QX4 Engine Overheating.. Any Advice?

[Khalid]

Hello everybody

I am quite new to this nice forum. I own a 2003 QX4 and it is a WONDERFUL car.. I bought it brand new from the dealer and it just passed the 100,000 km mark, so you can say i use it lightly as i have another car. I live in Saudi Arabia. Frankly speaking, I used to take the car to the dealer shop regularly for inspection, but I stopped that for quite some time now.

Lately, I started noticing that the engine temp is increasing gradually until it reaches almost to the H mark. To be honest, I started to notice this 'abnormal' increase in temp before winter season. But during winter the engine temp was very low, especially that I did not operate the AC for almost 3 months. However, as I started to operate the AC these days, the temp problem came back again.

About 3 years ago, I had a similar problem, but to less extent, so I took the car to the dealer shop. They replaced the radiator, thermostat, fan clutch and belts and every thing was great (aside from the $2.5k that I had to pay ).

This time, I decided to take the car to a nearby shop, but I was really shocked when the mechanic told me that the problem is in the engine!!.. He claims that there is an internal leakage in the cylinder head and he must open the engine. He also claims that the radiator and thermostat are OK. Although I am not a mechanic but I thought that if what he says is true, then I should lose the water in the radiator, which is not happening.

I believe that the problem lies in the thermostat or water pump. Last night, I ran the engine with the AC on for quite some time until the temp reached barely above the C mark (ambient temp was 65). The radiator cap was open and I could NOT see any clear flow of water through the radiator cap hole. Any advise? Many thanks in advance..




Khalid

[Khalid]

Hello again..

I forgot to mention that during short trips in town, the temperature is pretty stable (below 1/4), Even with the AC on.

The problem starts when driving at a higher speed, say above 80 kph where I notice the gradual and slow increase in temp until almost the H mark. When I stop at a traffic light or arrive home, the temp stays the same (no drop in temp at engine idle rev.). I hope this clarifies the issue.. Thanks

[Slumpert]

From what I read your engine actually has something like two thermostats in it...

This could be something as simple as a big air bubble in the system keeping it from working correctly, too a leaking head gasket.

First thing I think I would do would be to do a good cleaning of the AC coil... If that is plugged up then air can not really get to the radiator to cool down the water.

Next I would check for air in the sysem by following the FSM for refilling the coolant. Mine has a air bleed bolt that made all the difference in the world.

Next check, when engine is cooled down, sqeeze top radiator hose just to get a feel for how squishy it is. Put a pair of "cold weather" gloves in the truck. Take it for any kind of drive, as long as you drive for more than 10min and keep the AC on. Stop the truck, turn engine off, put on gloves, and do the same sqeeze on the hose. The hose should be very firm compared to the cold check. If the hose is hot and squishy then your system has a leak or a massive air bubble that should have been taken care of in step 2..

[Slumpert]

Ummmm.. Just saw
""I forgot to mention that during short trips in town, the temperature is pretty stable (below 1/4), Even with the AC on.""

Unless it is like 0 degrees outside your temp gauge should be hitting @ 1/2 mark just idleing for 10 min.

[Khalid]

Thank you Slumpert for the advice..

I did the 'squeeze' test you asked me to do. I noticed that the hose is a bit stiffer after the engine is warm (and obviously much hotter), but not that big difference when the engine was cold. (Note: i squeezed the hose without turning the engine off).

When you mentioned the 'Air Bleed Bolt', are you referring to the Air Relief Plug mentioned in the FSM? I bought an antifreeze coolant and I am planning to top the cooling system. Should I open this plug before filling the coolant in the radiator and reservoir?


Today, I took my kid to a nearby hospital downtown and the engine was kept running for more than 45 mim. continuously. I did not operate the AC as the weather was quite nice (70 F). The temp remains a little above the C mark and everything seems to be very normal. Driving back home, I meant to drive a bit faster (80 kph) and the temp reached around 3/8 and stayed steady. I kept the car running in the garage for another 10 min. but no change on temp. gauge. Conclusion: it seems that the temp increases only when driving fast (more than 2500 rpm) for an extended period of time (say 15-20 min.). Anything you can draw from this observation? Thank you all again..

[Towncivilian]

Inspect your radiator cap according to this TSB.

[ianh]

Fans on ?

[Khalid]

Inspect your radiator cap according to this TSB.

Thanks for the advice.. I'll check it tomorrow morning..

[Khalid]

Fans on ?

Both were on, the main one and the motor driven...

[Khalid]

Hello again..

let me share with you what I did this morning:

1. I started by checking the radiator cap as suggested by Towncivilian. The cap was very clean, no waxy stuff and no sign of swollen rubber. So this cause was overruled.

2. I bought an antifreeze coolant (Prestone) and filled the coolant reservoir. To my surprise, it took about half of the gallon to reach the MAX mark. I have never added any coolant in the car before. I also tried to fill the radiator from the open cap, but the liquid level was almost full. Then I started the engine. Level did not drop so I did not add any coolant.

3. I drove the car for about 30 min at a varying speed from 80 to 120 kph. AC was on. The temp was increasing very slowly until it reached 1/2 (see the photo below).

