Thread: 300tdi thermo fan

Remember what is important is flow of air through the radiator and intercooler and around the motor to carry away heat. NOT fans for their own sake. The fan with viscous coupling for my 300Tdi Defender has been stored behind seats of extended cab in case needed for all but about 200km of 100,000 over last 7 years. Can be readily screwed on if needed with shroud not there. Have temp sensitive switch on cylinder head through which wire to fuel solenoid on injector pump goes which opens and stops motor if it gets to 105 degrees. And push button bypass in case necessary to run motor for short time to move vehicle or whatever if it does.


I originally removed air conditioner condenser partly to do timing belt and also to replace it with a more appropriate and better installation when I get around to it. Including condenser not going in front of (standard) intercooler, where maximum flow of cool air is important - only radiator. Coarser fins that are probably less efficient when clean but less prone to dust etc blockage. Condenser originally had an electric thermo fan in front of it. Looked largely self defeating to me. Seems often would need switching on just because it is a significant wind obstructer in itself as well as difficult to clean around. Regarding the standard 300 Tdi fan shroud, this to me looks like an aerodynamic abomination regarding air flow through the intercooler. Lots of turbulence but not very high air flow.


I have cut air vent holes on rear of sides of both guards to allow increased airflow. With no shroud, looks like there would be several times the air flow past the left side of the motor compared with standard. This first passes mainly through intercooler, then past hot exhaust manifold etc.


Note that diesels are more thermally efficient than petrol motors and produce less heat out the exhaust and radiator for same power output,
Running without any fan installed, need to remember that if motor is left idling while vehicle stationary for a prolonged period in hot weather, it is likely to get hot and stop. Otherwise air flow is largely proportional to heat generated by motor moving vehicle. I have only put fan on for three short periods in seven years. Once after original radiator header tank split, as they all apparently eventually do, once after radiator blocked with wild oat seeds while driving slowly around paddock. Then once on a hot day with large wind obstructing loads on both tray of vehicle and tandem trailer behind. Think would get away without fan I similar situation after enlarging guard holes since. Also note I still have to get around to doing "tropical mod" in radiator.


I have seen reports by some who have had overheating problems about installing four instead of two row core radiators and /or larger intercoolers. Then if often seems these have had limited effect. Seems to me modifications to allow better airflow through standard ones could often be more effective.


Is desirable to have an overheat warning or engine shutoff device in case motor gets too hot when not running a fan. Seems a worthy consideration if installing electric ones on a vehicle is if possible have them very quickly and easily removable. Then it is relatively easy to do trials with and without. This would show that when vehicle movement creates air flow, in many circumstances when the fan switches on. if it and its mountings were not there obstructing wind, the fan would be necessary much less often in similar con\ditions.

Originally Posted by mox

Remember what is important is flow of air through the radiator and intercooler and around the motor to carry away heat. NOT fans for their own sake. The fan with viscous coupling for my 300Tdi Defender has been stored behind seats of extended cab in case needed for all but about 200km of 100,000 over last 7 years. Can be readily screwed on if needed with shroud not there. Have temp sensitive switch on cylinder head through which wire to fuel solenoid on injector pump goes which opens and stops motor if it gets to 105 degrees. And push button bypass in case necessary to run motor for short time to move vehicle or whatever if it does.


I originally removed air conditioner condenser partly to do timing belt and also to replace it with a more appropriate and better installation when I get around to it. Including condenser not going in front of (standard) intercooler, where maximum flow of cool air is important - only radiator. Coarser fins that are probably less efficient when clean but less prone to dust etc blockage. Condenser originally had an electric thermo fan in front of it. Looked largely self defeating to me. Seems often would need switching on just because it is a significant wind obstructer in itself as well as difficult to clean around. Regarding the standard 300 Tdi fan shroud, this to me looks like an aerodynamic abomination regarding air flow through the intercooler. Lots of turbulence but not very high air flow.


I have cut air vent holes on rear of sides of both guards to allow increased airflow. With no shroud, looks like there would be several times the air flow past the left side of the motor compared with standard. This first passes mainly through intercooler, then past hot exhaust manifold etc.


Note that diesels are more thermally efficient than petrol motors and produce less heat out the exhaust and radiator for same power output,
Running without any fan installed, need to remember that if motor is left idling while vehicle stationary for a prolonged period in hot weather, it is likely to get hot and stop. Otherwise air flow is largely proportional to heat generated by motor moving vehicle. I have only put fan on for three short periods in seven years. Once after original radiator header tank split, as they all apparently eventually do, once after radiator blocked with wild oat seeds while driving slowly around paddock. Then once on a hot day with large wind obstructing loads on both tray of vehicle and tandem trailer behind. Think would get away without fan I similar situation after enlarging guard holes since. Also note I still have to get around to doing "tropical mod" in radiator.


I have seen reports by some who have had overheating problems about installing four instead of two row core radiators and /or larger intercoolers. Then if often seems these have had limited effect. Seems to me modifications to allow better airflow through standard ones could often be more effective.


Is desirable to have an overheat warning or engine shutoff device in case motor gets too hot when not running a fan. Seems a worthy consideration if installing electric ones on a vehicle is if possible have them very quickly and easily removable. Then it is relatively easy to do trials with and without. This would show that when vehicle movement creates air flow, in many circumstances when the fan switches on. if it and its mountings were not there obstructing wind, the fan would be necessary much less often in similar con\ditions.

