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Found this when looking for threads pertaining to checking the vacuum switch at the booster. I have to say, it's a pointless mod from the perspective of making your bay 'cleaner'. If you like it, that's all that counts, it's your car.

Some factory system removal/deletes make sense - such as the SAS pump on 850/x70 series - this one not so much ;). There are three check valves in the system - the one at the manifold, one at the pump, and the one before the booster. Same design valve as used back into the '80's on Volvos, never ever heard of one failing 'closed'. Inside is just a small spring and a rubber disc. Manifold vacuum pulls the disc against the spring pressure.

The setup works well - I just added one to my old '91 Volvo to provide constant vacuum to the HVAC - on these the vent settings drop out pretty quickly once you get into positive pressure.

On yours, what would make the bay cleaner would be a better designed bracket to support the ECU - what you have does not look good. Even if you just painted it black it would be better, so it doesn't pop out
 

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When reading this thread something on my car came into my mind. A mechanic who was working on my car (in his spare time) has broken off one valve which i believe is part of the whole brake booster system. He fixed it by just replacing the valve with a piece of metal, see picture attatched. Is this in any way affecting the intended function of the whole system or is this okay the way it is now?
Sorry for highjacking, just thought when people are discussing the brake booster thing they can maybe give me a quick answer without me creating a new thread. Thanks!

131442
 

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Discussion Starter · #23 ·
Found this when looking for threads pertaining to checking the vacuum switch at the booster. I have to say, it's a pointless mod from the perspective of making your bay 'cleaner'. If you like it, that's all that counts, it's your car.

Some factory system removal/deletes make sense - such as the SAS pump on 850/x70 series - this one not so much ;). There are three check valves in the system - the one at the manifold, one at the pump, and the one before the booster. Same design valve as used back into the '80's on Volvos, never ever heard of one failing 'closed'. Inside is just a small spring and a rubber disc. Manifold vacuum pulls the disc against the spring pressure.

The setup works well - I just added one to my old '91 Volvo to provide constant vacuum to the HVAC - on these the vent settings drop out pretty quickly once you get into positive pressure.

On yours, what would make the bay cleaner would be a better designed bracket to support the ECU - what you have does not look good. Even if you just painted it black it would be better, so it doesn't pop out
I agree about the ECU bracket, it’s only temporary.

Removing the pump does make the bay cleaner, and eventually the ECU will be mounted more where the pump was. Thanks for the input though.


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Discussion Starter · #24 ·
When reading this thread something on my car came into my mind. A mechanic who was working on my car (in his spare time) has broken off one valve which i believe is part of the whole brake booster system. He fixed it by just replacing the valve with a piece of metal, see picture attatched. Is this in any way affecting the intended function of the whole system or is this okay the way it is now?
Sorry for highjacking, just thought when people are discussing the brake booster thing they can maybe give me a quick answer without me creating a new thread. Thanks!

View attachment 131442
Not 100% sure what issues that would cause but that check valve I believe is there to prevent excess boost from leaking back into the other side of the intake manifold, there is another one on the opposite side of it as well. That’s one that should 100% be there.


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When reading this thread something on my car came into my mind. A mechanic who was working on my car (in his spare time) has broken off one valve which i believe is part of the whole brake booster system. He fixed it by just replacing the valve with a piece of metal, see picture attatched. Is this in any way affecting the intended function of the whole system or is this okay the way it is now?
Not OK, as evy0311 said. You need the check valve. You can see what it looks like in my pic:

 

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Discussion Starter · #26 ·
Not OK, as evy0311 said. You need the check valve. You can see what it looks like in my pic:

To add to this I believe a generic check valve will work in this case, provided it supports up to 30psi. That way you don’t need to buy the whole hose.


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I agree with @lookforjoe and @evy0311. I think without that check valve the intake plenum will bleed boost to the turbo intake pipe and then back into the turbo and over again.

In mine there's two check valves: the one @Joshude is missing, which has the flow orientation to the intake plenum. And there's another at the other end of the pipe with flow direction to the turbo intake pipe after the MAF sensor. Basically both check valves with opposite flow directions. Can anyone confirm if this is ok?
 

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Thanks! The guy found the part number for the whole pipe including the valve, about 100$ from Volvo.
I do not have the part number, does anyone have it or a fitting generic checkvalve p/n?

Is this the right one?
 

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Thanks! The guy found the part number for the whole pipe including the valve, about 100$ from Volvo.
I do not have the part number, does anyone have it or a fitting generic checkvalve p/n?

