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Engine vibrations, vary with RPM: balance shafts? Posted by John Fitzgerald [Email]  (#77)  [Profile/Gallery]
(more from John Fitzgerald) on Mon, 19 Aug 2013 12:13:17
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My son recently bought a '95 9000 Aero and it has fairly low miles for it's age: 118000 mi. In the course of working on it and driving it, the degree of engine vibration is fairly high, especially compared to our other two 9000's w/ 195k and 245k miles.
Not so noticeable at idle, but as soon as you start driving, or rev the engine, all ideas of smoothness that are characteristic of a well-maintained B234R (good serp belt tensioner, good pulleys, all accessory bearings, motor mounts, timing chain, etc) start to disappear. There is no adverse noise from the engine, valve train, timing chain, as the compartment sounds (both at idle and when revving it up) all seem normal.
When I first drove the car on the highway, I wondered if a front wheel was bent or out of balance. After coasting down some fairly steep hills at 50-60 mph, I ruled out the tire balance. And, when letting putting the automatic trans into idle, the degree of vibration drops off dramatically.
Now, when I've just driven one of the other 'normal' 9000s ( a 97 Aero or a 98 CSE), I notice the vibes as soon as I put the trans into R or D and it is best described as almost a shuddering which varies with rpm.
So, my questions for all the fine fellow Saab shade tree mechanics:
1. Does this sound like the balance shafts are either misaligned or the chain is broken? The PO had the timing chain replaced at 95k; is it possible that the balance shafts either jumped a sprocket or were not oriented right if the chain was also removed or replaced?
2. Does driving it like this cause any excessive wear on the internals of the engine? ie, I'm not too concerned about the motor mounts, which I'd expect are certainly under more stress.
2b. Short of replacing the chain, is there any way to minimize wear? Keeping the revs low is pretty intuitive ...
3. Presuming it is a balance chain, is this a hard job for a DIY? Never done anything inside an engine - done all driven accessories over the years, ft main seals/oil pump leaks, plenty of valve covers, and several heater cores/hoses/blower motors, besides radiators, hoses, battery cables, various engine sensors, etc.
4. I realize the 2.0 litre 9000 engines had no balance shafts and were relatively smooth ... I'm guessing this was done with larger counterweights on the crankshaft. Curious if a 2.3 litre balance shaft turbo engine uses a smaller weighted crankshaft?
Thx for your time and consideration.
Sincerely,
John
Burlington, Wisc
'73 96 RHD sold after four years in Middle Barton, Oxfordshire, UK
'80 99 sold after 20 years/192,000mi
'86 9kT sold after 12 years/approx 121,000 mi
'87 9kT sold after 9 years/approx 174,000 mi
'97 CSE given to my son after 8 years @ 245k; he sold it at 254k mi
still driving:
'97 Aero 244,xxx mi
'98 CSE 194,xxx mi 'project car' for winter & for my daughters to drive
and a couple of 'non-Saabs':
'01 Suburban 141,xxx mi
'03 BMW 330 Cic 55,xxx mi
_______________________________________ John Burlington, Wisc '73 96 RHD sold after four years in Middle Barton, Oxfordshire, UK '80 99 bought new, sold after 20 years/192,000mi '86 9kT picked up at Trollhatten, sold after 12 years/approx 121,000 mi '87 9kT sold after 9 years/approx 174,000 mi '94 CSE given to my son after 8 years @ 245k; he sold it at 254k mi '95 Aero 146,xxx mi sold '98 CSE 248,xxx mi gave it away '97 Aero 317,xxx mi my daughter’s school car … gave away [we put 300k mi on it] still driving: '97 CSE 170xxx mi 'project car' for myself and my daughters to drive '07 9-3 2.0T 240xxx '08 9-5 191xxx mi my wife's daily driver and a couple of 'non-Saabs': '01 Suburban 201,xxx mi '03 BMW 330 Cic 84,xxx mi '14 Mercedes E350 103,xxx mi
, Mon, 19 Aug 2013 12:13:17 <-- Viewing This Message, Mon, 19 Aug 2013 16:01:06
, Mon, 19 Aug 2013 12:26:35, Mon, 19 Aug 2013 13:44:15, Mon, 19 Aug 2013 13:54:36, Mon, 19 Aug 2013 14:07:48, Wed, 21 Aug 2013 14:39:59
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