I recently bought an 03 E85 Z4 3.0i, I was able to enjoy it for a day before it overheated on me so after reading the forums, a lot of owners recommend refreshing the coolant system at around 80k miles (mines is on 75k).
So after purchasing all the parts (water pump, thermostat, expansion tank and hoses). I was able to do the water pump which I thought was going to be the hard part but then when I came to do the thermostat the lower left bolt snapped at the head. I tried all the standard methods to try and remove it including mole grips, stud extractors and even tried welding a nut to it, all were unsuccessful. The problem I now have is after attempting to drill it out and collapse it in on itself it still won't come out so I'm now trying to decide what my options are, one method I'm thinking of albeit a bodged one at that is to clean out the threads on the other 3 holes and secure it with just the 3 bolts as well as some RTV or some sort of sealant in that lower corner as a sort of reinforcement. As far as I understand the thermostat seals itself via the o-ring and not on the mating surface of the housing to the block. So my question is for the more experienced owners or mechanicaly minded members is do you think this would be a suitable "repair" and how long do you think it would be suitable for.
It's also worth noting that after the initial overheat I panicked and bought all the parts for the coolant system before checking under the car and then when I came to start the job I discovered the lower radiator hose had come off which is more than likely the cause of the overheat rather than any of the components failing so the refresh was more of a preventative task and now it's turned into a bit of a monster
Apologies for the long winded post and thanks in advance for any feedback. See attached picture for current state of the bolt.
So after purchasing all the parts (water pump, thermostat, expansion tank and hoses). I was able to do the water pump which I thought was going to be the hard part but then when I came to do the thermostat the lower left bolt snapped at the head. I tried all the standard methods to try and remove it including mole grips, stud extractors and even tried welding a nut to it, all were unsuccessful. The problem I now have is after attempting to drill it out and collapse it in on itself it still won't come out so I'm now trying to decide what my options are, one method I'm thinking of albeit a bodged one at that is to clean out the threads on the other 3 holes and secure it with just the 3 bolts as well as some RTV or some sort of sealant in that lower corner as a sort of reinforcement. As far as I understand the thermostat seals itself via the o-ring and not on the mating surface of the housing to the block. So my question is for the more experienced owners or mechanicaly minded members is do you think this would be a suitable "repair" and how long do you think it would be suitable for.
It's also worth noting that after the initial overheat I panicked and bought all the parts for the coolant system before checking under the car and then when I came to start the job I discovered the lower radiator hose had come off which is more than likely the cause of the overheat rather than any of the components failing so the refresh was more of a preventative task and now it's turned into a bit of a monster
Apologies for the long winded post and thanks in advance for any feedback. See attached picture for current state of the bolt.
