V8 Viscous Fan

[SteveGoodz]

The viscous fan on my 3.9 Discovery has given up the ghost .. it freewheels even when the water temp is almost into the red!

I'm looking to replace it but that won't be until the weekend and I need to use the car in the meantime.

I thought I recalled a post on here where someone described how to lock the hub and blade units together so that the fan runs all the time. Damned if I can find it though ... does anyone know how to do this?

TIA

[300TDi Disco]

I am in the process of changin my water pump, but i just cant get the viscous off it, Any Ideas???

[big tim]

I swapped mine which is a 1998 3.9v8 with a normal thread not left handed if thats any help

[doda456]

Its a reverse thread, well was on mty 200tdi last week,  and have you tried a blow torch on the nut? I had to on mine as it was very stuck

[300TDi Disco]

I am in the process of changin my water pump, but i just cant get the viscous off it, Any Ideas???

Just got it off, after a few loud words and some big hammers

[andrew2986]

Steve,
A mate of mine had the same prob and wound some string into the viscus coupling to jam it up, bit of a bodge but it worked

Andy

[Range Rover Blues]

Usually they are left hand thread but on the serpentine V8 they are right hand, the nut is bigger and obviously the blade run the other way.  It runs off the back side of the belt which is the clue.

You could try wrapping some hefty string round the back of the nut to jam it up for a few days but if it's going into the red you could have a problem.  I ended up swapping both my rad and viscous hub (got the pair for £200) when the LSE was getting a bit hot.

[SteveGoodz]

Cheers guys, I'm at home tomorrow so will see what I can do.

Did quite a distance on the motorway today - lower ambient temperatures and fairly constant high(ish) speed - with absolutely no problem  :dance:

Might have a ring around a couple of scrappies and see what I can find.

[Range Rover Blues]

Shame you aren't closer.

You might findone of something similar will fit but whether it will run at the right speed I can't say.  They are a common thread though.

[SteveGoodz]

Okay, I'm having second thoughts on the viscous coupling ... having removed the cowl from around the fan this afternoon I see that the viscous unit looks pretty new. Still shiny - hardly condusive with 10+ years of use. My initial comment about freewheeling may have been a bit off. At normal engine temperature I can turn the fan quite easily but there is some resistance to and when cold it certainly turns more freely.

I experienced overheating again today. Dropped the wife off to visit her mother in hospital about 5 miles from home. Temp was fine until I got about 1 mile from home when it started to increase and by the time I'd stopped outside the garage there was steam pouring out from every orifice around the bonnet and the headlamps. Popped the bonnet and water is boiling/bubbling out from the expansion bottle cap  :oops: Speed was never more than 40mph during the journey and the ambient was pretty cool. I didn't get stuck in traffic either.

A couple of hours later I drove back to the hospital to collect SWMBO (after putting about 1.5ltrs of water in) and it was fine both ways - never went above normal  :?

So, I'm thinking what can cause this kind of problem :-k Do we have any V8 cooling system guru's here?

[Range Rover Blues]

Possible blocked rad due to old age.

When it starts to get hot, try putting the cab heater on full bore and open the windows, does it make a diffenrece?

alternatively it is loosing water and once there is enough air in there to stop the water going round it boild over.  Take it for a slightly shorter run and see if any water has escaped, ideally before it overheats.

P.S> fill the coolant via the brass plug on top of the heater supply pie, not via the expansion tank.  If you havn't done this it will have air in the heater matrix.

[300TDi Disco]

Possible blocked rad due to old age.

When it starts to get hot, try putting the cab heater on full bore and open the windows, does it make a diffenrece?

alternatively it is loosing water and once there is enough air in there to stop the water going round it boild over.  Take it for a slightly shorter run and see if any water has escaped, ideally before it overheats.

P.S> fill the coolant via the brass plug on top of the heater supply pie, not via the expansion tank.  If you havn't done this it will have air in the heater matrix.

I have just completed a water pump change on mine. and i filled the whole system up through the radiator. I waited until i couldn't see any bubbles in the rad the screwed the cap in. Been round the block a few times and then checked the expansion bottle for pressure. I got a little bit of air rush out then went for a longer drive and it's now fine. I have got rid of the viscous unit and put and electric fan from a mondeo, engine is quite now)

[SteveGoodz]

Possible blocked rad due to old age.

