GB2089982A

GB2089982A - Detecting leaks in engines

Info

Publication number: GB2089982A
Application number: GB8040971A
Authority: GB
Original assignee: FROUDE ENG Ltd
Current assignee: FROUDE ENG Ltd
Priority date: 1980-12-22
Filing date: 1980-12-22
Publication date: 1982-06-30

Abstract

A method is provided of detecting a leak, for instance in the lubricant or coolant system of an internal combustion engine. Gas under pressure, such as compressed air, is supplied to an enclosed space of the engine. An electroacoustic transducer is used to search for the sound of gas escaping through a leak to the exterior of the engine. It is thus possible to detect a leak with the engine in a vehicle or on a test bed but without having to dismantle the engine.

Description

SPECIFICATION Improvements in or relating to methods of detecting leaks in engines The present invention relates to methods of detecting leaks in engines. Such a method may be used for detecting a leak in an internal combustion engine of the petrol or diesel type.

According to the invention, there is provided a method of detecting a leak in an engine, comprising supplying gas under pressure to an enclosed internal space of an engine and searching with an electro-acoustic transducer for the sound of the gas escaping through any leak to the exterior of the engine.

Such a method may be used to detect a leak in the lubricant system, for instance in the seal between a crank case and cylinder block of an internal combustion engine. Compressed air may be supplied to the crank case breather. The crank case is thus pressurized and the sound produced by any air leaking from the gasket seal is detected by the electro-acoustic transducer. The front and rear seals of the crankshaft may also be checked in this way. The lubricant filter cap generally forms a fluid-tight seal with the lubricant inlet, thus allowing the crank case to be pressurized.

Such a method may also be used to detect a leak in thesngine coolant system. Compressed air is then used to pressurize the coolant system and the sound of air escaping from any leak, for instance in the seal between the cylinder block and the water pump cover, is detected by the electro-acoustic transducer.

The gas may generally be supplied under pressure of up to 1 5 p.s.i. (pounds per square inch) without there being any substantial danger of damaging any engine seals or gaskets. A of 2-3 p.s.i. has proved effective in use. The pressure should be such as to cause turbulent flow of gas passing through any leak so as to provide a sufficient level of sound for detection by the electro-acoustic transducer.

The electro-acoustic transducer may be a conventional microphone. A piezo-electric type of microphone may be used and has the advantage of being relatively rugged and reliable. Such a microphone is relatively sensitive and does not place any different demands on an amplifier connected thereto other than a relatively high input impedance.

In order to monitor the sound detected by the transducer, an amplifier is generally connected to the output of the transducer. The amplifier output may be connected to a pair of headphones or a loudspeaker to provide an audible indication of the presence of a leak. The amplifier may include a filter, such as a high pass filter, for preferentially amplifying those frequencies resulting from the escape of gas through a leak. Thus, the sensitivity of detection may be increased without substantially increasing the level of signals caused by ambient or background noise.

When checking a lubricant or coolant system, the system should generally be empty or drained.

By way of example, in order to check the lubricant system of a petrol or diesel engine for leaks, a source of compressed air at 7 tn .R connected to the crank case breather. The tester wears a pair of headphones connected to the output of an amplifier whose input is connected to a piezo-electric microphone. The microphone is first held adjacent and pointed towards the engine oil filler cap to check for leaks so as to ensure that the crank case is pressurized. In order to check that the apparatus is functioning properly, the filter cap may be partially released so as to provoke a leak. The gain of the amplifier may be set to a suitable value to provide adequate sensitivity of detection.

The microphone is then held adjacent and directed towards the seal between the crankcase and the cylinder block of the engine, and moved around this seal while the operator listens for the characteristic sound of escaping air indicative of a leak in the seal. It is thus possible to determine the pressure and position of any leak in the seal. The microphone may also be moved to the front and rear seals of the crankshaft so as to check for any leaks at the front and rear bearings thereof.

Such a method can be used to check an engine when installed in a vehicle. However, it is more convenient to use such a method if the engine is mounted on a test stand for undergoing other tests. In either case, such a method allows leaks to be detected without having to dismantle or otherwise modify the egine in any way.

1. A method of detecting a leak in an engine, comprising supplying gas under pressure to an enclosed internal space of an engine and searching with an electro-acoustic transducer for the sound of the gas escaping through any leak to the exterior of the engine.

