A bypass valve or overrun cutoff valve is what's keeping your car's engine from undergoing what's known as an over-revolution. It's the car part that serves as the limiter to the amount of revolutions your engine can do.
It's dangerous for your vehicle to do an over-revolution or overrun because it damages your engine beyond repair. This valve is responsible for cutting off your engine before it runs beyond the maximum revolutions per minute. If your bypass valve itself is damaged, then read on to find out how to fix or buy a replacement for it.
Tips to Keep in Mind
- The Danger of Undergoing Overruns: An engine that's going through an overrun is akin to pouring hot water over an empty plastic water bottle. The sudden change in temperature will make your motor warp or even explode. This is because when you're going through an over-revolution, the friction will have heat spread instantly, thus cracking your cylinder block and several of your engine's pistons. This makes the overrun cutoff valve and important safeguard akin to your seatbelts and steering wheel airbag.
- Symptoms of a Damaged Overrun Valve: If you hear funny sounds of grinding gears at your car startup and if your engine overheats easily, then you should get it looked at. Those symptoms however aren't only applicable to a damaged overrun valve. It's best that you let a mechanic handle inspecting what's wrong with your engine and engine bay to see if it's an overrun issue or a lack of coolant. The dangerous thing about a damaged overrun valve is that once you do an overrun, irreparable damage will happen to you engine.
- Research Regarding the Valve's Battery Voltage Capabilities: There are many ways for this valve to malfunction. It could have a lose connection that keeps it from activating, it might not be in sync with your car computer, and various other issues. You should get a replacement valve that's programmed to limit the revs per minute of your engine at a set amount in accordance to your engine type. The valve should also get 12 volts through its terminals whenever your revs go over for let's say 1,800 RPM while your throttle is at zero.
- Shopping for the Best Valve: Don't buy a used valve, because you're asking for trouble there with its tendency to fail by its electrical connections. Most valves malfunction because of bad or loose connections that should be corrected. You should also avoid salvaged or refurbished parts that have mileage on them due to their increased risk of shorting out. Instead, go for a brand new OEM or OE-standard $40 valve with accurate pressure monitoring and can withstand high engine temperatures as well as high standards of quality control certifications.