More or less, every single semi-truck on the road today derives its stopping power from air brakes. At the heart of every air brake system resides a reciprocating air compressor. The compressor forces air into a closed reservoir until reaching the desired level of pressure. This air ultimately provides your brakes with power.
While most air compressors provide highly reliable results, as time goes on, the air compressors may develop problems that impede the performance of your air brakes. Truck owners should possess at least a basic understanding of common compressor woes. This article takes a closer look at two frequently experienced issues affecting air brake compressors.
1. Short Cycling
Short cycling represents a serious and all too common problem for all varieties of air compressors. As its name implies, short cycling involves a compressor that frequently turns on and runs for a short period. After another brief hiatus, the compressor then starts right back up again.
Short cycling puts a lot of strain on a compressor's motor and can lead to overheating or burnouts if allowed to continue too long. Short cycling may stem from a number of causes. That said, this issue often ties back to problems with either compressor's governor.
The governor determines when the compressor sends more air into the pressure reservoir. Once reservoir pressure reaches a certain level, the governor directs the compressor to begin sending its air directly into the atmosphere. Once pressure has dipped below the minimum cutoff, the governor instructs the compressor to begin filling the reservoir again.
Short cycling either may occur because of leaks in the governor itself or in the sensing line used to monitor reservoir pressure. A trained mechanic can often test for leaks in airlines by spraying them with a soap solution and then watching carefully while a helper pumps the brake. Any air escaping from the lines causes the soap to bubble up.
Checking for a faulty governor requires more involved tests. In that case, the mechanic must remove the governor. The technician then uses shop air in order to manually cycle the compressor. If the compressor behaves normally when the mechanic regulates it in this manner, the problem almost certainly lies in the governor.
2. Leaking Coolant
An air compressor generates lots of heat because of normal operation. Such heat can become problematic when the compressor must run for longer periods of time - such as when braking down a steep incline. In order to regulate temperature and prevent overheating, most compressors use their truck's coolant system.
Many air compressor problems stem from issues with the coolant system, especially if they result in an insufficient coolant flow into the compressor. Here the most common culprit is because of leaks. Leaks most often occur because of a damaged compressor head gasket.
Such damage may lead to either external or internal coolant leaks. External leaks should be easy for a trained mechanic to spot, as the evaporating coolant often leaves behind whitish stains. To diagnose an internal leak, a technician must drain the pressure reservoir to inspect whether excessive levels of water or coolant are present.
In either case, if a mechanic determines that the air compressor's head gasket is at fault, the only option will be to install a new head gasket.
Truck owners should make maintaining a safe and effective air brake system one of their highest priorities. If you suspect that your air brake system may suffer from compressor problems, please do not hesitate to contact the truck repair experts at Odessa Spring, Brake & Axle, Inc. We're happy to answer any questions you have.