Yesterday I tackled the exhaust manifold heat shield in advance of manifold replacement. I've read on here that they can be a right b1tch, and this doesn't surprise me because they seem to be that way on most cars. The combination of heat cycling, moist environment and age means the heads of the bolts rust while the threads seize up.
Anyway I took the car out for a short spin, just to get up to temperature. Then I sprayed WD40 locally around each fastener. It was hot so a lot of it evaporated (and made lots of smoke) but I suspect that it had a bit of a cooling effect within each fastener.
Most of the fasteners worked with an 8mm socket - tap it down onto the head with a hammer to make sure it's snug. You could use 5/16" which is slightly smaller and therefore a tighter fit. Tapping it may also help to free the thread. Use a hex/6 point socket, not a 12 point type.
Then turn anti clockwise, firmly but very gently, making sure the socket is at 90deg to the bolt head. All but 3 of the fasteners came out without a fight.
One of the fasteners was rusted enough that I managed to hammer a 7mm socket onto it and turn it. One of them broke off halfway down the thread. One of them I had to use a mole grip to turn the head.
I think four of the bolts are self-tapper types that screw into the vertical part of the shield; I replaced these too.
Once they were all out I replaced them with some stainless bolts with some high temp anti-seize. It's coming out soon anyway so this is just to make sure I don't have another fight when that time comes.
Good luck.
Anyway I took the car out for a short spin, just to get up to temperature. Then I sprayed WD40 locally around each fastener. It was hot so a lot of it evaporated (and made lots of smoke) but I suspect that it had a bit of a cooling effect within each fastener.
Most of the fasteners worked with an 8mm socket - tap it down onto the head with a hammer to make sure it's snug. You could use 5/16" which is slightly smaller and therefore a tighter fit. Tapping it may also help to free the thread. Use a hex/6 point socket, not a 12 point type.
Then turn anti clockwise, firmly but very gently, making sure the socket is at 90deg to the bolt head. All but 3 of the fasteners came out without a fight.
One of the fasteners was rusted enough that I managed to hammer a 7mm socket onto it and turn it. One of them broke off halfway down the thread. One of them I had to use a mole grip to turn the head.
I think four of the bolts are self-tapper types that screw into the vertical part of the shield; I replaced these too.
Once they were all out I replaced them with some stainless bolts with some high temp anti-seize. It's coming out soon anyway so this is just to make sure I don't have another fight when that time comes.
Good luck.
