Cooling Advice - RV8 4.6

[garrycol]

I have a Land Rover 101FC and have replaced the standard 3.5 with a 4.6 that does not have a dizzy so the timing cover etc is shorter than the 3.5 and the drive for the water pump is lower on the engine.

This means the the engine driven fan is about 3" further back from the radiator and about 2" lower and about an inch sideways. Looked at making a new shroud but is just too hard so going to electric fans.

A 16" electric fan fits perfectly in the hole of the old shroud so would pull air through the entire radiator rather the usual where the fan is up on the radiator fins. Unfortunately electric fans do not move as much air as engine fans but is still adequate. To improve air flow more I have room to fit two 10" fans at the top outside of the radiator to push air through the top of the radiator.

So my question is - would I need to run all fans at once or say just run the main 16" fan on the fan thermostat and only have the 10" fans cut in when things get hot or even the opposite - run the 10" fans on the thermostat and only have the 16" fan kick in when hot.

The current controller has a variable temp controller but only kicks in at the set temp - it can control two units and to save high power pull at start there is a 10 sec delay before the second one activates. I might try to get a different controller that brings on the second lot of fans at a higher temp.

I am interested in your thoughts on this arrangement.

Garry

[Ian Anderson]

My gut says you should only need the 16 inch fan.

When doing anything more than 20mph the natural flow of air should work. Below that the engine should not be working too hard/generating loads of heat (unless you are doing rock crawling)

Less than that and the engine would be at low rpm so the mechanical fan would move less air than the 16 inch electric one. A decent electric one could be anything up to 3000 cfm and a fairly standard one 2000 cfm

My 2c worth
Ian

[ChrisJC]

I would start with the 16" one and see what happens. Keep an eye on it when the weather is hot, the engine is working and you are only moving very slowly.

Chris.

[garrycol]

Thanks for those comments have helped top focus my thoughts. I have to consider our very high summer temps and being offroad in low range climbing hills at high revs.

I am going to use the 16" fan on the temperature controller as the main fan and keep the 10" pushers on a switch as a reserve.

Thanks

Garry

[Ian Anderson]

Did you have cooling problems with the 3.5?

If so is your radiator up to the job with good clear water passage?

If you have more space between engine and rad, could you fit a deeper/thicker rad?

Ian

[garrycol]

Hi Ian - radiator is fine - is is just a matter of getting enough air through it with the new arrangement of the 4.6.

[Ian Anderson]

Presumably plenty space for the air to get out the engine bay

[ChrisJC]

Yes, I was thinking of UK weather!!

If I lived where you do, I would throw absolutely everything at it, and have an overtemp alarm as well.

Chris.

[garrycol]

Yes, I was thinking of UK weather!!

If I lived where you do, I would throw absolutely everything at it, and have an overtemp alarm as well.

Chris.

I have what is called a TM4 Combo waterwatch system. It is a combined low coolant level alarm, temp display alarm - the temp alarm side of it does not measure coolant temp but the metal temp of the block so a more realistic reading. Once the engine is warm the readout stays relatively stable while on the coolant temp gauge it can go up and down a bit as the thermostat opens and closes - so I have a very good indication of what is going on with the cooling system.

Ian - yes plenty of airflow out of the engine area.

[SuperV8]

What thermostat are you using?
The standard 4.6 had a separate 'cows udder' remote stat in the lower radiator hose. These have a fairly high temperature open set point. The benefit of these is they block off the bypass circuit when open so all your flow goes through the rad.
I'm using a variation of this used on other landrovers - I think Disco - and there are various temp versions - mine is 82. This is also a pressure relieving thermostat so open with temperature (sensed from the bypass circuit) or pressure.
Also how is your heater circuit plumbed? as this can rob coolant flow from going through your radiator.

[garrycol]

I don't have the cows udder system - just the standard old 3.5 thermostat housing system - I think I have the 82 degree thermostat - I reiterate that the basic cooling system is fine - just wanting to change from the engine driven fan.

