Engine overheating issues during offroading

[Thomas Varghese]

Dear All,

From the start of the summer season I have experienced engine over heating issues in my X. I have experimented various ways to over come the same and spend lot of time and money to solve it. For the beginning I flushed the cooling system and cleaned it. No use.  I changed all the pipes, coolant. Didn't help. Changed the radiator and the fan clutch. Result was same. Fixed additional electric fans, the over heating issue remained. I was at my wits end and had almost decided to pull out from offroading altogether during summer. It was going to be a tough decision as I don't want my car to suffer at my off roading. Whatever time I do off roading whether its early morning or afternoon or night some sort of overheating issue remained. Did more and more research on various X forums and found out there is a solution which has been overlooked by so many mechanics. The fan clutch supplied by Nissan or for that matter any other manufacturer can cater only for general use and if manufactured in America it is calibrated keeping the colder climate into consideration. It cannot be used in hot demanding conditions as it comes in stock condition or for vehicles which tow heavy loads or for offroading. The additional electric fan which I fixed in front of my radiator was actually aggravating the cooling as it disrupts the air flow when the main fan is running. That additional fan only aids cooling when the vehicle is at a stationary position when the main radiator fan slows down or stops. 400 AED and time spend sourcing the fan and fixing it went in waste. 1 day I forgot to switch off that fan and was stranded as it drained my new battery. The overheating even took a toll on me as the ECM cuts off the AC when the engine gets overheated and imagine running in the desert now without an AC. I was feeling exhausted and delirious. 

EUREKA. I found out that the stock fan clutch can be enhanced by adding little more silicone fluid inside the reservoir. I decided to give it one last try or give up summer offroading altogether. Bought 2 tubes of Toyota LC fan clutch silicone oil rated at 10001 CTS and opened the fan clutch and poured into it. Each tube is 18ml and costs 20 AED in a local AC spare parts store. The car runs 10 degree cooler and takes little more time to reach operating temperature but the guage needle is only half way through from C to the 2nd level whereas it was over the 2nd bar when running on tarmac till now. Wow. Now my AC runs cooler than before, cools at even idling but there is a sound of the fan running even at idling speed. I don't care as I have a good audio system installed. The fan is tighter than before when the engine is stopped and engages much faster so that engine starts to cool early. I believe as the fan engages much earlier it engages the water pump which in turn circulates the coolant even more efficiently. Maybe I could do with just 1 tube of silicone oil instead of 2 to eliminate the fan engaging sound. Another thing I noticed is that the engine oil pressure guage runs more higher than it was previous. I suppose this has enhanced the oil circulation inside. No idea what is the connection between fan clutch and engine oil circulation. 

[Thomas Varghese]

[Chaitanya D]

Interesting @Thomas Varghese.

Share more pictures of how you did it?

 

[Lakshmi Narasimhan]

11 hours ago, Thomas Varghese said:

Dear All,

From the start of the summer season I have experienced engine over heating issues in my X. I have experimented various ways to over come the same and spend lot of time and money to solve it. For the beginning I flushed the cooling system and cleaned it. No use.  I changed all the pipes, coolant. Didn't help. Changed the radiator and the fan clutch. Result was same. Fixed additional electric fans, the over heating issue remained. I was at my wits end and had almost decided to pull out from offroading altogether during summer. It was going to be a tough decision as I don't want my car to suffer at my off roading. Whatever time I do off roading whether its early morning or afternoon or night some sort of overheating issue remained. Did more and more research on various X forums and found out there is a solution which has been overlooked by so many mechanics. The fan clutch supplied by Nissan or for that matter any other manufacturer can cater only for general use and if manufactured in America it is calibrated keeping the colder climate into consideration. It cannot be used in hot demanding conditions as it comes in stock condition or for vehicles which tow heavy loads or for offroading. The additional electric fan which I fixed in front of my radiator was actually aggravating the cooling as it disrupts the air flow when the main fan is running. That additional fan only aids cooling when the vehicle is at a stationary position when the main radiator fan slows down or stops. 400 AED and time spend sourcing the fan and fixing it went in waste. 1 day I forgot to switch off that fan and was stranded as it drained my new battery. The overheating even took a toll on me as the ECM cuts off the AC when the engine gets overheated and imagine running in the desert now without an AC. I was feeling exhausted and delirious. 

