Brake booster suction pump?

[03AudiA41.8T]

A few weeks ago I kept getting a brake booster vacuum leak. I then did a boost leak test and noticed a huge leak coming from around the brake booster vacuum pump. I then took it out and studied where it was coming from and noticed a hole where it looked like air was supposed to leak out. I am wondering if this is because of a faulty pump or because of another reason. This is leaking a massive amount of air out and think it could be the root of my problem. I used to get 18lbs of boost now only seeing 10. Sometime I notice it climbs to 15 lbs but then it seems to just give out and drop right to 10 lbs. I tried to block the line going to the pump and drive it to see if i was getting all 18 lbs and it still was crusing around 10lbs. Anyone having this problem and if so please help me troubleshoot. I also unplugged the hose going to the pump and did a output test on VAGCOM and i heard the pump kick on but didnt feel much air coming from it. I dont want to spend 350.00 if the pump is okay. Also the lines coming from the pump has no leaks. Like i said just on the pump itself there is a hole that seems to be leaking. sorry if its hard to understand but if someone knows what im talking about please let me know thank you...

[stelvio]

LINK --> THIS might help..? If you're talking about the Suction Jet Pump.

[03AudiA41.8T]

Nope, Im talking about the Brake Booster Vacuum pump. part number 8e0927317

[walky_talky20]

There should be absolutely zero boost that is able to make it from the manifold to the vacuum pump. So that is one problem. The boost from the manifold stops at either the SJP or the check valve that sits right above it, and should go no further under any circumstances. If you get boost beyond that point, you need to fix that.

Also, even if the vacuum pump was faulty (which it isn't), it definitely is not worth spending $350 on. Earlier cars (pre-2001.5) with the exact same engine as yours (1.8T with Tiptronic Automatic trans) were not even equipped with that electric pump. And those cars certainly weren't death traps without them (I drive one!). If everything is working correctly (check valves, the brake booster itself, etc), you won't even notice the difference if you rip the pump clean out of the car (other than maybe a Check Engine Light). At the very worst, you can get a replacement pump from the junkyard for probably $25.

[03AudiA41.8T]

Okay that is helpful. THank you. I just have to figure out why the boost is going through this pump then. I did a boost leak test and heard a huge leak. after narrowing it down I saw that it was coming out of the little pin whole located on the silver pump itself. I m not sure how to troubleshoot the issue thats causing the boost to pass through the pump. I never even knew what the part number 8e0927317 was used for. Any suggestions on what would cause this and how to troubleshoot would be great. Thank you guys

[walky_talky20]

There are 2 paths out of the manifold that could possibly be at fault. I've marked up this photo to portray the flow of boost. Brilliantly simple, if I do say so myself. *BAHahahaha*



As you can plainly see (*hold on while I stop laughing...whew.....okay*), boost leaves the manifold as shown by the green lines. Boost stops at the places marked in Red. Hold up, I'll just make a chart showing what all my crazy color choices mean:

Green - That's the BOOST, yo.
Orange - "Large L Hose"
Purple - Suction Jet Pump aka: SJP
Red - Boost stops here.
Blue - "S Hose" to PCV valve
Yellow - Vac only. Goes to brake booster and electric booster vacuum pump

So basically, during your boost leak test, if you pinch off the ORANGE hose and the boost stops leaking out of your electric pump - that means your Suction Jet Pump is not checking (stopping) the boost properly. If that doesn't do it, then it is probably the little tiny check valve that sits above it (ie: the other, shorter green path) that is to blame.

Hope that helps. Let me know if you need any more brilliant diagrams. ROFL.

[evo_ski]

Walky, thank you very much for that illustration. That stuff makes a lot more sense to me now. Thanks!

[walky_talky20]

You're very welcome. Let me know if there is anything else I can demistify with my worryingly good mspaint skills. lol

[evo_ski]

My pedal feels stiff after letting the car sit for 4 or so hours, so I may try to investigate this a little bit. I also just read someone else talking about this issue in the stupid questions thread and both you and OG said your oil cap should dance when you unscrew it. Mine doesn't, but I do have the 034 kit with the billet valve, which I remember you saying pulled more vaccuum than oem. Every now and again the idle will bounce around and fluctuate or rev just a little bit, so I am going to take a look at the SJP and surrounding valves and hoses. Boost holds to normal levels and the car drives solid other than a slightly funny idle every once in a while in park. It seems that with it in drive the idle doesn't bounce around, or maybe I just don't notice it.

[old guy]

Excellent work as usual Keith! One comment for clarification: The blue hose in your illustration is correct for the '02 and early '03 models. After that the blue hose gets connected to the TIP to provide a cleaner air source for the vacuum amplifier portion of the SJP and the hose from the PCV got its own dedicated connection to the intake manifold.

[walky_talky20]

^That's right. The blue hose would be off in a little different direction, but would still have a check valve for boost approximately the same distance away from the SJP. Thanks for the clarification.

[old guy]

^That's right. The blue hose would be off in a little different direction, but would still have a check valve for boost approximately the same distance away from the SJP. Thanks for the clarification.

Yep. It doesn't change your diagnostic advice but it could be confusing to someone who was still trying to figure out "where all that crap goes?"

