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  #1  
Old 02-23-2012, 12:00 AM
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i'm the guy with the flintstones 115...

... and I got new floorpans! And a new interior, new drivetrain, new suspension, etc... Picked up a well cared for 1969 220D with very little rust on Monday. As far as I can tell there is only one 2"; breach in the undercoating near the passenger side door. This car was a California garaged car for it's first 30 years (owned by a minister) and was kept outdoors under a carport and driven very little for the last 13 years...

Unfortunately, I have to keep the car outside in the elements, in the Pac Northwest. I am planning on putting the car up on ramps first sunny day, and using the POR-15 starter kit to touch-up any rust I see on the underside of the car and using the clear POR-15 to spot touch up any chips in the paint on the rest of the car... Anyone have any tips for finding hard to detect rust and dealing with it now, before I have another Flintstones car? I'm worried that there is rust that I can't see underneath the undercoating... (I have no reason to believe this, it's just a newfound general terror of rust) POR-15 seems to be the way to go...

On the spot where the undercoating is breached, should I cut back the undercoating, hit it with a wire wheel, POR-15, and then spot-reapply new undercoating? Would it be best to swallow my DIY-pride and take her in to a body shop for a rust inspection and let the pros patch it wherever t needs?

What do you guys do for rust "maintenance"? After I finish spot-touchup with POR-15, I plan on deoxidizing paint and waxing. Sorry, A lot of questions in one post... Too much coffee tonight...

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Old 02-23-2012, 03:07 AM
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Where the undercoating is breached I would remove it until you come to undercoating that's solidly bonded...then treat any rust you find and patch the undercoating. You just want to make sure you're not trapping rust or moisture inside the repair.

Don't forget to check under the carpets, and fix any water leaks...I've found rust often starts from the inside of the car where water is allowed to pool. Ditto with the door bottoms -- make sure the drains are clear.

Hidden rust should reveal itself with bubbled paint or pushed-out undercoating, since steel expands when it rusts. In critical areas that look suspect you can probe with a screwdriver or awl to see how bad the rust is...if the tip goes through the panel, it's bad.

One advantage you have, living in the PNW, is there isn't much salt used in the winter. The constant bath of fresh water doesn't seem to be nearly as rough on cars as the salt bath they get in places like the Midwest.
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Old 02-23-2012, 04:02 AM
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I think living with an old car that lives outside is all about the condition of the rubbers and keeping the paint clean and waxed.

This can turn into an alternative Sunday (almost religious) event - washing and (not so frequently) waxing your car!

Note I'm saying wax and not polish? (Subtle difference to those that may not know)


If the rubbers leak you'll see your car decay at an almost exponential rate.


Next check all of the drains on the vehicle and make sure that they are working properly - you'll find that leaves are not your friends. This is all about water management - don't let it pool either on or in your car.


As for the underside - angle grinder and wire brush attachment is most certainly the way to go. I know some people wince at the thought but seriously if the wire brush goes through into the inner parts of the car at an alarming rate I personally think it is better to know about the structural integrity of the vehicle when it is at a standstill; and not as you collide with that idiot mother on the way to soccer practice in her robo-I'm-indestructible-Volvo...

...depending on the finish of the underside that you wish to retain / gain / achieve I'd consider used motor oil as the cheapest option - messy but it works - to POR15 as you say - to POR15 with some sort of top coat. I wouldn't put any rubberised coating on the underside of the vehicle because if water does get through it just sits between the rubber undercoat and the steel and makes a mess like this =>



As far as I can tell the best thing to help with your situation is YOU

Regular inspections - knowing your car - and reacting quickly will keep it alive. For a lot of people that is just too much effort.
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Old 02-24-2012, 03:50 AM
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Quote:
If the rubbers leak you'll see your car decay at an almost exponential rate.
Am I correct in thinking that the front and rear windshield would be priority here? The door seals have seen better days, but aside from a little water on the rocker panels, nothing seems to be getting into the pans. Trunk seal seems solid...

In regards to the drains, I will have to find them and look into that... Not sure where they all are, aside from the two I know about on the passenger sides.

Any recommendations for a wax product? Both cars need deoxidized, after which I believe I can just wax them. Where there is exposed metal on the exterior of the body (chips and tiny perforations), I was planning on touching up those spots with rust converter and then spot touching them with a similar colored heavy duty alkyd.

Just picked up a 4 1/2" angle grinder and a POR-15 kit this afternoon, going to try to stay on top of it with my straight 115 (which I hope to pass on to my daughter), as for the other 115, she's looking at bare minimum new front/rear/trunk seals, new floor pans, and rust conversion/POR-15 triage here and there elsewhere...
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  #5  
Old 02-24-2012, 06:58 AM
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I would avoid undercoat. As Army said, once water gets under it, it starts to rust.

The key is to go beyond the rusted area with your repairs. You want to hermetically seal any rusted area from further moisture and air to stop the oxidation process. Get behind any panels that have rusted through

Good luck

PE
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  #6  
Old 02-24-2012, 12:36 PM
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@ Army and Orv: What have you seen longevity with as a top-coat? A lot of this repair will be under the car and needs to hold up to rocks/gravel/road debris... I already ordered a few cans of Permatex Rubberised Undercoater, but I don't think I'll use it now
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Old 02-24-2012, 01:31 PM
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I would have used the rubber undercoat, personally, but opinions clearly differ on this.

Partly it depends on whether you routinely drive on gravel or not. If you don't, paint should hold up fine. If you do, you might need the undercoat just to keep the paint from getting sandblasted off.
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  #8  
Old 02-24-2012, 03:55 PM
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I don't want to cause you any grief or extra money. Something is better than nothing even if it is black rubber or black bitumen undercoats.

