D3 TDV6 overheating on sand?

stu · 25th August 2012, 06:14 PM

I had a weird experience today at Stockon Beach. I'll take the Disco into the mechanic next week but I thought someone here might have some insight to help diagnose the problem...

I drove up from Sydney to Newcastle (150Km) without incident, but after about an hour on the sand the temp gauge suddenly shot up to red and the disco stopped. I had been in low range / sand mode for a while, with the revs in the 2-3k range beach / dune driving.

The was no steam, leaks or drama in the engine bay. I let it cool 10-15mins, restarted with the temp gauge reading half and got about 5 mins out of it before it shot into the red again.

I took it out of low range, out of sand mode this time. Paused, cooled and tried again. Same result.

I stopped for a 1/2 hour (ate my lunch) check, bled & topped the coolant (the level was fine, but I topped it just to be sure). This time, I got about 10 mins then the same thing happened, the gauge would sit at halfway, then suddenly move up to red and stop.

I eventually got off the beach by keeping the revs under 2k. If the gauge started to drift up, I'd drop the revs right off and I could bring the temp down again.

Once back on the hard stuff, I aired up and got all the way back to Sydney without the temp gauge ever moving above half. I was driving carefully at first, but once I got confident, I was passing at 120+km.

Safely back at home with the engine still warm I tried to reproduce the overheating by driving around the local area stuck in 2nd, keeping the revs up at 3k, but I couldn't get the temp gauge to move off halfway.

I'm a bit stumped as to the fault. The disco should be able to cope with reving above 2k for a sustained period, but it probably doesn't do it much on road.

We're off to fraser island in the school holidays, so I'd like to figure this out before then.

Anyone got any idea what might be going on?

thanks

stu

Tombie · 25th August 2012, 06:50 PM

What year Stu?

Has it done any mud running in the past?

I'd suggest checking...

Radiator
Thermo Fan(s)
Engine Fan Hub
Thermostat

If its getting up on kms or years it may be as simple as heading for a cooling system flush...

**gghaggis** · 25th August 2012, 07:54 PM

Sounds like the electronic over-ride on the viscous fan isn't kicking in. When you start the car the first time, there should be a roar from the fan as the car does a system check on the fan. If it isn't working, the viscous coupling will make it LOOK like the fan's working, but it isn't. The D3's cooling system is good enough to still keep the car in the normal temp band unless worked hard (eg in sand or towing up hill).

Could be as simple as a pin in the fan loom not making contact, or could be the motor or associated electronics.

Cheers,

Gordon

**cyclosarin** · 25th August 2012, 10:04 PM

Keep in mind the difference between running around your local roads in low range and doing it on Stockton Beach is the sand provides a hell of a lot more resistance. Means the everything works harder.

I often hear about fourbies of all colours having trouble in sand with the auto transmission oil overheating, but I dont think that would show up on your temp gauge.

stu · 26th August 2012, 05:55 AM

Thanks for the help. I'll check out the fan, as it certainly wasn't working hard. Hopefully it's as simple as that. It was my first time on real soft sand, and it does give the engine a workout. Cheers, stu.

**ozscott** · 27th August 2012, 05:02 PM

Originally Posted by stu

...the temp gauge suddenly shot up to red and the disco stopped. .. I let it cool 10-15mins, restarted with the temp gauge reading half and got about 5 mins out of it before it shot into the red again.
...

stu

Does the D3/4 have a system that shuts the vehicle down before critical overheat? Or do you mean you turned it off...or (I hope the following didnt happen) did it stall with the temp in the red?

Cheers

**gghaggis** · 27th August 2012, 07:03 PM

Originally Posted by ozscott

Does the D3/4 have a system that shuts the vehicle down before critical overheat? Or do you mean you turned it off...or (I hope the following didnt happen) did it stall with the temp in the red?

Cheers

The car will go into limp mode (no power) to protect the engine. In my case it was one pin in the fan harness that had worked loose.

Cheers,

Gordon

**ozscott** · 28th August 2012, 06:36 AM

Thanks mate. Clever system. Depending on the reason for overheat (so I am led to believe) actually idling instead of shutting down can help reduce heat and stop heat sink.

Cheers

**gghaggis** · 28th August 2012, 09:59 AM

It's hard to identify when the fault actually first occurs. The D3 cooling system is good enough that even without the fan running correctly, the car won't overheat in normal day-to-day driving. The only real test is starting the car when the engine is cold - the systems-check should engage the fan at full speed for a few seconds. You can hear this as a short roar, but it's easy to miss.

When you really load the engine, such as towing uphill, or playing in sand dunes, the temp gauge will finally climb and trigger an overheat warning. In hindsight, I would have been driving for 8 weeks or so without realising what had happened.

Cheers,

Gordon

**scarry** · 28th August 2012, 07:10 PM

Also if you do a lot of slow tottering around,such as on the farm,even in cool weather the fan will roar every now & then,but the temp. guage does not move.
Would that be the viscous coupling cycling or the electric override?

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