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2022-04-07- The majority of car repairmen deal with all kinds of engine faults every day, solve vehicle faults for countless card friends, and help them transport goods, make money and support their families!
- I was lucky to deal with a very interesting fault: the repair shop described that the car was terminally ill! The owner was almost desperate and said, “my car is foaming at the mouth. If Hua Tuo is still alive, he should be able to save it!”
- Today I will share this case with you, hoping to help friends in need and help you avoid detours in the maintenance process.
Case sharing for foaming at the mouth of the car
1、 Vehicle information
Vehicle manufacturer: Jiefang
Engine manufacturer model: Xichai 6dl2-33e3f
2、 Fault information、
- Fault phenomenon
- The vehicle has a serious oil-water mixing fault, a large amount of antifreeze seeps into the engine oil pan, a large amount of oil enters into the water tank, and the auxiliary water for foaming at the mouth of the car tank has become a milky white mixture.
- The oil drained from the oil pan is as follows:（left）
- The water discharged from the water inlet of the engine water pump is as follows:（right）
- Preliminary treatment process of repair shop
The car has been repaired in the repair shop for more than 3 months, and the fault has not been completely solved foaming at the mouth of the car. - According to the owner’s Description: “every time I came to repair my car, there was no problem at that time; after running for a week, the problem slowly appeared, and then it will become more and more serious; what you see now is the phenomenon after running for 10 days after the last repair (oil-water mixing in the above figure)”.
- (1) First maintenance
There is oil in the oil pan and oil in the water tank. The first thought of the repair shop is the sealing ring of the oil cooler; Therefore, the sealing ring between the oil cooler and the engine body was replaced.
- After this fault occurs in most vehicles, replacing the sealing ring can solve the problem. However, after replacing the seal, cleaning the water tank, replacing the antifreeze and changing the engine oil, the owner came back after using it for less than a month. The fault phenomenon is the same.
- (2) Second maintenance
The repair shop analyzed whether there was a problem with the cooler, so the cooler assembly (including the oil cooler housing) and sealing ring were replaced this time. The repair shop thought there should be no more problems after this repair.
Who knows, less than a month later, the owner came back, and the fault phenomenon is still the same. - (3) Third maintenance
Analysis of the repair shop: the oil cooler and sealing ring have been replaced and there is no problem. It should be caused by the problem of the cylinder head and cylinder block. So after several “words” with the owner, the owner agreed to replace the cylinder head first.
After replacing the cylinder head, the owner came back after more than a week. At this time, the fault phenomenon is the same.
At this time: the repair shop is helpless; The repair shop thinks it should be the problem of the cylinder block, but it doesn’t dare to replace it easily; The owner has not paid all the cost of replacing the cylinder head. At this time, the owner is clamoring to return the previous maintenance fee; After many twists and turns, the repair shop found the small rail and went to help determine the fault point.
- 3、 Lock the fault point foaming at the mouth of the car
- Fault analysis
- (1) Emulsification of engine oil and water inflow in engine oil: it indicates that a large amount of engine cooling water enters the engine oil; If only a small amount of cooling water enters the engine oil, the water will evaporate quickly (the engine oil temperature will be very high when the engine is working, which can generally reach 110-130 ℃) and will not cause engine oil emulsification.
- (2) Emulsification in the water tank and oil in the water: it means that the oil enters the water channel somewhere. When a certain amount of oil enters the water, the emulsification phenomenon occurs after the oil and cooling water circulate in the water channel.
