Engine Pitting (Pinking) Noise At Speed And Auto Gb Fault

[Simple]

My C8 (2.0 HDi, 109 PS, Auto) produces a faint pitting noise (similar to advanced timing or low octane in petrol engine) when acceleration gently between 50 - 70 mph, It does not produce the noise if accelerating hard. The clock has 116,000 miles now and I changed the cam belt 20,000 miles ago, after which I thought (just a feeling) the engine power was not optimum.

 

Could the pitting noise be a starting problem in the injectors or is it related to engine timing? and how to diagnose it.

 

I know how to check and adjust timing in petro engines using stroboscope, but how to check and ensure optimum engine timing in diesel engines?

 

Also, the car produces occasional transmission fault on misty days; when the temperature is around 5 degrees Celsius, and when the engine is not fully warmed up. switching off and back on removes the fault and the car drives normally.

 

Any suggestions?

 

Regards, Simple

 

[Simple]

Having used all system-cleaning agents, changed filters/oils, reset ECU and even edited Firmware for performance and everything else I could think of or read about; but to no avail. I became convinced that the problem is much to do with timing, after I heard a very loud knocking noise when using EGR cleaner.

 

I decided to take off the CAM belt cover and check the matter for myself.

 

Special tools needed:

1- Mainly 10mm, 13mm and 16mm sockets.

2- A clear marker like white correction fluid.

3- A telescopic arm with a mirror at one end or a straightened wire hanger with a small mirror fixed to its end.

4- 2 L shaped (one side 20 cm and the other 4cm) 8mm rods (I used a threaded rod 7.8mm cut into two 30cm pieces and bent 24cm and 6cm at 90 degrees to use with the cam and 120 degrees for the flywheel.

 

The process:

1- Remove the stabilization bar on top of the engine.

2- Jack up the front of the car, place it on secure stands and Remove the driver side wheel and the plastic arch.

3- Remove the serpentine belt.

4- Remove the two 10mm bolts and 10mm nut securing the cam sprocket cover, and remove the plastic cover to reveal the CAM sprocket.

5- Use a ratchet to rotate the CRANK pulley clockwise while trying to insert the shorter end of the L shaped tool into the flywheel through hole beside the starter motor. Please notice that tool will slide properly into one hole only.

6- Place a clear mark on the pulley and the pulley cover to identify the position.

7- Remove the L shaped tool securing the flywheel, Place the mirror such that you can see the position where the other L shaped tool needs to slide into CAM sprocket. Rotate the CRANK pulley clockwise until you see the cam sprocket opening and the hole are aligned (it is 4 o’clock on some engines and 8 o’clock on others). Notice that 2 CRANK rotations = 1 CAM rotation.

8- Place the other L shaped tool into the CAM sprocket to secure it.

9- With the CAM secured, check the markings on the CRANK pulley and cover. If they match, all is well and if not, then:

a. The belt is loose and need tightening

b. The belt is off by a notch

c. You may have an adjustable CAM sprocket that may need adjustment

 

In my case, I was overjoyed to see that the CAM and Flywheel securing positions did not match. My CAM belt was too loose and the CAM sprocket needed adjustment as the slippage was not quite a complete notch.

 

The timing adjustment process:

1- Ensure the L shaped tool is properly inserted in the correct CAM sprocket position to secure it.

2- Loosen the three bolts securing the CAM sprocket, and relax the belt tensioner.

3- Rotate the CRANK until the markings on the pulley and the case match and secure the flywheel using the other L shaped tool.

4- Tighten the tensioner to the proper tension

5- Tighten the three bolts on the CAM sprocket.

 

The pinking is gone and power has improved.

[paul.h]

Thankyou for getting back to us and well done for your persistence and fixing your car.

I have edited the title slightly to include 'pinking' noise to help avoid confusion.