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#1
10-02-2004, 11:05 AM
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Hood pad replacement
I am in the process of replacing the hood pad on my '82 300D. I have tried numerous types of solvents in an effort to remove the existing adhesive. Nothing works very well. Any suggestions would be appreciated. Secondly, would it be worthwhile to remove the hood from the vehicle when installing the new pad? It would seem that being able to lay the hood flat would make the installation of the pad much easier. But getting the hood back on "right" might be a challenge. Insights?
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#2
10-02-2004, 11:21 AM
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Put tape around the hood hinges to mark their location before you take it apart... or paint or scribe its location...
should be much easier with it supported upside down... 3m makes an adhesive dissolver... but depending on the type someone used before you might condider paint remover... If someone used Liquid Nails it becomes a different type job.... don't laugh...someone suggested this not too long ago....
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#4
10-02-2004, 11:34 AM
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What does the adhesive look like? The factory stuff is very thin, similar to properly applied 3M super trim adhesive, should be almost invisible.
If it's brown and thick, it's probably something similar to Liquid Nails and you are in for a long job..... Get a good scraper, sharp enough to remove softened adhesive but not so sharp you gouge the paint (use a plastic on, I think there is a "three in one" type at most auto or paint places), and get some top quality carb cleaner spray. Read the label, you want the stuff with toluene in it (don't breath the vapors!). Lift the hood all the way back by releasing the clips on the sides. Cover the engine with some light sheet plastic (disposable drop cloth plastic is best), and scrape all the remnants of foam off. Spray the inside of the hood with the carb spray and let is soak for a bit, then wipe it off with a cloth if you have factory adhesive in there. If it's anything else, you will have to attack it with the scraper again. Keep at it until you get it as clean as you can, you don't want old adhesive to fail under your new pad. When it's clean, fit the new pad dry. When you have it all tucked in and located correctly, put a broom near the center with the sweeping end up, handle behind the hood latch. Will be above center some, but this is OK. Peel the top back and hang over the broom, being carefull not to pull the bottom out of alignment. The broom will keep the pad in place on the bottom and center. Apply two or three LIGHT coats of 3M super trim adhesive (spray can, number 8090 ONLY -- any other product number will fail under the heat, and the pad will come loose). Two light coats on the exposed back of the pad, then let dry until just barely tacky (5-10 minutes). Press pad to hood, starting at the broom. Be carefull not to pull the pad out of shape as you go, it's not gonna come back off very well! When it's all stuck up, press firmly all over to seat the glue, then pull the bottom loose and use the broom to hold it up. Spray the adhesive on the bottom half as you didt for the top, allow to dry, and install and press down. Works perfectly. Takes about half an our or so to glue the new one in, took me almost three to get the old glue off, nasty stuff that didn't hold the pad up! Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#5
10-02-2004, 11:50 AM
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Keep in mind that you don't have to remove *all* the old adhesive, just the loose stuff. It's sufficient to scuff up the surface with a Scotchbrite pad so the surface has adequate "tooth." (A 3M thread is emerging here!) My personal experience is that the pad is what fails, not the adhesive.
Adhesive: I've used 3M Super Trim Adhesive, N. 08090. It comes in 19 oz. spray cans and is specifically recommended by 3M for hood insulating pads (says so on the can). If you follow directions for application you'll probably need a couple cans of the stuff. It runs about $12 per can. Russ M. '82 300cd (new hood pad, 2001) '82 300td (new hood pad, June 2004)
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#6
10-02-2004, 11:58 AM
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"Do NOT remove hood."--Rdanz
Sounds like a quote from somone who has help on projects... or has not had a four foot by four foot floppy item prepped with CONTACT CEMENT accidentally touch at the wrong place when trying to apply it... If you turn the hood upside down on padded saw horses... then , alone, you can follow the directions for contact cement.. very important....and use the ' 90' 3m spray on made for hood pads.... and take waxed paper and cover a dozen or so 1inch by 1inch sticks....then you can measure and mark on tape the center line for the hood... then you take the pad and place it the way it will go on the hood .... but held off the hood by the sticks.... and you can align it exactly above where you want it.... then starting in the center and pressing out any air bubbles as you go... ie, before taking out the next stick over.... you can apply the perfectly lined up pad to your hood ALONE..... they way I always have to plan projects... I do not agree that only loose old cement needs to be taken off... I think it needs to be chemically clean and dry before applying the spray on Contact Cement...
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#7
10-02-2004, 12:06 PM
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Taking the hood off is way too much work. Use a broom, it makes this job vrey simple.
Until you press the pad down firmly, it will come back off, so it can be adjusted for a while. The factory pads tuck under the sides pretty far, so perfect alignment isn't a problem. Proper coverage is more important that amount on the adhesive -- I used just over half a can for mine, three coats on each part. It's very good stuff, and you don't need complete coverage, just enough to hold it up (pad is less than a pound total weight, I think). Put it on like spray paint. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#8
10-02-2004, 12:20 PM
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The adhesive that I am trying to remove is the factory original. Yellow, like contact cement. 3M adhesive remover has no effect. Neither does MEK, contact cement remover, acetone, paint thinner, naptha. Carb cleaner is only marginally effective. Looks like it's going to be a long and slow process. Thanks for all the responses!!
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#9
10-02-2004, 12:31 PM
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It was probably contact cement originally .... and now has Petrified....
