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Hi kristoph42,
The big square 240 headlights use grey adhesive that is somewhat like bathroom or kitchen tile caulking. I dunno the composition, maybe a little silicon and acrylic.
I'll try and find some images to illustrate.
This same problem effects the 700/900 series with plastic headlights. These use the same grey tile caulk-like adhesive.
Should you remove and disassemble the head light assembly from your 1998 Volvo 240, or from a junkyard 1986+ 240, you'll see a recessed channel on the ABS plastic reflector body (or bucket). On the clear headlight lens side, you'll see a protruding edge that fist into the reflector body.
The grey adhesive fails from the headlamp heat, and maybe a limited duty cycle no matter the conditions. You'll get water intrusion through the opening seam between lens and reflector body.
The hot bulb can explode on contact with moisture, ruining the reflector and lens interior. Yet more likely the humid interior can leave a film on the fragile shiny reflector material, the fluted lens interior, and the reflector strip at the bottom of the lens interior.
When I performed this restore-repair this for me , there was algae and other green scum at the bottom of the headlight bulb chamber. (I'll label the headlamp interior, with reflector body at the rear and clean lens at the front the reflector body, the headlight bulb, or merely the bulb chamber.)
It is a little difficult to clean the fluted interior side of the lens. Though by cleaning it, and inspecting it, you may find the interior side of the lens beyond repair.
- You can use a very fine abrasive cleanser with a fine-bristle brush, like Comet (with a sodium hypochlorite bleach agent - yet Comet is not a very fine abrasive),
- or a very fine abrasive cleanser with some bleach, or, a phosphoric acid abrasive cleanser like Barkeeper's Friend (finer than Comet - do not mix another debriding or bleaching agent like bleach with the phosphoric acid).
- Alternatively, you can merely use some like dish detergent and a find bristle brush to clean the fluted lens interior.
- I've read other posts on our brickboard.com and I believe turboricks where some placed the lens in a sink and spray oven cleaner (as lye - sodium or potassium hydroxide) on the interior side, or both sides, of the lens and let sit for some hours. With your nitrile gloves on, use a fine bristle brush to clean the interior side flutes. The lens should appear less yellow and more clear. The lens should appear transparent and not cloudy as light travels through the lens. In a cloudy Volvo 240 1986+ big square headlight, the cloudy lens diffuses the light, and reduces the quality of light projected in front of the moving Volvo 240 - a dangerous operating condition, indeed.
You may want to try cleaning the lens interior side without an abrasive first, yet use a fine bristle brush, as you may remove what clouds the lens, yet the abrasive can actually induce some fogging while removing the bioguck yellow coating.
You'd need to peel away the metal reflector strip at the bottom of the lens and clean it as bioguck forms under it. Yet remove the reflector strip before using any method to clean the lens. You can use your thumb to peel away and remove any remaining adhesive left behind from the reflective strip before you clean either.
Use a strong clear light to pass light through the cleaned lens. Heavy pitting on the fluted side may mean a light bulb exploded at one point, so, you may have some glass embedded in the lens interior side. The lens may not be reusable. Some extra junkyard 1986+ Volvo 240 headlight parts can make for a mix and match success, too.
If yellowed on the lens exterior, it may means the UV resist coating on the lens exterior has failed for being parked outdoors too long. You can use plastic lens restoring kits from your auto parts store. Others would use the finest of polishing compounds on the lens exterior. Though if parked outdoors, with any UV coating removed, you may have to polish the lens exterior in a few years.
If the reflector is remains mirror-shiny, yet merely coated in some guck, you can give a good soak in dish detergent. Some will warn not making any contact with the mirror-like reflector coating in the headlamp. I've used a soft cloth or a new, unsullied sponge, with dish detergent, to very gently wipe away the persistent guck coating it.
Inspect the head bulb interlock that secures and retains the headlight bulb on the reflector body. If distorted from heat, the ABS plastic becomes brittle. In failed, leaking 240/700/900 head lamp assemblies, the moisture intrusion both fogs the
Yet before you do anything wet, you want to clean the sealing interface between lens and reflector body of all traces of the any adhesive or the scum is leaves behind.
You can use:
- The end of a clean standard screwdriver. May 1/4-in wide, to clean the recessed channel on the reflector or lens side. Like I said, I now forget the mechanical interface between the lens and reflector body that would contain the now-missing factory installed grey caulk-like adhesive.
