I am currently replacing the head gasket on my 91 300e and want to know how do i losen the timming chain tenssioner so that i can remove the head?

thanks in advance.

Loosening it won't get the job done. It would allow you to remove the head but would potentially cause damage upon reassemble. Remove the whole tensioner, disassemble it, push the toothed plunger all the way through and then start it back through so that oil pressure will ratchet it into position once the engine is started.

Good luck,

300e 103 timing chain tensioner

I noticed that there is a 12mm(? i think) hex screw on the outside of it. what would turning it do? I just want to be able to prefferabley losen (or remove) the tensioner so that i may hang the chain on the hood or something of the sort to keep the tension so that it would allow me to remove the head and replace the gasket easily.

Don't cut any corners. Follow the directions in the link Mr. Dalton provided. Shortcuts are very expensive.

Here's what can happen if you don't do it right:
M103 Timing chain snapped

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1989 300 SEL that mostly works, but needs TLC