Removing back windows for rust repair?


New member
Anyone had the urge to remove the back windows to work on the rust? i assume they are set with poly glue but am unsure the best method of getting out for reuse and what to reapply to set them in again once i clean and fix areas.

Also anyone have suggestions that work better than POR15 as i did cleanup other rusts spots on truck and the por 15 used according to directions still is allowing rust through after a year. Anyone try that rust converter gemplers sells?



Engineer In Residence
You need to convert the rust prior to re-application. Then use a zinc chromate or sulfate primer. These are etching primers. The zinc is sacrificial and blocks corrosion. Por-15 is not the best product and is very sensitive to exact application.

The rear windows are direct glazed with polyurethane adhesive.

You can use a cutter like this one to cut the adhesive. You may need a pull wire depending on the glass overhang. A helper on the inside would be needed in this case.

Use a sharp knife/chisel or one of these to remove as much of the adhesive as reasonable. No need to go to bare metal if the existing adhesive is bonded well. Fresh urethane will bond to clean old urethane.

Bond the window back in use window weld or equivalent windshield adhesive. You will need to work out your bead height. You will need a high ratio caulking gun. This stuff is THICK, and will wear your hand out otherwise.

Rear the instructions, this stuff sets up fast. Be Aware the bare metal and sometimes paint will need to be coated with a special primer before using the adhesive.
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Aqua Puttana

Poly - Thread Finder
Caulk Around Rear Windows

I had a spot on the bottom of my 2006 rear window that had rusted through to the inside metal. Inspection showed that the lower seal metal frame was slightly curved in. It looks like it was bad right from the factory. The lower sealant never bonded which allowed the water to get sucked in and rust heavily (probably since new so over 10 years).

Adding to that, there were a few spots around both windows where I could grind *most* of the rust, but not all of it. I was able to properly grind and repaint the outer... inner? curved metal edges though. That gave me a solid substrate.

I'm not skilled or ambitious enough to remove the rear glass, straighten the lower clinch web panel, and re-bed the window. I can paint and caulk.

I repaired the rust bubble areas all around the windows.

I then caulked all the way around both windows using Dicor Non-sag sealant. It comes in white, black, and some other colors. The sealant bonded well to the window edge and the metal channel.

I'm happy with the results. It ain't perfect, but looks pretty good even close up.

Here's some poor quality pictures.

The right window.

The left window left lower corner.

The right window right corner.

A section on the right window which I used heavy caulk. While caulking I noticed some rust that wasn't properly repaired. I put extra caulk on that area for over the winter. Next summer I will likely remove it and repair the bad spot. (The heavy caulk section is included in the first picture - upper left.)

Even that area doesn't really stick out.

This repair is similar to what I did for the front windshield rust problems. That repair has been good for over 3 years now.

I used white color sealant. I suspect that the black color Dicor will blend well with the window regardless of body paint color.

Also available at most local RV stores.


I used a similar treatment on my 2004 windshield. It is weathering well. No leaks to date.
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Hello Aqua,
I am curious how this repair is holding up? I have some rust on the rear widows. I took them out today, and the rust is pretty advanced. After I treat the rust and re-install the windows, I am thinking I will caulk them in like you did. Clearly the factory install method was flawed....

Aqua Puttana

Poly - Thread Finder
... Clearly the factory install method was flawed....
Not so much flawed if the paint held up like other brand vans/vehicles that I've owned. In my mind the Achilles heel is that the Arctic Whitewash rust bubbles extend into where they can't be completely cleaned out. That means they will pop again.

To answer your question. The Dicor sealant is holding up fine. So far there seems to be no downside to the "fix". I would do it again.

:2cents: vic

white whale

yes the urge got too much, years on the fix list, I have done it myself without issue past weekend...... had planned for both to be cut out along with windshield RE/RE work shortly. Every shop will give the same response,there is a chance of breakage when these get cut out. Figured I'd try. I have a the biggest Olfa knife and have the HB blades. Took about 40 mins for one side and multiple thin cut passes, key was to put some lube - I used seafoam - generously on the urethane to help the blade slide easier. The rust was outrageous on the bottom side of the lip, no perf but just nasty. It will take some time to clean and POR this.

I will post some pics when I get to the other side. The urethane bead looks perfectly rectangle shape so might have been tape vs a tube extrusion. I made a plexiglass insert
for the interior while I chip away at this.
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2004 140” HRC 2500 (Crewed)
I look forward to seeing the results. I’ve been holding mine for the last few years by spraying the rust seasonally with battery terminal wax. Looks bloody awful, but it is quite effective at preventing rust bubbles from progressing.


white whale

For those curious to see might be lurking under the glass.......

