VW Transporter T5 and T6 Sill Rust: What Mansfield Drivers Should Know
The VW Transporter T5 and T6 is one of the most popular vans on UK roads, and for good reason — it is well-built, practical, and holds its value. But there is one area where the Transporter has a known weakness: the inner sills. Sill rust is a recognised problem on T5 and T6 Transporters, and it is one of the most common reasons these vans fail an MOT.
At Star Welding Mansfield, we carry out sill welding repairs on Transporters and other vans regularly. This guide explains where the rust starts, how serious it can get, and what is involved in getting it properly repaired.
Why the VW Transporter T5 and T6 Rusts Where It Does
The sills on a VW Transporter are the sections of bodywork that run along the bottom edge of the van, between the front and rear wheel arches. They are structural components — they contribute to the rigidity of the vehicle and provide a load path between the front and rear of the body.
The problem is that the inner sill on the Transporter is a boxed section with seams and channels that trap water, road salt, and debris. Once moisture gets inside the box section, it has nowhere to escape, and corrosion begins from the inside out. By the time rust is visible on the outer surface of the sill, it has typically been working from within for some time.
This pattern is particularly pronounced on T5 Transporters built between 2003 and 2015. The T6 (2015 onwards) uses improved corrosion protection in some areas, but sill rust remains a known issue on older examples of this generation too, particularly those operated in urban areas where road salt exposure is heavy.
Campervans and leisure conversions based on T5 and T6 platforms are often more vulnerable because they spend more time parked outdoors, see frequent wet-weather use, and may have had additional holes made in the bodywork during conversion that compromised the original rust protection.
What Are the Inner and Outer Sills and Why Do They Matter?
The sill structure on a Transporter is made up of several layers. The outer sill is the visible panel you can see from the side of the van. Behind and above it sits the inner sill — a structural channel that is part of the body frame. Between the two, there may be intermediate reinforcing sections depending on the model variant.
The outer sill can be cosmetically damaged or lightly corroded without causing immediate structural problems. The inner sill is a different matter. It carries load and provides structural stiffness. When the inner sill corrodes through, the van loses rigidity in a structurally important area — which is exactly why MOT testers check this section carefully.
An MOT failure for sill corrosion on a Transporter means the inner sill has deteriorated to a point where structural integrity is compromised. The tester is not penalising surface rust — they are identifying a genuine structural weakness that would affect safety in an impact.