EUREKA. I found out that the stock fan clutch can be enhanced by adding little more silicone fluid inside the reservoir. I decided to give it one last try or give up summer offroading altogether. Bought 2 tubes of Toyota LC fan clutch silicone oil rated at 10001 CTS and opened the fan clutch and poured into it. Each tube is 18ml and costs 20 AED in a local AC spare parts store. The car runs 10 degree cooler and takes little more time to reach operating temperature but the guage needle is only half way through from C to the 2nd level whereas it was over the 2nd bar when running on tarmac till now. Wow. Now my AC runs cooler than before, cools at even idling but there is a sound of the fan running even at idling speed. I don't care as I have a good audio system installed. The fan is tighter than before when the engine is stopped and engages much faster so that engine starts to cool early. I believe as the fan engages much earlier it engages the water pump which in turn circulates the coolant even more efficiently. Maybe I could do with just 1 tube of silicone oil instead of 2 to eliminate the fan engaging sound. Another thing I noticed is that the engine oil pressure guage runs more higher than it was previous. I suppose this has enhanced the oil circulation inside. No idea what is the connection between fan clutch and engine oil circulation. 

Great. Try to observe performance continuously for some time!!!

[Thomas Varghese]

Its simple @Chaitanya D. Remove the fan clutch from the engine. Separate the fan clutch and the fan. The fan clutch is made of 2 circular parts secured with 4 or 5 screws. Unscrew them and tap on them to separate it. Before you do this make sure you mark the 2 pieces so that when you assemble them together the grooves inside align. There is a small wedge inside a groove in one of the circular ring and make sure you don't lose it when splitting them. Pour the silicone oil purchased previously from the AC spare part shop and reassemble making sure the outer O ring is perfectly placed and not pinched. Re fix the fan to the clutch and reinstall this assembly to the engine. The silicone oil is made by Toyota for LC and is 18ml in a tube. Grade you get here is 10001 cts which costs 20 AED. It would have been better if you get the lighter 7000 CTS grade but is not available anywhere. 

The principle behind this is the viscous fan clutch is actually a torque convertor you find inside your ATS gear box. There is a bi metallic strip which controls the opening and closing of the valve which holds the viscous fluid inside a reservoir. The valve opens when the bimetallic strip reaches the pre set temperature and releases the fluid into the grooves of the fan which then locks up both parts as a clutch. The fan then starts to rotate. Unfortunately the cars manufactured in America is calibrated to engage the clutch at a higher temperature to reach the optimal operating temperature of the engine faster as they have cold climate. So the fan doesn't engage for sometime as cold air is anyways flowing over the radiator. The scenario in middle east is different and its very hot climate. Its more aggravated when we take our cars to the desert. We cannot calibrate the bi metallic strip. Its pre set. The only thing we can do is increase the volume of the oil inside the clutch so that the grooves get filled up faster and lock up the fan. After this mod I think I put one tube more as the fan engages much early. Should have tried with 1 tube and then increased gradually if not satisfactory after a drive. I am not very unhappy too as my car cools even when idling as the fan gets engaged fast but the fan roar is something you have to live with when it engages. The increase of the fluid makes the fan's ratio to the pully also more and it runs faster. As I understand the max rotation of the fan with a fan clutch is not equal to the rotation of the water pump and probably fixed at 70 to 80%. In this scenario it almost reaches to 90% of the water pump's rotation. I suppose this is what makes the fan to roar. Its not always but you notice it while idling and accelerating. I have a good audio system and it doesn't bother me much. 

