Building a PVC Vacuum Reservoir

a foot of 3" PVC pipe with end caps painted black.
The electric pickup truck uses a vacuum pump to generate vacuum for the power brakes (and move vents in the HVAC system). It has a pressure switch that turns on the pump when the vacuum drops to under 15 inHg and turns it off once the pump has raised the vacuum to 25 inHg. The current system has a small 3″ by 1.5″ PVC cylinder as the vacuum reservoir. As soon as you press the brake the pump turns back on, and cycles on and off relatively frequently. I wanted a larger vacuum reservoir so that the duty cycle on the pump would be longer (it would stay on longer, but also stay off longer) and so that even when the vacuum drops to 15 inHg I could still operate the brakes several more times while the vacuum pump was working.

3" pvc pipe cap with a hose bib and vacuum gauge connection inserted

I used 3″ PVC pipe and end caps to build the Reservoir. I screwed a 3/8 inch hose bib (and a smaller adapter for a $25 vacuum gauge from AutoZone) into one end cap and then made sure it was air-tight by coating the inside and outside of the adapters with epoxy. After using PVC solvent and cement to attach the end caps, I also used epoxy on that joint, just in case. Spray painting it black finished the job.
PVC pipe and cap, with join double sealed with epoxy
Vacuum reservoir made out of PVC pipe parts


3 comments ↓

#1 S-10 Electric Pickup — Jay’s Technical Talk on 03.25.11 at 8:52 am

[...] Larger capacity vacuum reservoir [...]

#2 gerry on 10.05.11 at 5:35 am

hi mate
just like to know i have read you read ups on this but i need something for my breaks as the cam i have put in the car is to big and it is drawing way to much from the manifold . as you can see i have less air to get from stopping the car .
please reply back with some news

#3 Jay on 10.05.11 at 7:11 am

If the cam’s draw is continuous, you will need to improve your vacuum in some other way. If however it is intermittent, you could use a one-way (check) valve and a vacuum reservoir like this one to guarantee that your power brakes have vacuum even if the cam is lowering the vacuum pressure elsewhere in the system. You would have to arrange things such that when your vacuum pressure was high it would “charge” the reservoir, which powers the brake system. The check valve would keep the cam from drawing down your reservoir.

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