Brittle Vacuum Line

[calebtbay]

B6 S4

On the back of the engine there are these two vacuum controlled valves that look like they let coolant into the heads. They are operated by a rigid vacuum line that breaks if you breathe on it. I was going to get some new line and refresh it. Theres a Y connector that goes off to each valve. Does the line from bank 1 run behind the throttle body over to the Y near bank 2? I don’t see it in my photos and I think that’s because it goes behind the throttle body. Where are they getting vacuum from? Was there a rigid line running under the intake? Am I going to have to pull the intake back off to run the stupid vacuum line under it? Anyone have factory diagram of these things?

[VinnysS4]

B6 S4

On the back of the engine there are these two vacuum controlled valves that look like they let coolant into the heads.

These are combi valves. They let fresh air into the exhaust to warm the cats up

They are operated by a rigid vacuum line that breaks if you breathe on it. I was going to get some new line and refresh it.

Most parts stores sell hard emissions vacuum lines. You can replace them for cheap

Theres a Y connector that goes off to each valve. Does the line from bank 1 run behind the throttle body over to the Y near bank 2?

The line runs down the drivers side, goes to a tee and one goes to both combi valves.

I don’t see it in my photos and I think that’s because it goes behind the throttle body. Where are they getting vacuum from?

From the solenoid on the front of the intake manifold

Was there a rigid line running under the intake?

Nope

Am I going to have to pull the intake back off to run the stupid vacuum line under it?

Nope



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[calebtbay]

These are combi valves. They let fresh air into the exhaust to warm the cats up


Most parts stores sell hard emissions vacuum lines. You can replace them for cheap


The line runs down the drivers side, goes to a tee and one goes to both combi valves.


From the solenoid on the front of the intake manifold



Nope

Nope



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Thank You!

“Down the drivers side”, Behind the injectors?

My before photo and I don’t see it peeping out anywhere. On my phone its big enough to zoom real good and I don’t see it.




The solenoid? Looks like its headed behind the injectors. I should have taken more photos especially when it broke.

[VinnysS4]

Thank You!

“Down the drivers side”, Behind the injectors?

My before photo and I don’t see it peeping out anywhere. On my phone its big enough to zoom real good and I don’t see it.




The solenoid? Looks like its headed behind the injectors. I should have taken more photos especially when it broke.

In the front, it goes into a rubber elbow and the rubber elbow goes right into the solenoid pictured.
It runs down beside the injectors, down by where the manifold mates to the heads. Once it passes the last injector, or thereabouts, it tees off and one line goes to the drivers side combi valve and one to the passenger's side combi valve. If I remember correctly it goes right behind the intake manifold between the throttle body and plugs into a 90 degree rubber piece and into the combi valve.
I attached a picture of the solenoid .I deleted mine long ago, but this is the solenoid

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[calebtbay]

On the bank one side, the elbow right at the valve was leaking. I got new rubber vacuum line and new rigid line and refreshed all of it, making sure it didn’t leak by blowing in it. I think I got it all good to go. It’s probably not routed exactly perfect but it’ll be OK. As long as it’s not leaking I think.

[VinnysS4]

On the bank one side, the elbow right at the valve was leaking. I got new rubber vacuum line and new rigid line and refreshed all of it, making sure it didn’t leak by blowing in it. I think I got it all good to go. It’s probably not routed exactly perfect but it’ll be OK. As long as it’s not leaking I think.

As long as it goes from point a to point b, that's all that matters. You could run it down the fender and back if you wanted.

The entire system broken down:

So when you start your car cold, the ecu tells the Secondary air pump to turn on. Its The hair dryer sound on the passenger side when you 1st start your car in the morning along with the elevated idle. The air pump pumps air into a metal tube on the passenger side(usa cars) around the back of the engine and it goes to those combi valves. When this all happens, the ecu turns on that solenoid and it pulls a vacuum on that small hard line, which opens those combi valves. They let the air into the heads, which goes right into the exhaust manifold ports. The added air helps the catalytic converters warm up faster for emissions purposes. If you go catless, the system becomes pointless, except that it adds a louder cold start, so most delete the system when they go catless. I kindof like the extra sound on a cold start so its pretty much user choice at that point. Removing the system will result in a check engine light that can be sorted out with a tune.
Hope this helps!

