You might want to do it as a pre-emptive measure. Mine choose to go out when I was towing my 5er thru the Siskyious just as the snow was starting to fall. It fried all 8 glow plugs at once and I could hear the pistons smashing them to bits.

You never know when it will happen and the last thing you want to do is pull the heads if you don't have to.

Nate

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Nate Stanley
(Currently Benzless)
1985 F-250 6.9l 170K
2009 SCION XB 36.5K
2003 LS430 78K
2012 Kubota B 2320