- (3) Comprehensive analysis:
At the same time, there is water in the oil and oil in the water. The biggest possible fault point is on the oil radiator; There are two common causes of failure: one is the lax sealing of the sealing ring of the oil radiator, and the other is the corrosion, sand hole and cracking of the heat sink of the oil radiator;
Since the repair shop has replaced the oil radiator assembly, sealing ring and other components; Therefore, in order to accurately judge the fault point, the author adopts special means to judge the approximate position of the fault point first. - Troubleshooting
- (1) Special means:
In order to judge the general fault point and narrow the scope of troubleshooting, the author has taken special measures: - ① Remove the water pipe connecting the water tank and the engine, remove the warm air pipe, remove the connecting pipe of the auxiliary water tank, and other connecting water pipes; Use reliable pipes, sealing plugs and other components to seal all the connecting interfaces of the water channel on the engine (at this time, it is required to bear at least 4kg pressure without water leakage).
- ② Drain the oil and remove the oil pan.
- ③ Fill the engine water channel with water, and then inject 4kg of compressed air into the engine water channel;
- ④ At this time, observe where there is water leakage at the bottom of the engine.
- After waiting for about 10 minutes, it was found that the milky white mixture began to drip down from the oil collector of the car. No water drops were found elsewhere. It means that the water in the oil pan drips from the oil collector. So what’s next?
- ⑤ After checking here, the author’s first thought is to remove the oil radiator and check it. After removing the oil radiator, carry out the leakage test of the oil radiator;
The specific test methods are:
- After completing the above work, put the whole radiator into the water to see if there is air leakage.
The vehicle has been tested and there is no leakage of radiator fins.
After careful inspection, it was found that the sealing ring on the removed radiator was basically flat with the plane. - The repair shop found a new sealing ring for installation and test. It was found that the height of the sealing ring leaking out of the sealing plane was less than 1 / 5 of the diameter of the sealing ring; At the same time, it is found that the sealing ring feels hard in the hand.
- 4、 Fault handling
- Replace the rubber ring
Due to the poor quality of the rubber ring in the repair shop, I went to the Xichai accessories store to buy the original accessories. After comparison, the original seal ring is slightly thicker, soft and elastic. - Special treatment
After installing the original seal ring into the radiator, observe the protrusion of the seal ring, and it is found that the protrusion is still less than 1 / 3; For the sake of insurance, ensure that the problem can be completely solved this time. The author also adopted “special means” to deal with it - 5、 Troubleshooting test
- Engine water channel pressurization test:
The pressure test of the engine cooling water channel was carried out again, and the pressure was maintained at 4kg for half an hour. No water leakage was found from the bottom of the engine. - Commissioning user
The repair shop delivered the vehicle to the customer. After the customer used it for a period of time, the customer reported that the fault had been completely solved.
Summary and sharing for foaming at the mouth of the car
- In the process of troubleshooting, I have several points to share with you:
- 1. How did this fault happen? How does the water flow into the oil pan? How did the oil get into the coolant?
A: when the engine is running, the oil pressure is about 4-6kg, while the pressure of the cooling system is generally about 1-1.2kg, so when the engine is running, the oil will enter the cooling system through the place with loose sealing. - When the vehicle just stops, the temperature of the engine body and oil radiator is relatively high, and the sealing capacity of the sealing ring decreases; In addition, the coolant temperature is high, and there is a certain pressure in the water tank; At this time, the coolant will slowly drip into the oil pan.
- 2. Why should the engine cooling water channel be pressurized? Why should the pressurized pressure be 4kg?
Answer: (1) this fault is also a chronic fault. If the engine cooling water channel is not pressurized; It is very likely that the failure can not be seen on site, that is, if there are water droplets under the engine, it may not be seen;
(2) The reason for pressurizing 4kg is that the oil pressure is about 4-6kg, so when the pressure is added to 4kg, you can certainly see the phenomenon of dripping. - 3. Precautions:
(1) When the water channel of the engine is pressurized, the water tank and all water channel pipelines of the original vehicle must be removed and sealed with self-made sealing water plug; Otherwise, the cooling water pipeline on the vehicle may be damaged.
(2) The pressurization pressure should be controlled at 4-5kg, and the pressure should not be too large; If the pressure is too high, it is likely to damage some water seals in the engine.
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