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Old 08-02-2004, 02:07 AM   #1
Titanium Samurai
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Impreza GC8 I suspect a vacuum leak...

Last year, a savvy Subaru buddy -- damianq -- suggested that the quasi-hesitation in my MY99 TS was possibly a result of a leak in one of the vacuum hoses. Since there was no appreciable performance loss, he suggested I leave it; tracking a vacuum leak is apparently expensive.

Last week, as I started the car to go home from work, I noticed a high idle. I also noticed that the brakes were weak; I can't lock up the wheels (even with the summer hi-po rubber, I could lock the rears before). A few days later, I got a CEL.

Yesterday, I replaced the plugs -- a tad early but whatever -- changed the oil and filter, cleaned the K&N, and tested the plug wires. Resistances were nice and low, and the coil pack leads were fine. Still noticing the high idle and weird gear selection -- the 4EAT appears to be reluctant to engine brake now -- I reset the ECU overnight. Same problem. The reset trick for getting the ECU to re-learn the IAC position didn't help, either.

Visual inspection shows that everything's tight and in good condition.
Except one hose.
It's a fatty at the back from left to right, against the firewall, one end feeds into a slightly smaller pipe (?) that goes into a plenum-looking thing that sits under the intake manifold and the other end feeds into a slightly smaller hose that leads to the radiator??? (It is hard to trace) This sucker -- whatever it is -- is drier and more split up than your grandma. Who was buried years ago.

The problem occurs not only at idle, and started at the same time that I noticed a decrease in brake power. Numerous searches here indicate that the brake booster requires vacuum, but would a split hose for that also affect the engine speed?

Now, if I can get my hands on a replacement, what's the feasibility of replacing it myself? I'm going on vacation to the southern Rockies on Wednesday, and Monday is a statutory holiday; I might be able to get the part, but the dealers are hardly likely to be able to install a replacement in time. At the very least, I may be able to get the code pulled and work with that, but what can I do?
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Old 08-02-2004, 04:33 PM   #2
Titanium Samurai
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Impreza GC8 It's all so clear now...

I've noticed for a year and a bit that the brakes are always weak when the engine is running high. I was involved in a collision one year ago because the brakes didn't stop the car quickly enough, right after I was revving high. See here.

The vacuum hoses that I can see appear to be fine. What other vacuum lines should I look for?
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Old 08-02-2004, 06:13 PM   #3
Titanium Samurai
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Impreza GC8

This pic shows the four hoses I know about (highlighted in green), although the two outer ones are just breather hoses, right?



Here's a better shot of the vacuum hose that runs from the throttle body to somewhere below, and another (behind it) from the air chamber to somewhere else below.



I suspect that this hose is just for coolant; the upper rad hose was replaced after I bought the car, and the clamps have the same residue still on them as what's on here.



The brake booster vac hose appears to be perfectly fine also.

Last edited by TiTaNiuM sAMuRai; 08-02-2004 at 06:23 PM.
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Old 08-02-2004, 08:16 PM   #4
Titanium Samurai
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Impreza GC8

Okay, forget those. A stick of incense used as a tracer didn't help me find a suck point, and it was windy anyway. Regardless, the engine DID tell me when I got close.






The 'sensitive' area is somewhere between the oil fill and the battery, but a bit rearward. Does anyone know what vacuum lines pass through this area? All I really see are the cables coming from the positive battery terminal and heading off.

Also, does anybody know of a better tracer? I don't like the idea of sending smoke into the intake.
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Old 08-03-2004, 05:32 PM   #5
Titanium Samurai
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Impreza GC8

MAF recall hasn't been done yet. We'll see on Monday.
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Old 08-04-2004, 12:50 AM   #6
StrongBow
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You need to get the master cylinder checked out. Air can cause the soft pedal but if the brakes have been bled you shouldn't have that problem unless you have a leak somewhere else in the brake system. It could be your primary seal in the master cylinder giving you that soft pedal and lack of braking power, but 1st check all the brake lines and connections for leaks before you replace the master cylinder. Also check out your brake booster diaphram for a vacuum leak.
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Old 08-08-2004, 12:19 AM   #7
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I'll mention it to the dealer. thx.
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Old 08-08-2004, 07:01 AM   #8
2Stroke
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There are a couple ways to find a vacuum leak in the privacy of your own driveway.

