Timm's BMW E31 Headlight Performance Improvements
 

Do your 8-Series headlights give poor results? Everything gone a bit dull and fuzzy? Here's how to get them working properly again! Mine looked like this:

BMW E31 840ci 850i Headlight Performance Improvements

This is the dipped beam projector lens, it looks milky and produces a poor beam pattern....time to take it apart.

First, lift the bonnet and then remove the headlight cover by undoing the rear screw and then pushing the cover forwards:

BMW E31 840ci 850i Headlight Performance Improvements

The headlight can be lifted by rotating the manual raising screw:

BMW E31 840ci 850i Headlight Performance Improvements

The headlight glass is bonded to a plastic chassis which is secured to the headlight enclosure with six expanding clips, three on top, and three underneath. Start with clips situated under the enclosure. Use a long, flat-bladed screwdriver to prise the clip away from the enclosure while preparing to catch it as it pings off:

BMW E31 840ci 850i Headlight Performance Improvements

BMW E31 840ci 850i Headlight Performance Improvements

Use the same screwdriver on the top clips as shown:

BMW E31 840ci 850i Headlight Performance Improvements

Get ready to support the headlight glass once all the clips are removed:

BMW E31 840ci 850i Headlight Performance Improvements

Here's the reason that the dipped-beams give such poor performance. Condensation has been boiled off the projector lenses:

BMW E31 840ci 850i Headlight Performance Improvements

I have some anti-static LCD cleaning fluid and  soft lint-free cloths for the next bit. I will use it to clean the projector lenses and the reflectors. NOTE: The silvering is vacuum deposited  and is extremely fragile, only use a very gentle cleaning action otherwise the silvering will be removed:

BMW E31 840ci 850i Headlight Performance Improvements

BMW E31 840ci 850i Headlight Performance Improvements

BMW E31 840ci 850i Headlight Performance Improvements

That's a lot better:

BMW E31 840ci 850i Headlight Performance Improvements

If you have large hands and cannot get behind the lenses, they can be removed by undoing four screws:

BMW E31 840ci 850i Headlight Performance Improvements

The next stage is to check the headlight-glass unit for leaks. First, give it a good clean:

BMW E31 840ci 850i Headlight Performance Improvements

Give it a rinse and then fill it up with water to check if any water leaks through the joint between glass and plastic. The water should come out the drain only:

BMW E31 840ci 850i Headlight Performance Improvements

This unit is OK, the other unit on my car leaked at the joint between plastic and glass. So, first of all dry the unit:

BMW E31 840ci 850i Headlight Performance Improvements

I am using Loctite 595 to seal the joint, this is a clear 'flowable' silicone sealant. This does not sit on the surface, instead it seeks any leaks between plastic and glass and forms a good seal:

BMW E31 840ci 850i Headlight Performance Improvements

While the silicone cures the headlight assembly can be prepared. Pull out the foam sealing gasket:

BMW E31 840ci 850i Headlight Performance Improvements

Check the condition of the seal and replace if torn (part number 63121393855). Mine are OK so I will lubricate them with silicone grease (not sealant!) over the full surface area, this will rejuvenate the seal :

BMW E31 840ci 850i Headlight Performance Improvements

Once the seal is pushed back in place I lubricate the face with silicone grease:

BMW E31 840ci 850i Headlight Performance Improvements

Check the condition of the glass on the headlight front assemblies. If these are heavily pitted they can be made to look like new by spraying the outside of the glass with clear-coat lacquer. A few coats with a light rubbing in-between coats give excellent results. My units are OK but will need spraying some time in the future.

Offer up the glass unit to the headlight assemblies:

BMW E31 840ci 850i Headlight Performance Improvements

Spend some time getting the glass front exactly in the groove of the foam seal. Push the front with one hand while fitting a single clip to the top centre. Do not fit the other two top clips until the lower three clips are fitted. The lower clips are quite awkward to get in position and this has to be done by feel more than sight. Check the three positions first and note that each clip has to sit between two end-stops:

BMW E31 840ci 850i Headlight Performance Improvements

Fit the clip to the front first and then push back and upwards at the same time. If one clip fails to push into position, substitute it for another clip, some are tighter then others. Once the three lower clips are fitted, fit the remaining two upper clips. Now is a good time to swap out the old bulbs for Osram Night Breaker Plus bulbs (3 x H1 bulbs each side) and then refit the top cover:

BMW E31 840ci 850i Headlight Performance Improvements

The results are pretty exceptional for this simple routine! Here is the sharp cut-offs produced by the refurbished dipped-beams, I'm very pleased with the results:

BMW E31 840ci 850i Headlight Performance Improvements

Parts Used:

Syringes
Flowable Silicone Sealant
Silicone Grease
Anti-Static Cleaning Wipes
6 x Osram Night Breaker Plus Bulbs

All done, time for a cup of tea!

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