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Hi All,

I noticed the residue of a little coolant (see photo) around one of the allen head bolts (plugs?) at the top of the engine. I'm guessing I should unscrew it and re-seal it with something, but don't know what sort of sealant to use. Any suggestions?

Many thanks,
AA

1616892
ooze.jpg
 

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But Mad North-Northwest
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10,528 Posts
Someone will correct me if I'm wrong, but I believe those seal with an aluminum crush washer. Sealant on the threads can't hurt but probably should not be necessary: that's generally for tapered threads where the threads make the seal.

If the others are not leaking just leave them alone.
 

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It's pretty common. Getting alum allen plugs to tighten without stripping is not always easy. I wouldn't call it a "crush" washer but rather just a washer. Plumber's putty can help in addition to Teflon.
Early 101 and 750 head are way worse in this respect with hammered-in plugs.
Andrew
 

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But Mad North-Northwest
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Well, no, it's literally called a crush washer. Annealed aluminum. Molds under pressure to make a seal between the plug and the head. Tapered threads seal on the threads using sealant, straight threads seal via a crush washer.

You need to replace the washer every time, as once you use it then it gets work hardened and will no longer seal properly. Alternatively you can re-anneal it with a torch, but that's a little tough with the aluminum washers as they're rather easy to melt. The trick is to rub it with bar soap and then heat with a torch just until the soap blackens. But usually easier to just source a new one unless you're in a pinch.
 

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OK. In my aircraft and VW experience, crush washers have a soft rolled-on outer shell and an inner asbestos-like material. They are soft and designed to crush a standard amount. But I'm with you. Also depends on how much torque you put on them!
Andrew
 

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But Mad North-Northwest
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Yeah, absolutely true, there's different types. Some applications use fiber washers that work just like gaskets. Alfa seems to have typically used copper or aluminum (e.g., oil gauge sender, oil & transmission drains, temp senders.)

I prefer the copper ones myself as they're easier to anneal. Just heat it until it glows red, let it cool, and you can reuse it indefinitely.
 
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