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How can this be fixed? (paint)

Old 09-14-2002, 12:21 AM
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KBlair
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Cool How can this be fixed? (paint)

here are a couple pics that the current owner sent me (without me having to ask BTW). I've seen this kind of thing on about half the cars I've looked at over the past few weeks. Any ideas on how to fix this or what I should do? At the least, I want to keep it from getting worse till I can have it fixed properly.





Also, why does this seem to be so common? Is it because of the airflow over the wing?

TIA
Old 09-14-2002, 01:19 AM
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Dave H.
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from water being held between the spoiler and the paint.

you'll have to sand then down, repair the metal (esp the second photo) and repaint...
Old 09-14-2002, 01:26 AM
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KBlair
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Cool

That's what I figured on all counts. Anything I can do to keep it from getting worse till I can get it to the paint shop?
Old 09-14-2002, 07:26 AM
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Dave H.
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the top doesn't look too bad but you don't know until you get the spoiler off. either way, you have to sand down until the rust is gone, then prime and paint. you could prob'ly get away with just using touchup paint on the bare metal, but don't do primer only. primer absorbs water and it'll just get worse...
Old 09-14-2002, 10:39 AM
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John Struthers
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I agree, partially, with the water/grit theory.
However, from the few 'exposed'sharks that I have seen including some of the early 'trim only' cars the mount points seem to be the culprit.
Just looking at these semi-typical paint/corrosion damage photo's points to mount, clip holes or points.
Normally. an edged hole or mount point doesn't get the 'average' amount of primer or paint.
What ever gets mounted to that area will hold water and road grit. More to the point that mount point, especially, a clip type will, sooner or later, vibrate and rub against the edges - this can happen on plain old mating surfaces - the process is hastened when you add abrasive grit and once water gets involved electrolytic corrosion is practically assured.
All of the sharks I've seen with this problem had spots that were 'INTO' the metal, however you could see where the paint initially delaminated from the primer, like that round spot in your flicks. While this looks deep at first glance, it's only(sic) paint. Meanwhile, back at the ranch, the abrasive grit, water and vibration keep working on the primer. Yes, primers are more porus than topcoat finishes, but, commercial as 'compared' to spray can primers are damn near sealants. In any case, when the grit/water and vibration finally get thru the primer and to the metal you are hosed because now the etching can begin on the surface of the metal -lifting more paint- this etching can extend 2 1/2 times the diameter of the visibly damaged area. At the same time the etching starts on the surface of the metal, Granular corrosion rears its ugly head and starts working 'thru' the metal from an edge.
In aviation we cut the damage out at 3 1/2 times the diameter of the visibly damaged area, cleaned it up then used a 10 power magnifyer to look for etching or remaining granular corrosion.
The only TEMPORARY fix would be to pressure wash the trim/spoiler pieces to drive out the grit get some canned air or a compressor to blow the water out then set her in the sun for a few hours.
Tape off the trim/spoiler - this is temporary, right? - tape off and paper the area at least 1/2" to the outside of the lifting paint, sand with 280, 320, and 400 grit wet or dry. Use a good primer, krylon will do. the canned primers are basically, sandable primers which means they are thick. be judicious, go light. Practice on something! let it cure or use a hair dryer, shoot whatever canned paint you have, again be sparing.
Pull the tape before it dries at a 45 degree angle toward the paint hit her with the heat gun.. if you have the room move tape and paper line out anothe 1/2" feather on the edge, dry wipe or use tack cloth and shoot with a krylon clear, two coats.
Yep it's noticeable, less so if the primer and paint coats didn't go on thick. But this is only a temp fix right...
If you don't expose and remove the Rust nothing will stop it! If the metal is already crunchy don't waste your time get it done professionally. those rust gels only work on the rust they can reach , trust me, the naval jelly's won't reach half of what need to be neutralized.
HTH , good luck
Old 09-14-2002, 11:55 AM
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KBlair
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Wow John, thanks. Would removing the wing pieces help?
Old 09-14-2002, 02:05 PM
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dr bob
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Living and (mostly) working on the dry left coast, I often forget about the ravages of rust. I was in Illinois this weekm adn had the pleasure to park my brand-new rental Taurus next to what appeare at first to be a nice-looking 80's GM something. Hey, that's a GN! But under the paint at the wheelwells, the door edges, rocker sills, under the window trim, etc, there were big blooms of cancer. Ughh!!

Recently, the SoCal group did a motormount day. One of the subject cars was a very nice S4. Unfortunately, it was a former east-coast car imported to California. The bottom of the car was coated with oil from a sump leak, so we pulled the crossmember and the sump. Rust everywhere, bolts, bits, etc, even with the later-in-life protective oil coating. We replaced the corroded fasteners with new where we had new ones, but...


So I'm pretty much convinced that, even if I lived in Hotlanta, my shopping might be limited to west coast cars, or at least would include an inspection for body and undercarriage rust.


On the car that's in the pictures, getting all that out will be a chore, and the final 'fix' will undoubtedly include a repaint over whatever repairs you make. That top picture looks like the paint is way thick or is hiding a layer of filler, perhaps an indication of a prior repair in that area.

