Wheel end oil seal failed, lubricating oil seeped into the brake drum

When it comes to brake failure, what problems will you think of first? The answer includes whether there is a problem with the gas path, the brake pad or the brake drum is seriously worn, or where the valve body is damaged, it can be said that the brake failure is the vehicle problem that the card friends are most worried about on the road, if the speed is too fast or improper handling, it will lead to an unimaginable outcome.

There are many reasons for brake failure, some even unexpected, and in our recent visit to the market when we found a potential case that may lead to brake failure, through the personal experience of the card friend told us that sometimes a humble trailer axle lubricant may lead to our driving risk factor greatly increased.

It is reported that the card friend is a long-term round trip in Chengdu, Sichuan province to Lhasa, Tibet on the national highway route, the main bulk grocery transportation, driving himself is a matching three-axis trailer 6X4 tractor, and the whole process is standard load transport. Recently, in the process of his sports car, he found that the brake of the main car is somewhat strange, the braking distance is often too long, and the brake system is accompanied by abnormal work, making strange noises, and the strange phenomenon of braking can be obviously felt when driving mainly from the right steering wheel of the vehicle.

The card friend also said that the car is currently only driving for about three years, and he is also regularly maintained, because it is a standard load transportation, so the vehicle's gas path, valve components are in good condition, and there is no ABS type of failure light on the vehicle dashboard, but he always feels like a couple between the brake shoe and the brake drum when braking. Not only the brake foot feeling is abnormal, but also in the process of continuous braking, the two are often in the "on-off" state.

In order to drive safety, the card friend decided to use the rest time to disassemble the front wheel and brake system to see what was going on inside. By the roadside professional maintenance wheel end master judge, this situation is actually rare, but sometimes it will be encountered, that is, before the maintenance of the drum brake camshaft and CAM shaft bushing to add lubricating oil, due to the addition of too much, in the process of driving, resulting in lubrication grease through the gap slowly slip into the brake system, which has the feeling of the card friend.

After disassembly, it is proved that the judgment of the maintenance master is more accurate, remove the brake drum, we can obviously see that the color on the brake shoe is not normal, the feeling is "soaked" by some substance, the color is obviously darker, and through the field touch can find that the brake shoe that should only contain brake dust, relatively dry has become unusually slippery, obviously, It's been sponged off by something.

The outside of the brake drum has the same problem

By looking at the brake drum, we can further verify our guess. After being removed, one side of the brake drum basin has a color that is obviously different from other positions. From the perspective of its travel track, this substance permeates through the gap between the brake basin and the drum brake bottom plate. It is very close to the substance on the brake shoe both in terms of viscosity and feel, so it can be determined that the two are one substance.

Tips: Although street lubricating oil is cheap, the specific amount depends on the personal "experience" of the maintenance master.

In the maintenance of the card friend reflected that he had about six months ago in the maintenance of the wheel end and drum brake system so that the maintenance master added more lubricating oil, to help its lubrication, when the card friend felt that lubrication grease is a little bit more always no harm, the result so that the maintenance wheel end master added too much lubrication grease, which may be the main reason for its infiltration into the brake system. In this case, many card friends will mistakenly think that the brake shoes and brake drums need to be replaced trailer axle to ensure safety, and the operation of the maintenance master can greatly reduce our expenses.

After opening the brake drum, the maintenance master said he rarely encountered this situation, but the material analysis from the surface should be lubricating oil, so it began to remove lubricating oil, because the amount of lubricating oil is very large, the maintenance master first used a screwdriver to remove the lubricating oil in the brake shoes and rivets after opening, this process is very tedious, Because the number of rivets on the brake shoe is very large, it needs to be removed one by one, which takes a lot of time.

The next step is to use paper towels to wipe off the excess lubricating oil on the shoe, and it needs to be wiped as far as possible, and at this time, although the brake shoe has obviously restored some of the original color, but it is still attached to the lubricating oil. The next is to use a towel, soak in diesel, and repeatedly wipe the brake shoe, brake drum, this method can effectively use diesel to degrade the lubricating oil attached to both, but it should be noted that in the wiping process to try to wipe every corner clean.

Because the brake drum and the brake shoe are in a state of friction for a long time, the lubricant dirt in the brake drum will be even more. After wiping with diesel, we can see that the brake drum has basically restored its former luster, and then wipe off the excess diesel with paper towels to proceed to the next step.

After the natural volatilize of diesel oil for a while, then rinse the brake shoes and brake drum with clean water, and then the master will use the steel brush prepared in advance to brush the brake shoes and brake drum repeatedly dry, in the process of brushing we can see a lot of lubricating oil clots from the surface of the brake shoes, in this process to pay attention to, the steel brush must cover the entire brake shoes and brake drum, Make sure that the position seen by the naked eye can be brushed as far as possible until the brake shoe is fully restored to normal luster.

Here the whole maintenance process has basically ended, the whole maintenance lasted about half an hour, the two repair masters cooperate with each other to help the card friend solve this problem, and then the card friend also carried out a test, the brake has also returned to normal. In addition to the diesel is extracted from the fuel tank of the card friend a few liters, the cost is only about 150 yuan, compared with the direct replacement of the brake shoe and brake drum, this maintenance method is not only cheaper, and the effect is immediate, the vehicle can immediately resume operation.

However, according to our communication with the service station staff, this maintenance method can only "cure the symptoms" can not "cure the root cause", because although the maintenance master cleaned the lubricating oil in the brake system, but after a period of time, there will still be lubricating oil into the brake system, this situation will occur again, so why is this?

Logically speaking, why should there be grease between the brake shoes and the brake drum that should be dry and flawless? On this issue, we consulted the maintenance technician Guan Junquan of the FAW Jiefang Antai service station, and he said that excluding the excessive grease problem of the above maintenance-free wheel end, if the traditional axle has a similar problem, it should gradually seep into the brake system along the edge of the brake drum and the wheel end oil seal, and eventually lead to brake problems in the vehicle of the card friend.

There are two culprits for this situation, on the one hand, excessive lubricating oil is added in the wheel end, and it may also penetrate into the brake system because the wheel end oil seal is not well sealed, and eventually cause the brake performance to decay. From the actual situation, if it is a traditional axle product, adding excessive lubricating oil may be just an incentive, and more importantly, there is a trailer axle problem with the wheel end oil seal.

Wheel end oil seal is a sealing part between the brake system and the bearing, and its main role is to isolate the lubricating oil on the bearing into the brake system, and the oil seal this part is often a long maintenance or maintenance-free design, will not easily crack, aging, but if the wheel end of the vehicle, the brake system is often in a high temperature state, and the water cooler is not used in time, The oil seal may crack and age due to long-term high temperature.

Combined with the actual operating conditions of Caryou, he has been engaged in the transportation route from Xizang to Sichuan for a long time, along which there are high altitudes, large slopes, multi-curved mountain roads and national roads. For the truck with a total weight of 49 tons of vehicles and goods, this terrain can be imagined for the load of the brake system, even if it is timely cooling with the sprinkler, the temperature of the brake drum may remain high for a long time. This is not difficult to explain why the wheel end oil seal problems.

Therefore, here we still recommend that the long-term card friends who travel to and from the mountains should not only check the various parts of the brake system in time, but also do not hesitate to give up or forget to use water to cool down when there is a water sprinkler, resulting in early failure of some parts, and avoid excessive when applying wheel end lubricating oil, exceeding the sealing capacity of the oil seal. And the budget is more sufficient card friend is best to install the hydraulic retarder, with water or abandon water is the best choice for the mountain long downhill for the brake system to reduce the burden.