Why must you replace (or must you) the manifold gasket each time the intake manifold comes off? I have reused mine several times, once when the manifold had to come off a few days after I put the new gasket on and once when I didn't happen to have a new one on hand. There don't seem to be any apparent issues. Will a check engine light come on if the gasket is not sealing properly or are there other hidden problems that could occur like sucking in unfiltered air, poor mileage, etc.?

I do have a new gasket on hand now, but was just wondering. I will be taking my manifold off soon to remove, ream and re-antisieze the glow plugs. It's been a year and a half and after going through one breaking off on me, I'd prefer to take this preventative measure even though I'm not sure that using antisieze is the solution, but it makes me feel better.

Len
'99 E300 DT 99,500 miles