I have a leak at the manifold gasket, and was wondering if the studs were as prone to siezing and breaking off as on the 602/603 aluminum block engines. I was planning on using a fair amount of PB and heat as a precaution. Any advice on proceeding with this would be greatly appreciated as I'm pretty nervous about it.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Any 22 year old exhaust nut has a good chance of breaking off from thermal cycling stress and rust.

Soak it with PB a few times and let it soak overnight if possible. You might even get a handheld propane torch and heat up the nuts really well if they resist coming loose.

Once you are ready to put it together, use lots of high-temperature anti-seize on the studs and new nuts.

otoh the benz fasteners are the least likely to break of anything i have ever worked on.

just be careful and use the pb and heat if necessary. make sure you have your wrench or socket fully seated. if it is a tough nut get a high quality six point socket on it too.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

the best penetrating oil I have found is Free All its not cheap but it will break anything loose if you let it soak long enough and the good old gas wrench doesnt hurt I think free all is around 8 bucks a can but its a good investment

Most likely(or hopefully) you'll unscrew the stud from the block if the nut is stuck.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

The best is KROIL used overnight- and several times overnight if you have the luxury. Then you have the old stand by of melting candle wax on the threads- it seeps into and frees the frozen hardware. Old "blue lips" is also the ticket.