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So, I was driving to work last Thursday when a loud knocking noise started coming from the engine. It sounded like a valve noise due to its speed and tone. It didn't sound quite like a rod bearing, so I slowed down and limped into work. I let the car sit at work all day and when I started it that evening, the noise wasn't there. After I drove the car about ten miles (almost home), the knocking started up again. I parked the car until I could do some diagnostic work on it.
Today, I did a compression check and checked the valve clearances. For the compression check, I removed the spark plugs, propped the choke open, and took the reading after four pulses. The results:
Cylinders 1, 2, 3, 4
Dry: 135, 125, 125, 60
Wet: 155, 160, 150, 65
Intake: .016, .016, .018, .016
Exhaust: .021, .021, .021, .018
Of course, it looks like something is going on with #4's compression. The #4 exhaust valve clearance has tightened up by a couple of thousandths since I last adjusted valves, too. The wet check also makes it look like the rings are worn.
My questions include: What causes low, but not zero, compression? Is #4 exhaust valve burning or burnt? Why does the knocking only occur after the car has been driven awhile? Why did the knocking come on suddenly? What do you all think?
Oh yes - at Eric: I will try to perform a leak down test as soon as I can!
Thanks!
Today, I did a compression check and checked the valve clearances. For the compression check, I removed the spark plugs, propped the choke open, and took the reading after four pulses. The results:
Cylinders 1, 2, 3, 4
Dry: 135, 125, 125, 60
Wet: 155, 160, 150, 65
Intake: .016, .016, .018, .016
Exhaust: .021, .021, .021, .018
Of course, it looks like something is going on with #4's compression. The #4 exhaust valve clearance has tightened up by a couple of thousandths since I last adjusted valves, too. The wet check also makes it look like the rings are worn.
My questions include: What causes low, but not zero, compression? Is #4 exhaust valve burning or burnt? Why does the knocking only occur after the car has been driven awhile? Why did the knocking come on suddenly? What do you all think?
Oh yes - at Eric: I will try to perform a leak down test as soon as I can!
Thanks!