[4ePikanini]

My pajero is fairly heavy ion fuel so I'm doing small things to save on fuel economy. All these small things added together may help in fuel consumption. I have already gone down from 20l/100km to 17l/100km by checking spark plug gaps, advancing timing slightly and using high octane unleaded fuel.

My pajero has a 3 row core radiator which I got from dad as part of my rebuild so it cools very well under most circumstances. This makes the viscous fan a bit of a dead weight for the engine to carry and I believe I might shave another 1l/100km off my economy if I can replace it with an electric fan.

Thing is, I already have an electric fan installed that I wired to the A/C compressor clutch engagement feed via a relay, so wiring in the fan to keep blowing if the engine gets too hot is a simple procedure and only involves some wiring and another relay (don't want the compressor cycling on when the fan kicks in).

NOW...........

I have scoured through the workshop manual and there is a A/C temp switch on the thermostat flange that breaks continuity at approximately 112 - 118 degrees celsius......



.......which I can utilise with a 5pin standard automotive relay.



I have checked my thermostat from mitsubishi and it starts opening at 82 celsius ( which might be too cold )



as the manual states 88 degrees - can 6 degrees make a big difference?



So in the end my question is......

How hot is too hot for an engine? What is overheat temperature?

will my engine reach these temps under normal circumstances and if it is, will it be too late to switch the fan on?

[Gerrit Loubser]

Marius, I would be careful about replacing the engine driven fan with an electric one. It certainly would be possible to do this, but to get a setup that is as reliable as the original Mitsu system will not be trivial. I would rather have durability and reliability than a small incremental economy gain.

Also remember that you will need quite a powerful electric fan to be able to rival the air flow capabilities of the engine driven fan. This fan will be expensive and you will need accordingly sized mountings, wiring and relays, which will add to the cost. All this cost would have to be recovered in fuel savings before you get ahead of the factory setup that you already have.

Furthermore, a properly functioning viscous coupling does not lead to great power losses when cruising at part throttle. Under such conditions there is good forced airflow by virtue of the vehicle's motion and the water temperature is moderate, which means that the temperature of the air impinging on the viscous coupling would also be relatively cool. This leads to a reduction in the coupling ratio of the viscous coupling which then allows the fan to freewheel.

When the engine works hard at low speeds, the water temperature rises, which causes the temperature of the air impinging on the viscous hub to increase as well. This causes the viscous coupling to couple the fan more positively and the fan will absorb energy from the engine, but under these conditions an electrical fan would also be energised and would therefore also consume engine power.

[4ePikanini]

I would love to have the viscous but mine isn't working properly so it's robbing power. Replacing is close to a R1000

But my radiator is recored which improves on factory spec and hence the electric fan might be more than adequate.

[4ePikanini]

ok so I have found some thermoswitches.

The idea now is to wire in a manual override control with a thermo switch and status led until I can get a replacement viscous - upon which I will still keep the electric setup as a redundant feature

If the thermostat is rated at 82 degrees celsius, is that the fully open or starting to open, temperature?

what would be a good temp over the rating to switch the fan on given that the switch will be located inside the top rad hose about 20cm away from the thermostat.

[SimonB]

ok so I have found some thermoswitches.

The idea now is to wire in a manual override control with a thermo switch and status led until I can get a replacement viscous - upon which I will still keep the electric setup as a redundant feature

If the thermostat is rated at 82 degrees celsius, is that the fully open or starting to open, temperature?

what would be a good temp over the rating to switch the fan on given that the switch will be located inside the top rad hose about 20cm away from the thermostat.

Marius... I'm inclined to agree with Gerrit - while I do not know the technicalities, the fact that you're speculating somewhat on what temperatures certain actions are to be based, you could be error prone. I don't know if it could prove to be costly if wrong...

Surely you can source a used viscous?

[4ePikanini]

at the moment the viscous is useless IMHO. It never blows hard like I have heard viscous fans blowing. I can come from a long spirited drive and stop at home, let it idle for a few minutes to get it really hot and then I can still stop the fan by hand. Maybe my viscous is fine but the proper coolant and 3 row over engineered radiator is keeping things cool enough.

Ideally I want a new viscous but I feel I can improve on the system and add redundancy by adding an electric fan kick-in when temps climb.

Either way I have a genuine mitsu 88 degree thermostat on order from the stealer at R180 and I have 6 thermo switches on the way from fleabay

- 2x 90 degree
- 2x 95 degree
- 2x 100 degree

They were $1.99 each so I ordered a set for dad as well. the 90 or 95 degree will do the switching for me and the 100 will be the alarm connected to a buzzer.

The viscous replacement will come shortly when my next commission come in.

[4ePikanini]

I was thinking about using a 90 degree switch in the top hose.

