Dark Blue

I've read a bunch of threads on refinishing intake and cam covers. Mine are starting to flake so I'd lik need do it. Id theer a recommended list of vendors who can do this work well.

Also, is the issue with difficult cleaning limited to pre-S4's. I'd hate to ruin my engine just to pretty up peeling intake. Thanks,

Steve
'89 S4 Auto

GregBBRD

S4 manifolds that have been redone have ruined more engines than all the rest of the years, combined. They "hide" the abrasive material used to strip off the old coating in many places.

This job is a nightmare and takes hours and hours of both preparation, cleaning when the parts are returned, and then re-assembly. Ity is virtually impossible to charge someone enough money to make it worthwhile.....and because the pieces are magnesium and have "pits" the quality is always subjective.

NC928S4

Yeah but powder coating looks so cool, and you can't put a price on cool.

vanster

Wanna bet?

GT6ixer

First off why are they media blasting the insides of the intakes? What's the purpose of powder coating that surface?. And if the shop isn't capable of properly masking why not just have the old coating chemically stripped off? Or better yet have it dry ice blasted. Then there's no worries.

GregBBRD

It seems so simple, until you actually try it.

The old coating will not completely come off chemically.....I've had them professionally "soaked" for weeks. The magnesium surface is oxidized and needs to be blasted with something to get down to clean base metal to paint or powder coat....or paint. There's too many openings and too much pressure to mask it. I know of no powder coaters that have the ability to dry ice blast.

The GTS manifolds are worse....we hand "chip" that thick coating out of the runners and off the outside for hours on end....there is no other way.

I charge $600 over what the powder coating costs me to prepare and then clean and re-assemble an S4 manifold. I charge an extra $1200 to do a GTS manifold. And I loose so much money that I won't do it unless it is a good client or I'm rebuilding the engine.

It's a terrible job! You can "trick" a powder coater into doing one....but they generally will not "touch" a second without doubling their price.

And even then, when you get it back, you are going to spend 4 hours getting the inside clean and putting it back together.

GT6ixer

Yeah that sounds like a PITA. Dry ice blasting doesn't seem to have made its way into the automotive world yet. But next time you get a customer that has to have their manifold powder coated can't hurt to give these guys a call. Looks like they are near you.

http://www.dryicecleaningco.com/Anah...alifornia.html

FredR

When I see wise Sage's like Greg advising about such difficulty preparing these things it kind of makes the approach I took 10 years ago when preparing my current 928 seem reasonable.

My inlet manifold had been repainted externally and that was also failing. I had access to blasting facilities but I also knew they were going to be "severe" on the relatively soft magnesium alloy. I took a good look at the internals and figured there was no way I was going to be able to clean the internal surfaces so made a decision to just leave them as they were and accept that if any of the coating did flake off [hopefully] it would go through the engine without causing any damage. Rightly or wrongly I figured that Porsche would not be dumb enough to coat the surfaces with material that would trash the motor if and when it eventually flaked. This was not a decision I made with any comfort- it was simply "the lesser of two evils" as I saw it.

Ten plus years later my motor is running as good as it ever has and whether or not I am running on luck remains to be seen. To do the job we well sealed up the interior orifices and blasted the external surfaces best we could and only doing what was necessary to remove the previous crud. Nonetheless, despite our best efforts, the surface of the metal was peened leaving an uneven finish. After blasting we we blew the surfaces with a high pressure air blast to remove any small particles of non visible blast media that might be lurking in the microscopic crevices, degreased with a solvent and then used a special primer to seal the metal surface within 1 hour of blasting to prevent re-oxidation of the metal surface which takes place rapidly [the oxidised surface is the black finish you see after the paint peels off]. Important to get the surface "sealed" before oxidation occurs. After that we painted with a conventional cellulose Porsche silver paints system. The finish was interesting in that it left a "mottled" effect- a bit like that of a hammer paint system.

!0 years on the paint has not flaked but a light blast of the surface with "gentle" media and a new coat of paint would not go amiss. We also chemically clean the thing occasionally and have a product that enhances the surface finish letting it shine [not sure what it is] that might just bring it back to life a bit.

The consequences of trying to do the interior surfaces and failing are horrific and I am not at all surprised at the costs associated with doing the job correctly- thus why the finished manifold that Roger was selling at $500 a while ago was a real bargain in my opinion.