Folks on the list hare have shared repaint costs in the $$thousands, and delays of months in some instances. Add those numbers into your purchase calculator, and decide if there's any true economy in those 'low-cost' Florida cars. It starts to make a bit of travel look like a good investmnt.


Many cars have been pre-inspected by listmembers in foriegn places. Most of us now have or have access to digital cameras to do a mini documentary on a car for you before you ever get serious about a purchase. I'm almost ready to suggest that we keep a registry of cars we look at, listed by VIN and location, so that other listers/potential buyers can benefit from the knowledge and not waste time on examples that have already been screened out.
How many "rare" e-bay sales look tempting, if only there was an unbiased review/inspection available in the next 24 hours? I haven't heard anyone on the list complain of being submarined by a volunteer inspector, but have heard horror stories about misrepresentation (differences in opinion or judgement or terminology) by some sellers.


Anyway, you can do some cosmetic fixing of the obvious proble areas. The final cure is obviously a complete strip and repair of the affected areas, followed by a good prep and paint procedure to bring the car back to good condition. That's time and money though, as I mentioned above. If you have the time and repair capability, it's not anything show-stopping, just a chore.


Good luck with your project!
Old 09-14-2002, 04:32 PM
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Incendier
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I'm doing the EXACT fix right now of picture #2, in addition to making an attempt at the trim holes (against the advice of list members, but I've got nothing to lose).

I'll post the results when the surgery is complete.
Old 09-14-2002, 06:59 PM
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John Struthers
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KB,
I have to agree with the good DrBob.
If you don't HAVE to buy it, move on...
And, yep, take the spoiler off if you are going to buy it for a better look or, repair.
I know there is at least one screw involved -you can see it in the picture. As to the thick paint...could have been a touch up, a repaint without prepping the rusted area, or last, I see curling on the bottom which always seems to catch the eye and make the paint look thicker.
When you pull that fender spoiler you might as well look at the other, side too.
The spots aren't that big but the one running under the window seal will give you the fits. <img src="graemlins/crying.gif" border="0" alt="[crying]" /> As the quarter window and seal need to come out so you then think for a minute or two and pull the inside quarter upholstery...
the story goes on as James Erdmann could probably tell you.
If the rust hasn't gone all the way thru the metal, buy one of those small disk sander kits.
they usually come with a variety of snap on grit disk's. The tool itself has a shank(mandrel) that you slip into a variable speed drill or a small, cheapo, high-speed (16,000-20,000rpm)die grinder, Wal Mart or Lowes sell em' for about $20.
The die grinder clears things up FAST! Practice on something. High-speed grinder bits of different diameters and shapes are avilable and come in handy when hogging out rusted sections.
You can buy a airbrush kit for under $40 - practice a little - for priming, painting, and feathering (transition).
If you are going to remove damaged metal like James you have to locate exactly where the trim /screw holes are BEFOR you grind out the damage. They are a PITA to locate after the metal with trim hole is gone. I would extend some lines vertically and horizontally to locate the corners.
If I was doing it I'd cut the damage out make a backup piece and then scribe another piece of metal for the insert(flush) piece.
Try to do this:
Get a couple pieces of cardboard. On one edge cut out a 1" by 2" piece this is your imaginary rust to be removed. Lay the piece with the cut out on something flat. The reason I said to cut out a 1"X 2" piece was to show you that it is better to cut damage out dimensionally - not just the minimum - so that you can make a repair piece fit with a lot less work.
Now take another piece of cardboard, lay it
-online- under the edge with the removed 'damage'
, take a pen or pencil and draw a line ALONG the cut out edge ONTO the 'backing piece'. Pull the backer and cut out the marked piece, before you cut, Mark which way is up, left, right- good training-. This marked cut out piece is the flush part of the patch. Try fitting it to the piece you removed the 'damage' from... how does it look? Now, put a piece of cardboard under the edge, again. Mark the same cutout area on this piece. Extend a line outward from the marked cut out line. It should extend at least 1/2 inch beyond the cut out edges with the exception of the upper edge. This is the back up piece for the flush patch. Now do the same thing with metal. The flush patch needs to be close but not touching the cutout area edges -need a little room for expansion and shrinkage due to temperature changes. Basically, you will be using countersunk solid or pop rivets to rivet the backup piece to the car then rivet the flush patch to the backup piece. Since this is not a patch exposed to the stresses and vibration of an aircraft we can use a little mechanical license here. Minimum of four rivets tying the flush patch to the backup piece and two rivets per edge -side- of the backup piece tying it to the car. You can use more as long as they come no closer than 2 1/2 rivet diameters to each other and they are evenly spaced. After you drill the holes use a large drill bit or countersink -by hand- to remove the the ragged metal from the back side of car body and patch pieces. then light ly counter sink the outer body metal for the backup piece rivets and the outer part of the flush patch. Test by seeing how flush the rivets seat, if they are a little high just grind them down smooth with that sanding kit. A light coat of rubber cement on the MEETING faces of the car and patches to provide a thin, reliable corrosion barrier, dip each rivet in the rubber cement as you use them and rivet that puppy on.
Block sand (a foam rubber block, or a new, unused, dry, kitchen sponge) to see if you have to use a light sandable filler.
Now start practicing with that airbrush!!!
The above is for flat pieces, if you have bends... things get ugly... even with the right equipment
Old 09-14-2002, 07:20 PM
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Kevin in Atlanta
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My two cents says if there is corrosion at the spoiler be prepared to find it in places not so obvious. A paint job worthy of the 928 will cost at least $5000 in Atlanta. I have heard a fellow 928S with similar body work required $8200 worth the work. He's shopping that quote. But, you can see the neighborhood you are in. Ask yourself: What level of care does it take to not get that type of damage to occur? If you factor the paint cost into the sales price how good a deal are you getting?
Old 09-14-2002, 08:16 PM
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Incendier
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Well...a few suprises (as always).

