My 1995 Odyssey seems to be leaking between the block and the engine
oil cooler and I plan to remove the oil cooler to replace the o-ring.

Can anyone tell me the size of the hollow bolt that holds on the oil
cooler on? My biggest socket is 27 mm and it's not big enough.

Also, is there enough flex in the coolant hoses to move the cooler to
get to the o-ring without having to drain the cooling fluid?

I want to get this done quickly since I have no garage, it's below
zero most nights and there is little shade from trees in Vermont
winter. I was hoping to wait until spring, but I'm losing 2 quarts a
week. Thanks in advance!

Ed