E90 top radiator hose coming off leaking coolant

**Olu** · 05-25-2019, 01:37 PM

Hi everyone. New here but help is urgently needed. I drive a BMW E90 2005. It's got 114k miles on it. While driving on the motorway about a month ago, the top radiator hose popped off and leaked all the engine coolant. Low coolant warning came up on the dash. I put the hose back in and was able to get it off the motorway to the nearest gas station where I refilled with expansion tank with about 2ltrs of coolant (took it all in). The rest of the journey was uneventful. Drove about 70 miles with no incident. Two days after while running errands, hose popped out again and leaked all the coolant. Took car to the garage and was told top hose was warm and bottom hose cold. Thermostat (or housing) wasn't kicking in to regulate temp.

Thermostat was replaced as well as gaskets (not head gasket). Mechanic said no hose was found to be leaking or loose and head gasket was fine. Was told thermostat would kick in when engine reaches a certain temperature. It seemed a bit strange as I wondered how the mechanic would have diagnosed a faulty thermostat if it was meant to start working when the engine reaches a certain temp. The engine was still cold when I arrived at the garage which is just a 5 minute drive from my house.

Top hose popped out again 2 weeks and 200 miles after carrying out repairs. Breakdown mechanics told me it's the clip that held the hose in place that'd grown weak. Clip was replaced. They poured distilled water in the expansion tank and bled it for about 15 mins. There was a lot of air in the engine which they suspected to be abnormal. Again, they felt the top hose (which was hot) and bottom hose (cold) with the blower running, and told me it could be the thermostat. Told them I just replaced thermostat.

I've gone through a lot of threads and reckon it could be
1. A bad radiator cap
2. Bad hose
3. Faulty radiator.

Can anyone please advise?