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[oasis]

Combi: y - back of im - behind tb

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[oasis]

Front of engine: y - between injectors and valve cover - solenoid

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[calebtbay]

Im going back stock. My cats look great and there were not codes before I pulled the engine. Occasional lean code if I remember right. Based on the condition of the lines I doubt either valve was getting the vacuum it needed. Part of the line looked fine but I could blow in it and air would come out in several different places. Its all sealed up now. I did all soft line across the back of the intake instead of the back and fourth from soft to rigid. Its vacuum line and the distance is short so should be fine. I did rigid from Y to front like it was. I put a smidge of RTV everywhere it went from soft to rigid to make sure it stays and seals nice. I had to use a pick to get the brittle broken line out of the 3 soft transitions at the Y but I got them clean.

Thanks for the help!

[VinnysS4]

Im going back stock. My cats look great and there were not codes before I pulled the engine. Occasional lean code if I remember right. Based on the condition of the lines I doubt either valve was getting the vacuum it needed. Part of the line looked fine but I could blow in it and air would come out in several different places. Its all sealed up now. I did all soft line across the back of the intake instead of the back and fourth from soft to rigid. Its vacuum line and the distance is short so should be fine. I did rigid from Y to front like it was. I put a smidge of RTV everywhere it went from soft to rigid to make sure it stays and seals nice. I had to use a pick to get the brittle broken line out of the 3 soft transitions at the Y but I got them clean.

Thanks for the help!

Sounds like it should work great!

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[calebtbay]

Sounds like it should work great!

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Know the exhaust manifold torque spec? I figure the sequence is inside out to prevent binding. 3 ugga uggas or more like 5 or 6?

The crank pin plug is absolutely not on the dealers diagram. So I couldn’t order a crush washer for it. I ordered an oil drain plug crush washer hoping maybe its the same size, its less than $1. The biggest one in my crush washer set is slightly too small. Should I measure it and order one based on measurement or will a bead of rtv do the trick? Maybe an extra ugga?

Im so close I can taste it.

[VinnysS4]

I think this is the washer for the crank pin. Its a 18mmx22x1.5mm aluminum washer. Measure the plug to confirm

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[VinnysS4]

Same plug on another diagram, so I'd assume its the correct one


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[Black Jack]

Hey Caleb - Vinny's all over this but I have a recent video that talks about exactly what you're asking about and shows what I did to replace those shitty hoses, among other things. I don't like to spam the forum but...this is pretty relevant: https://youtu.be/tKMW9lEL1KM?t=68

[calebtbay]

Hey Caleb - Vinny's all over this but I have a recent video that talks about exactly what you're asking about and shows what I did to replace those shitty hoses, among other things. I don't like to spam the forum but...this is pretty relevant: https://youtu.be/tKMW9lEL1KM?t=68

You’re that guy! I have watched a bunch of your videos. By god you leave no stone unturned. Ill watch it later for sure.

[xpl0sive]

sorry to bump this up. trying to search what guys are using for the hard vacuum lines. I just took my engine apart and all of my lines snapped. I haven't tried digging the oil plastic line out of the rubber connectors. Am I able to re-use those and just get new plastic hard line?

[VinnysS4]

sorry to bump this up. trying to search what guys are using for the hard vacuum lines. I just took my engine apart and all of my lines snapped. I haven't tried digging the oil plastic line out of the rubber connectors. Am I able to re-use those and just get new plastic hard line?

Local parts store sells bulk hard emission vacuum line that works great.

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[Rol-co]

sorry to bump this up. trying to search what guys are using for the hard vacuum lines. I just took my engine apart and all of my lines snapped. I haven't tried digging the oil plastic line out of the rubber connectors. Am I able to re-use those and just get new plastic hard line?

I use parker pvc hard line and works fine, get out the broken ends with a drill bit 3,5mm with a little wiggle.

https://ph.parker.com/en/us/parflex-...master/nb4x-65


Edit: found some at amazon for you
https://www.amazon.com/Beduan-SAEJ84...1zcF9hdGY&th=1

[xpl0sive]

thank you. I ended up getting some 5/32" nylon line at the local parts store, they didn't have 4mm, but this was close enough. I was able to crush up the broken ends in the rubber connectors with a pair of pliers and then blow them out with compressed air.

[anthonyh75]

Great info. I am trying to resolve the P0491 issue as well.

[Rol-co]

thank you. I ended up getting some 5/32" nylon line at the local parts store, they didn't have 4mm, but this was close enough. I was able to crush up the broken ends in the rubber connectors with a pair of pliers and then blow them out with compressed air.

5/32 should be fine indeed, to take the brittle ends out can be done in different way's, drill bit, air enz.