I'd like to record this somewhere just in case it helps someone else out in the future.
Yesterday I was swapping out my thermostat and while hand tightening the three screws into the thermostat housing, the threads pulled out of two of the screws holes.
The thermostat housing is ERR1499 and looks to be around $300 for a replacement.
The bolts that hold the thermostat housing on are M6x1.0-40mm bolts and the housing has a considerable amount of material around the threads.
I chose to drill and tap the housing for larger bolts, specifically M8x1.25 because it is a very common thread pitch and size found readily pretty much anywhere.
A M8 tap requires a 17/64th drill bit. Drilling out the hole is very easy as the aluminum is soft and there is room to plunge through the housing. The hole will guide your drill bit to some extent, but you should try to get this as straight as possible. You should stuff some rags behind the water pump pulley so chips do not get behind the waterpump pulley. I left the old thermostat in the housing as I drilled to prevent chips from getting into the coolant.
Once the holes are drilled out, use the tap to make the threads. There is plenty of room to run the tap nearly all the way down.
The top housing, ETC5967 needs to have its bolt holes drilled out to 5/16ths or marginally larger. 5/16ths is the OD of the M8x1.25 threads. 21/64ths or 11/32nd would probably be a better choice as it will allow for easier installation of the cover. I would recommend doing this on a drill press of some sort as the holes are quite long and the soft aluminum is likely to grab the drill bit and break it if drilled by hand.
You'll need to replace the bolts with M8x1.25-40mm, which can be found at Lowes or Home Depot easily. If you cannot find a flanged head bolt, you can use a standard bolt with a washer.
An added benefit of this procedure is that you no longer need to have a 8mm socket to remove the housing as M8 bolts use a 13mm head.
Yesterday I was swapping out my thermostat and while hand tightening the three screws into the thermostat housing, the threads pulled out of two of the screws holes.
The thermostat housing is ERR1499 and looks to be around $300 for a replacement.
The bolts that hold the thermostat housing on are M6x1.0-40mm bolts and the housing has a considerable amount of material around the threads.
I chose to drill and tap the housing for larger bolts, specifically M8x1.25 because it is a very common thread pitch and size found readily pretty much anywhere.
A M8 tap requires a 17/64th drill bit. Drilling out the hole is very easy as the aluminum is soft and there is room to plunge through the housing. The hole will guide your drill bit to some extent, but you should try to get this as straight as possible. You should stuff some rags behind the water pump pulley so chips do not get behind the waterpump pulley. I left the old thermostat in the housing as I drilled to prevent chips from getting into the coolant.
Once the holes are drilled out, use the tap to make the threads. There is plenty of room to run the tap nearly all the way down.
The top housing, ETC5967 needs to have its bolt holes drilled out to 5/16ths or marginally larger. 5/16ths is the OD of the M8x1.25 threads. 21/64ths or 11/32nd would probably be a better choice as it will allow for easier installation of the cover. I would recommend doing this on a drill press of some sort as the holes are quite long and the soft aluminum is likely to grab the drill bit and break it if drilled by hand.
You'll need to replace the bolts with M8x1.25-40mm, which can be found at Lowes or Home Depot easily. If you cannot find a flanged head bolt, you can use a standard bolt with a washer.
An added benefit of this procedure is that you no longer need to have a 8mm socket to remove the housing as M8 bolts use a 13mm head.