2009 XC60 D5 Thermostat housing leak - fixed!

[JGEM]

20km away from the 240,000km mark and about 6 weeks away from its 15th birthday the XC60 sprung a coolant leak. The red warning triangle on the dash panel appeared and the message indicated low coolant level and the need to stop. The coolant reservoir was not completely empty so I caught things just in time.

I was grateful for the timing, as we had a week earlier completed a family pre Xmas 2000km trip around isolated parts of the lower South Island of NZ, and a breakdown there would have been a major hassle. (I always knew it was a gamble taking a high mileage 15 year old car on such a long trip...)

It turned out it was a leaking gasket in the thermostat housing. Water was steadily dripping out and down onto the alternator underneath. The whole thermostat assembly has part number 30777475 (mine was made by Wahler with the part number is cast onto the aluminium housing) and alternatives are available for about 40 to 100+ Euro - I saw over 10 different brands listed. (I use Spareto in Estonia for Volvo parts). My engine is the older single turbo D5244T4

All I actually needed was the gasket, but I couldn't find it listed anywhere.
Also, over Xmas time nothing was open so I had to work on an alternative solution. I went and disassembled the top part of the thermostat assembly - only 2 screws hold on the flange that is attached to the top radiator hose, so it's easy to disassemble. I disconnected the top radiator hose to gain more direct access one of the fasteners. Once apart I removed the gasket and then carefully scraped off the residual material and then used a sanding block with 220 grit paper to tidy up the 2 mating services. I used Permatex blue to make my own gasket - it's a silicon RTV type material and says on the tube that it's suitable for applications involving engine coolant.

After the recommended 24 hour cure time on the new "gasket" I refilled the coolant reservoir and been it's drip tight after about 200km of motoring and the coolant level is steady. Engine temp when warmed up around 88-89 degrees C.
I was reassured by how pristine and clean the inside of the aluminium castings were when I had things disassembled- that Volvo coolant really does a good job as regards corrosion prevention.

This is the 2nd cooling system problem I've had in the last 170,000km. The original problem was from memory about the 90,000km mileage mark and was a radiator leak necessitating a new radiator.

My XC60 has not had any dealer service for the last 6 years apart from the seatbelt attachment point recall a few years back and I took the opportunity. then to get them to upgrade the software as required.

I was cheered up recently by seeing a 2010 XC60 D5 advertised in the North Island with mileage of over 411,000km. (That's over 250,000 miles).