In this article, we explore two different problem areas within your brake system, including your ABS system. We provide you with possible causes as well as suggestions to repair them.

The Problem: The Latest Brake Legislations

Here are four possible causes and suggestions:

1. All new trailers above 3,500 kg GVM, built after 14th February 2004 in South Africa must be fitted with an ABS brake system that has been internationally approved. These new trailers brake systems must meet the braking requirements as described in the SABS ECE R13 brake specifications. These systems must also be kept in good working order at all times in order to pass COF tests.
                                                                                                                                                                                      
2. In addition, these new trailers must also be fitted with Automatic Slack Adjusters. Good quality Automatic Slack Adjusters are essential for continuous and proper operation.                                                                                                                                                                              
3. It is not a law in South Africa that trucks must be fitted with an ABS brakes system, however, most imported trucks come standard with either an ABS or an EBS brake system.                                                                                                                                                                       
4. A few other requirements that are listed in the SABS ECE R13 brake specifications are as follows:
   • According to SANS 20013 specifications, the flexible Suzy hoses must be part of the towing vehicle when towing a semi-trailer. According to this specification, the couplings are fitted on the Truck Tractor at the end of the fixed Suzie's and the couplings must be fitted with automatic shut-off valves.
   • The Emergency line on the semi-trailer is fitted with a fixed Male coupling and the Service line is fitted with a fixed Female coupling and a valve lifter, (striker plug).                        
   • The suzy hoses do not have to be coloured 'Red' and 'Yellow', as long as the Service and Emergency tags are coloured correctly.                                                                                                                                                                 

The Problem: Trailer ABS System

Here are four possible causes:

1. The 'Green' marker light is wired to the trailer's ABS system to indicate to the driver if the ABS system is functioning correctly. With the truck stationary and the brake pedal applied, the green light should come on for 2 seconds and then go out. If this happens it is an indication that the ABS system is functioning with no electrical faults. Any other sequence, (i.e. light stays on or light does not come on at all), indicates a wiring fault or internal failure of the ABS electrical components. The green light is electrically connected to the trailers 'stop light' wiring system.                                
2. EBS and ABS systems that are connected using permanent power cables, (this is compulsory if the towing vehicle is fitted with ABS or EBS systems), use the trucks dashboard indicator lights to check on the functioning of the truck and trailer's electrical brake systems. If permanent powered cables are used it is not necessary to fit a green light on the trailer. If it is fitted will only be there as a back-up system. Trailers fitted with green marker lights were originally fitted to trailers fitted with ABS brake systems that were towed by a truck that was not fitted with an ABS or EBS brakes system.                                                      
3. "WARNING!!!” never weld on the chassis of a vehicle that is fitted with an ABS or EBS brake system, or any other electrically controlled, system, without first disconnecting the main electrical feed cable to the ECU and all the sensor cables. Failing to do this can seriously damage the 'Mother Board' in the ECU, which is a costly unit to replace.                                           
4. Other than a damaged ECU, the other common reasons for an ABS system to malfunction are  due to one or more of the sensor cables being broken or faulty, or the gap between the sensor and the pole wheel, (exciter ring), being too great. If it is a gap problem, then by pushing the sensor in against the pole wheel should solve the problem. The sensor and pole wheel gap will automatically reset itself when the vehicle is back in motion. The sensor will not be damaged if it makes contact with the pole wheel as it is made of very hard material.

These are another collection of handy tips to repair your air brake system. If you need professional help, JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Please contact us today for all your brake system needs.

We explore four different problem areas within your brake system and provide you with causes as well as suggestions for each. We’ll help you repair your air brake system in no time.

The Problem: Insufficient Brakes

Here are a few possible causes and suggestions:

1. Brakes need adjusting, or linkages need lubricating, or drums and linings need attention, or mechanical parts like rollers and cam shafts need replacing.
2. Air pressure is too low. If air pressure is at the correct level, do not set the system pressure up above its designed setting, this will not solve the problem and could result in problems elsewhere in the system.
3. Wrong size boosters fitted or they are connected to the incorrect holes on the slack adjuster. Check the data plate for the correct information.
4. The angle between the booster push rod and the slack adjuster arm is less than 90 deg. When the brakes are fully applied. Cutting and shortening the booster push rod may be necessary to achieve the correct angle. Up to  30% brake efficiency can be lost due to incorrect booster to push rod settings.
5. Incorrect Load sensing valve fitted or load sensing valve linkage is not set correctly. See data plate for the correct settings.                                                                              

The Problem: Brakes Apply or Release Too Slowly

Here are five possible causes:

1. Restriction in either one of the control pipes or delivery pipes. Kinked nylon tubing is a common fault. 
2. Blocked airline filters on the trailer emergency or service lines. 
3. Incorrect clearance settings within the male and female couplings to the trailer brakes. This is a common because of the many couplings being imported that do not adhere to SABS or international dimensional standards.                                                                                                                                                      
4. No striker plug fitted to the trailer female coupling.   
5. Seized or sticking foundation brake linkages.

