Help - V8 overheating on the sand!

**Tyresqueal** · 14th April 2008, 01:28 PM

Hi All,

Every time I take to the beach, my D1 V8 starts to overheat – not good as a 10 minute drive turns into a 2 hour start/stop/cool drama. I have now stopped going onto the beach and have started to do some diagnostic work.

At first I thought that the thermo fan wasn’t working, but it seems to be spinning fine and trying to stop it with a large screwdriver doesn’t work – ouch!

Next, I checked the two electric fans and this has left me seriously puzzled. The near/passenger side fan seems to come on when I first start the engine from cold, but then stops soon after – it also looks like it isn’t spinning at full speed. The off/driver side fan doesn’t come on at all.

I read in another thread that the switch on the thermostat housing controls these fans and that bridging the switch should turn on the electric fans – not in my disco.

I then decided to check each fan with a direct live/earth wiring from the battery and neither fan rotated – I read that the direction of rotation depends upon the polarity, so wasn’t too concerned with which way round my connections were – will try different combinations tonight.

Please, please help as I’m now going mad – how can one fan work when cold and then neither fan work when connected to a direct power feed????

I should also probably mention that my A/C doesn’t work either, so could this be a contributing factor to their lack of movement when the engine gets too hot.

If anyone can educate me on how these fans operate and how I can test them etc. then please share before I light a rag in the fuel filler neck and run away!

**V8Landy** · 14th April 2008, 01:42 PM

I'm pretty sure that the thermos are for the air con only unless been altered sounds like one motor might be Knackered as the other one works(May be on a thermo stat to come on at a higher temp).Check your thermostat is opening as this will cause it to over heat but should do so in traffic not just on the beach.Radiator could need a clean or maybe(i hope not)your headgasket is going or a minor crack or something opens up under heavy loads.As always check the simple things first(water level)and go from there.hope this helps someone will have a better idea than me but it's a start.Cheers Brett

RonMcGr · 14th April 2008, 02:04 PM

Wrong way to check the fan hub

When you start the vehicle that fan should normally roar for a minute or so then stop.
When the vehicle temperature gets to half way up the dial, that fan should be making a load roar and sucking air through the radiator.

If it is not doing this, it's stuffed.

The twin electrics work with the air-condioner to cool the condensor.

Ron M

**Utemad** · 14th April 2008, 02:17 PM

I don't know what your particular problem is but the aircon fans also come on when your engine temp gets too hot. They will even stay on for a certain period of time after the engine is switched off if required.

The RAVE cd explains how it works.

That is for the update D1 anyway. What year is yours?

streaky · 14th April 2008, 02:28 PM

As others as said...the twin fans up front are for the a/c condensor.

If sand driving is causing the over heating problem than you are probably not getting enought flow through the radiator. Sand driving puts more strain on the engine than any other form of off roading...it literally saps the power out of the engine and you're oblidged to plant the right foot even more.

Get the rad flushed, replaced or re-cored. Use water wetter if you can find some.

Make sure that the fan shroud is correctly fitted...no big gaps down the sides etc.

Check the top and bottom hoses arn't collapsing under load also. If the thermostate is working them leave it in. Others have mentioned how to check the viscous fan...thats good advice.
Does the engine start pinking when under load? Thats also a contributor to over heating...not severe but it's worth getting the timing spot on.

I'd put my money on it being a radiator flow issue. Sand driving is what we do every weekend and I've learn't quite a bit on how to prepare my V8's for it.

Further down the road of investigation you may want to drop the water pump off. Corroded water galleries around the impellar can cause cavitation and poor circulation issues.

Good luck.

**Utemad** · 14th April 2008, 02:32 PM

Do you let your tyres down or flog it mercilessly at highway pressures?

Just a thought.

**PhilipA** · 14th April 2008, 02:58 PM

KISS
First thing to do is have the radiator dismantled and cleaned ( do not think that filling it with caustic soda or many other fixes will work. They will not) . Odds are you will have to replace the core for about $600 so be prepared.
If that doesn't fix it then you look deeper, but cross that bridge when you come to it.
Re the aircon fans. At first start up while the viscous is roaring, it is pulling a lot of air and may turn the aircon fans. The aircon fans move all the time at highway speed even if off , its just that you don't notice because if you are close enough to see , you will soon be run over.
Regards Philip A

RonMcGr · 14th April 2008, 03:26 PM

Originally Posted by PhilipA

The aircon fans move all the time at highway speed even if off , its just that you don't notice because if you are close enough to see , you will soon be run over.
Regards Philip A

LOL

Bit like aircraft cruising in the sky, that beater turns the motor over even when it's switched off!

**rovercare** · 14th April 2008, 03:47 PM

The front thermo's switch on the thermostat housing only operates at 100*C and is only back up, will also operate with ignition off at these temps

Your method to check the fan hub is crud, you can use your hand or simply check straight after you've switched off, "listening for a roar" isn't accurate

I'd do as PhillipA suggests first

**Tyresqueal** · 14th April 2008, 04:41 PM

Thanks for all the feedback and can add some additional info.

The thermo fan constantly roars, so suspect it is okay and this is probably what is turning the rogue electric fan. The engine temp doesn't budge even a millimetre on the guage when left on idle - so this would also indicate to me that the thermo coupling is okay.

There seems to be a contradictory view on the electric fans though. I was under the impression that these were primarily for the a/c, but are also supposed to cut in when the engine reaches about 95 degrees - as a secondary cooling support. My fans don't come on at all - even when the engine temp guage was up in the red and also when I bridged the switch. Any suggestions on testing these?

It's a late '94 build and '95 registered model.

I ALWAYS drop my tyre pressures to 16psi for sand work.

Given the advice provided, I guess that it's probably radiator flow that's causing the issue then. I'll also have a look at the water pump and pop in a new thermostat whilst I've got the system drained.

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Help - V8 overheating on the sand!

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