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Discussion Starter · #1 ·
Warning/disclaimer: The information in this thread describes modifying your vehicles brake booster assist system. I am not responsible for any damage to the car, any loss of braking, or anything that may be caused as a result of you taking the actions in this post. Please proceed carefully.

I’ve seen a couple of threads that reference people deleting their brake booster vacuum pump. I was confused a bit by this and was asking myself questions like “is that safe?” And “will this change the car in any way?”. Well, from my understanding, most vehicles do not come with a brake booster vacuum pump. The Ford Focus RS sold in Europe with the same T5 motor does not have a vacuum booster pump. The Mazdaspeed3 (different motor but many shared components) does not have a vacuum booster pump. Our cars do.

The purpose of this pump is to supply adequate vacuum to the brake booster (also known as brake assist) system in the event that the motor cannot generate enough vacuum to do so. Cases when this typically happens is if you lose power (engine shuts off) while driving and then attempt to use the brakes. The brakes will still work in this situation, but you will be using the full power of your foot and leg to do so, as the car will not assist you.

So why do our cars have it when most others don’t? The answer… likely safety. Volvo, bring the safety minded branded that it is, has supplied us with such pump so that in the situation where the motor shuts off and you need braking assist power, you have it. Again, the Ford Focus RS sold in Europe with the same (mostly) T5 motor does not have a vacuum pump.

Many people on this forum have deleted their vacuum pump entirely. The reasoning behind this varies from person to person, but overall it seems that the general consensus is to delete the pump for looks and space. The pump makes the engine bay look cluttered, and many people have built custom air intakes with the airbox sitting right where the pump does.

Originally, I deleted the vacuum pump by modifying the stock hose that was included on the car so I could keep the check valve. I HIGHLY advise against this. The reasoning? If the check valve goes bad, you will likely lose your brake assist power. It is not uncommon for these valves to fail. It is recommended to replace with a straight vacuum line like I will show you.

I won’t go into detail on how to remove the vacuum pump and it’s mounting bracket for two reasons: 1 it’s been documented before and 2, it’s fairly self explanatory if you look at it, the bolts you need to remove are the only ones connected to it. If anyone has questions on this though, I can definitely update this here!

Now you can remove the rest of the vacuum hose that routes to the intake manifold, OTE pipe, and brake booster.

Once that’s removed, go ahead and get your new vacuum hose. I chose a hose from Amazon. It is 12mm inside diameter. This is a little bit of a tight fit, but it gives me peace of mine knowing it won’t come off easily. Here’s what I ordered: Amazon.com: High Performance Silicone Vacuum Tubing Hose, ID 0.47" (12mm), OD 0.71" (18mm), 5 Feet per roll (1.5 Meter), Black 60 psi Maximum Pressure: Automotive

We need to cut the end of the existing vacuum hose that connects into the intake manifold so that we can reuse this piece for our new hose. I cut mine right around where the yellow arrow was below.



After that, insert the piece you just cut into your 12mm ID vacuum hose. I added a hose clamp on this just for extra safety, but it may not be needed.

Then, connect the other end to the brake booster vacuum hose that comes from the firewall. This is slightly larger than 12mm, so this will take some muscle to get on. I also included a hose clamp here just to be safe, but this piece likely doesn’t need it since it’ll fit on so tight.

Finally, we’ll need to plug the OTE pipe with a cap where our old vacuum line used to connect to. This prevents dirty and unmetered air from getting into the engine. I bought a pack of vacuum plugs at Autozone here: https://www.autozone.com/ignition-t...man-autograde-assorted-vacuum-caps/365550_0_0 I can’t remember what size I ended up using, but the kit includes one that slides right over this plug. I then used a zip tie wrapped around it to make it hard for it to slide off. This shouldn’t come off, but if it does I’ll likely switch it for a hose clamp.

And that’s it! Driving the car around feels like normal, and myself (as well as others) have noted that boost feels like it builds slightly quicker, as well as the turbo noises being slightly louder as well. This all might just be a coincidence, but it could also be a result of this mod!