Currently I have an electrical fan in front of the radiator pushing air through and get switched by the A/C compressor clutch feed.





So in the meantime I want to remove the viscous, add another fan and wire it in with the A/C pump, thermal switch and override switch located in the dash.

So when I can source (afford ) a new viscous It will just be added in and I'll keep the electric setup as a redundant feature.

the schematic looks complicated but the wiring is actually minimal, easy & cheap to do. I have a relay, wiring and terminals already so it's just the extra fan. It can be even simpler if I remove the status led lights and override switch but I like to know what's happening and have some sort of control.

A cylinder head temp alarm and coolant loss alarm is definitely on my to-do list.

[HBannink]

:shock:Personally I think you are itching where you don't want to scratch
Running at low speed or a relatively short "spirited" drive might not be enough to set the viscous in motion but believe me when you do a high speed run through the karoo during mid day in summer you will wish you had the viscous.

Air has similar properties and behave almost the same as liquid, at low speed the air would tend to be ram driven through the radiator but up the speed and you end up with a bow wave similar to that found when doing a water crossing. Lower density of air needs a bit more speed to get the same effect as water. To get adequate airflow through the radiator you would need a substantial fan to force the air through, this is where the viscous comes in to play.

The viscous coupler works by allowing a thick silicone based oil like substance to flow to the outer part of the housing and drive the fan shaft. A Chanel network allows the oil to return to the center reservoir from where it would be released again. In the front of the fan you would find a bi metal strip that operates a small valve that controls this action so you need the hot air from the radiator to expand this strip sufficiently. It might sound complicated but all it is is an outer housing that mounts on the pulley with a disk inside that is connected to the fan shaft, the small clearance between the disk and housing gets filled with oil and the disk is driven.

With your tropical cored radiator it is quite possible that you do not reach the required temp. under normal driving conditions in which case the viscous does not engage and does not rob engine power. Nothing lost, that is how it was designed.

You can carefully remove the bi metal strip and the pin just below it to replenish the viscous fluid with a syringe, I have had good results with wynns charge as fluid. Yes I was sceptical in mixing a mineral based product with silicone based but in the 3 years that my pajero has run with it I have had no problem. My 7 series bm had it in for 5 years and was sold without any further problem, just my experiences, the guy that taught me this trick has been doing it for many years professionally.

I have been down this road and fitted two electrical kenlowe fans that is just used as backup now, switching is done by a fan switch that was cut in to the thermostat housing and kicks in at 95 with a 19 deg variation. now days it mainly comes on when the vehicle is parked after a good run.

[4ePikanini]

Ideally I want the viscous working as it should.
In the meantime, while I don't have a working viscous, I will use the electric route and down the line the electric will become the backup redundancy.

I like the Wynn's charge idea and will give that a go. Thanks.

If I can recon the viscous and add the fans I will be a happy camper.

[RoelfleRoux]

Marius,

Has your temp gauge given you any reason to suspect that the mechanical fan is not doing the job?

My petrol Pajero has 60 000km on the clock now. During that time the fan has only “kicked in” on three occasions.

· Towing a huge 4-wheel trailer fully loaded with furniture between Barberton and Pretoria on a hot summer’s day – could tell by the massive heat dissipation from under the car at idle at end of trip. I raised a concern on the 4x4 Community at the time, with valuable input from you and others.
· Fighting my trailer through the thick sand between Richtersberg and De Hoop, with the wind and dust overtaking me from behind – could tell by the noise emitting from the dusty fan belt as it took up the load from the fan.
· In the Kruger Park on a 40C day (with interior temp set to 20C), also with a tail wind – could tell by a slight vibration through my feet. We kept the windows closed and stayed in the car. The heat outside was murder!

What I’m trying to say is: I do not think that it will be easy for me to quickly do a test to find out if the coupling kicks in or not. The additional cooling capacity in your radiator will make it even more difficult to do a definitive test on your coupling.

Just a few general observations:
The heat gauge has never moved a millimeter.
The heat extraction ability of that fan (when in anger) is unbelievable. I have never felt an electric fan move so much heat.

You seem adamant to want to go ahead with the project, so I’ll not push any harder. I agree that an electric fan will most probably save you a few drops of petrol and is quiet for 90% of its life.

Some advice (from somebody that has never done a conversion like this) is the following:
1. Make sure you have the correct cowling to match the fan to the radiator.
2. If there is a biggish flat “dead” area in the cowling, cut vents in it and cover with lightweight flexible rubber. That way the air can force it open at speed, but the fan can pull it shut at low speed.
3. Try and get some definitive numbers on the air displacement ability of the existing mechanical fan compared to that of the new electric fan.
4. I suppose an 110kw 3.0V6 generates less heat than an 184kw 3.8V6, so there is a better chance of making the electric fan work on your car.

Good luck and keep us posted.
Roelf