Eric, Eddie and I brought our three rides to Pak Lok on Sat (9/15) for service check and oil change. For me I went back for nostalgic reason (my favorite breakfast street - Tung Tai Street) and seeing old friends working at the garage. My last oil change was on 5/19, roughly 4 months ago. And I did only 3'300 kms only. This time I did not use the Miller Synthetic but took Pak Lok's advice and used the twice more expensive Castrol Edge 10W-60. If it is good for BMW M and I think it will work okay in my AMG grandpa. Eddie's X5 has been using this oil for a few times and reported satisfactory engine response. Pak Lok recommends this oil for German engine over 3.0L in size.
A note after 3 days of motoring: The Edge proves to be very good oil even though it feels highly viscous, it is smooth and friction-free. It does not feel like watery like those Japanese racing oils. Engine is quiet and loaded with plenty of low-end response. I can feel that the fuel economy is improved. As I have been using all kinds of oils in the past 20 years, I become both neutral and critical about what people are telling me about engine oils. But this is one of the good ones.
I also removed the K&N air filter and replaced it with the standard factory item. I think the standard item gives slightly better response and torque below 3000rpm. Acceleration seems more solid, even though it might be slower than it was with the K&N. For K&N the C36 feels lighter when it was asked to accelerate at full throttle. And K&N makes the butterfly valve more dirty because of the more generous filtering of the suction air.
I did not have any faith of curing the clunking noise in the front suspension, which grew louder and more frequent every day since last time it was cured at ML 3 weeks ago. Nevertheless I have never given up the idea to improve the rigidity of the C36. There was a marked difference between the ride and solid feel between my 1995 and Steven's 1997. I do not believe the chassis has changed so much in two model years.
Bingo! We found that the rear bushings for the front lower arms were both torn. This explained very well the tire scrubbing (my inner thread of my both front tires) and potential toe-out, because of the undesirable flexing during braking and/or lateral loading.
Anyway two lower arm bushes and one wheel hub universal joint per side was replaced with genuine factory parts. While the springs were removed I found out the left side spring pad (top side) was punctured, causing the sharp corner end of the spring coming into contact with the front spring metal pocket. Eureka! This explains very well the clunking noise. The corner of the spring end has punctured the thin side wall in the recess area of the rubber spring pad. The spring rotates under load (braking, going over speed bump, or extreme steering angle) and hence scrapes the metal pocket and make the clunking noise.
For me the solution is simple - change the spring pad from the current "one-dot" thin spring pad to a "two-dot" thicker spring pad. It is thicker by 4mm and hence lifting the front of the car by as much. The rigidity and the thickness of the new spring pad will make sure it takes much longer for the sharp spring corner to puncture the spring pad. For added assurance, a ball of grease was applied to the spring socket, providing some lubrication if the spring choose to rotate, hence lessening the stress on the spring pad. I think it will work even I am not 100% sure.
For some reason, the 4mm increase seemed like an inch increase in ride height. That's just my wrong perception, and according to my experience, the ride height will drop slightly and settle down with 100 to 200kms of motoring.
After all the work the toe angle was much affected. After some very rough adjustment it was drivable. Anyway the ride height is different (hence less negative camber) and then my front tire shapes were a kind of slanted to the inner side, and not in symmetric way. So the steering effort to left and the right is different. And the car would not go absolutely straight some times but not all the time. However I think after the tires have been 'broken in' they would be as quiet and smooth as before, and track better after 100 to 200kms. Already this morning I didn't notice the difference in steering effort, left vs right. I love the new found firmness and tightness. And the car seemed to cruise more effortlessly, indicating a reduction in drag.
If I replace with the new tires, I would need another wheel alignment to be done. Right now since there is no hurry and the front tires (still has 30% of life left) seem to work well in terms of ride comfort and grip, except in the wet, I am not in a hurry to change tires until next month (October). The rear tires are wearing evenly and healthily and still have more than 50% of life.
