high temp maverick

[andrewk]

Much better to test the sender in situ under conditions most similar to its normal environment

In the workshop manual for my Y61 Patrol, it says that the resistance of the temperature sensor should be 170-210 ohms at 60degC and 47-53 ohms at 100degC.

Now, perhaps you can explain to me how to measure those temperatures accurately with the sender in situ? Better still, tell me how you can even get the water temperature to and keep it at 60degC or 100degC in situ, so that you can measure the resistance. If you run it up to the temperature at which the thermostat opens (82degC) then all you know is that the resistance should be somewhere between the 47ohms and 210 ohms - but where exactly? Thermistors are not linear devices.

Dangling it in a pan of hot water is practical and works well -- and you can tell for sure whether the sensor is within spec or out of spec.

Cheers
Andrew

 

[jkata]

you dont need to get the water to 100 degrees.

If the sender is at fault it will be pretty obvious when you get the meter on it, as I said, been there done it.

You may also find, if it is an older engine and the sender has never been removed you will really struggle to get the sender out without breaking it.

 

[Deleted Member S]

Good option to see if the fan is kicking in- when it gets hot stop straight away and have a look under the bonnet.

That won't make any difference as the fan always turns :roll: On start up you will often hear the fan rawing away for a little bit & on the road mine often kicks in whilst going up long drawn out hills & you can hear rawing away & you will often notice a drop in performance until the fan has done it's job :roll:

 

[Jocky]

Good option to see if the fan is kicking in- when it gets hot stop straight away and have a look under the bonnet.

You can stop and check, but on a T2 you can hear it roaring, just like electric fan starting. First time I heard mine kick I thought I had a problem as I hadn't heard it before. I also now it wasn't working when temp shot up when towing caravan. Never kicked in unless I was towing as temp never got that high.

:smile:

 

[Jocky]

Some of you guys are confusing the hell out of me.

My understanding of viscous fans is that they behave exactly like fixed pulley driven fans, except that they are supposed to slip at high engine revs due to the viscous coupling and hence reduce the overcooling that would occur with a fixed fan and also, to some extent, reduce the amount of engine power consumed by the fan. I've no idea what you mean by the fan "kicking in" - they run all of the time that the engine is running. The amount of power consumed by a fan increases as the cube of fan speed. As the engine speed increases, there comes a point when the fluid coupling will not transmit enough power to further increase the fan speed - whereas, a fixed fan would just be driven faster, consume more power and overcool the radiator/engine.

If/when viscous fans fail, I think the car will overheat when stationary or at low speeds. As a rule, engines do not need fans at all for 95% of the time and definitely not when running at speed - so the behaviour of the fan is irrelevant in this case. If you stop the engine, you'll be able to rotate the fan by hand whatever the engine temperature. This is just normal behaviour.


Cheers
Andrew

What we mean is the fan engages and turns at the same speed as the pulley it is connected to . Just the same as a fixed fan.

Viscous fans were originally fitted to reduce drag and hence reduce fuel consumption. The fan spins when the engine is cold because the oil in the coupling is thick and it drags the fan. The coupling fully engages when a certain temp is reached, the same as an electric fan starting.
It has got nothing to do with the speed of the engine. I think they are controlled by a bi-metalic spring, similar to an old automatic choke. Metal expands and contracts due to temperature changes.

If the engine temp rises the fan engages to cool the rad.

:smile: A fixed fan will not overcool the engine as the thermostat would close as the temp dropped stopping water going into the rad.

A viscous fans or electic fans are only fitted to reduce drag and save fuel. The problems only happen when they don't start, just the same as when the themosat didn't open, no cooling high temps.

 

[ronypony]

I think you got your wires crossed there Gego m8...your explaination is incorrect...consider this ...

