Fan is on as soon as engine starts

Hi and merry christmas.
The fan comes on straight away on a cold start. Is this normal?
I've been having heater probs and wonder if this could be the cause or do all discos have a fan that's permanently on?

If the fan is 'not' supposed to be on all the time, what could be causing it to be always on and how do I remedy it?

Have you checked your coolant leavel, maybe too low to heat up the truck and also the temp sensor may not be able to read thye temp. Or the temp sender is failing or shorted.

Checked the coolant level which was ok and then bled any air out (there wasn't much) but noticed the fan comes on as soon as the engine starts and I was wondering if a previous owner could have bypassed the thermo (like they used to do in the old days with a hairpin). If so, how would it be undone?

Oh, another observation, the brass nut at the top of the radiator had no thread on bolt or hole, is this normal? It simply pushed in or pulled out.

I have a long journey from my area (Peak District) to Leicester and then from there to Conwy castle tomorrow night so hoping all will go well. My pal has let me borrow his 40ft yacht in Conwy marina which is at the foot of the beautiful Conwy castle so should have a cool new years eve throwing a party on his boat and watching the fireworks from the castle as long as the Disco runs cooly LOL.

Is your a/c on? The fans come on with the a/c immediately. Another thought is it might be a coolant temp switch. Again, not sure on diesels, but gas one's we have a coolant temp sending unit for the gauge and a switch for high heat that triggers the fans. Might be a bad connection or sensor.

It is perfectly normal for the clutch fan to come on when you first start the truck. All of the fluid settles to the bottom of the viscous clutch housing and until it is distrubuted by the fan turning it will be locked up. Just the nature of the beast.
It should only happen when it has set overnight or all day at work. If it is really hot out and you turn the truck off the heat build-up under the hood can lock the bi-metalic spring on the front of the fan too.
 

Tdi has a viscous fan - yes it will turn when the engine is first started.  With the engine off and cold you should be able to spin the fan by hand.  With the engine off and hot the fan should be locked tight by the viscous coupling.  If the coupling is locked while the engine is cold then there's something wrong with the viscous unit and it'll need replacing.

I thought he meant the electric fans...

quote:

ORIGINAL: okdiscoguy

I thought he meant the electric fans...

I thought he was talking about the heater fan in the cab.

I was referring to the radiator fan in this thread, however in another thread I was referring to my heater blowing hot and cold even though coolant is full.
 
A further development is after a 100 mile trip, it's running too hot. Not checked water level yet.
 
I'm sure all these things are related. Hope it's not the engine. Could it be?
 
 
 

I doubt it is the engine. I would replace the thermostat. It is cheap and a good place to start.

quote:

ORIGINAL: The Image

I was referring to the radiator fan in this thread, however in another thread I was referring to my heater blowing hot and cold even though coolant is full.

A further development is after a 100 mile trip, it's running too hot. Not checked water level yet.

I'm sure all these things are related. Hope it's not the engine. Could it be?

 
When you say engine fan, are you talking about the fan driven by the engine or the electric fans in front of the radiator. If it is the one driven by the engine, replace your fan clutch. Get a genuine one becuase aftermarket ones have a tendency to lock more than they should. They way they work is, being filled with fluid, as the fluid heats, it causes the fan to slip less. When they go out, the fan is locked into the pulley at all temperatures and RPM's. It will cause your fan to come apart and go through the hood.
 
If your truck is staying hot, the fan will stay locked. Check your coolant level frequently and might even have your radiator replaced later on. With the heater ( no heat) problem and your fan combination, it tells me you are loosing coolant. If you find this to be true, get it checked and fixed quick.

I dont understand why the fan will come apart if the clutch locks up. The fan is designed to turn at any speed. If your climbing a steep grade in low gear and it is 120 degrees out the engine is going to get hot and then the fan is going to lock and then explode? Horse hockey. 
I have been a truck driver for 15 years and have had more than one clutch fan go bad on my truck and the only thing that happens is the fan runs all the time, it is very noisy and the engine runs cold. And this happend once with a steel blade fan and again with a plastic fan.
I just have a really hard time believing that the fan will explode. I have to believe that there would be all kinds of lawsuits and I also trust that engineers would factor this in.
I just do not think that there are people allover the world driving their Rover with a fan blade stuck in the hood.
 

if they read this, they will respond and tell you.
 
Not as big of a problem with the diesels, but it happens.
 
FYI, I was ASE certified to work on Cat engines 12 years ago.

So you are familure with the Cat 3116? I put 450,000 on mine and then 500,000 on my Cummins ICX, much prefured the Cat. It didnt care what I did to it. I ran it with the front of the radiator clogged with leaves, temp gauge was pegged for a week. I never ONCE broke down to where I couldnt get home.
The Cummins was a different story, it left me stranded about every 30k with a ruptured fuel line. I would leak INTO the crankcase and cause it to overfill and then it would smoke out the exhaust and then die. And of course the ECU would shut it down 30 sec after a fault come up, it sucked.
I have been through 4 trucks and all had Cats except my Frieghtliner and Cat is by far hands down the better powerplant.

Cat engines are great, but they messed up with the C-15. It tends to sludge up for no reason on extended drains. Doesn't happen to all of them either. But yeah, I love cats. I dropped twin 3208's in my boat a few years ago and never had the slightest hiccup.

The radiator is only 6 months old so unlikely to be that. Can't see any noticable signs of coolant leaking. One thing I have noticed thjough is that my fan belt is slipping a lot, especially in wet weather. Could a slipping fan belt be the cause? How easy is it to tighten a fan belt or should I just get a new one. Current one squeals like hell in wet weather especially when on a slow tight turn.

I would just replace the belt. If the fan/water pump is not turning fast enough the engine will run hot and the fan will run more.

That's more likely to be your power steering drive belt than the alternator belt if it's squealing while turning the steering to full lock.  Check the power steering fluid reservoir ASAP or you might risk wrecking the PAS pump.

If your thermostat is stuck open your engine (and therefore the heater) will run cold until the engine is put under load, like climbing a long or steep hill or towing a heavy load.  If it's stuck open but not fully open, towing or hillclimbing may make the engine overheat, or at least make the temp gauge show hotter than it should.  Either way, replace the stat as they're pence to buy and easy to fit (10 mins max).

Cheers,

Yes fan will explode when viscous coupling is seized. I had that issue and fan exploded took out the maf, intake tube,  upper and lower shroud, went through hood, battery box, radiator. make sure coupling is not locked on if it is replace immediately.

That sounds a sober option. Thanks.

I notice it's using a lot of water (needs topping up every 150 miles or so. Could a faulty thermastat be causing that?

shouldn't use any water. A thermostat wouldn't cause water loss...
 
I'll let Adz confirm that one...

"Oh, another observation, the brass nut at the top of the radiator had no thread on bolt or hole, is this normal? It simply pushed in or pulled out".
 
No on else has commented on this so I've probably misunderstood what you are saying.
 
But if you are referring to the cooling system bleed screw on the top of the radiator then something is wrong.
 
As per its name this screws into the opening in the radiator and has a sealing washer.  If you have a non-threaded "plug" in this position then I'd be very worried. It's probably leaking under pressure (as the engine warms up) and may also be preventing the engine from reaching operating temperature.
 
Cheers
JRH1946 
 

 

This is a 1994 TDI. Lower rad temps and not hardly any pressure...
 
Not any diesels here in the US, so I left that one to Adz. He is familiar with them...