4. I returned home, the temp dropped a bit below 1/2. I checked the coolant level in the reservoir and did not notice and drop in the level. Then I stopped the engine.


OBSERVATION (!): I stopped at a traffic light and I was alone. When turned green, I accelerated quite fast and when the engine reached 2,500 rpm, I heard a strange sound like a water flowing inside a pipe for a couple of seconds (!). I could not identify the exact location of the source, but it sounds as if it is coming from underneath the gear stick. I tired this 3-4 times, every time I accelerate fast the sound comes again for 1 or 2 seconds.. Isn't that strange?!..



I am still hoping that someone will identify the cause of this high temp.. At least gives me some assurance that it is NOT related to cylinder head leakage..

[Towncivilian]

There is air trapped in the cooling system somewhere if you can hear coolant flow. Does your heat work well? Keep an eye on the coolant level in the reservoir and top it off as required.

[Khalid]

There is air trapped in the cooling system somewhere if you can hear coolant flow. Does your heat work well? Keep an eye on the coolant level in the reservoir and top it off as required.

I rarely use the heater. I live is Saudi Arabia.. it is hot and humid most of the year. However, the last time I operated the heater, it was OK.

I will go with your advice to top the coolant when needed. I tend to believe that there is some air trapped in the system.

Two questions:

1. the FSM states that I should use 50% antifreeze coolant + 50% demin water, but I am filling only the coolant. Is that OK or do I have to mix it with demin water?
2. I am thinking of opening the Air Vent Plug and fill the coolant from the radiator cap, just trying to get rid of any trapped air. Is this a good practice or I should not mess around with this plug? Should I fill the coolant while the engine is running?


Thanks again for the advise..

[Towncivilian]

It is OK to add premixed coolant, or demineralized / distilled water; the ratio can be a little off without issue, especially in hot climates.

Elevate the radiator above everything else (park on a curb or hill) and open the air relief plug, but not the radiator cap just yet. Run the engine for a while and see if the air burps that way.

[ianh]

first comment is that 1/2 on temp gauge is normal, that's where thermostats open. It should rise rapidly in 2 - 3 miles and stabilize.

If its slow to rise the thermostats are either stuck open or missing.

Yes the gurgling is Air in the system as said above.

[Slumpert]

Just a real quick check..... how is your Oil level and does it look funky.

You said your second recent mechanic told you it was a internal loss and the fact that you had to add over 1/2 gallon plus thier is air all in the system means you have a definate leak somewhere.

When you had all that work done 3 years ago, was it was due to the truck over heating? If it was it is very likely that is when the head gasket was damaged.

[Slumpert]

Also, how does your transmission fluid look?

[Khalid]

Just a real quick check..... how is your Oil level and does it look funky.

You said your second recent mechanic told you it was a internal loss and the fact that you had to add over 1/2 gallon plus thier is air all in the system means you have a definate leak somewhere.

When you had all that work done 3 years ago, was it was due to the truck over heating? If it was it is very likely that is when the head gasket was damaged.

Hello..

I checked the engine oil. It looks quite normal, a bit brownish but normal look after more than 1000 km. The level was OK. No signs of any water or any viscosity issue...

Yes, when I took the car to the dealer, it was because of the temp. rise to more than 1/2 the gauge.

[Khalid]

Hello everybody..

Let me give you the 'daily update' abut this case..


1. As recommended by Slumpert, I started the day by checking the transmission oil. The level was good, the color was very normal (reddish light viscous oil).. No sign of any water...

2. I moved the car on the garage ramp to have radiator above the vent port as recommended by Towncivilian. Then I removed the vent rubber cap. To my surprise, the port was TOTALLY blocked with dirty brownish/black stuff (see photo below). It looks that the dealer shop did not have this cap opened during the replacement of the radiator and fan clutch. I had to use a hanger wire to clean it through. The material was black grainy stuff.

3. Then I opened the radiator cap. Suddenly, the vent line 'burped' dirty black material (see photo). I think this was the remaining of the material that was blocking the vent line. But it wasn't that much.

4. I think I made a BIG mistake when I started the engine while the radiator cap was still open and the car is ramped. Man.. did I have a big fountain of coolant coming all over the engine!! (see photo below). It was a big mess and I had to stop the engine immediately. I think at least 3/4 to 1 liter of coolant came out through the radiator cap (and possibly through the vent line but I am not sure).

5. I moved the car back to level then opened the radiator cap again. I thought I will see the level inside the radiator very low, but it was full up to the opening lip. For a while I thought that the small hose connecting the radiator neck to the coolant reservoir is blocked so I removed it from the radiator side and blew inside it. It was not blocked although I can feel a resistance to blow through it. I returned it back.

6. Later in the day, I checked the level inside the radiator while the engine is off and it was still full. I filled the coolant reservoir (I added about 3/4 liter).


Vent Port Totally blocked:



Dirty Stuff coming from Vent Port:



Coolant Fountain !!!




