Engine overheating issues during offroading

[Thomas Varghese]

20 minutes ago, Zed said:

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 😊

I replaced the fan clutch with a new one just 2 weeks ago. The thermostat valve was eliminated at the same time and coolant is now free flowing into the engine. When I removed the fan clutch to refill the silicone oil the reservoir took in additional 2 tubes of 18ml to become full. As its a new fan clutch and after thorough inspection no leak was found. My older fan which was replaced 1 year ago was found with a leak and that is why new fan clutch was bought. 

Edited June 15, 2021 by Thomas Varghese

[Zed]

Awesome @Thomas Varghese! So it's a new fan clutch but for some reason was not in "full-tank" mode 😂 Glad it wasn't because of a leak... as an owner of 2002 LC, I also replace old parts and hope it will last for another 10 years 😅 Another question: any specific reason why you install the SPAL fans in front of radiator (Pusher) type? This does block air flow and that's why most recommend behind radiator (Puller), _unless_ space is an issue ☺️

[Thomas Varghese]

Ohh I forgot to mention. The 1st tester of this technique was @Shaaz Sha. We discussed this problem of over heating and the probable solution of filling up with silicone fluid was suggested by our regular mechanic in Ajman. @Shaaz Sha promptly tested it day before yesterday and found his engine temperature maintained at manageable levels and promptly reported to me. I did the same yesterday and found it worked for me too. Everything is good except for the fan rrrrooooaaaaaarrrr when you accelerate. @Shaaz Sha also complained about the roar but its still ok if we can offroad with AC blasted on without overheating issues. 

7 minutes ago, Zed said:

Awesome @Thomas Varghese! So it's a new fan clutch but for some reason was not in "full-tank" mode 😂 Glad it wasn't because of a leak... as an owner of 2002 LC, I also replace old parts and hope it will last for another 10 years 😅 Another question: any specific reason why you install the SPAL fans in front of radiator (Pusher) type? This does block air flow and that's why most recommend behind radiator (Puller), _unless_ space is an issue ☺️

I fixed additional fans for solving overheating issue as it seems these fans are bought by everybody and installed. The fans are sold like hot cakes from the shops as outside temp rises. As you correctly said these fans block air flow and it actually only helped when the car was in idle by aiding the AC to cool whereas the AC was cut off during this idling time. If you run these fans during running time it tends to increase the temp guage and I suspect these fans disrupt the air flow to the main radiator fan. By the way @Shaaz Sha's fan clutch also took 2 tubes of silicone fluid to become full. Its also a relatively new fan clutch. I suspect the manufacturer doesn't fill up the reservoir completely for some reason known to them. 

Edited June 15, 2021 by Thomas Varghese

[Thomas Varghese]

2 hours ago, Gaurav said:

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.

Thank you @Gaurav. Enjoyed your technical views on the fan clutch. I have 1 doubt if you may please clarify. The fan was not making the roar in OEM silicone fluid level and was keeping the engine cool on tarmac. As per mechanics explained by you and various other forums the reservoir should be full. It was not the case with 2 fan clutches we experimented with. Both are relatively new. When we topped up the reservoir with additional fluid the temperature dropped. The fan roars when we accelerate and the sound wanes away soon after. If by theory the fan clutch only operates at constant speed then why does it roar when topped up? The roar is caused by increase in air suction which is the result of increased speed of the fan clutch. If not it should roar everytime the fan clutch engages.  

[Gaurav]

20 minutes ago, Thomas Varghese said:

As per mechanics explained by you and various other forums the reservoir should be full.

I never commented anything on the "level" of silicone fluid.

On call too I mentioned that if any traces of leak is there then topping up silicone fluid can service the clutch.

Now level is another issue that can only be answered by Nissan engineers who knows why they are keeping fluid level so low, probably that depends on when clutch should engage vs not - just my educated guesswork here.

[Thomas Varghese]

1 minute ago, Gaurav said:

I never commented anything on the "level" of silicone fluid.

On call too I mentioned that if any traces of leak is there then topping up silicone fluid can service the clutch.

Now level is another issue that can only be answered by Nissan engineers who knows why they are keeping fluid level so low, probably that depends on when clutch should engage vs not - just my educated guesswork here.

Absolutely correct. There must be a reason from Nissan engineers why they don't fill up the reservoir. This can only be answered by them. We are novices and learning from experimenting. 

[Thomas Varghese]

UPDATE. We experimented on last IM drive with @Ale Vallecchi and the temperatures were kept normal which shows our technique worked. Bonus point was we could drive all the time with AC on with good cooling in the desert heat.  

[Ahab Shamaa]

Hey @Thomas Varghese,

What’s your phone number? i have a friend with an XTerra who’s having overheating issues as well…

Oh, and thanks for the cool picture you took of my car on our last drive. It is now my profile picture 😀

Edited June 19, 2021 by Ahab Shamaa

[Thomas Varghese]

0552690503

[Ahab Shamaa]

 @Thomas Varghese 🙏🏻🙏🏻🙏🏻