dhutch
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| posted on 5/11/12 at 11:27 AM |
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Viscous Fans?
Never had a car with a viscous fan but I think the fan on the new tow car (E36 Compact) had died, symtoms being that it stays stable and at the
right temperature on the dual carrageway even going uphill with a large box trailer (apprently they often suffer waterpump impellor failure) but
then overheats messing about reversing up my drive with the trailer.
However my question is, how stiff should they be cold, and how stiff should they get when warm?
- Currenly when cold it spins fairly freely, maybe manage 3/4 of a revolution if you spin it as fas as you go.
- When warm (having just boiled) its still far from locked, but maybe 2 or 3 times more visous than when its cold.
Dont know what they look like inside, but I assume if the fail through being not viscous enough its down to leaking and loosing oil? Are the then
sealed for life, or can you refill them?
Daniel
[Edited on 5/11/2012 by dhutch]
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tony.g
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| posted on 5/11/12 at 11:41 AM |
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Sounds more like you need a new thermostat to me!!
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RickRick
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| posted on 5/11/12 at 11:44 AM |
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My E39 needs a new thermostat, and it does what you describe, even putting the heater on inside the car rapidly looses engine temp, the thermostat
isn't just an open/close job, it's got wires and stuff and changes the direction of the water flow as well apparently to help speed up
warm up time
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Mr Whippy
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| posted on 5/11/12 at 12:11 PM |
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this time of year is when folk usually find out the thermostat was knackered all summer long, very common prob but easy to fix, little chance it has
anything to do with fans. Viscous fans are sealed for life and are not serviceable, their also rubbish tbh and your better off with an electric one as
they waste engine power
[Edited on 5/11/12 by Mr Whippy]
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adithorp
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| posted on 5/11/12 at 01:23 PM |
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They go very stiff when failed, usually due to a siezed bearing) and you get a lot of fan roar and even loss of power can be noticable.
Yours sounds more like the stat stuck.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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dhutch
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| posted on 5/11/12 at 02:21 PM |
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Edited the origanal post as my use of 'stays cool' was rather open to misinterpretation, in the I mean 'doesnt over heat'
rather than 'fails to get upto temperature' which is how it read.
- Apprently the car had a new stat/housing just before sale, due to it not reaching temp, which it then did and does.
Just overheated when doing slow speed work, hence leading to me thinking fan.
Daniel
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dhutch
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| posted on 7/11/12 at 06:45 PM |
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Just been out playing, heater now blows cold and it appears I can get it to boil, static on the drive, with the temp sender reading normal temp,
although its fine driving to work and back (5 miles) so im presuming it now also has air in it.
Daniel
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me!
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| posted on 7/11/12 at 07:10 PM |
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I have a E46 325i and it was a bit of a pain to bleed the air out of the system the first time I did it. Mine never over heated, it just threw up low
coolant level lights until I managed to do it properly. Might be worth checking, sometimes my coolant level would look ok and other it would be really
low- I assume it changed as the air moved around the system? Not sure if this applies to E36's but here you go.... I filled the cooling system
with the bleed screw removed until bubbles stopped appearing- this leaves the coolant level very high in the tank. I then replaced the bleed screw and
tank cap, started the engine and revved to 3/4k a couple of times, and turned it straight off. The wires RickRick mentioned open a valve in the
'stat above a certain rpm/load. This allowed the coolant level in the tank to drop, so I topped it up until it was correct and checked it
regularly over the following week- didn't move in my case but it can do.
I'm not familiar with E36's, but I know E46's have quite delicate cooling systems, if you have just got it and have no evidence
it's been done recently I would put a new water pump in as a precaution. Some of the hoses can go as well so check them over, and check the tank
for cracks.
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britishtrident
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| posted on 7/11/12 at 09:26 PM |
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Loosen some of the upper hoses and any bleeders and see if it vents any air if no luck with that I would rig up a pressure test and test the
system when stone cold.
Premature boiling can often mean the system isn't holding pressure due a minor leak, on modern cars the normal running temperature can be
up to 115c before the temperature gauge moves above "N" . Temperature gauges these days are driven by the ECU they are programmed to
stay firmly on "N" between 75c and 115c so as not to worry the the plebs. As a result if the system isn't holding pressure it
can be quietly boiling away be the gauge is still on normal.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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coyoteboy
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| posted on 7/11/12 at 10:34 PM |
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Sticking stat would be most noticeable at high load high revs like towing uphill. If the stat was stuck shut it would overheat at speed may also do so
at idle. If it's stuck open it'd run cool at idle and normal at speed.
Knackered viscous fan would be most noticeable at low speed and virtually un-noticeable at higher speed when the air pushed through the grille is
higher speed than the fan can create anyway.
FWIW our viscous fan failed with exactly the same symptoms (when hot it was not much more stiff than when cold). The replacement was virtually locked
when hot and about the same as the knackered one when cold.
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dhutch
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| posted on 7/11/12 at 11:48 PM |
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quote:
Originally posted by coyoteboyFWIW our viscous fan failed with exactly the same symptoms (when hot it was not much more stiff than when
cold). The replacement was virtually locked when hot and about the same as the knackered one when cold.
Thats the sort of thing I think.
Obviously it now has air in it, which is going to cause issues, and effect the heater but can be resolved. It also appears that the waterpumps are
well know to fail, but that doesnt appear to be the issue here.
Its also interesting the point about fact the temp gauge could be reading 'smoothed' information rather than the real temp, it does seem
very very stable in the middle, unlike the 306 which did used to creep a bit higher under load, when the fan failed, etc.
Previous owner said he had recently changed the stat/housing as it was running too cool, but that might not have been idling and or reversing a
trailer up a drive!
Daniel
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