View Full Version : Quick Vacuum question

01-30-2011, 11:37 AM
I done the vacuum and check valve delete a while back on my car. After doing so, my brakes have felt a bit odd, like it takes more pressure to get it to stop. I recently put new pads and rotors all around, calipers seem to be working fine. I still have the vacuum line with check valve hooked up from the manifold to the brake booster. I was wondering, if re-attaching a vacuum line from the manifold to the vacuum reservoir inside the fender, would help with my braking problem. Also after doing the delete my cruise control stopped working. Is there something vacuum wise that would cause it not to work?

01-30-2011, 11:45 AM
i think the cruise control is controlled by vac i could be wrong though

01-30-2011, 12:37 PM
Yep, on the non-DBW cars the cruise control actuator is a physical unit that pulls the throttle plate open using a vacuum diaphragm. It requires a constant vacuum source from the vacuum pump to do this. Without a constant vacuum source, it will not operate. If you removed some of the vacuum lines, you may have inadvertently deleted one of the vacuum lines for the cruise system.

Also, the vacuum reservoir is not used to supplement or supply the brake booster with vacuum. It is used for other devices like the Leak Detection Pump (you probably have a code for that one), EVAP (probably have a code for that too), etc. You have to be very careful and methodical in what you delete vacuum-wise on these cars if you want crap to remain working properly.

The difference in brake feel may be caused by the type of hose you used or a leaky factory check valve. If you deleted any secondary in-line check valves, those may have been helping cover up the problem. The older AEB 5-speeds had the simplest of all the 1.8T vacuum systems, so it shouldn't be too hard to correct. I guess I'd have to see what exactly was deleted as far as the brake booster vacuum supply line, and what it looks like now.

01-30-2011, 12:52 PM
I deleted the lines from the purge valve on the passenger side fender, the line coming up from the tip, that crossed the firewall to the drive fender, and the lines from the bottom of the manifold. I left the line from the manifold to the brake booster as is.

So in order to get the cruise control back, would I just re-attach the reservoir to the manifold?

01-30-2011, 12:59 PM
For the cruise, I would start by checking the vacuum line from the vacuum pump to the actuator, and check the actuator at the same time. If that checks out, then you probably didn't cause anything doing your vacuum changes. There is a common failure of the cruise module where the solder points fail on the board. So I'd check that out next. While you're at the module, you may want to check the wires to make sure the "set" signal is actually getting to the module (checking the switch and the wiring all at once).

01-30-2011, 01:57 PM
Ill have to check the vacuum line to the cruise control later once I get more time. The warm weather we had here, just isnt lasting long enough. I did find that the cap that closed off a nipple on the check valve on the brake booster was cracked and falling apart. I found another nipple, in what seems to be a bit better material, and stuck it on there. Hoping that might have been the problem, Ill find out soon though.