Good thought. How do I check for a partially blocked rad?

When it starts to get hot, try putting the cab heater on full bore and open the windows, does it make a diffenrece?

Certainly does. I drove most of the way back from Gaydon on Sunday with the windows open and heater on full blast. Got pretty damned hot inside the car I can tell you  :(

alternatively it is loosing water and once there is enough air in there to stop the water going round it boild over.  Take it for a slightly shorter run and see if any water has escaped, ideally before it overheats.

P.S> fill the coolant via the brass plug on top of the heater supply pie, not via the expansion tank.  If you havn't done this it will have air in the heater matrix.

I'm pretty sure that I've got all the air out of the system and it doesn't lose water except when it's boiling out of the expansion tank.

[Range Rover Blues]

Ok, all sounds reasuringly like a blocked rad and nothing worse.

 I checked mine with a laser thermometer, a non-contact optical one I'd borrowed but basically if you get cold spots near the corners that's a sign of a crusted up rad, also it's age will suggest it and the condition of the insides of the rad and header tank if you can see, but the best way to tell is by swapping it I find.

The fact that the cab heater can keep the engine cool speaks volumes, if the water stays in until it gets too hot then I don't think it a head gakset or worse, new rad I say.

[SteveGoodz]

Thought I'd update this with what's happened recently.

I fitted a brand new viscous coupling and changed the thermostat. No difference, except that the new coupling is noisier than the old one :doh: Anybody want to buy a BNIB viscous coupling? Only been used for about 10 miles   :D

My tame mechanic checked for head gasket leakage using one of those syphon things that samples the air in the coolant expansion tank. Ran the engine for quite some time and the liquid stayed a nice blue colour ... so the heads are okay. The system was pretty well pressurised though. As soon as we cracked the filler cap off boiling hot water came out - no steam/hot air first.

I removed the cowl from around the radiator to get access to see if there are any cold spots. Hmm, what constitutes a cold spot? After a short run with the temp gauge reading normal (just about half way up the gauge) the top third of the rad is uncomfortable to touch for more than a second or two and it gets cooler as you feel further down. At the bottom I could comfortably leave my hand there indefinately - it's warm but not really hot. Trouble is, I don't know how much cooler the bottom should be than the top anyway.

This morning I deliberately got the engine really hot - needle almost into the red [-X - the top of the rad was <insert Anglo-Saxon word for fighting> hot! Too hot to touch without going OUCH!! Bottom half of the rad was a lot hotter than before but I still don't know if that's right or not. The problem is a new rad is like mega-bucks and I'd rather not spend that much dosh only to find it's not the problem  :-$ Anybody got a known good used one for a reasonable price or one I can borrow for a couple of days?

Whilst pondering the problem this morning I heard what sounds like steam escaping and water boiling. The sound is coming from somewhere around the inlet manifold/plenum area. I also realised that the valley gasket is damaged (i.e. almost non-existent) at the front and the seal and clamp are missing. I'm gonna have to replace the inlet manifold gasket anyway but is this likely to be the cause of the problem or, as I'm inclined to think, just a symptom.

This is really starting to pee me off as it's stopping me from getting the blasted thing muddy  :'(

Suggestions/ideas anyone?

[doda456]

If you supect the rad, It cant  hurt to remove it and wash it, inside and outside you will be amazed what comes out.
Just be carefull if you use a pressure washer, as it can bend fins if you get to close,

Also have you taken the front grille and cowling off at the same time, and tried to look through? You should see lots of daylight through the mesh. If theres no mesh you may have found a problem


Dan

[SteveGoodz]

If you supect the rad, It cant  hurt to remove it and wash it, inside and outside you will be amazed what comes out.
Just be carefull if you use a pressure washer, as it can bend fins if you get to close,

That may be a job for tomorrow, or Monday

Also have you taken the front grille and cowling off at the same time, and tried to look through? You should see lots of daylight through the mesh. If theres no mesh you may have found a problem


Dan

I haven't taken the grill off yet but looking through it it's hard to see cos the aircon rad and fans are in the way. Still, if I'm taking the rad out for a clean it won't matter :-)

[J.D.]

