Jump to content

Viscous fan - is this right ?


Stu2985

Recommended Posts

Quick question - I have a 300 tdi Disco 1 Auto with aircon

when is start it up in the mornings the viscous fan starts up straight away. Is this right that it runs all the time ?

if i have the heater on higher than 2 the temp needle on a icy morning doesnt move in the 5 mile drive to work. If i turn the heater off it then the temp goes up

Does this sound about right ? its the first winter that I have had the vehicle

Link to comment
Share on other sites

Stu,

Can't help directly but I hope this description aids your cause.....

I have a basic Disco (manuall no air con) in which the inside heater starts to get warm at around 1 - 2 miles.

Engine temperature guage starts moving up towards its midway point (from which it rarely wanders under normal conditions!) at around 3 miles even in the ice.

Very pleased and never been different so it should be better.

My blasted viscous fan is whisling around, the same as yours, even at minus 5 degrees which has never made sense to me and was going to fit an electric version (to improve warm up and reduce drag and so increase performance and fuel efficiency) until I read the negativity of doing so from elsewhere on this Forum.

So have not gotten around to do anything yet but then as it does not affect comfort its easy to see why.

I've read this before and I'm not competent enough (newbie) to advise what to do on your truck but there are others that are well qualified and will no doubt pick up the thread.

By straight comparison - something needs doing.

Hope this helps the enquiry on its way.

Paul.

Link to comment
Share on other sites

Take the viscous off for the winter whilst you think about it - unless you do a lot of uphill towing.......

Maybe for the summer a electric fan, i have one and only ever need to switch it on occasionally - they simply don't run that hot as normal.

Link to comment
Share on other sites

Well,

You are asking if the viscous fan should turn all the time.

The 'YES' answer you have got is quite correct, but it doesn't cover the points you should be asking, IF you knew how the fan viscous coupling works.

Check with the bonnet open.

Reach in and flick the fan round by hand, noting how far it goes round for each flick. the coupling should be fairly stiff, and in fact indicates the hot setting.

On an engine left standing overnight, in the morning the fan will ALWAYS turn at high speed, producing much noise and air flow for the first couple of minutes. After that time, the fan will (should) noticeably slow down. Well, you notice the change in sound and airflow, you cannot 'see' the speed difference.

Now stop the engine, reach in and flick the fan round by hand. The fan should spin noticeably more easily than it did a couple of minutes previously. This is the cold setting.

If you get this pattern of operation it's almost certain the fan VC is OK, the only aspect you haven't tested is when the radiator is really hot.

Sometimes the fan VC will fail seized, so this stops the fan changing to it's slow / quiet mode, and overcools the engine.

Sometimes the fan VC will fail by excessive slip when hot, which causes the engine to overheat.

Of course, you may not have anything wrong with the fan VC. The thermostat may be stuck open.

You should now have enough information to fault the system (I'm assuming you already know how to check thermostat operation with it in-situ).

HTH

Link to comment
Share on other sites

Well,

You are asking if the viscous fan should turn all the time.

The 'YES' answer you have got is quite correct, but it doesn't cover the points you should be asking, IF you knew how the fan viscous coupling works.

Check with the bonnet open.

Reach in and flick the fan round by hand, noting how far it goes round for each flick. the coupling should be fairly stiff, and in fact indicates the hot setting.

On an engine left standing overnight, in the morning the fan will ALWAYS turn at high speed, producing much noise and air flow for the first couple of minutes. After that time, the fan will (should) noticeably slow down. Well, you notice the change in sound and airflow, you cannot 'see' the speed difference.

Now stop the engine, reach in and flick the fan round by hand. The fan should spin noticeably more easily than it did a couple of minutes previously. This is the cold setting.

If you get this pattern of operation it's almost certain the fan VC is OK, the only aspect you haven't tested is when the radiator is really hot.

Sometimes the fan VC will fail seized, so this stops the fan changing to it's slow / quiet mode, and overcools the engine.

Sometimes the fan VC will fail by excessive slip when hot, which causes the engine to overheat.

Of course, you may not have anything wrong with the fan VC. The thermostat may be stuck open.

You should now have enough information to fault the system (I'm assuming you already know how to check thermostat operation with it in-situ).

