My Qx4 is overheating

[longhornsqx4]

This is for an 01 Infinti Qx4

So this weekend was the first really hot weekend, and i went on a road trip, about 200 miles. The whole freakin trip, my temp gauge was about 2/3-3/4 up on the gauge.

It would stay there and never get hotter. It would get cooler when I got into slower traffic though, its perfectly fine when cruising @ 40mph and 2000rpm. But at 65mph and 2800 rpm, the temps rose up.

When I pulled over, you could hear the coolant bubbling in the radiator under the cap with your ear close.

I waited for it to cool, and checked the fluid level, which was fine. It took about a 300ml to top it off, but nothing significant.

I felt both upper and lower rad hoses and both were hot as sin (to me that meant thermostat IS openning? properly.)

Im no exactly rich so I love some insight on how to tell what the problem is.

Has anyone ever done a waterpump swap on these cars? I just looked at the manual, seems VERY tricky

[Q45tech]

Eight and half years is a long time to expect a radiator to function as brand new. Clean out the trash between condenser and rad, examine rad fins for damage and oxidation.Flush out radiator core to remove internal blockages with a mild chemical flush. Then flush with clean tap water 2-3 times then refill will proper A/F and distilled de mineralized water mixture.

[longhornsqx4]

There defientely are a fair ammount of damaged fins on the rad

I flushed the rad earlier this year

When you say, clean out the trash between the condensor and rad, you mean the a/c consensor? they are connected with a rubber hose? and how would i clean such contaminents out

The coolant itself looks perfect, and the fluid level was perfect. I did just replace the rad cap a few minutes ago.
Modified by longhornsqx4 at 11:50 AM 6/15/2009

[longhornsqx4]

and would you trust this rad as a proper replacement, its fairly cheap, but there meaurments are the same. I just dont know if quality comes into play with a radiator. Im just quite broke at the moment

http://cgi.ebay.ca/97-98-99-00...%3A50

[Q451990]

I just dont know if quality comes into play with a radiator. Im just quite broke at the moment

Quality certainly differs between OEM and some aftermarket parts, but if you're broke and this fits your budget vs. OEM new, I would go for it. 80 or 90% as good as OEM is certainly better than one that's causing an overheat!

Heath

[longhornsqx4]

Well yeah an Oem one is about $500

The aftermarket ones are $150-200

Quite the savings for a college kid, thats 3-4 weeks worth of food for me

[longhornsqx4]

I am also unsure if thats even the problem at this point, but do you guys think thats the most logical thing here? A clogged/old/heatsoaked radiator

Cause it doesnt overheat after like 20-25min of in town 40mph driving

[Q45tech]

The idle heat output is ~~ 10 HP or 120,000 BTU/hr2,000 rpm cruise is 3x or 360,000 BTU/hr.Acceleration can be in the Millions, but few accelerate for more than 30 seconds................so it only adds 25,000 to prior to acceleration heat level.

Now driving up an incline or mountain can be severe due to time!

Obviously 1/3 goes out exhaust and 1/3 in conducted/radiated away to unhood/hood/body/transmission housing, leaving the cooling system/radiator to get rid of the rest [1/3].

Often much can be gleened from data logging* [real exact coolant temperature] from a COLD start [<100F] to warm up vs seconds/minutes AND RPM in PARK no ac, then doing the exact same thing with ac on [adds 3 HP or 36,000 BTU/hr.

With a +- 1F accuracy you can see in data when the thermostat opens.

* with Consult or other software and OBDII adapter/laptop.

When you replace radiator be sure to visually check condenser for air blocking bent fins, whether auxillary condenser fan works [controlled by ecu and HVAC computer thru ecu], replace upper and lower heater hoses and thermostat [usually fails open = no warm up but helps in winter].

Luckily the cooling system is 90 year old technology so every radiator shop can diagnose often better than dealers can.........not their specialty!

The problem is the rad shop may not have Nissan specific OBDII test equipment to accurately read coolant BUT much can be done with an IR temp measuring gun but spot on accuracy is lacking as the hood must be opened to read coolant and that will change things SIGNIFICANTLY!!!!!!!!

[SteveTheTech]

How many miles do you have on yur QX4?

The QX4 can get tricky and expensive whne attempting to diagnose an overheating condition. You may want to pull the spark plugs and check for signs of coolant burning. There is one thermostat on these but there is water control valve located at the rear of the motor on some of these.

Although an overheating concern is not common they do happen and without a proper diagnosis you will be making expensive guesses.

Are you noticing any smoke from the tailpipe?

Is your overflow bottle empty?

What kind of maintenance have you performed on the cooling circuit?

[longhornsqx4]

I have 114k on the car

I did flush the coolant today, simply drained it, filled it back up 2-3 times with tap water and drained it again, then just let the hose run through it for a few minutes, then drained and filled back up with proper coolant

So I guess we will see what happens.

If it overheats again, I guess its safe to say my rad should be replaced?

I also notice zero changes in fluid levels of coolant, overflow stays right at the max line, no smoke from the exhaust, or sweet coolant burning smell

[SteveTheTech]

I also notice zero changes in fluid levels of coolant, overflow stays right at the max line, no smoke from the exhaust, or sweet coolant burning smell

That is a good sign.

I would say that in this case a radiator may be at fault, but I would not be surprised if it were something else. So you might want to prepare yourself.