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      11-12-2012, 10:22 AM   #1
baege
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Rust on Z4's

Lately I have been thinking more and more about possibly keeping the coupe for another 3-4 years (seems the love is just growing), which brings me to wonder if I should bother with rustproofing?

I drive maybe 2-3 times a week in the winter in Toronto Canada so she does see some salt and road grime.

For those who have 2003 to 2004 Z4's that are winter driven are you seeing rust?
If not did you rust proof?

What are people's views (assuming exposure to salt) on rust proofing a z4?

I do wonder whether a sophisticated car like the Z4 could possibly be hurt by all that gunk being sprayed up everywhere, but that could possibly be overly worrisome.
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      11-12-2012, 10:32 AM   #2
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i found this... seems for BMW's 2006 and later there is a 12 year warranty against rust.
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      11-12-2012, 10:56 AM   #3
baege
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Quote:
Originally Posted by v3.2mc View Post
i found this... seems for BMW's 2006 and later there is a 12 year warranty against rust.
found this thread on e90 post which has me thinking:

The body of the e90 is dipped in a phosphate blend, this does NOT prevent rust. It does however clean the metals of contaminants and de-grease them. What this does is allows the base coat, paint, and primer to adhere to the metal much better which in turn is the rust prevention strategy.

The drivetrain including front and rear sub-frame DO NOT go through this process and are NOT painted. They are still highly susceptible to rust.

The BMW corrosion warranty is a PERFORATION warranty which covers ONLY THE BODY of the car. It does not include the subframes.

The 06 and 07 subframes are already starting to rust, especially around the carrier bolts.

Keep in mind that rust oxidation is caused by a chemical reaction between oxygen and the metal. Pure water does not cause much rust at all, however oxygen carried in the water will cause rust oxide. Salt will speed up the process via an electro-chemical reaction (electrolytes) very similar to how a battery works.

The undertray on our cars does not prevent all moisture from reaching our subframes unfortunately, nor do they help with humidity.

Rust proofing is very simple. It's a thick grease that the water (and oxygen) can't penetrate. If the oxygen can't get the metal, no rust.

It is not necessary to rustproof inside the doors, under the hood, trunk, etc. unless there is some type of damage that has penetrated the paints and to the metal. The hinges of doors, trunk, hood should be rust proofed for good measure. Rust proofing the subframe, especially the rear subframe is very important, especially the carrier bolts.

Washing the underbody after a salty drive will not prevent rust. You are now combining the oxygenated water with salt, making salt water and blasting it into crevices that potentially were not exposed to this previously. There are also undertray panels preventing you from spraying in a lot of areas where water from puddles and moisture in the air could penetrate. Including salt water, rain, snow from going in through the front kidney grills, ducts, around headlights, etc. and moisture getting onto the front subframe, bolts, etc. which can't be washed from the underneath.

It is not expensive to rust proof just the subframes. If you care about your car I wouldn't do it any other way. And if you have an early model e90 and you think rust proofing is a waste then ask a mechanic to put it on a hoist, take off the underpanels, and take a look yourself. You'll change your mind.
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      11-12-2012, 11:38 AM   #4
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i'm pretty sure both subframes on my ///m are painted in a semigloss black. the only items not painted are the control arms (aluminum), the front spindles, the rear knuckles, engine block, motor mounts, transmission case, and rear diff. everything else appears to be painted black. maybe this an ///m thing only? looking through chris's (crfine88) build thread, his appears to be the same.
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      11-12-2012, 12:17 PM   #5
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Mine has rust spots in the seat rails, apparently in the winter getting in with your feet full of snow will cause some of that snow and salt to get in, it then stays there until it dries. Very visible from the side of the seat when you get in.

I'm also concerned about the door hinge area were water can build and remain there for long periods. Same with the trunk gate there seems to be built in water reservoirs for when you open it so the water and snow builds up there but there is no way for the water to get out?

I think we will be ok with the easily replaceable side skirts. As far as underneath the car It looks pretty new

I have an 03 that I drive in chicago all season so I think I would be likely to begin seeing issues

As far as rust proffing...I used to sell cars and would recommend my customers to get their car rust proofed at least once a year

But all bs aside..If anything it will make the water stay up there longer and damage your frame faster. the water needs to get out...it will just plug it up there longer
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      11-12-2012, 04:48 PM   #6
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I grew up in the Detroit area and was a car owner there from the late 60's through the late 80's. For most owners the first place they would go after buying a new car was to Ziebart to have their car "rust proofed". I don't remember it being a grease, but a black, tarry substance that was not only sprayed on the entire undercarriage of the car, but holes were drilled in doors, fenders, and trunk lids to spray inside those cavities.

The worse part was doing any maintenance on a car that had been "rust proofed". That stuff had to be scraped off any nuts or bolts, parts were coated in it, and it was basically just a completely messy job. The first car I ever bought after a couple of hand-me-downs from my parents was a '66 Ford Fairlane that I bought in 1969. I was only 19 and unknown to me the left front fender had been replaced because of an accident. It hadn't been properly primed or rust proofed and was rusted through by 1971. I used to just sell my cars after 60,000 miles to avoid any problems with rust. I had a new '74 Toyota Celica GT that I kept for 80,000 miles and the front fenders were rusted through. As manufacturers starting offering better and longer warranties against rust rust proofing became less popular.

I sure don't miss that!
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      11-12-2012, 07:09 PM   #7
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      11-13-2012, 07:33 AM   #8
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For the first 2 and 1/2 years of its life, my car lived in Florida and never saw salty winter roads. Since 2009, I have stored it during the winter so again, no salt road driving. This year, I am building a nice new garage, so in adition to winter storage, the car will be garaged each night so its clean and dry most all the time. By doing this, I plan for my car to have an exceedingly long and happy life.
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