Head gasket gone? 850 T5
 

I'm pretty sure the answer is yes but will ask anyway.

The level coolant had dropped from max to about 1cm below min with car standing for 3 days, so about 1/2 to 1 pint. I checked below the front of the car and see no obvious leaks.

Also at the MOT last Friday I did notice what appeared to be steam out of the exhaust, not a huge clouds, but more than I would expect on a warm day with engine warmed up.

I dropped some engine oil today and it has an opaque dark brown colour, like coffee with a tiny amount of milk, compared to oil when changed that has a black/brown colour of strong coffee and no milk.

To me that is pointing to a head gasket failure or cracked block. :(

Engine has done about 170k miles without any issues.

If it is HG, then I may be able to do it myself, but a trashed block may mean the end of my car.

Is there a way to confirm a HG failure?

And for those that had garage do the work, what was the cost? I'd expect around £500 - 1,000)

Photo shows oil dropped; second photo shows old oil (left) compared to dropped oil (right).

I just did a search for cost of HG replacement and came across the same question on this forum which says it is rare for the HG to go, and more likely to be the oil cooler/ radiator going.

I replaced the radiator, can't recall when; it is relatively new, maybe 50 k miles or less.

How do it tell if it is the HG or oil cooler?

HG failure is VERY rare in these, usually only happens when the car has been severely overheated or otherwise abused. MUCH more common is failure of the oil cooler in the radiator - the RH end of the radiator is the engine oil cooler (and if auto, the left hand end is the auto box oil cooler) and these are very prone to failure. I'd be suspecting this long before I worried about the head gasket. When they fail, sometimes you can see the leak on the outside, but if they fail on the join between the engine coolant and the engine oil, then the two will mix giving the symptoms you describe. Is the coolant crisp, clean and clear? Any sign whatsoever of oil in the coolant is another indicator of the above.

Difficult to check for sure, but I'd be changing the rad first!

HTH

I found the invoice for the radiator, May 2017, so less than 30k miles. Don't recall brand.

Coolant is perfect, no sign of oil.

As above, head gasket failure is rare unless there has been severe overheating. I've not had one go on engines of 405K, 176K, 110K and 105K. Having said that obviously it does happen - but I would suspect the oil cooler first.

Regards
John

When was the heater matrix last changed? My P80 had just started losing coolant because the original heater matrix was leaking where plastic shrouds meet the metal surface of the matrix, 250,000 miles on the original matrix, which is not bad.

Matrix swapped out for new one, no more coolant loss.

A decent garage should be able to do a pressure test for a coolant leak and a compression test for head gasket failure

Heater matrix? If that has gone then surely I'd be seeing coolant either inside or outside the car?

Re. HG failure, I understand there is a chemical due that can be bought which changes colour if there are combustion gases in the coolant, anyone tried that?

What about disconnecting the oil lines to the radiator and seeing if coolant drops out of the radiator connectors?

Do a compression test first, you should get somewhere around 12 - 14 bar on all 5 cylinders with the engine warm. A 2 bar variation shows a potential issue, but I would repeat the test wet first.
Have a look at Youtube, where you can find a vid by the excellent 'Robert' who will talk through some checks to make on the 5 cylinder engines as a guide to see if the HG had failed.

Thanks - I'm aware of Robert so will check it out.

re: radiator/oil cooler fail: If this were the cause, would there not be oil in the coolant? When engine is not running, as the coolant is at the highest point in the engine, it will drip down into the oil but when running, the oil pressure should force oil into the coolant?

I've bought the combustion gas test kit and will attempt a cylinder compression test - I have the gauge but know that it is a bit of PITA trying to screw in spark plugs in the deep recess.