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Re: What does the a failing pinion bearing sound like? Posted by Ari [Email] ![]() ![]() In Reply to: What does the a failing pinion bearing sound like?, JoeK, Thu, 12 Jun 2003 07:39:09 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Agree with Nathan. Pinion bearings sound more like a whine than a hiss. Definately varies with engine speed.
When I hear the word 'hiss', I think air, not spinning machinery. Does it occur when you *slightly* back off the gas, or when you really back off the gas? With pinion gears, even the slightest change in load/unload makes a noise difference.
If you back off slightly on the gas, you'll load the bearings differently, but engine vaccum will stay pretty much near atmospheric pressure. If you really back off the gas, the bearings will still be loaded but there will be very high engine vacuum (well below atmospheric).
In fact, the highest engine vacuum (most suck) would be with your foot off the gas, at speed, in a lower gear. That's the most engine RPM. The engine is just an air pump - the faster it turns, the more it pumps. With a fast turning engine and a closed throttle, you'll get a major vacuum in the intake.
So why bring up vacuum? If you hear a hiss, I wonder if you've got a vacuum issue. This could be a leaky hose under the hood, running to the boost gauge, or to the fuel cut-off switch under the dash. I vaguely remember that the 900 uses vacuum for vent controls.
Check all your air lines for leaks - vacuum lines, anything on the engine side of the throttle.
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