glowplug removal merc OM642

[Trustmeimadoctor]

any advice at all? seems i have one or more gone so im looking at doing them BUT i see many horror storys when replacing them any advice at all?

[Rat_Fink_67]

Best advice I can give is to get the engine nice and hot first. I'm a ex-mercedes tech and can't recall ever snapping a 642 glow plug with a hot engine.

[Classy6]

I've snapped a few on 642's Problem is the plugs are pencil thin!

As above get the engine stinking hot and before you do that, soak the glow plugs in engine oil liberally.

Only other thing I'd mention is are you sure it's the plugs? The glow plug control units used to fail for a past time on those engines too.

[Trustmeimadoctor]

no idea really havent tested the plugs need to do that first i suppose

[Rat_Fink_67]

As above, usually if the glow plugs fail, the control unit/relay gets back fed and fries. There'll be a fault code stored for it more often than not though.

[Trustmeimadoctor]

What value should working plugs give when i test them?

[chammyman]

The relay will have a burnt out leg most likely.

You can mod them to take an external fuse.

As for the glow plugs some come out fine some don't, they usually don't.

Ohm checking them should be about 1 ohm iirc

[Alexdaredevils]

I've almost changed all of mine in my 147k miles om642 all came out no issue with a hot engine, except one!!! the one I left for a month of so to change....It undid ok but once I got past the threaded part the shaft was so gummed up couldn't remove it even with a slide hammer, ended up chucking loads and lots of lube on hole area and with the engine started (using the compression to pop it out) and a air ratchet she eventually came out after 6 hours

But most took me less than a minute to change

You will need a deep 8mm 3/8 drive socket