I am losing coolant in my engine but, there are no obvious signs.

It was fully topped up before a 150 mile drive on motorways yesterday and this morning, my expansion tank was empty.

The engine runs at normal temperatures.

There is no milk on the oil cap or dipstick. There is no white smoke.

What are the common causes?

Loads of places it could be, one common one is the expansion bottle itself, a small split will leak when driving and the system is under pressure... worth taking it for a run, get it nice and hot, stop, open the bonnet and listen with the engine on, if you can't hear anything turn the engine off and you may hear where it is escaping...  Pete

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Good news is that it’s not the head gasket. To be honest I think it’s rare. On a car of this age it is much more likely that one or more of the 1,001 coolant hoses, pipes or connectors need replacing. And then you find that once you’ve done one you just move it to the next weakest spot etc. So in my opinion when a car gets to that age in its life just change the lot. It’s cheap, looks better and keeps the leaks away.

Sorry, I'd forgotten to mention I have replaced the expansion tank as a previous preventative measure.

Bl4ckD0g wrote:

Good news is that it’s not the head gasket. To be honest I think it’s rare. On a car of this age it is much more likely that one or more of the 1,001 coolant hoses, pipes or connectors need replacing. And then you find that once you’ve done one you just move it to the next weakest spot etc. So in my opinion when a car gets to that age in its life just change the lot. It’s cheap, looks better and keeps the leaks away.

Look very carefully in the 'V' with a torch. You may well see dried coolant. If so, there is a good chance it is your plastic thermostat housing that has split. It will leak under pressure into the 'V' where the heat evaporates it leaving your orange stain! My betting is that this is where your problem lies.

Is there a best position to view it from?

Take off the plastic cover and point the light down towards the front/middle of the 'V'...easiest bit to get to luckily! It won't be too hard to see!

Thanks.

I will check that.

I have the long drive back tomorrow but, will ensure it's topped up before I leave, check the temperature during and, carry spare coolant with me if needed.

Then, I'll have a good look with a torch when I get home.

Sounds like a good plan! If it isn't the actual thermostat housing it may equally be one of the plastic pipes that go between the engine and the thermostat..same difference repair-wise!

EGR cooler?

From the limited amount you can see in the engine bay without moving things, there is no sign of any pink inside the V of the engine.

So, it's most likely a hose/hoses.

I'll have to put it into a garage to find the culprit(s).


Weirdly, this morning, I topped it up again (needed about 150ml after 150 mile run yesterday) and after allowing the engine to cool for 3 hours, I checked and I now have more coolant in the expansion tank than I did this morning after I'd topped it up.

sorry to thread hijack, what are the plastic housings like to replace?
mine is losing coolant and i do remember seeing the pink in the V....... 2007 TDV8 Vogue SE
2005 BMW E63 645ci
2009 5.0 Supercharged autobiography
2024 Porsche Macan

There's a thread on this site of a top end strip down to replace the EGRs. Replacing the thermostat housing is the same job with the final few steps removed.

It's not a massive job by the looks of it - mainly removing the intakes, sensors and manifold, in order to reach the thermostat. 2015 Range Rover Autobiography 4.4 SDV8

ah ok, not too sad then, thanks for replying 2007 TDV8 Vogue SE
2005 BMW E63 645ci
2009 5.0 Supercharged autobiography
2024 Porsche Macan