Topic: Driver side plastic trim from lower dash,A pillar side 74 450 SEL

[Olds57]

Greeting, Broke narrow plastic trim from lower dash to floor(Yes I was stupid)drivers side. Any color but would prefer red.
Thanks for your attention.

[nathan]

I think this is THE hardest interior part to find in good condition, in any colour! good luck, but notoriously brittle and people inevitably break them trying to remove them.

[Squiggle Dog]

You might try melting the broken plastic parts back together with a soldering iron from the backside so the "welds" are not visible. There are a few good YouTube videos showing this process.

[daantjie]

Agree this must be the most ill fitting piece f trim on the 116.  Overall the fit of the interior parts is excellent, but on this piece the top tab is squeezed very tight by the dash, so removing it in one piece is quite the feat.

[Olds57]

Reply to ALL...... thanks for your thoughts  i will try to weld... cannot believe i was so reckless.
thanks again

[raueda1]

One of my pieces is also cracked so I've been pondering this problem.  Fortunately my crack it isn't too bad. 

Anyway, as an alternative to the welding/solder gun technique, I wonder if anybody has tried plastic model cement, aka 'airplane glue.'  These solid molded pieces are made of ABS, a close cousin to the polystyrene used for plastic models.  The trick would be to use such a tiny amount that a bead isn't formed on the front when pieces are squeezed together.  Or perhaps clamping the parts and running a bead on the back side.  The cement will soften and partially dissolve the surface of the plastic, so swirling around the bead before it dries (with a toothpick perhaps) would strengthen the bond.  Let dry at least 24 hours (or even 48) without movement.

I haven't tried this but I'm pretty confident it would work IF there isn't much stress applied to the fixed molding.  When I get done with other ongoing projects I'll give it try and report back unless somebody else beats me to it.

[Squiggle Dog]

Methyl ethyl ketone (very toxic stuff) is supposed to be good for bonding plastic, because like the plastic model cement, it melts plastic together.

Using plastic prybars right at the clips seems to help with removing these pieces, though it's still tricky.

[raueda1]

Methyl ethyl ketone (very toxic stuff) is supposed to be good for bonding plastic, because like the plastic model cement, it melts plastic together.

Using plastic prybars right at the clips seems to help with removing these pieces, though it's still tricky.

I've used MEK before for stuff like this.  MEK will absolutely bond this plastic.  However, it's extremely "thin" and hard to work with.  It will instantly penetrate the crack and almost certainly leave a small bead on the surface where material is squeezed out of the crack while it's clamped together.  Plastic model cement has (or used to have) MEK in it as one of the solvents (among other things).  Model cement also has plastic dissolved in it, that's why it's viscous.  Hence a bead of cement on the back would provide some strength.  I'd try model cement before messing with MEK.

[full disclosure:  I used to be a chemist in the area of some plastics, elastomers and adhesives.  Unlike old cars it something I (used) to know something about!  ]

[floyd111]

See, I knew it! Full disclosure, my foot!
People, there are nerds here, hiding in the bushes. Chemistry and whathaveyou. What else haven't you told us, Raueda?

[Olds57]

Again thanks to all replied to my trim piece problem.
Used plastic weld, it actually works.. But had to place a FINE chrome screw near the top to mate the correct configuration.
The engineers  are rolling in their graves.
Have a detail color person showing up to cover up the glue break.
Thanks to all for your comments
Regards,

[raueda1]

See, I knew it! Full disclosure, my foot!
People, there are nerds here, hiding in the bushes. Chemistry and whathaveyou. What else haven't you told us, Raueda?

LOL!!  I guess we all bring our special gifts to the world of W116's.  And I haven't told you that I ski all winter -retired! 

But in seriousness, most of my career was spent with a Swiss chemical company developing and making stabilizers & antioxidants for plastics, rubber and adhesives (they made lots of other stuff too).  Auto hoses, belts, molded rubber stuff and all the auto plastics were a huge part of it.   Designing these material was (and is) always a balancing act between expected longevity, price and cost-of-failure.  What passes for acceptable reliability in a car is NG for a diesel locomotive or submarine.  Mercedes seems to use extremely specific designs for absolutley everything so I perceive a greater risk of substituting something because there might be some unknown design criterion.  I don't think twice about that stuff on my chevy truck.  So that's what I know about.   

[Squiggle Dog]

I remember when I needed an ASD (Anti Slip Differential) hose for my roommate's 350SDL, I was told by several sources that it had to specifically be a hose rated for hydraulic fluid--a hose for coolant, fuel, or transmission fluid wouldn't cut it as those would eventually get soft and leak. Fortunately there was a compatible hose at the auto parts store.