Bolt sizes

[nicktennear]

Hi, I'm about to replace the metal pipe that runs into the thermostat from the pump, and the actual thermostat (not actually replacing the thermostat because there isn't one currently ) All bolts are seized, rounded or seized and rounded and will need to be replaced by nice and new ones but can anyone help me with sizes/lengths? I want to pick them up before I attack the existing ones. Thanks.

[itchyfeet]

M8 cap heads, 20mm will be about right, 5 mm for the flange 15mm penetration

[nicktennear]

Thanks, saved me some hit and miss.

[CovKid]

However, I recommend you get a slightly longer bolt and run a 13mm nut beneath it. This then gives you two ways to remove them if an allen key rounds out the bolts in future. I came up with this cunning solution when I was reinstalling mine and had probs removing the old ones. If the old bolts are stubborn, an irwins bolt remover (at a slight angle because of space available) will shift them - use lots of plusgas.