2. A method as claimed in claim 1, in which the engine is an internal combustion engine and compressed air is supplied to a crank case breather of the engine so as to pressurize the crank case.

3. A method as claimed in claim 1, in which compressed air is supplied to a coolant system of the engine.

4. A method as claimed in any one of the preceding claims, in which the gas is supplied under pressure of up to 1 5 pounds per square inch.

5. A method as claimed in claim 4, in which the gas is supplied under pressure of between 2 and 3 pounds per square inch.

6. A method as claimed in any one of the preceding claims, in which the electro-acoustic transducer is a piezo-electric microphone.

7. A method as claimed in claim 6, in which the microphone is connected to the input of an amplifier whose output is connected to headphones or to a loudspeaker.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to methods of detecting leaks in engines The present invention relates to methods of detecting leaks in engines. Such a method may be used for detecting a leak in an internal combustion engine of the petrol or diesel type. According to the invention, there is provided a method of detecting a leak in an engine, comprising supplying gas under pressure to an enclosed internal space of an engine and searching with an electro-acoustic transducer for the sound of the gas escaping through any leak to the exterior of the engine. Such a method may be used to detect a leak in the lubricant system, for instance in the seal between a crank case and cylinder block of an internal combustion engine. Compressed air may be supplied to the crank case breather. The crank case is thus pressurized and the sound produced by any air leaking from the gasket seal is detected by the electro-acoustic transducer. The front and rear seals of the crankshaft may also be checked in this way. The lubricant filter cap generally forms a fluid-tight seal with the lubricant inlet, thus allowing the crank case to be pressurized. Such a method may also be used to detect a leak in thesngine coolant system. Compressed air is then used to pressurize the coolant system and the sound of air escaping from any leak, for instance in the seal between the cylinder block and the water pump cover, is detected by the electro-acoustic transducer. The gas may generally be supplied under pressure of up to 1 5 p.s.i. (pounds per square inch) without there being any substantial danger of damaging any engine seals or gaskets. A of 2-3 p.s.i. has proved effective in use. The pressure should be such as to cause turbulent flow of gas passing through any leak so as to provide a sufficient level of sound for detection by the electro-acoustic transducer. The electro-acoustic transducer may be a conventional microphone. A piezo-electric type of microphone may be used and has the advantage of being relatively rugged and reliable. Such a microphone is relatively sensitive and does not place any different demands on an amplifier connected thereto other than a relatively high input impedance. In order to monitor the sound detected by the transducer, an amplifier is generally connected to the output of the transducer. The amplifier output may be connected to a pair of headphones or a loudspeaker to provide an audible indication of the presence of a leak. The amplifier may include a filter, such as a high pass filter, for preferentially amplifying those frequencies resulting from the escape of gas through a leak. Thus, the sensitivity of detection may be increased without substantially increasing the level of signals caused by ambient or background noise. When checking a lubricant or coolant system, the system should generally be empty or drained. By way of example, in order to check the lubricant system of a petrol or diesel engine for leaks, a source of compressed air at 7 tn .R connected to the crank case breather. The tester wears a pair of headphones connected to the output of an amplifier whose input is connected to a piezo-electric microphone. The microphone is first held adjacent and pointed towards the engine oil filler cap to check for leaks so as to ensure that the crank case is pressurized. In order to check that the apparatus is functioning properly, the filter cap may be partially released so as to provoke a leak. The gain of the amplifier may be set to a suitable value to provide adequate sensitivity of detection. The microphone is then held adjacent and directed towards the seal between the crankcase and the cylinder block of the engine, and moved around this seal while the operator listens for the characteristic sound of escaping air indicative of a leak in the seal. It is thus possible to determine the pressure and position of any leak in the seal. The microphone may also be moved to the front and rear seals of the crankshaft so as to check for any leaks at the front and rear bearings thereof. Such a method can be used to check an engine when installed in a vehicle. However, it is more convenient to use such a method if the engine is mounted on a test stand for undergoing other tests. In either case, such a method allows leaks to be detected without having to dismantle or otherwise modify the egine in any way. CLAIMS

8. A method as claimed in claim 7, in which the amplifier includes a filter for preferentially amplifying those frequencies resulting from the escape of gas through a leak.

9. A method as claimed in claim 8, in which the filter is a high pass filter.

10. A method of detecting a leak in an engine, substantially.as hereinbefore described.