The Problem: Binding Brakes

Here are a few possible suggestions:

1. Kinked or blocked system delivery or control pipes.  
2. Binding trailer air brakes are often caused by the hand brake valve not delivering enough air pressure through to the trailer control valve to balance it off. When the hand brake valve internal plastic cam eventually wears out and it does not fully open the valve mechanism to allow maximum pressure through. In this case the hand brake valve has to be replaced. Some hand brake valves can only handle a certain level of pressure and if someone manually sets the system operating pressure up too high, this causes an imbalance of pressure to the trailer control valve, resulting in the trailer service line pressure not releasing completely and cause the brakes to bind.
3. Sticking or seized brake valve or foundation brake linkages.
4. Restriction in the trailer service line causing the service brake pressure to not release completely when brakes are released.                                                                                                              

The Problem: Insufficient Park Brakes Holding Capability

Here are a few possible suggestions:

1. Brakes need adjusting, or linkages need lubricating, or drums and linings need attention.                  
2. Wrong size Spring Brake boosters fitted. (Check the data plate for the correct sizes).                  
3. Unless Double Diaphragm Spring Brake boosters were fitted as standard, (like on some American trucks), do not replace the piston-type boosters, (as found on most European trucks), with Double Diaphragm boosters. The spring force of the main spring in the piston-type units are anything up to 60% stronger than the ones in Double Diaphragm units.

These are just some of the handy tips that you can follow to sort out your air brake system. If you need professional help, JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Contact us today for all your brake system needs.

In the first article we looked at some of the most common issues involving your air brakes. Now let’s explore a few additional issues that can result in a failing brake system.

The Problem: Oil or Water in Air Reservoirs

Here are a few possible causes and suggestions:

1. Although Air Dryers are designed to capture most of the oil and water before it reaches the air reservoirs, a certain amount of the oil and water still gets through. It is therefore advisable to drain the air reservoirs on a daily basis. Excessive water in the reservoir normally indicates that the Air Dryer cartridge is blocked and needs changing. Excessive oil in the reservoir normally indicates that the compressor is passing too much oil out of its delivery pipe. This could either indicate that the compressor piston rings need replacing or if the compressor inlet pipe is coupled to the engine inlet manifold, then the engine turbo charger is passing oil vapour into the inlet manifold and this is being sucked in by the compressor and discharged out the delivery pipe. Slightly damp or dry oil at the exhaust port of the Air Dryer or Unloader valve is normal. However, excessive or wet oil is a good indication that the compressor needs attention. It is always a good idea to overhaul a compressor before it breaks down, which occurs very often, when the vehicle is many kilometres away from the workshop.                                                                                                                                                                                   
2. In many cases it is advisable to fit automatic drain valves to all the reservoirs to try to keep the air reservoirs as clean and dry as possible.                                                                                                                                                                             

The Problem: Reasons for the Valve to Leak

Here are three possible causes:

1. The leaks at foot valve exhaust ports are very often caused by a feed-back of pressure coming from control port 42 of the Trailer control valve. There is a diaphragm that separates the chamber in this control port and the chamber in control port 43. This diaphragm occasionally ruptures due to wear and allows the air pressure in chamber 43 to enter chamber 42 and travel up this control pipe back to the delivery port 22 of the Foot valve and escape out of this valves exhaust port.                 
                                                                                                                                                                    
2. The leaks at the Load Sensing valve exhaust ports are often caused by pressure leaking back from one or more of the spring brake booster's service ports and escaping out of the Load sensing valve exhaust port. This is due to the collapse of the centre seal in the spring brake booster that separates the air pressure in the rear spring chamber from that of the service chamber. The pressure used to keep the main spring compressed and the park brake released, leaks into the service chamber and back along the delivery pipe to the Load sensing valve and out the units exhaust port.                 
                                                                                                                                                                    
3. If a booster's diaphragm is replaced, leaks between the diaphragm and the clamp band often occurs if the diaphragm is not lined up properly. This is often due to the fact that the diaphragms are dry and are not easy to centralize. It is not good practice to lubricate the diaphragm with oil as it will contaminate to material of diaphragm. The best way is to dust the diaphragm with chalk dust or talcum powder, this allows the diaphragm to centralize itself automatically during assembly.                             

The Problem: Fitting New Air Reservoirs

Here are a few possible suggestions:

1.  When installing new air reservoirs to a truck or trailer, make sure that the drain port is facing perpendicularly down towards the ground to ensure maximum drainage and that the longitudinal weld that runs close to the drain port, is facing down and away from your legs. The longitudinal weld itself is the strongest part of the reservoir, but the weakest points are at either side of the weld. So if a reservoir is going to burst, maybe due to rust, it will most likely burst along the outer part of this weld and therefore it is better that it bursts down and away from your legs than down and into your lower regions.

Whether it’s an air dryer or a valve, with these handy tips, you’ll find it much easier to determine the problem within your air brake system. JMR specialises in brake systems and parts and we uphold the highest standards in workmanship. Contact us today for all your brake system needs.