to the larger transmission cooler, using this radiator my car never ran above 1/3 on the temp gauge even during our hot and dry aussie summers. do you have any kind of "vapor" lock where there could be an air pocket within your cooling system?

Donkeypunch

didn't know there was an upgrade for the 00-01

scotty64

on the aussie model the transmission cooler was longer and the fan mounting holes where different,the early model radiators had a wedge style locator.the later updated radiator had round locating holes.that was the visible difference, not sure if the internals of the core had any design change.

maxinout93

No vapor lock that i know of so far. Heat comes out hot everytime i need it, I am currently running an aftermarket radiator thas still under warranty if it acts up.

maxinout93

Ok guys just a small update. Ive been driving the car everyday, and even 70 to 90 mph on the freeway for hours. I changed the coolant temperature sensor, and the problem has not come back so far, and its been a week or 2. BUT I did notice that the hose from the coolant overflow tank to radiator is not very secure at the connection. I saw signs of dried up coolant there and i can squeeze the hose and see green coolant attempting to seep out. Maybe Ive found the source of the air getting into the system?? Yes or no?

ukmastermind

So you weren't really overheating then. You had a bad sensor sending incorrect info to a gauge.
You should replace that little hose or put a clamp on it.

maxinout93

Yeah thats what im gonna do man get that hose fixed

maxinout93

hello all im back again after 2 months. Proud to say that the problem has not came back after driving numerous miles in this car. Ive replaced the radiator. But it seemed as if something else was wrong also, i would get these burst of power on the freeway, and then loose power slightly , then the problem got progressivly worse to the point of the car barley having any power at all. But not codes would show up, only a flashing engine light sometimes but no specific code. Thought it might has been a converter!!. Then one day i leave my lights on for an hour go to start the car and she wont crank. im like wow its never done this before. Now ive had this car for 2 years, but something told me to check the battery cables. Lo and behold the positive cable was really loose!!!. Im looking like dam that is why ive been having so many issues! I tightnd it up and got a boost, and the car has been back to normal since then and even threw a code for po301 coil. Fixed it and for now things are good! the power is back!

CMax03

iTrader: (3)

Coolant sensor (water Temp Sensor) or water temperature sending unit? These are two different things! The water temp sensor is for the ECU and the water temp sending unit is for the water temp gauge....