'97 VW Passat Intermittent cruise The cruise control on my '97 Passat V6 automatic is very intermittent, and seems to be more predictable in warmer weather or perhaps once the interior or engine compartment warms up. In extremely cold weather (below about 20 degrees Fahrenheit) it simply won't work at all. I've replaced the vacuum vent valve on the brake pedal and it's properly adjusted. The brake light switch is working properly, and it makes no difference if I pull up on the brake pedal when trying to set the cruise. When it works, it works great with the exception of sluggish response in an extreme condition, like going up a steep hill, or being passed on a windy day by a semi.

here is a breakdown of the under-dash version. Sorry for any confusion. This unit is less susceptible to cold weather, but may still get old and brittle. The good thing is, you may be able to hear any leaks while driving under cruise control. Just have your passenger stick their head under there instead of you. First check the supply hose from that storage cannister you found to the system.


here is a breakdown of the under-dash version. Sorry for any confusion. This unit is less susceptible to cold weather, but may still get old and brittle. The good thing is, you may be able to hear any leaks while driving under cruise control. Just have your passenger stick their head under there instead of you. First check the supply hose from that storage cannister you found to the system.

There are 2 solenoids--one to open the vacuum and one to open the vent. So the vent valve could be leaking or the diaphram itself. Pull the hose off the vacuum servo and use pull a vacuum. If that vacuum holds, the diaphram is good. Next, move downstream to the "T" and pull a vacuum at the "T" with the vent hose connected. If the vacuum does not hold, the vent valve or line is leaking. Does this make sense? If you still don't see the leak, try switching and connecting the vacuum line while pulling a vacuum on the "T". This will test whether the vacuum valve/solenoid is leaking. It's all about isolating the various pieces to find that pesky leak. There are 2 solenoids--one to open the vacuum and one to open the vent. So the vent valve could be leaking or the diaphram itself. Pull the hose off the vacuum servo and use pull a vacuum. If that vacuum holds, the diaphram is good. Next, move downstream to the "T" and pull a vacuum at the "T" with the vent hose connected. If the vacuum does not hold, the vent valve or line is leaking. Does this make sense? If you still don't see the leak, try switching and connecting the vacuum line while pulling a vacuum on the "T". This will test whether the vacuum valve/solenoid is leaking. It's all about isolating the various pieces to find that pesky leak.