[Tuan]

Morning all, I have been trying to remove the serpentine belt tensioner; I believed it to be a Torx 55, too big, tried Torx 50, too small, then I managed to get a mirror down there and saw that it had a Hex head(Allen key) so tried a 8mm Allen key, too small, the 10mm was too big, so I presume that it must be a 9mm which I don't have and will get tomorrow, can anyone confirm this? Thank you

 

[Gidner]

It’ should be an 8mm hex. Maybe dirt or something built up in the bolt hole?

 

[Jeremy R.]

It's definitely an 8mm hex, but it's a tight fit. I prefer to use a 5/16" bit or hex wrench most of the time because it fits a little easier.

 

[unclemiltie]

as said, 8mm hex. you'll need a "stubby" one or will have to cut off one of yours to leave enough room to get the bolt out.

FWIW once it's loose a 1/4 drive ratchet will fit into the head and take it out. not enough grip to loosen the bolt, you'll need the 8mm allen for that, but after that it's much easier to use the 1/4 ratchet.