Odd coolant loss

sklooner · Post by **sklooner** » 22 Aug 2025, 12:44

010 xc60 3.0 T6 325000km- so about a year ago the low coolant warning came on and I poured in about 500ml of coolant- kept checking and it was fine, last week took a trip and all was fine until I stopped for a bit on a hot day and drove away after 30 minutes- the warning came back but it was only about 5mm under the min so I drove for another 50 km till I could stop and cool it down- about 30 minutes later I undid the cap and no pressure, poured in 250ml of coolant and went on. The next day I drove about 1 km stopped and it leaked out about 2l of coolant so I refilled it and it did the same thing the next day on a short trip- I cant see where it is coming from and due to the engine pan it leaks out of whatever side is lower- I drove it 200km and it was down 2l again then I had the homebound trip of about 1400km- I stopped after 50km and it was full, drove another 50 full then 100 full then kept going and got home and it is still full-there is no evidence that the pressure cap is leaking but I did order a new tank and cap as this one seems old, any insights ?

Vova585 · Post by **Vova585** » 22 Aug 2025, 12:50

Leaked 2l?
I would vote for pressure testing coolant system. Do not throw parts at it(expension tank cap is ok cost), without knowing what is going on. Can also do a exhaust gas text in coolant as 2nd step. I would also check your oil level. If above norm limits it is possible you have water there.

sklooner · Post by **sklooner** » 22 Aug 2025, 13:44

I guess I forgot to say that I see puddles under the thing- I did put a new tank and cap on and now it holds pressure- it's weird that it will dump coolant after 2km then be okay for 1200

Vova585 · Post by **Vova585** » 22 Aug 2025, 16:49

Were you able to pinpoint general location of the leak. Right side of the engine or left, front rear? Still in would pressure test the system and hopefully you have your old tank and cap, i would test them too. I would like to be certain i can take this car on a road without "what if" thoughts

Post by **chrism** » 24 Aug 2025, 06:52

Remove the belly pan so that you can get a better idea of the location of the leak. Another thought- I don’t know if it’s still the case but the older Volvo water pumps often had a habit of leaking when the engine cooled down. As long as the engine was running and warmed up the pump wouldn’t leak.

sklooner · Post by **sklooner** » 25 Aug 2025, 10:49

It seems that it is coming off the back of the engine- I will check the pump as well-

sklooner · Post by **sklooner** » 26 Aug 2025, 09:34

I thought it was off the back but it looks like the thermostat housing is leaking and really bad- so will swap this afternoon

Post by **scot850** » 28 Aug 2025, 22:56

If your car has the newer style plastic thermostat housing, at this mileage it will be warped and leaking. Plastic housings are terrible. Sorry!

Neil.

AlanS · Post by **AlanS** » 24 Sep 2025, 06:07

I just went through this. Odd leak, could not find it. Finally put a dye in the coolant after I throughly washed the engine of all the leaked coolant. Black light...whammo! It was the thermostat housing. A small leak that would increase with engine heat and milage. Get some coolant dye (I got mine from Amazon, AC Delco) There is no consequence to the engine by using this dye.

122sPhil · Post by **122sPhil** » 25 Sep 2025, 14:45

glad it was a fuel pump or related leak. At the beginning it sounded a lot like a head gasket issue. common for engines to barf the water through the head gasket intot he exhast when the head gasket fails.