Your vehicle has a 'large radiator' at the front of the car...its full of water which circulates around waterways in your engine to cool the metal parts down ...cos they gets hot when engine is running....when you are bombing along the road cool air passes through your radiator fins ..this cools the hot water passing through the radiator ..the water pump then recirculates the cooled water to the engine to continue its cooling effect on the engine.
If you are stationary or moving slowly then air will not be passing through the rad cooling the hot water down...this is when you need a fan..the fan provides moving air to cool the hot water down. Viscous fans do not 'kick in' as an electric fan does. The viscous coupling of the fan acts as a 'clutch'..When the temp of the engine begins to rise (stationary or moving slowly) the fan is engaged...when the engine is cold or cool (bombing along the road) the viscous clutch 'slips' i.e. is not engaged cos no cooling effect from the fan is required.

 

[Jocky]

I agree what you are saying, but when you are towing a caravan up a hill with the engine under more load and there is air flowing through your radiator the temperature will still increase. If the fan doesn't engage your temps will still rise.
Yes if there is no air flowing through the rad when sitting at idle the temp will increase and the fan will engage, but it will take a long time to get to that stage at idle if the rest of the cooling system is working as it should.

You don't need a fixed fan these days because the rad is more effient than they were 20years ago. they have a bigger surface area so the air flowing through them when you are bombing down the road. In other words there are more fins to exchange the heat.

You need a fan to increase the air flow, when the engine is under excess load towing a caravan up a hill. If it doesn't engage (viscous or electric) you will overheat if you continue applying the same load on the cooling system.

So please don't tell me how heat exchangers work, I been working with them all my adult life.

All I'm saying is if the viscous fan is not working you will overheat in certain circumstances like towing. A viscous coupling usually lasts for 60000miles

 

[ronypony]

Sorry m8..didn't mean to cause any offence..its was just that Andrew had posted that he was confused with members suggesting that viscous fans 'kick in'...like electric ones do.

 

[rustic]

A viscous coupling usually lasts for 60000miles

Hi gego, what happens to the viscous coupling when it ages?
Does it fail to engage ie cause over heating?
or does it couple all the time causing excess cooling?
Just wondered, mine has done 83k no problems so far, although I do cover the upper part of the rad in winter for quick warm ups.
Also I still hear it reduce the roaring about 2-300 metres down the road from cold.
best regards, Rustic

 

[Jocky]

ronypony, no offence taken :smile:

rustic they either work or they don't, when it fails it just won't engage when it should. Mines worked till 95K then going across A66 with van on the back it didn't engage and it nearly overheated. Mines normally engaged when temp gauge was about 3 quarters of max. New waterpump with new viscous coupling and all was well.
As I said earlier if its working you do hear and feel when it starts and it cools rather sharpish

The noise you hear when its cold is normal, thats what it sounds like when it is engaged when temp is high, it runs when cold because the oil in the fluid drive is thicker so it drags the fan.

How does it fail with age? well its mechanical and all mechanical things wear out. I got the 60k from my brother in law who is an experienced mechanic.

Just so members know, if the viscous coupling fails you need to change the waterpump as they can't be separated on a T2/Mav.

:smile:

 

[rossco]

Simple question:

If I park up and idle my motor (truck motor) and place a blanket over the front grill and leave it, at what point will I hear any difference in the fan noise and if I don't hear a difference is my viscous fan broken?

Please a simple answer: less than 50 words :wink:

 

[ronypony]

Personally I don't think you would hear any difference in fan noise. If you want to find out if your viscous fan is operating correctly you could try this...you need to be carefull though.

When you start engine from cold the viscous coupling will not be engaged and the fan will not be 'locked'..i.e. it should have little resistance if you were to try to prevent the fan from rotating with a long wooden stick of some description. You should be able to prevent the fan from rotating.

Once the engine has warmed up things should be very different ...might take a while untill you get a high enough engine temp though.
Once a high enough temp has been reached if you try to prevent the fan from rotating with the stick you will find considerable resistance since the viscous coupling will have 'locked' the fan.

If your viscous coupling is not working you will still be able to stop fan rotating.

If you do this test at your own risk use a fairly flimsy wooden stick...one that would break easily under load and not do damage to the fan blades....make sure you know which way the fan rotates so you can bring stick to fan from the side.

Oooooer that must be more than 50 words....sorry