Rgds

Fred

Adk46

My powder coating guy - sternly warned - was able to seal the openings fairly well before grit blasting, and did it gently enough not to harm the magnesium. He air-blasted the insides afterwards, took it to a power wash station, and then I did more air-blasting, scrubbing, picking and brushing; a stiff boiler brush was helpful. I was removing only very fine powder, which I eventually decided was mostly magnesium oxide, not sand. The inside coating had gotten flaky, so I chipped away at all the loose stuff. Clearly, flakes had been going through the engine for some time, and probably still is.

(I thought about having my dental hygienist do the final cleaning....)

I drove the car about ten miles, then changed the oil and filter, in the foolish hope that this would purge the engine of any remaining debris. That was a few thousand miles ago.

Apparently, many people have exercised sufficient care, while a small number (?) have not, or been unlucky with some unseen casting defect/sand trap. I'd be real nervous about doing it for a customer's engine, or without being directly involved. The risk to my own car must be compared to the ever-present risk it faces from its inexperienced mechanic.

WallyP

I discovered that I could chip/scrape the outer silver layer off of the '90GT intake in a couple of hours with plastic scrapers, leaving the original gray "primer" (?) coating intact. A few coats of silver wheel paint worked well, and has lasted well. There are a few tiny bubbles where I apparently painted over some pits. Safe, fast, easy, cheap and looks almost as good as powder coating.

DonaldBuswell

I just Plastic Media Blasted my S4 intake. I've read the nightmare story's about engines going to the dump after media wasn't cleaned out and ingested into the newly built motor. Wow, crazy! Excuse me in advance, but, I don't see how media gets trapped inside, and, how one can spend hours and hours cleaning these up? I just cleaned mine up, took no more than 120 minutes of media blasting. Intake sides off and blasted inside and out, and down in the runners as far as I could reach. The MAF assy housing was off and I had full access to the intake large orifices for a full media blast inside. The 2 side covers; both fully media blasted. The Cam covers; both blasted outside AND inside. Why do the inside...?? Why not! There was factory paint on the insides, so, I did my own set. I think I could do these as a set (Intake, Cam Covers) for 90-120 minutes time. What would be most economical is having like 3 sets at one time to do.

I took my Intake as far apart as possible down to the bare casting, the only non-cast part I left in were the Butterfly bearings, which will be changed out for new ones. Excuse my questioning on this, but, I can't see how Media gets trapped in these S4 intake manifold castings. Since I don't know what you all were using in terms of media, air, etc., here's what I use: 50hp screw 3ph air compressor, 180+ cfm at 30psi = a very large volume of air with a light media stream introduced. Media that is NOT an impact cleaner but designed to be a non-abrasive media (Plastic) which your run of the mill hobbyist can never afford to buy the supporting equipment to run plastic.

Here's a video before, and here's pictures after (No video of after...yet). https://www.youtube.com/watch?v=uEcm9KAnxw0

DonaldBuswell

...I'm not going to go powdercoating on these items. I'm going to use my Epoxy primer which locks down very tightly -- almost as tightly, and, dare I say as tightly as powder does! Why? A uniformly prepared surface, professionally media blasted which has the right mix of media to give it a uniform profile for the Epoxy to really stick, and, the powdercoater I visit is greatly pleased with the profiles I provide him for their applications of powder in a successful manner. I'm going with Epoxy as I am not totally sure what color I will hue these items. I think I will match them to the wheels, which, also I have Plastic Media Blasted (PMB) internally in-house at drblast, so, epoxy will be the way to proceed. Of course, over time I will report how it all holds out.

Hilton

You should remove the black plastic plugs in the cam covers - they're held in with circlips on the inside, and there's an o-ring sealing them to the cover which will need to be replaced as the old rubber will be hard and a point of failure for oil leaks in future.

worf928

What Greg said.

If you run the intake through a dishwasher about a dozen times, turning it 90 degrees on all three axes as you go you can get it clean.

If you think you can sand blast and just blow it out or something, you may well be in a world of hurt. Or just plain lucky.

Now, you can strip, bead blast, clean and coat an intake and not destroy your motor. That has happened far, far more times than have motors been destroyed. But, if you think your work - from stripping it to cleaning it - hasn't been a bitch that you never want to do again, then you've probably missed something.

DonaldBuswell

I looked at my Cam Covers today, and removed those black plug things, thanks Hilton!

I guess I don't see the issue with the S4 intake manifold being problematic. Mine is clean as a whistle, and there is no hanging media anywhere in it, I must wonder if you all left the side covers on and sand blasted? Then if so, certainly media will remain inside.