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cdblues
10-21-2007, 09:23 PM
I just replaced the timing chain, spockets, tensioners as a kit. I also pulled the head and had a valve job done. Now after I have everything back together, I am getting a tapping noise from the driver side valve train. The car is also ocassionaly back firing. Is it possible that the timing marks on the new chain are wrong? If so, how can I verifiy the number of links between the marks? Could I have a sticking valve even after the valve job? What else can I check?

Any help would be appreciated.

Mike F
10-22-2007, 05:55 PM
Hi cdblues,

If the noise is coming from the DRIVER'S side, as you've said, it is less likely to be related to the chain/tensioner, since the the chain is on the passenger's side. Sometimes it is difficult to pinpoint a noise under the hood, so it would be a good idea to get a mechanic's stethoscope (available inexpensively from auto parts stores) so you can be sure where the noise is coming from. A tapping noise coming from under the valve cover, near the driver's side could be a sticking hydraulic lifter or excessive valve clearance (outside the hydraulic lifter's range of adjustment). Did you or your machinist check the valve clearances carefully? Although hydraulic lifters adjust to eliminate clearance, they need to operate in a specific range of clearance, generally from about 0.020 to 0.060-inch. If you found that the noise is coming from the passenger's side, it could also be caused by incorrect tensioner adjustment.

The backfiring is concerning. This would seem to indicate a problem with a particular valve not opening/closing correctly, possibly related to a bad hydraulic lifter or a lifter outside its operating range.

Valve timing (marks not aligned correctly) is also a possibility, but it would cause the engine to run poorly overall. Keep in mind that even experienced mechanics have trouble getting timing marks aligned correctly. If you have any doubt at all, remove the timing cover and re-check your alignment marks. It would be exceedingly rare that the parts would be manufactured incorrectly.

I hope that helps.

Thank you for using Haynes manuals!

cdblues
11-18-2007, 06:23 PM
Mike,

Thanks for your response. After pulling the valve cover, double checking the timing, checking with the machine shop and scratching our heads, we were still at a loss as to the source of the tapping noise. The stethoscope was the key. In the Haynes manual 87020, on page 2A-16, picture 12.16, shows a picture of the top of the head. Notice on the right hand side of the picture (the rear of the engine) there is a plate with 2 bolts. I have yet to find reference to what this system does, but we had left the two bolts loose. This was the source of our tapping noise. It was blowing air out and was also causing excessive air to blow out of the oil filler cap. Tightening these two bolts cleared all of the problems including the missing/backfire noise.

Although I have worked for years on my own cars (V8 and 6cyl), this is my first experience at this level with a DOHC 4cyl, front wheel drive vehicle. Can you shed any light on to what this function of this part?

Again, thanks for your help.

Charlie

admin
11-19-2007, 04:42 PM
Hi Charlie,

That part is a block-off plate for the EGR port, which is apparently used in some markets, or perhaps on a different vehicle, but not the Saturn.

Glad you found the problem!