Once I got to the Fein tool and started busting off the crud i did get a decent sized perf hole.
The inset pic shows what I first thought was a miss in the weld is one of three vent gaps.
Good idea but might have been not thought through 100%. A great breeding ground once the sun hits and you have some moisture percolating away in behind. But then again rust was a feature ordered from the factory so would not have mattered.

POR will chemo this mother dry, I'm supremely convinced based on other touch ups already road tested.


white whale

Chemo sessions are done. Thinking I may remove the doors to do the finish coat.
I've left the windows out until that is sorted out and will just run with the the plexi for now.
Plastic hopefully never needed again but a good back up in case of breakage. This glass is not easy to get . I did come across a good temp resource at the dealer - you see in the pic the printed film - is a very agressive adhesive film they use for laying down on carpeted areas during service work. Works great as a quick cover when the glass is out.

The Quick Steel / JB weld product is excellent for patching the areas where the rust had perfed the steel.
Both doors had holes at the bottom corners. Weep holes not the best design IMHO.

Getting the glass out was not as bad as I thought. Not sure if the glass shop would use the mechanical string method on these. I can see that being a better bet to getting a busted window in the end. The urethane is a tough mother to cut.

POR 15 tips.
The degreaser is an excellent cleaner. I mix with boiling water to dilute and used foam pad brushes to keep wet for a while.
metal prep - just a splash of hot water and same process.
I wash them both down with a kettle of boiling water.

The black undercoat from a fresh can is extremely thin and levels flat really well. It is really easy to get too much on the foam pad, the stuff spreads a long way. The dry time between coats was 4-5 hours. Recoat they want the surface to still have some drag on your finger sliding over it. The can has since
flashed a bit and the dry time is now under 2 hours. The best tip is to use some cling wrap plastic on the can lid. If you leave the can without and have spashed some on the can lip
AND the can sits for months plus you will NEVER get the lid off without busting the can open and pouring into another can. I've also poured the remainder of the original 1 lt can into a fresh 1 pint can so i can extend the shelf life with less empty space in the can.

The top coat is much thicker, faster dry time. I am having the thin the product now with Xylene. Since I first bought, POR now sells their own thinner but it still just plain Xylene.
Just the tiniest amount however. I found easiest way to paint is to do a heavy dip of the foam brush and put in to a paper cup for the actual work. Way safer and cleaner than carrying the can around. Gloves!! - the black especially is a bugger to remove from skin. Great stuff. Sprinter rust , the gift that keeps educating me.



2004 2500 140WB high roof
Mine looked pretty similar to yours, though I also had some metal gone on the right window and post-wire brushing and grinding, there wasn't much left of the left window's bottom. I was able to build it back up with a lot of bondo hair. Doesn't look pretty if you peak up inside the door, but the visible parts look ok. I also filled in my license plate light holes and bought some lights from superbrightleds which have LEDs integrated into a 6mm bolt for the plate (no pic of that installed though). I repainted with monstaliner.


white whale

Finally got the rehab done. Final bonus for having plastic plexi in the window was transporting a 17' eves trough, made a little doggy door. I have glass again! Was waiting to get time and space to remove the doors and paint inside and make the glass install easier for me. Door removal, easy.... re-install for another thread, whoa. I know the tricks for next time. What a PITA.

Used this product:
overtop spot fills with POR 15. It is a pretty decent match. Give it a 7 as far as a easy and cheaper DIY option. Two coats with a foam brush. Bonus I am finding that the POR has a longer shelf life than expected, it even painted and dried well in temps around 10 c. I've made sure to clean the lid and can lips well and used a few drops of Xylene thinner on the top of the paint before capping. I also use a folded layer of plastic food wrap between the lids to avoid what i learned first time, both the black prime and top coat will dry a can shut permanently given enough time with two paint surfaces touching.

Clear coat for another time.


white whale

Further add-on. I did rely on my glass shop to give me the supplies for the glass reinstall. The product says primerless but they suggested using the liquid primer ( very thin black material you apply with one of those wool ball daubers) as well. Got an end of the can freebee. I should have wasted a line or two of the urethane on some cardboard before using just to get the hang of the flow from the gun. The nozzle tip gets a special custom cut to give the proper profile. I still have a 1/3 of a tube to use up. Thought there might be spots underneath in the frame area. Any suggestions?1612203461392.png

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