Is this the right one?
The specific one in the hose is grey, so the value might be different, or the tube OD might vary. In any event, the plastic tube has to be heated carefully to press the valve into it, so it shouldn't matter. The softer hose going to the intake should stretch OK.
 

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@lookforjoe

Any chance you can confirm the flow direction of both check valves? (See my previous comment) Thanks.


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@lookforjoe
Any chance you can confirm the flow direction of both check valves? (See my previous comment) Thanks.
Do you have a pic of the tubes? On my 2012 C30 T5, the tube fitting on the inlet pipe is part of the vacuum tree that attaches to the plenum, brake booster & vacuum pump.

The one from the underside goes back toward the bulkhead - I assume for HVAC - I've not looked specifically - you can see where it doglegs over the engine harness casing



Typically, any/all check valves are there to prevent positive pressure pushing back - so the "motor' (draw) side of the valve will always face the vacuum source (intake hose/pipe, plenum, etc. You can confirm this by applying suction to the valve & then try blowing into it. You should be able to draw through the valve from the plenum end and from the inlet end, but no pressure should pass.
 

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I’ll check it out when I get back home, but as far I saw it is a tubing that has check valves on both ends with opposite flow directions.


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Do you have a pic of the tubes? On my 2012 C30 T5, the tube fitting on the inlet pipe is part of the vacuum tree that attaches to the plenum, brake booster & vacuum pump.

The one from the underside goes back toward the bulkhead - I assume for HVAC - I've not looked specifically - you can see where it doglegs over the engine harness casing



Typically, any/all check valves are there to prevent positive pressure pushing back - so the "motor' (draw) side of the valve will always face the vacuum source (intake hose/pipe, plenum, etc. You can confirm this by applying suction to the valve & then try blowing into it. You should be able to draw through the valve from the plenum end and from the inlet end, but no pressure should pass.
Dang, I’m an idiot. The pipe has a T fitting connected to the evap solenoid. Didn’t see it before. Now it makes sense.

I thought it was just a pipe and check valves on both ends with opposite flow directions, in other words: pulling a vacuum on a pipe that is connected to nothing.

Thanks for your answer.


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When reading this thread something on my car came into my mind. A mechanic who was working on my car (in his spare time) has broken off one valve which i believe is part of the whole brake booster system. He fixed it by just replacing the valve with a piece of metal, see picture attatched. Is this in any way affecting the intended function of the whole system or is this okay the way it is now?
Hello again!

I have another question regarding my missing checkvalve.
Yesterday i replaced my front-brakes on my T5. On the first testdrive i did some smooth braking to get the coating off the discs. After the first hard braking to get the brakes going (was from 60km/h to zero, moderate to hard braking, cluch depressed) the engine was running VERY jerky with hard cutoffs in power under load (WOT and just a little load).
Back home i got these codes:
133024


After letting everything settle, deleting the codes and going for another testdrive everything was back to normal. Can this be related to my missing checkvalve? Because as i understand it, it has something to do the the brake booster.
 

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Discussion Starter · #35 ·
Hello again!

I have another question regarding my missing checkvalve.
Yesterday i replaced my front-brakes on my T5. On the first testdrive i did some smooth braking to get the coating off the discs. After the first hard braking to get the brakes going (was from 60km/h to zero, moderate to hard braking, cluch depressed) the engine was running VERY jerky with hard cutoffs in power under load (WOT and just a little load).
Back home i got these codes:
View attachment 133024

After letting everything settle, deleting the codes and going for another testdrive everything was back to normal. Can this be related to my missing checkvalve? Because as i understand it, it has something to do the the brake booster.
I doubt those codes were caused by missing check valve.

In conjunction with that alternator code it sounds like voltage was weird and caused those codes to be set


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Okay, letting the codes come from a faulty voltage... The engine running that jerky, can that be caused by the missing checkvalve after a hard braking?
Or was maybe the voltage too low (car was sitting for weeks without running) and due to hard braking the electronics just were doing funny things? Hard Braking was maybe 1km after starting the car, so no time to let the battery load properly
 

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Discussion Starter · #37 ·
Okay, letting the codes come from a faulty voltage... The engine running that jerky, can that be caused by the missing checkvalve after a hard braking?
Or was maybe the voltage too low (car was sitting for weeks without running) and due to hard braking the electronics just were doing funny things? Hard Braking was maybe 1km after starting the car, so no time to let the battery load properly
Honestly it could’ve been from the check valve missing if it was running jerky but I’m not 100% sure, you said it runs fine now? If no codes come back and it runs fine I’d say maybe valve was it.


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