(Home) Towing/overheating

After over a year of (virtually) trouble free motoring in my Townace I fitted a towbar (£224 inc delivery and twin electrics from Watling Towbars.) Caravan 18cwt fully loaded. Trip to Wales. (long hills) Hot weather. The townace is not the best tow vehicle I have used, but by and large I was satified with the overall performance.Until.. After one hour of being transfixed by the temp gauge (that's the problem with reading all the postings on this site-looking for symptoms before the occur!) I noticed for the first time ever the temp gauge moved up.Within a couple of seconds of me noticing this the viscous fan kicked in. Scared the S*** out of me, never heard it before. After the long hill climb I pulled into a layby and there was the much reported bubbling in the expansion tank.
I let it cool for a time and continued with care. No icon on the dash had reported a loss of coolant and on my next brief stop no bubbling could be heard. After arriving in Barmouth and doing the caravan set up I check the expansion tank. A light on the dash now confirmed the level was low. I topped this up twice during the next two days but after the return trip no overheating, and by now I was used to the fan kicking in. Since that incident I have done the same journey without the caravan and no overheating, no bubbling nothing.No loss of water.The van ran like a dream.With the idea that the viscous fan can reduce power by 8HP!! I would definitly like to fit the electric option for the occasional towing. I realise my over-heating experience is totally due to these extream driving conditions, but perhaps the symptoms can help other diagnose their problems.

- (#5127) jeff willcott, 16 Aug 02

The viscous fan runs all the time. You're hearing the additional electric fans cut in (4x4 auto?), meaning the coolant temp is exceeding 105c. Pretty hot! That means that you're reaching the limit of what your cooling system can handle. Next stop, turn the heaters on!
You sound fortunate- the same degree of overheating ha cracked and warped heads for others...

- (#5128) david miller, 16 Aug 02

Greetings from Moscow,
Now I'm a little confused about the overheating/fan situation.
I have noticed on my townie that a fan or something kicks
in from time to time. It sounds like air being sucked through
a filter. At first i thought it was only when I ran aircon.
but it seems to be more often. I posted a message on that
and i believe, Ian responded with the thought that it is
the viscious fan making the noise. i hear this noise quite
often now and am wondering if it could be due to the engine
getting dangerously hot??? The temp gauge never makes it to half way
and i never hear the exp. tank bubbling and never need
topping up. As I posted in my message yesterday, I noticed on my
last 800 mile trip that a subtle tapping, ticking sound noise coming
from the engine when accelerating. It almost sounds like an
exaust leak. Could this be a result of the engine getting too hot?
I am going to my mechanic next week, but any advice would
be appreceiated as my mechanic is pretty much townie ignorant.
Thanks so much
Mervin

- (#5129) Mervin, 16 Aug 02

Jeff,

I also tow with a towmie, 2wd manual and hear the the fan cut in as you describe. from my understanding of the viscous fan as the temperature rises the coupling locks hence the noise, as the fan cools the engine the coupling frees up again. I reakon your experiance proves that your fan is working correctly.

- (#5130) Rob, 16 Aug 02

I doubt if you would hear the viscous fan engaging. As David mentions, the fan runs all the time but, the "drag" of the viscous fluid, will increase as the engine/rad temperature rises. The drag is increased, proportionly to the temperature rise, because a temperature controlled valve, in the body of the fan, is allowing the silicon fluid to pass into the "driven" chamber, from the "slipping" chamber. An old, worn out coupling may well have lost it's fluid and will appear to work satisfactorily upon inspection. However, at higher engine & vehicle speeds, the fan may slip and even stop turning. It's a good test to run with the passenger seat up and observe the fan at motorway speeds. If it slows down, or stops, at speed, it has to be replaced. There is no locking of the viscous drive system, it's a gradual procedure, not unlike the operation of a torque convertor or fluid flywheel, but in the case of a viscous fan, the amount of "drive" or "slip" is matched up to the temperature of the air passing over the radiator and onto the fan body.

- (#5131) John Davis, 16 Aug 02