View Full Version : What is this box??

98 Catera
02-23-09, 11:22 AM
What is this plactic box (about 5x5 in size) and what is its purpose? It has 2 vaccum hoses going to it (one is bigger that the othe), under the hood, by thte radiator, to the left, at the bottom of all the untake tubes, near the frame. Whatever it is it was broken so I replaced it.


02-23-09, 12:36 PM
its a vacuum reservoir, it supplies vacuum "pressure" to the rest of the vac line system when the car is under full acceleration.

98 Catera
02-23-09, 02:46 PM
Oh ok, thanks for the answer. maybe i should put the broken one back on.. ever since i fixed it the car is slower then it was before... oh well.

02-23-09, 09:08 PM
If anything, it should be faster by allowing the vacuum solenoids to open during wide open throttle acceleration.
They vary the intake manifold plenum lengths and connections to optimize torque through four different RPM ranges.
When you go WOT, vac drops to 0in/Hg and you need the reservoir there to temporarily provide the normal vacuum pressure for these solenoids to operate properly.

Its possible that there are other vacuum leaks or crisscrossed lines that are messing up the operation.

98 Catera
02-23-09, 09:24 PM
Ok, maybe its in my head that its slower.. I don't know? But its wierd that it didn't give me any problem when it was broken. The only reason I knew it was broken is my mechanic told me he saw it was broken (the larger or the 2 hoses was just sitting in the hole with some sort of duck seal holding it in and the plastic slide in tube was snapped off) when it was in for the recent timing belt / water pump job. so i found one and installed it myself.