Noteworthy item #1 - Porsche applied _very_ heavy layers of paint. I never noticed before.

Noteworthy item #2 - there is no rust under the bubbling paint. Do I say "woohoo" or "what the hell"? Not what I expected.

From what it looks like, water rolled off the spoiler and between the top and second layer of paint. The second layer of paint and the primer are completely untouched.

I dunno how this happened, but it removes the repair from the realm of bodywork to simple paint repair. I'm going to use the standby - feather the edges/work up a few layers of paint/sand down/buff and see what happens.

Only obstacle so far is that the thickness of the original paint will require multiple passes of new paint. Or one sloppy, drippy coat

I'm going to need a fair amount of paint for both this repair and the (former) trim mounting holes. Standard-issue automotive paint doesn't exactly match. Can anyone point me to a source for Porsche (spray) paint? (standard-issue Black)

Thx.
Old 09-14-2002, 09:18 PM
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KBlair
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Cool

Well, ask and ye shall recieve I guess. Theanks for such an indepth discussion on this topic, I never expected such a response. With this info, I'm in a much better bargaining position than I was before, you guys are just great.

Dr bob, to make it worse, not only is this car in a humid climate, it's also in Wisconsin so I'm going to have to do a very thourough undercarriage inspection because of the road salt issue.

James, those are some encouraging results you've found. I'll post my results froim the inspection so we can compare. Hoepfully, there is no rust/corrosion and it's just paint, but the second photo sure does look like rust beneath the paint.

John, how about I just come let you do the repair? thanks for the info, great resource.
Old 09-15-2002, 09:20 AM
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DaveW
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The likleyhood is that you have just got surface rust localised around the spoiler mounting but It's worth checking a few other places.

Look carefully around the filler cap recess and the rear vertical edge of the panel where it meets the rear bumper as these are the places that will go next. On the rear quarters the rust tends to come from the inside out as these cars don't have the rear wheelarch liners of the S4. Have a look up inside the arch in these areas. If there is anything there then be careful as it is an expensive fix. These panels are galvanised which holds corrosion at bay for a long time, but when that protection gives out they go fast. BTDT

DaveW
Old 09-16-2002, 12:00 AM
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Dave - curious. As far as "wheel arch liners" go, to what do you refer? There is a thick layer of undercoating inside each of my wheelwells. Was there additional protection on the S4s?

Thx.
Old 09-16-2002, 12:15 AM
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John Struthers
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James,
Some people have all the luck...!
One of two or three things probably happened.
1. Due to a primer supplier, formulation problem you ended up with a bad batch of primer from the factory. This is rare. I think they purchase primer by the railroad tank car. However if you have a high density of pick-up trucks in your area
you may have noticed a batch of full sized Chev./GM pickup'in the early - to mid 90's with fender and beds that the paint just up and flaked away. Cost GM bazillons!
2. Related to #1 , As I recall the GM case was not resolved as there were some preparation issues that supported the primer supplier (in part). These ranged from paint shop temperature, contaminated air-line feed/supply, and primer cure times also related to assembly line production schedules, temp., humidity.
3. I think in your case it has been repainted and some overspray or block sanded matierial did not get wiped/blown off during prep.
Which would give you a 'boundry layer' where the paint would cover but not adhere to the primer
'in spots '. Enter water, heat & cold cycles... .
4.Tied to my earlier blurb on mount holes, clip holes (and edges) not getting as much paint.
Actually, all locations get, pretty much, an equal thickness of primer and paint. I can't explain the physics but the paint 'pulls and shrinks from edges including the edges around holes faster than a flat or curved surface. Also, for amateurs and pro's alike these edge areas are, typically, where runs develope.
That was good news though, James.
Kb,
Good luck on that purchase. Like a lot of other folks I have to agree that a good paint job or refurbishing the 928 interior is a major financial undertaking. Easily on par with major engine /drivetrain repairs.
Personally, I ADORE all sHARKs but I won't sell the house to maintain a seriously sick sHARk.
I grew up on a farm...sometimes you would have to put a favorite animal or pet... down. <img src="graemlins/crying.gif" border="0" alt="[crying]" />

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