Thread: D4 Cooling system differences?

Might be worth taking a look at your thermostat. These cars are getting on in age now. Radiators tend not to have to many internal blockages these days due to excellent coolants. Thermostat couldn't be to expensive.

Is there an actual way of testing the thermo fan operation or only listening after cold start up for the roar?

Looking at previous posts other older D3s have seen the gauge rise in heavy driving and on soft sand.

I suspect between full electronic lock of the fan (the roar) and part way viscous engagement some of the fan effectiveness may get lost on older cars as engine temp rises.

Originally Posted by PerthDisco

Is there an actual way of testing the thermo fan operation or only listening after cold start up for the roar?

Looking at previous posts other older D3s have seen the gauge rise in heavy driving and on soft sand.

I suspect between full electronic lock of the fan (the roar) and part way viscous engagement some of the fan effectiveness may get lost on older cars as engine temp rises.

The vehicle does a self test of the fan,but not at every start,which is the roar.

With the Gap tool,you are able to keep an eye on both coolant temperatures,and fan speed,and of course many other parameters,which will help diagnosing an issue.

I BT mine to the iPad,so its on a large screen and easy to see,particularly with someone else at the wheel.
You are able to see many parameters on the one screen,in different formats.

If the engine is very hot,i would presume the fan would be roaring,as it would be electrically locked up.

Originally Posted by scarry

The vehicle does a self test of the fan,but not at every start,which is the roar.

With the Gap tool,you are able to keep an eye on both coolant temperatures,and fan speed,and of course many other parameters,which will help diagnosing an issue.

I BT mine to the iPad,so its on a large screen and easy to see,particularly with someone else at the wheel.
You are able to see many parameters on the one screen,in different formats.

If the engine is very hot,i would presume the fan would be roaring,as it would be electrically locked up.

Yes I heard it roar but I wonder if the viscous operation deteriorates or fails over time?

Originally Posted by PerthDisco

Yes I heard it roar but I wonder if the viscous operation deteriorates or fails over time?

Yes,the fluid weeps out,which is an issue with them over time,but i haven't heard of it happening in D4's.I have heard of the electric locking failing.

If the viscous is deteriorating,the electric should lock up once the engine gets to a certain temperature,i presume?

Gap tool is what you need,it will reveal all.

Without it you are guessing.

Originally Posted by scarry

Yes,the fluid weeps out,which is an issue with them over time,but i haven't heard of it happening in D4's.I have heard of the electric locking failing.

If the viscous is deteriorating,the electric should lock up once the engine gets to a certain temperature,i presume?

Gap tool is what you need,it will reveal all.

Without it you are guessing.

Yes it’s a suspicion because when the needle went up to the high mark the roar started and the temp came down again promptly. (As it should)

If the viscous part is old school in that the oil gets thicker with heat causing more lock up then how does the ‘lectronics see and record that function?

Originally Posted by PerthDisco

Yes it’s a suspicion because when the needle went up to the high mark the roar started and the temp came down again promptly. (As it should)

If the viscous part is old school in that the oil gets thicker with heat causing more lock up then how does the ‘lectronics see and record that function?

Probably doesn't,it just sees the temp rising,above a certain limit,and demands the fan on,electronically.

As i said,with the GAP tool,you can see fan revs,so if they are not going up as the actual coolant temp on the Gap tool rises,there is an issue.It can be seen on the same screen,at the same time,great bit of kit.

I was watching it on the last trip back from the property,relatively cool weather,but i could see the fan revs going up and down,coolant was relatively steady.We were travelling on the speed limit,100Km.

You are only guessing without the tool.In my opinion,it essential to have one if keeping the vehicle for a while.

On older vehicles,some used to use the newspaper trick,heat the engine,if the fan can be stopped with a piece of newspaper,it is shagged.But thats a bit dangerous,particularly if the electronic part cut in while holding the newspaper against the fan.

Easy to check viscous fan, would be number 1 check.
I have replaced a couple on different vehicles.
Cheers