Cheers

Garry

[SuperV8]

I don't have the cows udder system - just the standard old 3.5 thermostat housing system - I think I have the 82 degree thermostat - I reiterate that the basic cooling system is fine - just wanting to change from the engine driven fan.

Cheers

Garry

Noted.
ONLY regarding fans then; the old Viscous fan from Rangerover classic was 17", the P38 had grown to 18" now all 'large/proper' landrover's have 500mm fans (19 1/2") from the Rangerover L322 and newer. Including the latest Defender/Disco 5.
Interestingly Landrover are still using engine driven fans - through an electrically controlled coupling. You have to look at their small cars - freelander and Evoque to find an electric powered engine fan.
The reason is simply engine driven fans can move much more air as they are not limited by a small electric motor power.

Compared to your 16" electric and your worst case (hot) climate conditions. I would 'feeling' is an 16" electric fan might be marginal - but it really depends on your usage as well, will you be pottering around locally or maxing out the vehicle's weight and towing a trailer in 40degrees?

Also to note not all 16" electric fans are equal - a SPAL may work ok but a cheap ebay no brand 16"er may not?

Can you just move your radiator a couple inches so the cowl lines up? obviously need a P38 fan as the water pump rotates the opposite way to the earlier engine.

[garrycol]

Thanks you make very good points about the 16" fan - that is why there are also additional 10" fans as well, so I think with all going at full blast I will have enough air going through the radiator. I have a V12 Jag that runs two 12" fans as standard and even in bumper to bumper traffic on hot days they are able to provide more than adequate cooling so the system I have should work - I hope.

You are correct about the 4.6 engine driven fan being quite large - hence 3 electric fans to replace it. Anything is possible as far as moving the radiator but its position is not the issue and it would be a pain to move it with no gain - the 4.6 has the fan in a different position to the 3.5 - the fan is lower and offset closer to the passenger side so I would have to build a completely new shroud from scratch - just too much trouble. Hence using the original 3.5 shroud with the 16" electric fan attached to it in the same basic position the old 3.5 engine driven fan would be with the two other 10" fans pushing from the front.

I haven't measured it yet - but I suspect that with the electric fans and shroud in place - the original engine driven fan might still fit to help suck air into the engine compartment and still help suck air through the radiator - I would only consider this if the electric fans do not cope.

Appreciate the comments.

Garry

[SuperV8]

My supercharged 4.6 only has a small 12" fan - and no oil cooler - and this works fine for me - though my car only weights 700kg so I just don't get the opportunity to put large amounts of heat into the cooling system at slow speeds. Also its rare to see 30deg days here. Completely different use case to a 2+tonne 101 truck used in Australia!

The 4.6 serpentine water pump turns the opposite way (driven of the back of the belt) to the 'V' belt water pump so you wouldn't be able to use your old 3.5 fan.
My thinking was moving the radiator an inch or two so you would just bolt the standard shroud to it - aligning the shroud up with the new water pump location.

If you already have the electric fans, wack them on and give it a go. I would use two thermo switches at different temp set points - so the additional fans only come on at a higher set point if the main fan can't cope.

[Ian Anderson]

In the GT40 it has twin 11 inch high capacity fans. They were turned on by a thermostatic switch and two relays as current draw was high. On a hot day like 40 degrees going to Le Mans and stuck in a jam in Rouen, the fans would cycle on and off, but I noticed my temp gauge would climb a bit. So as I also had an override switch I ran them permanently ans the engine temp stayed normal

Of course there was 7 foot of pipe engine to rad and another 7 foot rad to engine.so a lot more distance than a landrover

Temp gauge sensor was in manifold, the radiator switch at the radiator exit.

Yes you want to set the rad fan to come on based on the temp of the water leaving the rad, after all the thermostat may be sending 82 degree water out but with the fan running you may get 50 degrees being returned and if sensing the radiator input temp you have no idea if the radiator and fan is doing it’s job.

We found that the Ford parts bin did a number of thermostatic switches with different temperature on and off points.

Ian