All this info I got from X forums prevalent in Australia as they have similar issues of overheating as theirs is a hot climate in the desert similar to Middle East.

[Chinthaka Ruwan]

6 hours ago, Thomas Varghese said:

I'm so surprised to see that you have done more than 600000kM on your X.  👌

[Thomas Varghese]

Take good care of your car and it will run for ever

[Gaurav]

7 hours ago, Thomas Varghese said:

As I understand the max rotation of the fan with a fan clutch is not equal to the rotation of the water pump and probably fixed at 70 to 80%. In this scenario it almost reaches to 90% of the water pump's rotation.

Viscose clutch fan doesn't work like a PWM controller to operate fan at variable speeds.

To best of my knowledge they either fully engage the clutch (100% crank pulley speed) or not (40-50-60% depending on manufacture design). They might take few seconds to engage and disengage from 50-100% same way thermostat open and close in slow motion. BUT once engine bay temp hits the set degree required, they remain open.

Water pump is mostly running 1:1 irrespective of the fan clutch engage or not as pulley and belts move at same rate without any interaction with silicon fluid inside the viscose clutch. You can switch to smaller "Water Pump Pulley" if you want faster flow.

If you hear fan more now, that means your old clutch must be dead and congrats you have serviced it in low cost, as these viscose clutch are close to thousand dirham (at least for my Pajero). And sadly, most mechanic here never recommend doing such silicone top-up service, that is very famous abroad.

For most off-road cars that tend to overheat borderline, switching to direct clutch fan is the first good remedy here in UAE if you wish to off-road during summer.

Many years back I waited for this first step as many brainwashed me over fan noise, fuel mileage drop, loss of hp, and operating temp will take long time to reach ideal temp. Sadly all of these claims were either bogus, or not applicable here in UAE.

I am running direct clutch since last 5 years and didn't felt the loss of 1 or 2 hp over 225 ponies (must be lot more with AT tires), and didn't felt 0.5L/100 fuel mileage drop as we burn more rich fuel at 6K on long climbs.

If you drive this more on highway, you can keep a two set of clutch. Buy another from scrap and give it to turning shop to put two bolts across and seal it. Don't do single bolt as many lazy mechanic does, as it will result in irritating rattle.

Use the direct clutch in summer and switch to OEM one in winter. Easy 50-100 dhs solution for more cooling.

[GauravSoni]

More info can be found on this link!

 

[Zed]

8 hours ago, Thomas Varghese said:

All this info I got from X forums prevalent in Australia as they have similar issues of overheating as theirs is a hot climate in the desert similar to Middle East.

Great job finding the solution @Thomas Varghese, however the engineer in me is curious for the "climate" reason 😁:

1. You have a Thermal-type Fan Clutch: there is a spring that's when heated between 70C-100 Celsius, it opens up the valve and releasing the silicone fluid that allows the Real Fan to engage and cool your engine.  

2. The temperature that triggers the spring in the bi-metal fan clutch is the temperature at clutch's face. So if engine is already overheating + middle-east weather of 50 C, this should actually make the fan clutch engage faster 😊

3. You have fixed the issue by re-filling the silicone fluid, which _may_ indicate that there was already a Leaking Silicone Fluid issue. This would explain point #1 & #2 above where the extreme hot weather + engine overheat actually triggers the spring in the bi-metal, but because there was not enough silicone fluid, the fan did not engage (or engage some time later slowly).

4. Since your XTerra is 2008, has your fan clutch been replaced during its 13-years tenure? This would also prevent future mechanical failure of the clutch + spring issue + valve stuck in open/closed state which cannot be fixed by just re-filling silicone fluid. Granted, it's a AED 450 OEM replacement (Part Number 21082-EA200) . Or a cheaper but Heavy-Duty Hayden's 6601 

But glad you solved the issue and brought interest to the fan-clutch-supposed-to-engage-fan-at-certain-temperature thingy 😊