Citroen C6 2,7 HDI - Drain, change and flush coolant completely

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Citroen C6 2,7 HDI - Drain, change and flush coolant completely

Post by cit-rotti »

I had to change my water/oil exchanger because it was leaking and about 1 1/2 litres of engine oil was being pressed into the cooling water. It is a C6 2.7 HDI 2008.

I changed the water/oil exchanger with a new seal (located in the middle of the engine between the cylinder rows with the oil filter) and it looks OK. I was able to suck out most of the oil again, because oil always floats on top. But there is still some oil left in the cooling water.

I would therefore like to drain off all the cooling water if possible and carry out several rinsing processes and also use a cleaning agent that dissolves oil.

However, I can't find the right places to drain as much cooling water as possible or the places to flush the cooling and heating circuits with clear water under low pressure.

The radiator cooler only has a connection "at the top" and a vent hole - there is supposed to be a drain plug at the bottom left - but I can't find it.

There is also a drain plug on the engine block - I haven't found it yet either.

Conveniently accessible would be the water connections on the water/oil exchanger of the gearbox - can these be used???

Does anyone have experience with this and can help me and tell me exactly where the drain plug on the engine block and radiator are.
I would be grateful for any information - and if possible I would like to dismantle as little as possible.

Greetings Wolfgang

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Re: Citroen C6 2,7 HDI - Drain, change and flush coolant completely

Post by Armidillo »

Greetings, Wolfgang!

I have some good news, although I suppose whether it is good or not depends on your perspective!

Seeing as the 2.7 litre HDi is a V6, there will almost certainly be a drain plug in each bank - so one each side of the block. Naturally you have to access them from below, so that when you unscrew the plug the coolant drains on you!

I have not had the pleasure of working on a V6 HDi, but I have a couple of 3 litre petrol V6's (a PRV and an ES9J4s). Getting the car onto wheel ramps should give sufficient access room, but using a hoist would be better. Careful scrutiny should reveal the drain plugs, although on the PRV engine, the front one is concealed behind the alternator, and is definitely only accessible once the alternator is removed. If you are lucky the drain plug may have an inner section to which a piece of tubing can be fitted. If so, you only need to loosen this centre plug, and the coolant should start to flow through your piece of tubing.

I have found that a really thorough draining of the block does require removal of both plugs. If you cannot locate a radiator drain plug, you may have to remove the lowest hose from the radiator.

No doubt you are aware that when refilling with new coolant, very thorough bleeding of from the system is required.