Aluminium Intake

[cdavie2002]

What coating goes on the intake manifold of the CSI.

Mine is in bits for cleaning, it has oxidized & is quite porus but is quite clean.

It doesn't look like it was ever painted, but I'm curious if it ever had a coating?

 

[Tierfreund]

No paint, no coating originally. Just the cast alloy that quickly oxidizes slightly and that oxidization is that actuall finish (sounds worse than it is, that initial oxidization gives it a nice even protective matte grey coat). Impossible to replicate (unless you cast a new one). Basically stays that way for ever unless you let it stand in the rain. Unfortunately it takes to dirt very easily and thus starts looking shabby one day.

But cleaning, maybe bead blasting will give you a nice alternative surface. Just not as long lasting.

 

[cdavie2002]

Thanks for that, im thinking of taking a wire brush to them to see how they come up.

 

[rsporsche]

have you thought of media blasting them? probably quicker than wire brush

 

[Nicad]

I'll be treating mine with Alodine after blasting. Pretty standard in aircraft parts and perhaps BMW did this as well.

 

[Stevehose]

+1 and it will be very diffiult to get all the crevices to match the rest with a brush.

have you thought of media blasting them? probably quicker than wire brush

 

[cdavie2002]

It does look worse than it really is, a going over with a wire cup on the end of a drill should clean it up.

Is alodine the only way to protect but keep a semi original look?

 

[Stevehose]

Won't this turn them yellow?

I'll be treating mine with Alodine after blasting. Pretty standard in aircraft parts and perhaps BMW did this as well.

 

[Nicad]

Henkel makes a clear alodine as well as a Golden tinged one. I am going to Alodine my 2002 intake manifold perhaps today so will post photos.

 

[Stefan]

cdavie2002,
I guess you need to media blast (glass) these heavily oxidized aluminium parts.
Afterwards spray the blasted parts with a thin layer of clear coat and you are done

 

[Tierfreund]

Did these come from the Titanic? I hope the rest of the engine/car is in better shape. And i wouldn´t trust the injectors...

+1 on the media blasting. Cheap and effective. I´ve spent too much time in my life trying to clean or even polish alloy parts from engines manually or even with power tools. Enldess work, probably not good for your health (I believe alloy dust is really bad for the lungs), and never looks as good as blasted parts.

 

[Nicad]

Gave my 2002 intake manifold an Alodine treatment yesterday .

Here is how it started. The rest of the engine is the most gunk covered I have ever dealt with. Took more than 2 days to degrease it and I am hopefully painting the Bloc with POR 15 engine paint next week



After degreasing and bead blasting with Fine grade beads




After three minutes of Alumiprep 33 and then 3 minutes in Henkels clear alodine




In case anyone has any magnesium parts, I gave the same treatment to my Corvair magnesium fan and it came out looking like they did when new according to the Corvair forum gurus. It was a dull Silver before the Alodine treatment and really reacted to the acid etching as the stuff was looking pretty active for those 3 minutes.




One part that had some troubles was my 2002 valve cover. It was bead blasted as well, but came out with a mottled pattern and some staining that looks like a chemical was put on the valve cover that did not agree with the aluminum (Degreaser perhaps??)
I sanded it down, re blasted it and repeated the process but it came out the same

 

[Stevehose]

Looks great

 

[RogerW]

As an FYI - I would NEVER media blast an intake manifold or valve cover with glass beads. There have been documented cases where the glass beads get into the engine after reassembly and ruin the cylinder walls. I personally know a person who had to replace the engine in his BMW from this exact process. What happens is that the glass beads imbed themselves on the INSIDE of the maniford or valve cover, and then when the engine heats up they come loose. Many try to tape off the openings, but I would not chance it.

Instead, use walnut shells for the blasting media. If they come loose, they will break down and not harm the cylinders, and are recommended.

None of us would want to be the person who's block is ruined from glass beads.

Another product you can try and use is Alumabrite for cleaning aluminum parts. Many in the E31 community use it with very good results.

 

[Peter Coomaraswamy]

Thanks Roger, very timely information

 

[Nicad]

Yes good info, I will be extra thorough in cleaning them out. Your reasoning makes perfect sense. I think I will go to the coin car wash and let them have it for a few minutes.

 

[Nicad]

Thinking more about Roger's warning I figured there was no way I could clean all the glass bead that might be trapped in the baffle of my valve cover with water, degreaser and compressed air, so I drilled out the rivets that hold the cover in place. This would require quite a bit of soaking to loosen this stuff up, so Roger's warning is really something that I am glad I heard before putting my motor back to use. I am pretty confident I can clean out the intake manifold now that I have this in mind, but I would not glass bead a valve cover without removing this plate.