Sliconizing engine block
 

I'm having rings replaced in my 88 sl. My mechanic says he has to send the block out to be siliconized but he's having trouble finding a place that does this. Any help?

Tim

I have been messing with engiens for about 45 years and have never heard of siliconizing. Sure he is not trying to sell you a left handed monkey wrench? Pls. let me know what this proceedure is and what is supposed to do to the engine.

siliconizing
 

Supposedly the cylinders have a silicone coating on them thats put on at the factory and if your doing this extensive amount of work you may as well recoat the cynlinder walls again. He says this process should cost about $50 but he's having a problem finding somebody. I believe him to be very reputable as he has a wonerful reputation in Montreal.

siliconizing 2
 

He did show me the inside of the cylinders and it did appear to have some kind of coating on them to me.

Ah!, the wonders on modern technology.

Tim,
I believe your SL has the M117 engine which indeed is an alusil block just like the Porsche engines of the same vintage. Try this thread:
http://db.mercedes.cx/sec/200109/06/0052.html

Cheers, Andrew Seidel.

Alusil
 

Thanks for the info. I found tons of info on the aluminum block and the silicon impregnated cylinder walls. It seems what my mechanic totally checks out.

Thanks again,

Tim

There is an interesting description on cyl. honing an al. block on the Tech Help site under 'cylinder honing an aluiminum block'.

Came across the aforementioned link earlier today when I was looking for an answer to that very same question. Unfortunately, that link is dead :(
WHile I understand the basic metallurgy involved (I'm a Mech E), I'd like know exactly how the bore is treated to re-expose the silicon crystals (after honing I presume)? As always, I'd appreciate your help, thank you.

I believe BMW calls it Nikasil - probably the same process. FWIW.

best,

Dave

Sorry, nikasil is not the same as alusil...my mistake. Nikasil is apparently a more expensive and superior coating.

best,

Dave

I just read up on the Nikasil/Alusil issue with BMW's by "Googling" it and all I can say is,
"Wheeeeeeewww!!! That one is a biggie !!!"

I can just imagine the horror stories Bimmer owners have when their cars run like a POS after 30K miles when they were new. BMW took a money bath on that oversight.

Yes..actually Nikasil was the problem material that degraded in the mid-1990's with US fuels, causing many a short block to be replaced in beemers....

I always thought that "recoating" the cylinder bores meant replacing the cylinder liners, but I could be wrong. If you've ever seen that it's pretty cool - you heat the block in an oven (to make it expand) and freeze the new liners in liquid nitrogen (to shrink them) - it's pretty exotic.

Well,
In case it didn't register, I was referring to refinishing the ALUSIL M117 blocks, I've heard that a leather swap dipped in acid is supposed to melt away the aluminum matrix on the surface, but I was hoping for a little more detailed information on the subject matter, thank you.

Nikasil isn't the same as Alusil. Both however are surface treatments to aluminium to improve its wear characteristics and were first employed in automotive applications during the 1980s when alloy blocks were designed without the use of steel liners to save weight.

Porsche and Daimler Benz were the first to build linerless blocks. They went the Alusil route and their engines have given excellent service. When BMW followed some years later, they went the Nikasil route. BMW got into lots of trouble with Nikasil both in the US and the UK. Nikasil just couldn't withstand the relatively high level of sulphur that was in gasoline then and the coating literally fell-off the cylinder walls. BMW have now changed to Alusil which is less prone to this failure mode.

--
bobw
1983 380SL
2001 Ford Mondeo Zetec S V6
2004 Ford Ka Luxury