audijim113

(No, not with a vacuum cleaner) I replaced all vacuum hoses and thought others who plan on doing this, might appreciate a tip. Several of the hoses are long. Even if you can see both end connections, some hoses are routed underneath places where hands don't fit.

After taking one end off, I used a small wooden dowel (can be anything that fits) to connect old hose and the end of a long section of new hose. (started with 15 ft ). when I disconnected the other end of the old hose. I gently pulled the new through. This routed new hose (under, around etc) the same path as the old. Once through, disconnected joined hoses and pushed on the new. This allowed me to cut the other end. (leaving a little for slack) and connect the other end.

Per D2's suggestion, this seems to have solved my erratic cold start RPM fluctuation. I did this yesterday but wasn't too cold this morning so it might take a few cold days to verify. I checked the old hoses buy sucking (still got nasty taste in my mouth) and didn't feel any leaks but it's not exactly scientific.

In the meantime, I found a post from a while back from someone with a 2000 A8 with exact problem as mine. His problem apparently "went away"' but I saw a suggestion to clean the throttle body and thought it might be a good idea.

Back in the old days, we cleaned a carburetor by spraying carb cleaner while revving the engine. Can that be done with the throttle body? What's the best way to clean TP?

Razman

Thanks for this tip. I've been having some starting issues (even after replacing my plugs) so I'm now thinking it is a vacuum hose somewhere; I replaced several before (a year ago when I got the car) but I couldn't reach the ones that went to the reservoirs in the side panels of the engine bay. Speaking of them, how did you replace those?

As for cleaning the TB, I've read you can stick one of the vac hoses into a cup of Sea Foam and it will suck it right in - but others with more technical knowledge should chime in.

Eric

keithinthesouth

Sadly vacuum issues have been PITA for me for some time. Looking back I can't help but feel that I could have saved a ton of dosh if I'd tackled them years back when they were first evident. Theres no doubt in my mind that I could have avoided changing Oxy sensors and Cats as symptoms remain.

Changing the front vacuum pipe was easy though I have yet to find anyone who could help me with the block / manifold / throttle body vacuum pipes. After years of ongoing vacuum issues on my A8 D2 2.8 Q my symptoms have gone way-past cold start lumpiness and over fuelling (still evident) and my issue is now manifesting into a 'soft brake pedal issue' though I gather that these are all related and indicate a need to explore the dreaded 'behind the block' manifold area.

I've collected a lot of advice in the past including this: Replacement of breather hoses at rear of engine - A8 Parts Forum and this: 26 rear engine hoses.JPG

...though sadly online advice is evidently no use to a garage proprietor who doesn't 'believe in it' and prefers that I continue to invest in his Euro holiday home.

Mix vacuum issues with a dreaded power drain resulting in an occasional limp mode reverse issue (perhaps the F125 switch) and I fear I may be buying an extensive to said holiday home.

If anyone can recommend an independent D2 specialist in the northern home Counties who can assist my challenges without requiring foreign real estate investment or shirt removal, I'd be grateful.

audijim113

I was only able to find the passenger side vac line by pulling the bottom of the air box up (after taking the top off and swiveling out of the way. Removing the box is difficult with the headlight in place. I had it out several months ago as was necessary to reach the connector for the windshield washer pump. In order the lift out the box (two nuts on back upper side), I had to loosen the headlight to let it move forward an inch or so for the air box to swing up. Once the air box is swiveled up, you can see the vac line. The fabric covered/rubber hose connects to a harder, plastic hose which I didn't replace.

In retrospect, I might have been able to see this connection and maybe reach my bear claw hands down there. This was before I hit upon the idea of pulling new line through the maze with the old line. The right side (drive side) also connects to a harder plastic line and nothing to move to see it. Just follow the line to the point of juncture.

twentysevenlitres

Vacuum in an inlet manifold occurs after the throttle plate. So sucking something through a vacuum hose will miss most of the throttlebody, but will get into the manifold.

Spraying carby cleaner (which is now called carby and throttlebody cleaner) onto the throttle plate (butterfly) is the best way to clean the throttlebody short of pulling it off.

Sea Foam seems to be the manifold cleaner of the year - though some blokes (Sam?) Don't like it.
Can't get it down here, but there are a few manifold cleaners around now. Subaru dealers sell a good one.

audijim113

Still have surge after replacing all vac lines. Definitely want to clean TB. Can I just take the big tube off and spray carb/TB cleaner into butterfly with engine running?

aTOMic

Thanks for the good tip. I hope Audi has switched to silicone tubing by now. And don't get me started on the special stiff plastic tubing designed to turn to glass after ten years.
RE cleaning TB I can only offer one useful tip; be careful not to"fry"your lambda sensors. I think I may have cooked one with too-highly concentrated techron.
QUOTE=keithinthesouth;24614718]
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I've collected a lot of advice in the past including this: Replacement of breather hoses at rear of engine - A8 Parts Forum and this: 26 rear engine hoses.JPG
...
[/QUOTE]

Good pictures, thanks for that!
Wow what a clusterfark of idiotic design putting all that under the manifold. Keeping the Audi mechanics busy I suppose is their goal.

-Tom