HTH

thanx for the replies

I am not sure how to test the stat still in-situ. I only know how to test by removing it and dropping it in boiling water

When I tried turning the fan before starting it up after sitting all day it was quite stiff to push - ie can push it with fingers but wont freely spin and had some resistence to it. So when the engine has run for a few mins the fan should be able to move around a lot easier by pushing it ?

If you could tell me how to do the stat I will give it a shot at the weekend.

Link to comment
Share on other sites

So when the engine has run for a few mins the fan should be able to move around a lot easier by pushing it ?
Yes.
If you could tell me how to do the stat I will give it a shot at the weekend.
This assumes the thermostat is at the engine end of the top hose, and that the coolant flows through the thermostat, then the top hose, then the radiator. This configuration is so common it's almost standard, but there are variations. The BMW diesel engine has the thermostat at the engine end of the bottom hose, so the coolant flows through the radiator before it flows through the thermostat.

Back to the 'standard'.

Start the engine from cold. Constantly monitor the temperature of the top hose with your fingers. The hose should remain cold, if it gradually gets warmer and warmer it's likely the thermostat is open, partially or fully doesn't really matter. Slightly open is enough to mess things up, especially in a diesel.

What should happen is that SUDDENLY the top of the hose gets very hot, especially at the engine end, while the underneath of the hose is still cool. Naturally it doesn't take long for the temperature to equalise all around the hose. It is the SUDDEN change from cool to hot, with a significant change in temperature, that indicates the thermostat WAS fully closed, and then opens.

If the top of the radiator is metal, you can monitor the top of the radiator where the hose is attached, rather than the hose. The advantage of this is that the rubber hose insulates the radiator from the engine. Although heat is conducted along the hose the rate is so slow that you cannot be mislead by heat conduction through the structure (metal and rubber).

Again, the test point of the radiator will be cold, until the thermostat opens, when it rapidly becomes finger burning hot.

This RAPID change is why I wrote CONSTANTLY monitor the temperature. If you don't keep a close check you won't spot the change point.

HTH.

Link to comment
Share on other sites

  • 2 weeks later...

My wife's 'new' Tdi300 was slow to warm up heater & engine-wise, had a seized viscous fan (taken off imediately the piece of crâp!!) so I put in a new thermostat costing £3.50+vat.

The difference is "night & day" !!! Now the heater starts putting out warmed air within a couple of mins and the engine is warmed up within 2-3 mls.

Makes all the difference in this cold weather.

Took 5-10 mins and no intelligence to do :i-m_so_happy:

Cheers all, Merry Christmas & a very Happy, Healthy and Safe New Year

Dave

Link to comment
Share on other sites

My wife's 'new' Tdi300 was slow to warm up heater & engine-wise, had a seized viscous fan (taken off imediately the piece of crâp!!) so I put in a new thermostat costing £3.50+vat.

The difference is "night & day" !!! Now the heater starts putting out warmed air within a couple of mins and the engine is warmed up within 2-3 mls.

Makes all the difference in this cold weather.

Does that mean to say that all 3 of your Discos are Viscous-less?

How do they all do during the summer (?!), towing, long journeys and traffic jams?

I'm poised to remove mine but only during winter and then nervously!!

Link to comment
Share on other sites

Does that mean to say that all 3 of your Discos are Viscous-less?

How do they all do during the summer (?!), towing, long journeys and traffic jams?

I'm poised to remove mine but only during winter and then nervously!!

Hi PaulN, I'll answer your question car by car if I may.

Disco TDi 200 '93 manual - had the fan off for 3yrs, winter and summer, solo and towing - NEVER any temperature problems, NOW SOLD;

Disco TDi 300 auto - fan off for 1 yr, winter and summer, throughout the Morocco trip up to 38°c, solo and towing - NEVER any temp problems

Disco TDi 300 manual - recently purchased, immediately removed fan, achieves normal temps quicker with less noise - NO temp problems.

I believe in doing this as long as you take the responsibilty of keeping a very regular eye on the header tank coolant levels. Never had any problems, but I check every two or three days - why wouldn't you it takes 20 secs??

Cheers

Dave

Link to comment
Share on other sites

Hi PaulN, I'll answer your question car by car if I may.