Get hold of some central heating cleaner, most plumbing places will sell it, stick it in the coolant system and take the car for a spin. I did this on a few vehicles and it is amazing the amount of rubbish it pulls out of the system.

Note though - make sure you get one which isn't too corrosive or which doesn't agree with aluminium.

[SteveGoodz]

Get hold of some central heating cleaner, most plumbing places will sell it, stick it in the coolant system and take the car for a spin. I did this on a few vehicles and it is amazing the amount of rubbish it pulls out of the system.

Note though - make sure you get one which isn't too corrosive or which doesn't agree with aluminium.

Good idea, JD. One of my neighbours suggested it too but Fernox (and similar ch flushes) are fairly corrosive and have to be neutralised afterwards. I've bought some Wynns rad flush so I'll give that a try first.

[SteveGoodz]

Okay, so I've ordered a new inlet manifold gasket and will fit that before I flush the radiator just to save on anti-freeze.

This afternoon I was bored with studying so I popped outside to check on the temperatures in the radiator using a K-type thermocouple plugged into my DMM. To make my life easier I removed the viscous fan and cowling and took the temperatures by inserting the thermocouple into the fins on the engine side of the rad. I took 10 measurements - 5 about 2" from the top and 5 about the same distance from the bottom. The temperature gauge started off pretty much on normal but, as you might expect, rose fairly quickly with no air flow through the rad. The measurements were:

Top (inlet side to outlet side): 70 - 75 - 78 - 71 - 66
Bottom (same orientantion)  : 62 - 64 - 56 - 52 - 48
Difference                                 : 08 - 11 - 22 - 19 - 18

So, I'm surprised that there is such a difference in the differences (if you see what I mean). Am I right in thinking the radiator consists of an upper and lower chamber (running the full width of the rad) connected by vertical water ways down which the hot water falls as it is cooled?

Your thoughts, please :-)

[Rossko]

Your thoughts, please :-)

I think it's telling you the rad is choked.   With a good flow of water, and no airflow (so it's only, err radiating) there should be little temperature difference along the width, and not much top to bottom either.     You've eliminated the thermostat.  Poor flow then - unless you have something unusual for a V8 in way of broken/corroded water pump vanes - is most likely choked rad.   It might improve with some caustic treatment, might not, may just spring a leak!  Recored rad is the surefire fix.

cheers, Ross K

[Range Rover Blues]

If it's like the RRC then it will be a full width full flow (cross flow) rad, once up to temp you shouldn't be seeinng so much variation side to side so I think it's blocked.

Also, I know you have no 'stat any more but those readings are a little low, the 14CUX will run rich until you clear 80 degrees.

[SteveGoodz]

Cheers to Rossko and RRB - you confirmed what my feeble brain had been trying to tell me all along  :lol:

Replacement (used by guaranteed) rad turned up whilst I was out today ... so that's this weekends job decided  :clap:

[SteveGoodz]

Okay, so now I'm seriously miffed 

Took the original radiator out of the Discovery this morning and slotted in the replacement one ... it leaks like a sieve  :-. We are not amused!

No alternative but to flush the old one and refit it. At least it doesn't leak. I'll be on the blower to Amazon 4x4 first thing in the morning to get my money back

[SteveGoodz]

And finally ....

... refund from Amazon 4x4 for the "less-than-watertight" radiator is on it's way  :)

... a huge thanks to "Staffy" for letting me have a reconditioned rad for much less than he could have got elsewhere. Cheers Phil, you're a true mud-clubber  :clap: The beers are on me next time our paths cross  :dance:

... overheating now appears to be a thing of the past - touch wood  [-X [-o<

Driving up to Stoke was a bit of a nighmare yesterday. Hottest day for some time so I was balancing speed on the motorway against engine temperature. Just around J3 of the M5 the temperature gauge suddenly shot up into the red. BU66ER!! Turned out to be a split heater hose which was fixed by the nice recovery man. From there, all the way to Phil's place and back was a very warm experience ... driving with all the windows and both sun-roofs open and the heater on full blast  [-X

Well worth it though  :lol: