Problem with brake servo

[sportscott]

I fitted a Waeco Magic speed cruise control in my Van and done everything by the book, after the first drive my back left brake locked on, then they were all locking on and the only way I can release them is by pulling the vacuum hose off the servo. Now with the cruise control completely disconnected. The servo slowly builds up vacuum and applies the brakes driving on straight roads without using the brakes. What is going on? and does anybody know or can check if the brake servos the same between a petrol and diesel mk5. I should have been on the road tomorrow but doesn't look like it's going to happen unless I can fix the problem. I think I can see some brake fluid leakage on the servo, just an idea I've just had and been reading about how a brake servo works, it can be I've blocked the air inlet port with anti corrosion wax, need to take a look in the morning.

[sportscott]

Spent all night scouring the web and studying how a brake servo works. Decided that it must be the atmospheric valve not closing, that's the one that opens when you press the brake pedal, it was leaking letting air slowly in allowing the vacuum side to apply the brakes. You won't find much about this on the internet only about servo leaking and not pulling vacuum it must be rare but can happen. Swapped out the servo and now everything is ok.