McLaren 765LT Rear Windows Are Falling Off

McLaren has an issue with the 2021 765LT

Under certain conditions—like driving fast with the windows down—the rear polycarbonate window can decide to make a dramatic exit from the car, turning itself into an unwelcome risk for other road users.

This recall affects 163 examples of the 765LT hardtop. The problem stems from the adhesive used to bond the polycarbonate rear window to the car. According to NHTSA documents, owners complained in several warranty claims about rattling noises from the back of the cabin, which turned out to be the adhesive letting go.

Note, the recall only affects the coupe version of the McLaren 765LT without a factory-installed roof scoop. McLaren says cars with the roof scoop use a different process to secure the polycarbonate window. The 765LT Spider does not have a polycarbonate window and is also excluded.

The company couldn’t replicate the failure under normal testing conditions, but after digging deeper, McLaren found cars that saw track use, where side windows are required to be down for safety, showed a correlation. At high speeds with the side windows down, the aero pressure inside the cabin seemed to overwhelm the adhesive, leading to the de-bonding. McLaren says it didn't factor this load into the initial assembly process design.

McLaren added that it could not rule out potential non-compliance with the bonding process during assembly, the company didn't disclose what it uses as a bonding agent. When working with carbon panels, usually, the surface will require preparatory scuffing and a thorough cleaning with acetone, before an activator is applied, followed by the bonding agent—probably some form of Sikaflex.

The fix involves McLaren installing physical fasteners to keep the rear window securely attached to the carbon frame. In the meantime, owners are being told to keep speeds below 96 mph if the side windows are down. For those who can’t resist a track day, dealers can apply extra adhesive as a stopgap solution, though it’s not a permanent fix.

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