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What Are The Bad Symptoms OF Camshaft

What Are The Bad Symptoms OF Camshaft

December 20 , 2023 0

Driving often meet such as large cargo bulling, starting difficulties, engine weakness and other problems, most of the reasons may be camshaft bad symptoms, this article shares a few reasons to detect whether the camshaft failure, how to effectively avoid camshaft failure

What Are The Symptoms OF Car Camshaft Broken?

After the car camshaft is damaged, it will show a series of obvious symptoms:

1, starting difficulty: even if the car has a high pressure fire, the starting time will increase significantly until it can finally run.

2, crankshaft reversal and intake manifold tempering: In the starting process, there may be a crankshaft reversal phenomenon, at the same time, the intake manifold may also be tempering phenomenon.

3, idle instability and jitter: the car may become unstable when idling, and there is serious jitter, which is similar to the failure of the car when the cylinder is missing.

4, insufficient acceleration: when the camshaft of the car is damaged, the acceleration ability of the car will be reduced, even if the speed is more than 2500 RPM, the vehicle may not be able to run quickly.

5, high fuel consumption and excessive emissions: the vehicle will have high fuel consumption, exhaust emissions will exceed the standard, and the exhaust pipe may even produce black smoke.

The performance of the broken camshaft is ineffective, difficult to start, unstable idle speed, unable to add oil, engine weakness, car shaking, failure lights continue to light, sudden flameout when the hot car, driving failure, engine wear speed. The camshaft is a part of the piston engine that controls the opening and closing of the valve. The main body of the camshaft is a cylindrical rod with approximately the same length as the cylinder, which is covered with a number of cams for driving the valve. The camshaft is supported in the camshaft bearing hole through the camshaft journal, so the number of camshaft journals is an important factor affecting the camshaft support stiffness.

Causes OF Wear And Deformation OF Automobile Camshaft

The common faults of camshaft are abnormal wear, abnormal noise and fracture. Abnormal wear often precedes abnormal noise and breakage. The camshaft is almost at the end of the engine lubrication system, and the lubrication condition is not optimistic. If the oil pump is used for too long, the oil supply pressure is insufficient, or the lubricating oil channel is blocked, the lubricating oil can not reach the camshaft, or the bearing cover fastening bolt tightening torque is too large, and the lubricating oil can not enter the camshaft clearance, it will cause abnormal wear of the camshaft. Abnormal wear of camshaft will lead to increased clearance between camshaft and bearing seat, and axial displacement and abnormal sound will occur when camshaft is moving. Abnormal wear will also cause the gap between the drive CAM and the hydraulic tappet to increase, and the CAM will collide with the hydraulic tappet when combined, resulting in abnormal sound.
Sometimes, the camshaft will break and other serious failures. Common causes are: hydraulic tappet fracture or severe wear, serious poor lubrication, poor camshaft quality, camshaft timing gear fracture.
In some cases, camshaft failures are caused by humans, especially when the camshaft is not removed correctly during engine maintenance. For example, when removing the camshaft bearing cover, knock it with a hammer or pry it open with a screwdriver, or when installing the bearing cover, the bearing cover does not match the bearing seat due to the wrong position, or the tightening torque of the fastening bolt of the bearing cover is too large. When installing the bearing cover, pay attention to the directional arrow, position number and other marks on the surface of the bearing cover, and tighten the fastening bolts of the bearing cover with a torque wrench in strict accordance with the specified torque.

Diagnosis OF Wear And Deformation OF Automotive Camshafts

In the use of camshaft, the metal friction of timing gear is often caused by gear mismatch and lubrication failure. Check the meshing clearance of the timing gear pair during maintenance; Check the axial clearance of camshaft and the thickness of camshaft flange.

(1) camshaft axial clearance:

Determined by the thickness difference between the thrust flange and the timing gear spacer ring, the inspection is generally within the range of 0.05 ~ 0.18mm, remove the timing gear cover, pry the camshaft forward, and then insert the thickness gauge between the thrust flange and the end face of the timing gear. The measured clearance should be about 0.10mm, and the use limit of the axial clearance is generally 0.25mm. If the axial clearance is too large, it is easy to cause abnormal wear of the CAM and the bottom of the tappet, and the thickened thrust flange or the thinned spacer should be replaced for adjustment. During installation, the side of the thrust flange with the thrust boss should face the timing gear (sprocket).

(2) Detection of camshaft bending:

Use V-shaped iron to support the journal at both ends of the camshaft, place the dial gauge on the intermediate journal of the camshaft, and gently turn the camshaft once. At this time, half of the difference between the maximum reading and the minimum reading of the dial indicator pointer is the maximum radial runout of the camshaft (that is, bending degree), which should not exceed 0.03mm, if it exceeds the limit, the camshaft can be straightened or replaced by cold pressure.

(3) Measurement of CAM height:

The wear of the CAM will change the valve lift rule and reduce the maximum lift. Replace the CAM when the maximum lift drops by more than 0.40 mm.

When detecting CAM lift, a dial indicator can be installed on the upper end of the push rod, and the dial indicator probe can be connected to the push rod with A

Check the CAM height. If not, replace it with a new one.

(4) Detection of the gap between the camshaft journal and the seat hole:

Measure the journal with an outer diameter micrometer, and then measure the inner diameter of the journal seat hole on the cylinder head with an inner diameter micrometer. The difference between the two is the fit gap. If the specified value is exceeded, replace the camshaft or cylinder head, or in severe cases replace it all together.

Automotive Camshaft Wear Deformation Troubleshooting

The focus of camshaft removal is to pay attention to the correct timing mark, because the timing mark determines the valve timing of the engine, and the valve timing is the key to the engine's power performance. Therefore, before removing or assembling the camshaft, locate the timing mark and align it with the corresponding fixed mark on the cylinder block.

The intake camshaft and exhaust camshaft sprockets on the cylinder head are marked accordingly. When installing, the mark should be on the corresponding point, and then the transmission chain should be installed to ensure accurate ignition timing.

After installation, the timing belt that drives the timing gear of the camshaft should have a certain pre-loading force, which should be adjusted by the belt compression wheel. Special tools should be used to tighten the roller bolts. When removing the camshaft from the cylinder head, the CAM bearing cover needs to be removed, and each bearing needs to be numbered. Disassembling the bearing cover should be carried out in the following steps: First, loosen the bolts of bearing cover 1 and 3 and remove the bearing cover; Remove 2 and 4 bearing caps; Then remove the 5 and 7 bearing covers; Finally, remove bearing covers 6 and 8; Remove the camshaft and disconnect it from the drive chain.

The purpose of removing the bearing cover in the above steps is to balance the stress on the camshaft and prevent bending and deformation. Reverse the above sequence when assembling the bearing cover.

Automotive camshaft wear deformation maintenance precautions

As the main component of camshaft valve mechanism, it plays an important role. Due to various reasons of the engine, the camshaft surface is often worn in advance, affecting the full performance of the engine and bringing unnecessary waste to the user, which should be repaired in time.

It should also be noted that if a new hydraulic tappet is used in the valve mechanism, the engine should be started 30 minutes after installation to prevent the valve from damaging the piston. In some engines, the connecting rod cover is also equipped with a nozzle from which part of the engine lubrication system is ejected to cool the lower part of the piston. Pay attention to the direction of the nozzle before disassembly, and must not make mistakes during installation.