* Power Steering System: A problem with the power steering pump, hoses, or rack and pinion can cause the steering wheel to bind and inadvertently activate the brakes. Low power steering fluid is a common culprit.
* Brake System: A problem with the brake lines, calipers, or master cylinder could be causing the brakes to engage unexpectedly.
* Steering Column: Damage or a malfunction within the steering column itself could be causing the unintended brake application. This is less likely but possible.
Do not drive the van until this is resolved. Driving with this problem is extremely dangerous and could lead to an accident. Have a qualified mechanic diagnose and repair the problem immediately. Ignoring it could result in serious injury or damage.