That's all well and good if the car is doing sufficient speed to create airflow, but what about when it's doing low range crawling, or is in traffic? The only flow it will get then is from fans.
As for bigger radiators, the point is to a; have more volume of coolant to be heated, and b; greater surface area for the airflow to act on for cooling. Once again, the vehicle's forward speed will determine if the airflow is sufficient to do this. At low speed, with the engine under load, it won't be without fans.

Originally Posted by johntins

That's all well and good if the car is doing sufficient speed to create airflow, but what about when it's doing low range crawling, or is in traffic? The only flow it will get then is from fans.
As for bigger radiators, the point is to a; have more volume of coolant to be heated, and b; greater surface area for the airflow to act on for cooling. Once again, the vehicle's forward speed will determine if the airflow is sufficient to do this. At low speed, with the engine under load, it won't be without fans.

And the only ones that roar their guts out at low or no road speed, engine at idle in 40 degrees are thermos.

DL

An example I remember to show that what is needed is adequate cooling air over hot surfaces, especially radiators, not fans for their own sake. In the 1950's an uncle of mine had a Riley sports car. It had one belt which went round the generator (before alternators appeared) and water pump and the other for the radiator fan. He drove it around Melbourne for 8 years without the fan belt on. Before the days of electric thermo fans. Reckoned the only times overheating looked like being a problem was when stuck in traffic jams in hot weather. However problem solved when a clear run ahead. Would quickly cool down while maybe dragging off most other vehicles on the road. Reckons on very hot days he often sailed past cars stopped with bonnets up. Including FJ Holdens - supposedly made for Australian conditions. Around that time he also owned one for a while before selling it in disgust and has never had another Holden.


From reports I have seen on this forum, it seems others with Defenders have had significant overheating problems despite lots of fan capacity in some conditions where mine without fan installed would not.


With a good cooling system and minimising wind obstructions, there should be little or no need for a fan except when stationary for long periods or the motor generating a lot of heat driving a heavy load for more than short bursts while wind from slow forward speed is inadequate.

Originally Posted by mox

An example I remember to show that what is needed is adequate cooling air over hot surfaces, especially radiators, not fans for their own sake. In the 1950's an uncle of mine had a Riley sports car. It had one belt which went round the generator (before alternators appeared) and water pump and the other for the radiator fan. He drove it around Melbourne for 8 years without the fan belt on. Before the days of electric thermo fans. Reckoned the only times overheating looked like being a problem was when stuck in traffic jams in hot weather. However problem solved when a clear run ahead. Would quickly cool down while maybe dragging off most other vehicles on the road. Reckons on very hot days he often sailed past cars stopped with bonnets up. Including FJ Holdens - supposedly made for Australian conditions. Around that time he also owned one for a while before selling it in disgust and has never had another Holden.


From reports I have seen on this forum, it seems others with Defenders have had significant overheating problems despite lots of fan capacity in some conditions where mine without fan installed would not.


With a good cooling system and minimising wind obstructions, there should be little or no need for a fan except when stationary for long periods or the motor generating a lot of heat driving a heavy load for more than short bursts while wind from slow forward speed is inadequate.

My father owned a Riley. Also a Daimler DB18. Both cars were slow, understressed and with a large frontal area. Both would overheat if left running when stationary, the Daimler more so. These cars ran absolutely NO accessories. They also had no emission controls foisted on them, and there was a lot of room in the engine compartment. Also, they were light for their size, especially the Riley. Compare that with even a D2 TD5, which is heavy, has to run climate control, has to run hot and reach that temp quickly in order to meet the pollution control of the time, is choked by EGR, has a small frontal area relatively, has to drive all the 4WD gubbins, carry five people and all their stuff and tow 3.5 tonnes, all from an engine the same size as the one in the Riley. It has to be able to do this while crawling up a rocky track, or a muddy bog, or a sand dune, in 40 plus degree heat. It should also be noted that a viscous coupling driven fan is at it's least efficient in those situations.

I wasn't disagreeing; if you can create sufficient airflow then the car should cool. I was merely pointing out that many of our cars will be in situations where that won't happen without the assistance of a fan. Modern engines generate enormous amounts of heat. I drive a 17 litre V8 diesel, mostly carrying around half the weight it's designed for, but I simply cannot stand next to it when fuelling it up after a run; it is too hot. And it has the frontal area of a house.

Originally Posted by 350RRC

And the only ones that roar their guts out at low or no road speed, engine at idle in 40 degrees are thermos.

DL

Dunno about you, but I'd prefer a little noise to a cooked engine.

Originally Posted by mox

Reckons on very hot days he often sailed past cars stopped with bonnets up. Including FJ Holdens - supposedly made for Australian conditions. .

I'm not surprised. The FJ Holden, in fact all Holdens before Commodore, were merely shrunk Chevrolets. GM would have done better bringing the bigger Chev here, but Chiffley wanted "Australia"s Own Car". Beats me why people restore them, they were rubbish when new, so they're sure rubbish now. Gelignite Jack beat them hands down in the Redex. In a Puegot.