I think undercoat can be a product of the devil - particularly when used by someone who is trying to hide stuff. My problem with the Mercedes rubberised undercoat is that you can not see what is going on underneath. And when the underside starts to feel crunchy you know it is too late.

For my car I will probably end up using a combination of rust treatment products / zink based primer, colour coat, and a clear coat undercoat. I want to be able to see if something is going wrong down there.

For the top coat - paint work - I think a good clean and T-cut will get rid of your oxidised surface. But go easy with that abrasive T-cut. You might even get away with a less aggressive polish before going for the T-cut; there's only wasted time if it doesn't work. After that I'd go for an OK to good quality wax. Go for a slightly more expensive to mid range cost stuff rather than the bargain basement stuff - don't bother with anything that says you can wash, repair, restore, and protect in one. That is all total BS in my opinion. There's nothing that can replace good old fashioned hard work for this job!

EDIT - In response to the gravel stones and rough road surface resilience requirement. If you are off roading / dirt tracking and it is going to be that bad then the best thing you can do is to check for damage frequently. As I said before it is down to YOU (and how YOU deal with it) are the best weapon against rust. But whilst you are at war with rust - don't forget to take it easy once in the while and actually enjoy your car! You can't save everything.
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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Old 02-24-2012, 07:30 PM
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Thanks for the replies. Got underneath and did a little grinding/rust conversion. Looking not too bad so far. A little concerned about the rear pans between the sound-proofing and undercoater, seems like if any water got in there it would quickly become a nightmare.

1. What is the rotted plug in the photo called? It will definitely need to be replaced, as now it will let water into cabin. Unfortunately it's installed under the sound-proofing. Which leads to #2.

2. Do I need to tear out the soundproofing to check for rust? If so, is it available after-market, so I can replace it?
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i'm the guy with the flintstones 115...-plug_pic.jpg   i'm the guy with the flintstones 115...-passenger_pan.jpg  
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  #10  
Old 02-24-2012, 07:30 PM
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P.S Have new front/rear glass seals coming in a few days.
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Old 02-24-2012, 09:31 PM
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Congrats on doing the right thing. Looks like you found a good foundation for resto this time.

The mercedes undercoating is indestructible and that is a good thing until water gets into the interior. As far as the sound deadening material on the interior on the floor pans goes I feel it is always better to remove it and fix the rust then just paint. That stuff is a real liability as all it takes is one rain event where some one forgets to roll up the windows or whatever and then you have water between it and your floor pans. The windshield seals are critical as well, a small bead of sealant around the seal to car and seal to glass is often necessary to prevent water infiltration into cabin.

As far as the underside goes por15 is good just wear a good respirator. Let cure thoroughly and then undercoat with 3M or better yet WURTH undercoating.

The body plugs can be gotten from many sources Mercedes would be best but all cars have them and you could probably bring one to your local parts store and find a good match. I just save them from junked cars and so have extra.
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Old 02-24-2012, 09:36 PM
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Has anyone had any success removing the undercoat? I am thinking of some sort of chemical stripper and heat, but don't want to recreate the wheel if people have found things that work.
Thanks,
Shane
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  #13  
Old 02-24-2012, 09:49 PM
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A heat gun and real good paint scraper are how I do larger areas but 3M strip discs and or a grinder also work pretty well for smaller areas. That stuff is tough and there is no real easy way to remove it in my opinion. A razor knife helps as well. Just be VERY careful with the heat method especially around rocker or pillar areas where you run the risk of setting the waxoyl inside there on fire. I bought a parts car once where the guy had a welder unfamiliar with these cars repairing the area in the drivers footwell. He lit some of the rustproofing up in the A pillar on fire and didn't realize it and the whole front half of the car burned. He had already put a few thousand into suspension and drivetrain work. That 4K car quickly became a $400 car.
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1982 240D auto
1978 300CD auto
1985 300D auto
1983 300TD auto
1984 Porsche 944 5 speed
1973 Opel GT 1900 4 speed
1967 Chevy C30 350 Sm420
1973 Mustang Grande Convertible 302 C4
1981 VW Pickup 1.6D Turbo 5 speed
1983 Rabbit 1.6D Factory Turbo 5 speed
Plus parts vehicles...
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  #14  
Old 02-25-2012, 11:53 AM
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Quote:
Originally Posted by DIESELVOLVO View Post
A heat gun and real good paint scraper are how I do larger areas...
X2 the only way that I've found to work. But becareful of the fumes - they are not good for you.

Abrasive removal methods such as sanding disks / angle grinder + wire brush attachment work for a short time but you end up pushing the (now) hot undercoat around the car rather than removing it...

...depending on your level of patience you can play around with it for a while before you say "buuger it" and reach for the fire!
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #15  
Old 02-27-2012, 03:11 PM
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Originally Posted by Army View Post
X2 the only way that I've found to work. But becareful of the fumes - they are not good for you.

Abrasive removal methods such as sanding disks / angle grinder + wire brush attachment work for a short time but you end up pushing the (now) hot undercoat around the car rather than removing it...

...depending on your level of patience you can play around with it for a while before you say "buuger it" and reach for the fire!
Guys who build rally cars have to deal with this a lot, since removing all the undercoating, seam sealer, and sound deadening is usually part of the car prep process. (It both reduces weight and, more importantly, exposes the spot-welded seams for stitch welding.)

Some of them swear by freezing the stuff with dry ice and then chipping it off once it's brittle. Doing undercoating that way is probably impractical without putting the car on a rotisserie and flipping it, though.

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