Viscous fan test

tom1979 · Aug 27, 2019

Can anyone confirm how to test the viscous fan?

Just come back from towing our caravan 70 miles (D2 auto) and temps were getting to 114*C

Even with the ac fan running

sierrafery · Aug 27, 2019

If you can stop the blades with a rolled up newspaper with engine at idle and hot radiator the viscous unit is slipping and if the fan is not locked solid then it has no cooling power... the electric fan kicks in anyway if the coolant temp exceeds 110*C , that's how it was conceived

tom1979 · Aug 27, 2019

sierrafery said:
If you can stop the blades with a rolled up newspaper with engine at idle and hot radiator the viscous unit is slipping and if the fan is not locked solid then it has no cooling power... the AC fan kicks in anyway if the coolant temp exceeds 110*C , that's how it was conceived

My AC fan seems to keep blowing fuses but that’s another issue

Even when it did kick in it seemed to make little difference, I ended up wedging a piece of plastic in the relay to keep it on. I suspect the fan could be most likely, if the thermostat was stuck I’d have much bigger problems by now.

I hope it is the viscous fan, that’ll be a nice easy fix.

Thanks @sierrafery

sierrafery · Aug 27, 2019

Do something ASAP cos 92 fuel temp is dangerous but it's the result of the high coolaant temp as it's cooled by the same coolant, 68 IAT is very high as well.... if the electric fan blows the fuse it means it might have a short in the winding and even if it's running it doesnt spin up to the desired rpm so inefficient... that fan is supposed to deliver more than 2500 cfm so a motor at least as strong as the original is needed, those cheap ebay fans are a bad joke they can't push more that 1500 cfm whatsoever, unfortuately those motors are not available in Europe , the cheapest is here https://www.rockauto.com/en/catalog...air+conditioning,a/c+condenser+fan+motor,6920

tom1979 · Aug 27, 2019

Just been looking and the viscous fan was fine but the radiator cold

sierrafery · Aug 27, 2019

Then you have 3 options: thermostat is stuck closed, the rad is clogged or you have an air lock

tom1979 · Aug 28, 2019

sierrafery said:
Then you have 3 options: thermostat is stuck closed, the rad is clogged or you have an air lock

Going to change the thermostat and give it a good bleed and see how it goes. Radiator got hot when I switched the heater to hot

tom1979 · Aug 31, 2019

I changed the thermostat on Thursday night and did very gently filled up the coolant and gave it a good bleed. I don’t know how people lift the header tank as hoses and cables prevent mine lifting. Anyway it seems to be fine now. I actually suspect there was an air lock in the heater matrix as thinking back there was an occasional gurgling noise when accelerating hard. No more hot engine. I can still get it to 105*C if accelerating hard up a long hill but I suspect this is normal. Normal driving around sits around 90-95, although the thermostat is stamped 82*C so thought it would run a bit lower than that?

sierrafery · Aug 31, 2019

tom1979 said:
although the thermostat is stamped 82*C so thought it would run a bit lower than that?

that's the temperature when the thermostat starts to open not when it has full flow... on a long run when it's warm outside the fact that it opens sooner will not be so relevant cos once it got full flow and the ECT gets above 95 no matter if it opened sooner ... that lower opening temp helps for short journeys... fitb a proper D2 thermostat and the temp will go lower IMO

tom1979 · Aug 31, 2019

sierrafery said:
that's the temperature when the thermostat starts to open not when it has full flow... on a long run when it's warm outside the fact that it opens sooner will not be so relevant cos once it got full flow and the ECT gets above 95 no matter if it opened sooner ... that lower opening temp helps for short journeys

I see. Do you think an airlock in the heater would cause a gurgling sound when accelerating? It seems to have disappeared

sierrafery · Aug 31, 2019

An airlock not but air in the system yes though the flow in the matrix won't affect ECT... you should have struggled a bit with the wiring and hose as to be able to lift the tank above the bleed hole otherwise you can't bleed it well whatsoever and air is still trapped in it but maybe in other place

tom1979 · Aug 31, 2019

sierrafery said:
An airlock not but air in the system yes though the flow in the matrix won't affect ECT... you should have struggled a bit with the wiring and hose as to be able to lift the tank above the bleed hole otherwise you can't bleed it well whatsoever and air is still trapped in it but maybe in other place

The way I did it was to very slowly fill the coolant and then run the engine at idle with the coolant cap off and heater on until the temp got up to around 85*C.

sierrafery · Aug 31, 2019

tom1979 said:
The way I did it was to very slowly fill the coolant and then run the engine at idle with the coolant cap off and heater on until the temp got up to around 85*C.

which will not bleed the bypass circuit at all as it opens only above 1500rpm but while your stat is with stroinger spring on the bypass who knows when it opens, at least partially release the bleed screw as to get flow and keep the rpm at let's say 2000 untill no bubbles are coming out then tighten it back

btw, heater on or off it's irrelevant cos there's continuous flow through the matrix, the heater setting is no factor

tom1979 · Aug 31, 2019

sierrafery said:
which will not bleed the bypass circuit at all as it opens only above 1500rpm but while your stat is with stroinger spring on the bypass who knows when it opens, at least partially release the bleed screw as to get flow and keep the rpm at let's say 2000 untill no bubbles are coming out then tighten it back

btw, heater on or off it's irrelevant cos there's continuous flow through the matrix, the heater setting is no factor

....after this I used a piece of wood to hold the revs at around 2500 for 20 minutes

sierrafery · Aug 31, 2019

It should be OK then

tom1979 · Oct 16, 2019

Little update, I couldn't stop the gurgling so decided to whip the head off a couple of weeks ago. Gasket fully intact, the only potential problem I could see was around the 5th cylinder where it looked like the head had been fretting and some minor corrosion around one of the coolant galleries - I suspect perhaps the final 45* stage of the head bolt torqueing process had not been done properly before. So all good there, still the occasional gurgling though despite numerous bleeds!

sierrafery · Oct 16, 2019

The 5'th cylinder is in worst shape in all td5s cos it doersnt have a glow plug and the difference is obvious compared to the other 4 all the time

tom1979 · Oct 16, 2019

sierrafery said:
The 5'th cylinder is in worst shape in all td5s cos it doersnt have a glow plug and the difference is obvious compared to the other 4 all the time

They could have easily had a glow plug there and put the FPR somewhere else, I can't see why it has to be ON the cylinder head

sierrafery · Oct 16, 2019

tom1979 said:
They could have easily had a glow plug there and put the FPR somewhere else, I can't see why it has to be ON the cylinder head

i agree... i think that at the very moment when that was designed those guys were a bit drunk

tom1979 · Oct 24, 2019

Sooo, still getting the gurgling!!!

Is there a better way of bleeding other than what is covered in Rave ?

Also I have noticed that when not towing the coolant temps while driving range from 85-90*C but when towing our caravan (around 1.6 tonne) it can range from 85-105*C, the higher of that range being on hills/acceleration. Is that normal ?

Viscous fan test

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