Disco TDi 200 '93 manual - had the fan off for 3yrs, winter and summer, solo and towing - NEVER any temperature problems, NOW SOLD;

Disco TDi 300 auto - fan off for 1 yr, winter and summer, throughout the Morocco trip up to 38°c, solo and towing - NEVER any temp problems

Disco TDi 300 manual - recently purchased, immediately removed fan, achieves normal temps quicker with less noise - NO temp problems.

I believe in doing this as long as you take the responsibilty of keeping a very regular eye on the header tank coolant levels. Never had any problems, but I check every two or three days - why wouldn't you it takes 20 secs??

Cheers

Dave

When you remove the fan do you just simply unbolt the fan or remove the belts and assemblies etc

Could you please explain what is exactly is involved in removing it for a 300tdi auto with aircon

Link to comment
Share on other sites

The temperature gauge should read just above halfway up.

Take the viscous fan off and fit a new thermostat-a genuine LR one.

In theory, fan or no fan the warm up time of the engine will be the same.

The stat does all the work to set the engine temp.

The engine warm-up time will increase with the interior heaters on.

There is one minor risk of no fan fitted & that at slow road speed under load. There is a risk of overheating. All be it small.

The advantage of removing the fan, as stated by a member above, is the fuel saving & a bit more power.

Personally, I like the fan there, just incase I get stuck & don't want the risk on overheating.

A few pence of fuel each week is a small price against the cost of a head gasket job. . . . .

Your choice.

Link to comment
Share on other sites

I take the fan off all my Discos imediately after purchase, just like new oils, new filters, De-EGR - it's just part of the std initial service and checkover package.

They always stay in the boot however, just in case I'm ever caught in slow-moving traffic for extended periods. Takes about 30secs to put it back on.

Cheers

Dave

Link to comment
Share on other sites

I would think so as they have a higher reving all alloy engine which the diesel is not.

So just unbolting the fan will not only help warm up faster but will also help slightly with fuel consumption and possibly slightly increase power or do you need to do furthur mods to get teh benefit of fuel and power ?

Link to comment
Share on other sites

So just unbolting the fan will not only help warm up faster but will also help slightly with fuel consumption and possibly slightly increase power or do you need to do furthur mods to get teh benefit of fuel and power ?

That alone will slightly increase power and consumption. The fan creates a dit of drag and restricts rotation of the engine slightly. Anything that takes its drive from the engine will have a similar effect. e.g. air con, power steering, water pump etc. Obviously you wouldn't want to do without the latter 2 though. ;-)

Link to comment
Share on other sites

One thing you must remember when you say that your engine 'never overheats' with the viscous fan removed is that the standard LR gauges LIE. The Defender 300Tdi gauge reads 'in the middle' from 40°C to 110°C! The Disco gauge is probably no better, they are designed to do this. The Defender TD5 gauge is the same, even though made by VDO. If you have a Nanocom you can monitor the TD5 temp, as the ECU knows exactly what the temp is.

The problem is that you can be driving along thinking everything is ok, and yet you can be dangerously close to overheating your engine. I live in a mostly hot country, and thought to remove my viscous during the winter months especially as my VDO gauge was not showing much above 80°C on my short trips to work and back, no motorway use or traffic either. Then one evening I had to drive to the centre of town in traffic, mostly 3rd and 4th gear stuff, and I suddenly noticed that the engine temp was heading towards 110°C. Luckily I have a manual Disco a/c fan fitted in front of the a/c condenser and radiator, so switched that on. The next day I replaced the viscous fan.

Re: testing viscous fans... If they fail either locked or free there is no problem with diagnosis. For the rest, I look at the spring on the front. If it is oily then the fan is on its way out. A TD5 fan you can hear working when the engine is hot, the Tdi and V8 fan doesn't make enough noise to tell.

Link to comment
Share on other sites

I would never ever take the fan off a V8. The reason you can get away with it on a Tdi is because they are vastly over-cooled, i.e. the radiator is much bigger than the engine really needs, which is one reason it takes a week for them to warm up during the winter and you can run a rad even with most of the fins rotted out! A V8 produces much more heat (witness the fact it warms up very quickly) and doesn't have the same excess of cooling.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy