Lucas L745 lens cracking/gasket
Posted: Thu Jul 24, 2025 12:15 pm
For the second time in a year or so one of the lenses on the rear lamp units on my 1969 car cracked where the attachment screw is located. This made the lens insecure and at risk of falling off. New lenses are aviable from ESM but they are expensive. All of them are inherently brittle, new or old, but old ones are especially brittle.
Since a lens broke twice and I was on my third lens I decided to think about why this is happening. Obviously, the lens to lamp body screws must be tightened with great care but I had been careful. I discovered the old grey foam gasket was very hard and not acting as either a seal or a cushion to the lens. My theory is that with a hardened gasket the lenses were cracking when there was a large jolt such as the car going over an unexpected pothole or possible with sustained lower level vibration or even expansion/contraction with extremes of temperature. I have replaced the gaskets with new (they are now black) and we shall see if my theory is correct!
Stephen
Old hardened gasket
New gasket
Since a lens broke twice and I was on my third lens I decided to think about why this is happening. Obviously, the lens to lamp body screws must be tightened with great care but I had been careful. I discovered the old grey foam gasket was very hard and not acting as either a seal or a cushion to the lens. My theory is that with a hardened gasket the lenses were cracking when there was a large jolt such as the car going over an unexpected pothole or possible with sustained lower level vibration or even expansion/contraction with extremes of temperature. I have replaced the gaskets with new (they are now black) and we shall see if my theory is correct!
Stephen
Old hardened gasket
- IMG_2327.jpeg (2.54 MiB) Viewed 8639 times
New gasket
- IMG_2328.jpeg (2.08 MiB) Viewed 8639 times