Compensator load spring, the compensator does exactly what it says on the tin it compensates for load in the back. When you put weight in the van the suspension depresses causing a high tension spring to open a valve which lets in more breaks fluid for a better stop under load. When you take weight out the reverse happens so there is less fluid. if it was to remain open without load then the car would skid with the higher pressure involved. This is your issue the spring is not holding attention any more, it’s a clever idea this bit it’s a shame they never put the same effort in to protecting the compensator due to its position it is open to a real hard life, the job is a bit of a dog but can be done with moving spare wheel and rack out, jacking up and supporting the van and removing rear right wheel.
