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Re: vacuum system and dielectric grease questions Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 1 May 2001 13:19:00
In Reply to: vacuum system and dielectric grease questions, Erik A, Mon, 30 Apr 2001 18:11:04 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I can't address the DI question, but I can talk some to the vacuum lines -
What do you mean brake vacuum? The power assist for the brakes comes from the ABS pump - there is no vacuum system on the ABS-equipped 9000. The ABS pump pressurizes a pressure accumulator, and that pressure is used to drive the ABS and provide brake boost. When the car sits for a while, that accumulator leaks down pressure. When you start the car, and as you use the brakes, the ABS pump runs to re-pressurize the accumulator. When you start the car, you'll notice the BRAKE FLUID and ABS (ANTI-LOCK) lights both come on, then wink off after a few seconds (up to 30-40 on older cars). Until those lights go off, you don't have minimum accumulator pressure. You'll have brake boost, but I can't speak to how much. You shouldn't drive off until those lights go off. For example, if your ABS pump just upped and died, those lights wouldn't go off, and you'd have absolutely NO brake boost - if you drive off with those lights on, you can't be sure you'll have brakes the next time you need them.
As to the boost gauge under compression braking, that's normal. The gauge doesn't sit at zero with the engine off - it sits at atmospheric pressure, and unless you're on the moon, that's not zero.
Under compression braking, you have the throttle closed, but the engine is still running. That means the pistons are pulling air against a closed throttle plate. That spells partial vacuum to me. A non-turbo engine always runs at partial vacuum in the intake manifold - if it didn't, it couldn't pull air in to run. With the throttle closed, you get high vacuum because the engine is just a pump sucking against that closed throttle.
A turbo engine is no different. Under compression braking, the throttle is closed, and you'll have partial vacuum in the intake - hence, the boost gauge is below atmospheric (namely, in the white section). It's the same area as when the car is idling, but more so. At idle, you've got only about 800-1000 rpm, but with compression braking, you've got a lot more RPM, so that engine 'pump' is pulling more.
The charcoal canister is in the right hand (facing forward) fender. I have no explanation for the Haynes manual there. To see it, simply unbolt the right front turn signal assembly. It's only one or two screws. The canister is right behind it. Make sure the hoses are still on.
, Tue, 1 May 2001 13:19:00 <-- Viewing This Message
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