- Once the big chunks are cleaned away, you can use one of those nylon pads, like a 3M nylon pad, or, one of the consumer nylon scrubby pads from the grocery store that comes in blue or green, though I don't like these scrubby pads as the blue or green dye used to color these nylon scrubby pads leave behind a color reside that is sort of indelible and can interfere with replacement adhesive contact efficacy. Use a scrubby pad with very warm water and dish detergent. Rinse well with a very warm water rinse.
When dry, follow with 90%+ isopropyl alcohol and a fresh scrubby pad. Though well-rinse the new scrubby pad first. And clean both interfaces. (Sorry, I'm not even finding my own images I posted on the i-net, and these are not on brickboard.com image gallery.) Let dry.
You may want to use a fine sand, emery, or carborundum paper to abrade the sealing surface. The recessed channel in the reflector body the protruding lens edge seats into. To maximize adhesive contact and strength when the adhesive has out-gassed and cured. (Though it can be some months for the Amazing Groop to complete out-gassing.)
So, the best replacement adhesive sealant I've found is the Eclectic Products "Amazing Goop". Use the UV resistance varieties such as the RV or Marine versions. I found three tubes of the RV version, and I was so grateful for it, at Walmart in an aisle between the Auto and Outdoor Recreational sections. A 3.7-ounce tube. Buy several.
Slightly off-topic ... I found Amazing Goop RV and Marine to be useful with extending the Volvo 240 taillights. Especially the 240-six panel wrap around tail lights from the junkyards. Most people buy the six-panel taillights with the newer flexible circuit board set up for the dual-filament lower and outer brake light red lens position, yet installed into a 240 with a wire harness connectors that expects to see only a single brake light filament. Or other combinations. Or the wrong bulb holder in the lower, outer brake light position. So, when position or headlights are on, you actually have the brake light filament on, and all the heat rising causes the red lens to weaken and distort, and the black ABS plastic above to crack, causing leaks. One could write a long illustrated manual on treating and preserving Volvo 240 taillights for maximum safety and reliable operation.
So, you use the Eclectic Products Amazing Goop RV or Marine and run a heavy bead around the lens edge and also around the reflector body. Press them together, and point the lens upward. Wipe away excess that presses out of the exterior. It is okay to have a heavy bead inside the lens around the edge for more adhesive strength so long as it does run down forward into the lens too much.
Eclectic Products Amazing Goop Marine epoxy is a new product with a wider application duty cycle temperature range. 3M may have adhesives that may also be useful for this application, yet have found none, though I'd not looked recently.
Use some paper to protect the lens and use some packing tape to tightly and securely hold the headlight assembly together. (The tape adhesive can remain stuck to the lens exterior; why you use paper over the clear lens.) You may want to suspend the headlamp assembly so air gets into the the bulb chamber so you have the Goop curing on both sides of the sealing seem. Place a fan or fans on it. Let it alone for six to 12 hours. Yet let some 72 hours to cure.
Reassemble. Clean the bulb with isopropyl (running) alcohol and clean cloth to remove all reside.
While you are at it, you can dissembles the front wrap around position / turn siganl light assemblies. The fluted lens interior get dirty as does the reflector material and the bulbs. Some detergent. Some will repaint the reflect bowls on these with a silver thermal paint. Handle the bulbs as with the headlamp bulbs. Really, even the low-power bulbs suffer if you leave dirt of finger print oils on the bulb glass envelopes.
You may also want to treat your tail lights. I prefer an aggressive approach in keeping the stupidly designed, flexible circuit board 240 tail lights in fine fettle and as reliable as possible. I've already treated these taillight issues in many brickboard posts. Many wait until the bulb out failure illuminates on your dashboard head.
Electrics on the 20+ year old RWD Volvos are sort of like Lucas Auto electrics. Like revisiting the era of ever not so reliable Lucas Auto electrics on your not so old MGB, Triumph, Morris, and you name it English car.
Like the Volvo 240 fuse box. Great gravy. Clean and lube that too. Not just the fuse end contacts, but the wire harness connections to the fuse box. Horrible design.
Yet so is the relay platform box under the center console, and behind the cigarette ash tray in the 700 and 900 series. It got better on later 940.
Get to know your DeOxIt. I forgot the name of that stuff for some time until the brickboard reminded me.
Does that help?
Questions?
Yes, sorry to go on so.
This brickboard.com post courtesy of:
Ahmad Brand Aromatic Early Grey Tea in the 500-gram / 17.6-ounce tin, with hunny and milk.
Eclectic Brand Amazing Goop UV-resist versions "RV" and "Marine"
And well, I dunno.
There you go.
Buttermilk and Sourdough MacDuff Gettin' all Carbed up and Fatter.
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The Volvo 164: The Mightiest of All Volvo Automobiles in Perpetuity
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