Radiator Full of Coolant while the engine is running (after the big mess!!):

[Towncivilian]

That's a mess indeed! Hopefully you've burped out all the air now with the help of the now-unclogged vent cap. I don't know what could have caused it to clog like that.

Your Pathfinder does not have cruise control? I noticed the large extra space at the passenger's side of the engine behind the fuse box, it looked odd.

Your brake fluid looks basically black, when was the last time it was changed? Brake fluid is hygroscopic and absorbs moisture, lowering the boiling point of the fluid and promoting corrosion. It should be flushed every two years to keep the water content down, and clean fluid helps promote life of the brake components (master cylinder and its seals, brake lines, wheel cylinders, etc).

[ianh]

looks like stop leak to me !!!

Maybe corrosion byproducts. What caused radiator failure earlier ?

[Khalid]

That's a mess indeed! Hopefully you've burped out all the air now with the help of the now-unclogged vent cap. I don't know what could have caused it to clog like that.

Your Pathfinder does not have cruise control? I noticed the large extra space at the passenger's side of the engine behind the fuse box, it looked odd.

Your brake fluid looks basically black, when was the last time it was changed? Brake fluid is hygroscopic and absorbs moisture, lowering the boiling point of the fluid and promoting corrosion. It should be flushed every two years to keep the water content down, and clean fluid helps promote life of the brake components (master cylinder and its seals, brake lines, wheel cylinders, etc).

I do have a Cruise Control in the car.. and it is NOT a pathfinder.. It is Infiniti QX4

Regarding the brake fluid, thanks for the info.. I didn't know that, and it is true that I have not changed it for a long time. However, what you see in the photo is the reservoir which is made of a black plastic, so this is not the real color of the fluid. Nonetheless, I will check the fluid color tomorrow morning. Thanks for the tip.



Khalid

[Khalid]

looks like stop leak to me !!!

Maybe corrosion byproducts. What caused radiator failure earlier ?

I don't really know if the old radiator really failed or not. When I took the car to the dealer, as usual, they don't tell where is the exact problem. Their 'engineer' just said that I need to change this, this, this and that.... without much explanation. I had to agree because I was pressed by time for a long trip.

[Towncivilian]

Oh, my bad, I didn't realize you had a 2003 which has an electric throttle body, which eliminates the need for a vacuum actuator of a separate cruise throttle cable.

The black reservoir is the power steering fluid; the clear reservoir near the driver's side firewall is the brake fluid master cylinder reservoir.

[Slumpert]

Sounds like you made good progress.

I would put the truck back up on the ramps, open the vent bolt, open the radiator cap, and then using some sort of vacum device wether hand pump, shop vac with reducers just something to pull coolant out of that vent tube..
You dont need to pull all of it out, but try to get a 1/2 litter or so pulled out so you can see if you have anymore "gunk" pulled up.

Also be sure to turn your heater on full before you drive up on the ramps and let stay on as you drive up... ( you dont need the heat, but that opens the heater core valve so any air can get out.

As too what that gunk is...maye it is some RTV or chunk of a hose / themostat piece that got chewed into billion pices by the waterpump or stop leak stuff.

The overflow tube is restrictive so I would not worry about it if you can blow through it. I worried about mine once and took my air compressor to it.. That fountian you described occured right in my face! so never do that unless you like a coolant shower..

[Slumpert]

And by the way.. starting with the vent removed was possibly a accident of brilliance... When the themostat is closed when under 170 degress the waterpump just circulates the water inside the engine.. By opening the vent, your on the pressure side of the system so that likely helped clear most of the "floaters" out along with the air pocket..

[Khalid]

Hello again..

This is the daily update of my testing (probably the last one)..

1. I started by checking the brake fluid as recommended by Towncivilian. I thought that there was a little dipstick to check the liquid but there was none. Towncivilian; you are right, the fluid looks quite dark and probably it is time to have it changed and check the whole braking system (tends to be a bit weak).

2. I decided to take the car for a long drive on a highway to check the temp increase. I drove the car for more than an hour with an average speed of 110 to 120 kph, AC was on. The temp increased gradually until it reached to 1/2 gauge and stabilized (I thought I could drive it for another couple of hours without seeing any change in the temp).

3. When I arrived home, the temp was 1/2 and I kept the engine running for another 10 min while the AC is still on. The temp dropped until it reached a bit above the C mark ~ 1/3 (I would say almost a normal engine temp). I took some photos for the temp during the trip as shown below.

4. I checked the coolant fluid in the reservoir and it is still the same from yesterday, so I didn't add any.


CONCLUSION: Temp. increases when driving the car fast and reaches up to 1/2, then drops back to 1/3 at low or idle speed.

OBSERVATION: I can still hear a water flow inside the engine when pushing hard on the accelerator and run fast. I don't know what can be done to remove the trapped air inside the engine.

I will leave you with the photos in order...


Temp After 20 MIN of Start:




Temp After 30 MIN of Start:



Temp After 40 MIN of Start:




Temp AT END OF TRIP (1 hour):





10 MIN After Finishing Trip (idle speed with AC On):

[Towncivilian]

See page MA-16 of the factory service manual, steps 5 through 8, to bleed air from the cooling system.