Do you know how to read a vacuum gauge?
The key is having a reliable engine vacuum gauge and then knowing how to read it properly. We’ve said it before, but an engine vacuum gauge is an extremely valuable tool. It’s so valuable, in fact, that OnAllCylinders contributor Lori Sams put together this visual cheat sheet to help you understand common gauge readings.
Is it possible to detect a leak in a vacuum?
The detection of leaks in both pressurised and vacuum systems, as well as their elimination, management and/or accountability, is a serious business but unfortunately is often considered to be a trivial matter—which it most certainly is not. But what exactly is a leak?
What should the vacuum gauge be at at idle?
Starting with the engine at idle, slowly increase engine speed to 3,000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3,000 RPM. If vacuum decreases at higher engine RPM’s, an excessive exhaust back pressure is probably present. With the engine Idling, the vacuum gauge pointer will drop sharply, every time the leak occurs.
Can you hear a gasket leak in a vacuum?
But noise from a running engine can make it impossible to hear a hissing sound coming from leaky vacuum hose or gasket. For this you have two options: You can use a mechanic’s stethoscope that helps to amplify the sounds in your ear, or you can use a length of hose for the same purpose.
Is there a way to read the vacuum gauge?
You can hook a tee-fitting into an existing vacuum source or pull a line, such as one that leads to your transmission. Check to make sure all vacuum hoses are connected and not leaking. Once you’re engine is up to operating temperature, you can begin reading your vacuum gauge.
Is there a way to detect a vacuum leak?
I have heard of numerous DIY methods to detect those pesky vacuum leaks but it usually involves the use of a propane connected to a hose or carburetor spray cleaner aimed at suspected leak sites while the engine is running. Both of these methods can present a nasty fire hazzard when used around a hot engine.
Starting with the engine at idle, slowly increase engine speed to 3,000 RPM, engine vacuum should be equal to or higher than idle vacuum at 3,000 RPM. If vacuum decreases at higher engine RPM’s, an excessive exhaust back pressure is probably present. With the engine Idling, the vacuum gauge pointer will drop sharply, every time the leak occurs.
But noise from a running engine can make it impossible to hear a hissing sound coming from leaky vacuum hose or gasket. For this you have two options: You can use a mechanic’s stethoscope that helps to amplify the sounds in your ear, or you can use a length of hose for the same purpose.