How do you clean cloudy headlights on an SLK 200 (R171)?

[jeffers104]

How to Clean Headlights at Home (Temporary Fixes)
Lemon
As a first task, if you pour baking soda on a halved lemon, then rub the lemon all over the headlight, you can remove some of the hardened yellowed oxidisation and end up with a fairly clear headlight. Take care not to leave the lemon juice on the car’s body, as its acidic nature can damage unprotected paint. Once that has been cleaned and dried then toothpaste is the next application to remove the residue.
Toothpaste
One of the more effective (and cost-effective) solutions to clean headlights is toothpaste. Toothpaste is abrasive enough to scuff away the yellow, yet gentle enough to not scratch the plastic casing. heck that your paste is 'gritty'. If not add a few crushed (very!) soda crystals). But expect to do this task every year, if not multiple times per year, to get the best results.
Abrasion (Use P3000, P5000, P7000 and P10000 wet and dry sandpaper with velcro)
Using a hand moulded buffer (with velcro) in the palm of your hand and keeping everything very wet, just gently rub the pad over the area in a circular motion. You are aiming for a uniform “cloudiness,”gradually reducing each step as the abrasive used gets finer. The polish applied with the rotary sponge further improves things.
I think it is very important to use something like a plant spray bottle to keep the sanding area thoroughly wet during sanding.
T-Cut & UV Polish Coat
Use T-Cut after the kits cutting paste is used as a second and final finer treatment before applying the final sealant coat (UV protection polish coat). Then polish with the soft micro-fibre cloth which will bring a nice shine to the finish.
Acrylic Clear Coat Spray (at your risk!)
With a sanded and clean headlight and a thoroughly protected car body, as an additional protection, you can now spray a few thin layers of clear-coat spray paint over the headlight casing for a long-lasting effect. The big problem is that clear-coat paint is not meant to be used for headlights that are constantly exposed to sunlight and high temperatures, so applying the clear-coat isn’t a permanent fix-all. In fact, you may see streaks of oxidisation over time if the application of the clear-coat wasn’t done properly.

 

[Blobcat]

Hello and welcome,

Lots use the kits, quite a few threads on here

 

[Wearsafoxhat]

Good evening and welcome,

always a good subject and always lots of remedies and ideas. Always a discussion, to clear coat or not.

 

[Doug1234]

A good quick fix that lasts a few weeks is to just rub wd40 on them with a rag or tissue

 

[markben]

Good advice - and hopefully effective in many cases. But only if.. (!) that 'cloudiness & yellowing' is on the surface of the acrylic lens. In some cases, when the UV degradation has gone too far (i.e. penetrated through the entire lens thickness due to any or all of ageing, a lack of regular cleaning etc), no amount of polishing & renovation will fix it - Sorry!

From frustrating experience on my otherwise immaculate 2004 W220: the original 19 year-old NSF Bi-Xenon headlamp lens defied all efforts to make it crystal clear again, whilst the 'only' 12 year-old OSF OE replacement headlamp & lens remains crystal clear with equally regular cleaning. My best guess is that the NSF lens had simply degraded UV wise, and beyond repair. You tell me?

Only a suggestion.. but if your acrylic H/L lenses are 'terminally' faded & yellowed etc despite all efforts to restore them, one option is to replace them with relatively inexpensive aftermarket lenses from a Chineseum supplier via 'ebuygum' etc.

In my case: I did this relatively easy DIY job and 2 years later, and the 'Chineseum' replacement lens (Cost approx £30) is only showing slight.. yellowing and remains clear. No issues with beam focus & clarity etc, so all good in the past 2 MOT tests.

By my logic: even if a new 'cheap Chineseum' replacement lens only last a couple more years before degrading further (due to probably inferior materials compared with OE?), replacing it again will be a tiny fraction of the cost £££ of a new OE complete headlamp unit (on a W220 S Class approx £600 ).

Hope this helps for anyone here with a similar 'Irretrievably cloudy / yellowed' headlamp lens dilemma?

Mark B.

'The Best or Nothing'.

 

[mersum1es]

I just refreshed my C219 headlights, I used sand paper and vaporized resin stuff... I was amazed how it works...

https://www.amazon.com/Headlight-Restoration-Atomizing-Renovation-Headlights/dp/B0BBG2R315?th=1

edit: now when we are talking Mercedes; not all cheapo chinesum aftermarket lenses work, if you change whole unit. There has been big problems with automated and turning options.

 

[rifiki]

How come MB plastic lenses go yellow, poor quality materials?
I use have a Nissan Primera sold after 11 years use and the plastic lenses were like new.

 

[jeffers104]

Sensible point by Markben and good advice! So it would be good practice to try your 'magic' solution to a small area of the headlamp lens first - just to see if there is any improvement. Otherwise you may ruin what you have!

 

[w204benz]

How come MB plastic lenses go yellow, poor quality materials?
I use have a Nissan Primera sold after 11 years use and the plastic lenses were like new.

The ones on my MB had a slight cloudiness along the top edge at 11 years, barely noticeable. I've seen multiple different brands with headlights that are practically opaque, and I've not noticed MB to be particularly worse (or better).

To my understanding, clear plastics that are inherently UV resistant are too brittle to be used on the front of a car, so an anti-UV coating has to be used.
I'd imagine the rate at which this coating wears off (which is probably affected by dozens of factors) would have a big role in determining how quickly the lenses start to degrade.
But it might be the quality of the materials too.

 

[w204benz]

I've had good results with the wet sanding followed by polishing method. The improvement was noticeable even though the lenses looked OK before I started (just a slight cloudiness along the edge.

I didn't want to repeat this on a regular basis, so I spent some time looking into protecting the results.
In the end I went with a UV resistant ceramic coating, but PPF would have been a good alternative (the ceramic was cheaper and probably easier to DIY).

What I really wanted to do, was to finish it off with a couple of coats of clearcoat (using proper automotive 2K clear) - under the assumption that it would be at least as durable as the factory coating.
The reason I didn't go with this option is that I wasn't too keen on spraying it on the car. Then I realised I had to remove the front bumper to get the headlights off - I wasn't too comfortable doing that.

 

[daibevan]

How come MB plastic lenses go yellow, poor quality materials?
I use have a Nissan Primera sold after 11 years use and the plastic lenses were like new.

I recon its where you park it in relation to the sun. I parked my Primera on a south facing drive and after 6 years the headlights looked like they had fake tan on them. Came up lovely with a Mguires kit. Though now I use fine grit wet and dry and finish with the left over paste from my old kit, and I still get a good result.

 

[rifiki]

diabevan, you could be right, I park facing north but the CLK had usual problems. Used chrome polish worked quite well.

 

[daibevan]

diabevan, you could be right, I park facing north but the CLK had usual problems. Used chrome polish worked quite well.

They always go, no matter what you do. I only mentioned it because my Primeras were really bad, I had an advisory on them at MoT time.