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#10
10-02-2004, 12:35 PM
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Factory adhesive is very thin spray on stuff. If you have thick, yellow junk in globs, it's not factory.
The right carb cleaner (DON"T get any with methylene chloride in it, it will REMOVE the paint!!!!) will soften the cement, not melt it. It will then rub with a shop towel (cloth) or scrape with a metal hooked type scraper (looks like a paint brush sorta, with two slightly more than right angle flat sheetmetal "blades"). Have a care not to damage the paint. This is a BIG PITA -- factory stuff comes right off with 3M remover or good carb spray. Liquid nails or "permanent" contact adhesive (usually not applied to the pad, I've found!) take forever to get off. They will not dissovle in the solvents, just get "gummy". Usually not in a nice even coat, either -- heavy on the stiffeners, a couple big slops around the edges, and some globs in the center. Runs, almost 1/8 inch thick, etc. I'd be shocked if this was factory, I'd fire anybody wasting that much material to do such a poor job. The pad in the 300D fell apart -- it was only glued on the stiffeners and a couple random areas, not evenly like the long dead one in the TE. That one won't get replaced until I repaint the hood -- gotta knock out some dents. Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#11
10-02-2004, 12:40 PM
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"I do not agree that only loose old cement needs to be taken off... I think it needs to be chemically clean and dry before applying the spray on Contact Cement..."
The directions on the can says only that the surface has to be free of wax and oil. Certainly, you can't overprep a job like this, but the cured adhesive I encountered under my original hood pads was not coming off without a struggle -- so I concluded that it wouldn't be a problem as long as the new adhesive stuck to the old stuff. After a few goings-over with a brown Scotchbrite pad soaked in adhesive remover, any old glue that was likely to pose an adhesion problem down the road was gone. The process also resulted in a nicely roughed up surface. Final step was a wipedown with prep-sol, similar to the way you'd prep a paint surface for a respray. Three years later, the pad on my coupe remains firmly affixed. I took a similar approach on a wagon I bought more recently. The jury's still out there, I guess. Psfred, if you managed to apply three coats of adhesive to the pad using only half a can of the stuff, you are the maestro of aerosol! I had a little left over from the second can on my most recent pad, but not that much. Russ M
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#12
10-02-2004, 01:03 PM
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The problem is we don't know Exactly what the composition of the existing glue is... therefore .... it would be safer to get it all off... if you spray new stuff on it and it SOFTENS the old stuff... that might be a problem....
It is always safer to take it down to paint surface and be sure wax and silicone are removed.... ie, treat it just like you would a paint job... Klix88 is the common cleaner right before painting to get everything including accidental touches by hands off...
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#13
10-02-2004, 01:14 PM
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Yeah, I managed to paint the hood of the 280 SE (canary yellow replacement on a navy blue car) with about three cans of spray paint in two colors to get a match. Almost perfect except for the lumpy finish (spray cans have the WORST spray pattern you can imagine, to say nothing of spitting globs...).
You want a very even, very thin coat of adhesive. You should require three coats to get complete coverage since the stuff is much too thick to flow out -- I make quck, overlapping passes (you get a vertical line of goo) over the hood and pad. Don't expect to actually cover the surface, just get an even coat of "dots". By the third pass (do the coats at right angles if you can, or at least close), the entire surface should be nearly completely covered with overlaping spots. You aren't gonna get a nice smooth coat -- if you did, you are likely putting too much on and it won't dry very fast, leaving you with the possibility that the solvent won't leave fast enough and next hot day the adhesive will "melt" -- down comes the pad!. Too much adhesive is much worse than too little!. Do the same thing with the pad. The spray will "vanish" into the pad, so don't try to get a visible "coat" on it. It will absorb a huge amount, and you only need a small amount on the surface, nothing else is gonna stick anyway. Last, don't be in a hurry to put the pad in place. The adhesive will still stick just fine for at least an hour (longer it's below 70F). If too wet, the adhesive will pull apart (or worse, peel off the hood!) leaving the pad only partly attached. Let it dry for at least 5 min after the last coat. That way, if you just lay it up, it will peel off until you press it down hard. The broom works like magic, makes this a one-man job (I got this tip from my friend Hans who does this all the time). Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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#14
10-02-2004, 01:28 PM
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"Do the same thing with the pad. The spray will "vanish" into the pad, so don't try to get a visible "coat" on it "
Since my experience is typically with leather (very absorbant ) going on to something non absorbent I suggest that you DO need to do enough light coats so that you have some left on the surface.... we are talking CONTACT cement... the cement on each side must be there on top for it to stick to the other one....
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#15
10-02-2004, 03:10 PM
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Leatherman:
Yup, right on! You must use very light coats to get it to "build" on the surface. If you spray a bunch on, it just sinks out of sight before drying, and you don't get any more than if you give it a light spritz. It won't stick any better, either, as the glue is now 1/8" or more from the surface. Once it's tacky, it will stay up. Three light coats was enough on mine -- there are spots along the edges that don't stick completely, but I didn't get a whole lot of adhesive on the hood there either, not wanting to coat the outside, too. If you want to really get carried away and use the lead foil padding, you will likely have to find another way to hold it up, I don't think the foam will hold the weight vertically like that, no matter what adhesive you use! Peter
__________________
1972 220D ?? miles 1988 300E 200,012 1987 300D Turbo killed 9/25/07, 275,000 miles 1985 Volvo 740 GLE Turobodiesel 218,000 1972 280 SE 4.5 165, 000 - It runs!
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