I did some tests with braking, and it all feels the same as it did before. The only time it feels different is if the car is turned off and you continue to press the brake, but it isn’t often that the car dies on itself and you need to brake in an emergency. Even if you do, you CAN still stop the car, it just won’t be assisted (again, like most cars on the road today).



The engine bay sure does look a lot cleaner! Now I need to sort out my air intake situation and move that ugly looking ECU bracket I made…

I think I covered anything here, but if I missed something or anyone has any questions, feel free to reach out!


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Is there a reason you chose this over the pretty pretty RS mod hose thats like $30? Just asking if there is a difference.
 

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Discussion Starter · #3 ·
Is there a reason you chose this over the pretty pretty RS mod hose thats like $30? Just asking if there is a difference.
Well I got the hose for like 18$, and it’s a lot thicker than the hose that’s included in the RS mod. Also, from what I’ve seen all of the stuff for the RS mod is sold overseas in Europe, and I didn’t want to wait for shipping times etc.


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Well I got the hose for like 18$, and it’s a lot thicker than the hose that’s included in the RS mod. Also, from what I’ve seen all of the stuff for the RS mod is sold overseas in Europe, and I didn’t want to wait for shipping times etc.
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Makes sense, thank you.
 
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Most modern cars with VVT or Turbochargers don't make enough vacuum for more than one pump of the brake pedal.
More modern cars with direct injection need them too.

On the engineering side, one thing you might consider is putting a steel sleeve or bushing inside the plastic pipe you cut off for the vacuum source. Long term the plastic can soften, deform and collapse in on itself from clamp pressure. You want a firm connection there in case of an intake backfire which could blow the hose off.
 
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Discussion Starter · #6 ·
Most modern cars with VVT or Turbochargers don't make enough vacuum for more than one pump of the brake pedal.
More modern cars with direct injection need them too.

On the engineering side, one thing you might consider is putting a steel sleeve or bushing inside the plastic pipe you cut off for the vacuum source. Long term the plastic can soften, deform and collapse in on itself from clamp pressure. You want a firm connection there in case of an intake backfire which could blow the hose off.
It’s interesting that our cars have one, but the focus RS in europe doesn’t. My guess is if that motor doesn’t that they deemed it safe enough to operate without it. Any thoughts on that?

So far I’ve had no issues, I even tested it turning the car off while driving and I was able to stop fine.


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European nations all have different emissions standards so maybe their cam and ignition timing has less effect on vacuum than our markets, or get a waiver because of limited production.
Do they have electric turbos by chance?
 

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Discussion Starter · #8 ·
European nations all have different emissions standards so maybe their cam and ignition timing has less effect on vacuum than our markets, or get a waiver because of limited production.
Do they have electric turbos by chance?
No electric turbo, same exact motor except the turbo is actually a larger K16 turbo instead of the K04 that comes on our cars.


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Cost to install = 2 hose clamps. Maintains all factory connections and doesnt allow for the line to the booster to get pressurized when the manifold is.

Braking during high idle start up (little to no vacuum) is very firm, I wouldnt recommend running this on a daily car. But to each your own.


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Discussion Starter · #10 ·


Cost to install = 2 hose clamps. Maintains all factory connections and doesnt allow for the line to the booster to get pressurized when the manifold is.

Braking during high idle start up (little to no vacuum) is very firm, I wouldnt recommend running this on a daily car. But to each your own.


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The problem with this that I can possible see happening is if that valve that’s built into the hose poops out, you’re gonna have no brake assist since it could get stuck closed and there isn’t a vacuum pump in the other side to generate vacuum.

This is what I originally did though and it worked fine!


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The problem with this that I can possible see happening is if that valve that’s built into the hose poops out, you’re gonna have no brake assist since it could get stuck closed and there isn’t a vacuum pump in the other side to generate vacuum.

This is what I originally did though and it worked fine!


