From what Ive read so far the same sensor as was suggested to me earlier has been used for boost pressure projects. The MAP sensor (Manifold Air Pressure / Boost sensor) goes on the inlet which is at lower pressure than the ambient air pressure.
You are never going to get anywhere near a true vacuum. The brakes vacuum assist servo works on the diference between the air pressure and lower pressure on the vacuum pump side.
The pressure on the vacuum pump side is still a positive pressure and should be in the range of the sensor.
The vacuum pump is designed to lower the pressure by the same amount as is in the inlet manifold.
The sensor just needs to be within a working range.
Its on its way so Ill report back when I get it.
If it works it will be a cheap way of getting a robust amplified pressure sensor working at 5v and with an output between 0 and 5v. Ideal for the Arduino.
As to the safety aspect again.
The problem with my brakes has already been fixed with the new pump. I just want to monitor it.
As I said earlier I wasnt going to drive it home without brakes and neither would I drive it if I thought I would endanger myself or others with this very minor and safe modification.
After all its its also got the EGR sensor attached to it on a thinner hose theres no additional risk with adding my extra sensor.
Gordon