One is to purchase an automotive stethoscope for ~20 bucks at autozone and use it to look for a whistling type sound coming from anywhere that has vacuum. Big leaks are easy to find this way, smaller ones are hard to hear over the sound of the engine.

The second method involves spraying carb cleaner (or fuel injector/throttle body cleaner) onto suspect hoses, fittings, etc. while the engine is running, and listening for a change in engine speed. If you spray the cleaner onto a leak, the vacuum will suck it into the engine, and the engine will usually slow down, stumble, or (rarely) speed up. Any significant change in rpm after spraying is an indication that you've found a leak.

The carb cleaner method is more effective and less expensive, but can be messy. Use the little tube to spray thru when possible.
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Old 08-08-2004, 04:04 PM   #9
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brake cleaner!!! very flammible so your engine will speed up if you find a leak, shoots in a powerfull jet stream so you can get at the tough spots and it evaperates almost instanly and will actually clean as you go . there are two different kinds that you can get, i believe that one is less or non flammable, get the flammable one.
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Old 08-08-2004, 07:19 PM   #10
Titanium Samurai
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10 points for Jay!! thx to 2Stroke, too.

The mechanic on the phone mentioned that Brake Kleen (sp?) was a good way to check for leaks.
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Old 08-08-2004, 07:33 PM   #11
2Stroke
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One of the best ways to get a bunch of knowledgeable people on NASIOC to reply is to post the code for your CEL. That narrows the problem down tremendously, & the people that have had that specific problem will usually offer help that's spot-on.

BTW, your car shows all the classic symptoms of a vacuum leak except for the hissing sound, which you'll probably find upon closer inspection.
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Old 08-08-2004, 09:32 PM   #12
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Your post is exceptionally well written, you've included many clear photos, but you put it in the wrong forum. This forum is primarily for topics relating to computerized management of turbocharged engines. The discussions in this forum are probably the most technical and esoteric of any forum on Nasioc.

I would suggest the "normally aspirated" forum as the best choice, where the folks browsing the forum have cars like yours.
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Old 08-08-2004, 09:39 PM   #13
sideways slut
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Quote:
Originally Posted by 2Stroke
Your post is exceptionally well written, you've included many clear photos, but you put it in the wrong forum. This forum is primarily for topics relating to computerized management of turbocharged engines. The discussions in this forum are probably the most technical and esoteric of any forum on Nasioc.

I would suggest the "normally aspirated" forum as the best choice, where the folks browsing the forum have cars like yours.

i have to agree
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Old 08-10-2004, 12:00 AM   #14
Titanium Samurai
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Ah, yes. That would it explain it, then. It also explains sideways' presence. I'd regarded the NA forum as a catch-all. Oh well, whatever; I learn just as much while talking to myself anyway. =]

As for the code, I brought the car in this morning to get the MAF recall work done and some investigation. When I picked it up, apparently no one had written down the code pulled. Yeesh.

I was told that
1. The IAC was gunked up. I had read posts like this, but a stuck IAC doesn't explain bad engine speed while driving. $200 to clean.
2. The MAF sensor was dirty. The dealer blamed my K&N. The recall replaced this.
and
3. The throttle cable was mis-adjusted, which was holding open the throttle. Um, the IAC was holding open the throttle, ney? Or maybe the nut on the cable took walk one day while I was at work. The techs were playing with some brake-kleen, and noticed with giddy excitement that the engine ran higher. Having exchanged a full deck of cards for some Brake-Kleen, they then charged me some more, since the brake booster loss was no longer apparent. To them.

Neither they nor I can yet really explain why the engine -- while racing -- is fighting the brakes.

Oh, and $165 for an ATF flush.

...I still think my brakes are too soft...
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Old 08-10-2004, 12:06 AM   #15
Titanium Samurai
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For the sake of anyone else doing a search in the future, it would be nice if this post could be moved to the right forum. Does anybody know how to do this? I don't see a 'Report this post' button now...
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Old 08-10-2004, 03:24 PM   #16
2Stroke
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Quote:
Originally Posted by TiTaNiuM sAMuRai
For the sake of anyone else doing a search in the future, it would be nice if this post could be moved to the right forum. Does anybody know how to do this? I don't see a 'Report this post' button now...
It's this little button to the left: A moderator has to move it.
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