Skip to content

Difficult Lexus RX450h cooling system Fault Example

a Toyota Lexus RX450h hybrid SUV, mileage 28 000 km, the car air conditioning system does not reflect the user out warm air. Specific symptoms after a running period of the vehicle, the air conditioning system even when the temperature was adjusted to the maximum temperature, or the cool air-conditioning outlet.

According to the symptoms described in the user, I determined that failure may be responsible for regulating the temperature of the air conditioning system actuators problems or jammed, causing the system has been in a position of cold air. It may be within the engine cooling system or an air leak occurs, resulting in no sufficient air conditioner circulates coolant radiator.

First check the air conditioning system of a normal air flow, a blower proved normal. Dedicated fault diagnostic system for testing the air-conditioning control, did not find any fault codes. Then I decided to test the air conditioning system is performed in the temperature regulator without disassembly and without removing any parts using the dynamic fault diagnostic test function. After testing, the normal temperature adjustment actuator during the test no galling, abnormal noise situation, and no fault code is generated, it is possible to exclude a portion of the air conditioner problem does not cause the warm air conditioning.

Next, I decided to check the engine cooling system. It is observed that water can be seen in Table dash indicates the intermediate position, indicating normal. To confirm the accuracy of the engine coolant temperature, the author uses the fault diagnostic into the engine control system reads the relevant dynamic data flow. As can be seen from the data stream, the engine coolant temperature of 88 ℃. After the vehicle is off, hand touch and outlet water temperature of the radiator air conditioning feeling at a temperature of about 30 ~ 40 ℃, the engine coolant temperature which is a great temperature difference. Normally, if the engine temperature reaches 80 ℃, should open the thermostat, the cooling system is in a cycle, the temperature difference in the cooling system should be less than 10 ℃, the problem appears to arise in an engine cooling system. Find the approximate direction of the problem, then look for the real cause of the problem will not be very difficult. I check the coolant level in the reservoir, found in the reservoir was empty, and no coolant. Cotton cloth covering the radiator cap, loosen the radiator cap, check the coolant in the radiator, the radiator is also found empty, no coolant. The lack of internal reservoir and radiator coolant added to the normal position, tighten the radiator cap newcomerDynamic engine, so the engine reaches normal operating temperature, then check the air conditioning system, heater back to normal, it seems the problem is the air conditioning system cooling system leak caused.

the engine idling, it proceeds to leak check the engine cooling system. After careful observation at the interface of each pipe, found no trace of pink left after the leakage coolant. Then I checked the air conditioning condensate drain hose, upon inspection of the drain hose is very dry, you can exclude the possibility of air conditioning radiator leak. Because if the air conditioning radiator leak may leak from the air conditioning condensate drain, leaving traces. Parking period after turn off the engine, the cooling system using the detection means to a pressurized cooling system, check whether maintaining the pressure, when the pressure is applied to 80 kPa, gauge observed decreased pressure gauge pointer was found, proof cooling system the existence of leaks. Since visual inspection found no leakage, that would be a leak which part of it? Of course, cause damage to the cylinder head gasket coolant into the cylinder there is a possibility, but the probability is very low. In addition, in view of the water temperature when the vehicle instrument panel to indicate the water table has been normal, further evidence of the possibility of the cylinder head gasket problems are smaller.

FIG 1

FIG. 2

In order to find the source of a problem, the author again in the the water cooling system of each check, when the rear of the engine is checked and found a small cooler (FIG. 1), the query data that is cooler EGR cooler system (car characterized by read instructions, inquiries the car due to the use of the Atkinson cycle engine, in order to meet environmental protection combined hybrid system will minimize exhaust emissions, Toyota turn to disable years of EGR exhaust gas recirculation system used again, in order to reduce nitrogen oxides compound emissions, and a cooler is provided, the engine cooling system shown in Figure 2), just to check there is not inadvertently when checking. If the internal EGR cooler is leaking, it is impossible to find a leak place during visual inspection, since the coolant leaks into the exhaust gas, and then discharged from the exhaust pipe. To demonstrate leakage of the EGR cooler, it removed the middle of the exhaust pipe, if the liquid coolant in the exhaust pipe can be determined EGR cooler leakage. After removing, cooled EGR confirmedIt is indeed a leak. Careful observation, can be seen at the exhaust pipe 2 at the cylinder exhaust path has antifreeze (FIG. 3), then the cooler side EGR valve watermarks (FIG. 4), then the normal side of the catalytic converter (FIG. 5). After

replacement of the EGR cooler, the cooling system is again pressurized to 80 kPa and duration 10 min, without pressure variations, troubleshooting.

Figure 4

Figure 5

FIG. 6

summary: whole car repair process in diagnosis time spent about 1 h, if the erroneous determination occurs because the diagnostic process diagnostics of ideas, and therefore more likely to disassemble check engine cylinder gasket, thereby fault expansion, and really because the problem is not found. Therefore, before repair work begins, we need to understand the structure and working principle of critical need of repair parts. In addition, the inspection process more carefully, and in a progressive approach to the process step by step.

(For YANG)

Leave a Reply

Your email address will not be published. Required fields are marked *

Exit mobile version