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Id recommend a new/aftermarket valve if it's really concerning you. Factory booster was never intended to see boost pressure in any scenario. But hey, many RS guys are running the same, what do I know!


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Discussion Starter · #12 ·
Id recommend a new/aftermarket valve if it's really concerning you. Factory booster was never intended to see boost pressure in any scenario. But hey, many RS guys are running the same, what do I know!


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Ive been looking at a potential new valve to fit into this setup as like you mentioned I’d like to keep boost out of the brake booster. I think this is called a Venturi valve but can’t remember


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One could add a generic vacuum check valve and or a vacuum reservoir like on big cam muscle cars. A reservoir will allow for a couple extra pedal uses.
 
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No electric turbo, same exact motor except the turbo is actually a larger K16 turbo instead of the K04 that comes on our cars.
On a sidenote, we also had Focus ST which uses literally identical engine with the same K04 turbo, those didnt have brake booster either. I have seen the same discussion threads on UK forums with people wondering of purpose of this booster on Volvos but there was no concensus either.
Personally - i wonder if its because of Focus ST/RS of that generation being available only with manual tranny and somehow I think that you use brake pedal much more often on AT? but I may be totally wrong on that, just loud thinking.
The "its because its Volvo so needs extra safety" explanation is much more plausible though..
 

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Ive been looking at a potential new valve to fit into this setup as like you mentioned I’d like to keep boost out of the brake booster. I think this is called a Venturi valve but can’t remember


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What did you gain, other than space?
 

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Discussion Starter · #16 ·
What did you gain, other than space?
A cleaner looking engine bay as well.

Part of this is in preparation for a custom air intake I’m building like many others have done. Some have even installed the focus RS airbox here as it’s located here on those models.


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Discussion Starter · #17 ·
So after doing some digging and talking with others, im almost positive that there is ANOTHER one way check valve before the brake cylinder.

Talked with some people who work on Volvos a lot (specifically P1s) and they said they believe they remember another valve behind the firewall/battery box before the vacuum line goes into the brake cylinder.

I wanted to confirm this so I loaded up VIDA.

129661


In the above image you can see part #10 which is the vacuum hose that connects to the vacuum pump, intake manifold, air intake pipe, and the brake booster. Right after that, you can see part #11, which is the hose that comes through the firewall and connects to part #10. Looking up part #11, which is Volvo part # 31406272, we can see what looks to be a one way check valve built into this hose.

129662


You can see it right above the "U" in the "FCP Euro" watermark. Im almost positive this is a check valve, and will do more digging to confirm. But i think that this keeps the brake booster safe from any sort of boost going into it.

I've talked with a handful of people who have ran with a straight hose for years and have had no issues at all braking, so I think this mod (as well as the nicer looking Focus RS hoses) are safe and should not damage the brake master cylinder, etc.

I'd love some input and thoughts on this though to confirm my findings, etc. Thanks all!
 

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Perfect timing. A very similar setup on my XC70 is on its way out, causing CEL on fuel system too rich (a common problem) and I can't really be bothered to replace it with a complete, new setup, instead of just replacing it with a length of hose and calling it a day.

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Perfect timing. A very similar setup on my XC70 is on its way out, causing CEL on fuel system too rich (a common problem) and I can't really be bothered to replace it with a complete, new setup, instead of just replacing it with a length of hose and calling it a day.

Thanks.
It’s only going to effect pedal feel and if you have emergency braking if the car lost power you just have to make sure you have enough leg strength to make it all work but with deleting the vacuum booster will give you better control and feel over the brakes, or racing. (No booster). Just wanted to see where the OPs head was at.


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It’s only going to effect pedal feel and if you have emergency braking if the car lost power you just have to make sure you have enough leg strength to make it all work
Thanks for the reminder. No worries. I've raced thousands of laps in pretty heavy endurance series touring cars with no power-assisted brakes so losing it with regular street pads and cool brakes won't probably cause issues. And if it does, it's still a Volvo, the ultimate street-legal bumper car.
 
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