Thread: Water pump failure?
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Old Aug 20, 2013 | 10:54 PM
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onehundred80
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From: Ontario
Default Re: Water pump failure?
Originally Posted by ala_xfire
You can get stainless steel socket head cap screws ( bolts ) from Grainger.
They have the M6X45 package of 10 for $12.72 before shipping.
I'm sure you can also find all the other bolt sizes there also.

BTW: call Rob at Needswings, he often has low cost access to these items.
You can call me dumb but if there was aluminum alloy screws in the engine when new then I would replace with aluminum alloy screws now.

Aluminum and stainless steel are too far apart on the galvanic corrosion scale and should not be used together. Stainless steel treated with a plated coating would be acceptable.

Stainless steel is -.10, aluminum is -.90, magnesium and magnesium alloys are -1.75, the worst on the scale is beryllium at -1.85. I have mentioned this before when replacement screws for the valve covers have been discussed, you will note that magnesium alloy is even worse with stainless steel.

Galvanic corrosion needs an electrolyte and I'm thinking the front of an engine sees a lot of moisture, salty road water and possibly radiator coolant.

When pieces off corroded aluminum fall of it is too late.

I doubt Mercedes specified aluminum alloy screws for their lower price.
 
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