[03AudiA41.8T]

Can someone point me in the direction to a new check valve that was mentioned above? I am not sure if they are all different or not. My case has become more often now. It "fixed itself" for about 2 days then went right back to only getting 10 lbs or so. Im hoping its just a weak check valve that is causing the boost to go through the electric brake pump

[walky_talky20]

There are 2 check valve devices there. Not sure which one you wanted:

http://www.ecstuning.com/Audi-B6_A4-...ses/ES1884320/
http://www.ecstuning.com/Search/Site...8791/ES258791/

You can pinch off the hoses individually during your boost leak test to figure out which one is to blame.

[Charles.waite]

Walky that diagram is killing me. You should change careers and be an illustrator, you clearly have the skillz, yo.

[stelvio]

There are 2 paths out of the manifold that could possibly be at fault. I've marked up this photo to portray the flow of boost. Brilliantly simple, if I do say so myself. *BAHahahaha*



As you can plainly see (*hold on while I stop laughing...whew.....okay*), boost leaves the manifold as shown by the green lines. Boost stops at the places marked in Red. Hold up, I'll just make a chart showing what all my crazy color choices mean:

Green - That's the BOOST, yo.
Orange - "Large L Hose"
Purple - Suction Jet Pump aka: SJP
Red - Boost stops here.
Blue - "S Hose" to PCV valve
Yellow - Vac only. Goes to brake booster and electric booster vacuum pump

So basically, during your boost leak test, if you pinch off the ORANGE hose and the boost stops leaking out of your electric pump - that means your Suction Jet Pump is not checking (stopping) the boost properly. If that doesn't do it, then it is probably the little tiny check valve that sits above it (ie: the other, shorter green path) that is to blame.

Hope that helps. Let me know if you need any more brilliant diagrams. ROFL.

You have no idea how long I've been looking for an answer as to where the PCV line goes to: whether it went straight to the IM or through the SJP. Your diagram is priceless :) Thank-you!

[old guy]

You have no idea how long I've been looking for an answer as to where the PCV line goes to: whether it went straight to the IM or through the SJP. Your diagram is priceless :) Thank-you!

The answer is both ways depending upon the model year. If you have an '02 the PCV pulls through the SJP as shown above. In '03 the PCV received a dedicated line to the intake manifold and the SJP received a supply line from the TIP. This cured the issue of the SJP getting gunked up from the PCV blow-by gasses by giving the SJP a filtered fresh air supply. It also increased the block ventilation as a way to reduce the sludging problems that were starting to appear more often.

Since yours is an '04 or newer (1.8T 6 speed) your PCV connects directly to the IM.

[diagnosticator]

Can someone point me in the direction to a new check valve that was mentioned above? I am not sure if they are all different or not. My case has become more often now. It "fixed itself" for about 2 days then went right back to only getting 10 lbs or so. Im hoping its just a weak check valve that is causing the boost to go through the electric brake pump

There is no way the low boost pressure is caused by the air escaping through the brake booster vacuum pump. The normal flow direction for air when the vacuum pump is running, is from the plumbing hoses and check valve connected to the brake booster, then through the vacuum pump that exhausts to the outside air. Pressurized charge air will also flow this way when the vacuum pump is not running, from the intake manifold. When testing for boost leaks, the connection to the brake booster and vacuum pump must be disconnected and plugged for the test.
During normal engine operation, with boost pressure in the intake manifold the amount of air that can leak through the vacuum pump is very low compared to the air mass flow capacity of the engine. The turbo does not even "see" the small amount of boost charge air lost through the vacuum pump. Boost is blocked from the brake booster by several check valves anyway.

Therefore, there is some other reason for the low boost condition occurring. I recommend checking the boost pressure control system for a sticky wastegate etc.

The electric vacuum pump is used on the Tip 1.8T, because with the torque based electronic throttle control, it is possible that during certain conditions the ECU will open the throttle valve during low load operation to limit pumping losses, and the intake manifold absolute pressure with an open throttle at low load/RPM, is to high and there is not enough vacuum for the brake booster for normal brake assist. When this is the case, the ECU runs the brake booster vacuum pump as needed. This has nothing to do with boosted operation. No one applies the brakes with the turbo boosting the intake, and if they try, the ECU applies brake authority and cuts the throttle valve to idle position, even if the accelerator pedal is pressed.

[stelvio]

The answer is both ways depending upon the model year. If you have an '02 the PCV pulls through the SJP as shown above. In '03 the PCV received a dedicated line to the intake manifold and the SJP received a supply line from the TIP. This cured the issue of the SJP getting gunked up from the PCV blow-by gasses by giving the SJP a filtered fresh air supply. It also increased the block ventilation as a way to reduce the sludging problems that were starting to appear more often.

Since yours is an '04 or newer (1.8T 6 speed) your PCV connects directly to the IM.

Once Again you're very much correct. I got in the garage and I have 2 inputs to the IM whereas my [older] IM in my basement has only one. Thanks!! Good memory on what car I have btw :)

[diagnosticator]

Okay that is helpful. THank you. I just have to figure out why the boost is going through this pump then. I did a boost leak test and heard a huge leak. after narrowing it down I saw that it was coming out of the little pin whole located on the silver pump itself. I m not sure how to troubleshoot the issue thats causing the boost to pass through the pump. I never even knew what the part number 8e0927317 was used for. Any suggestions on what would cause this and how to troubleshoot would be great. Thank you guys

See reply #18,

[DiertyEuroSpec]

My brake pedal seems to be getting stiff when left overnight, especially at my girl's apartment which is parking on a hill. What can be causing the pedal to become so stiff after sitting? I have the 034 PCV kit and have a high idle which I am going to change back to OEM PCV but could it have caused something in the brake booster area to fail?

[stelvio]

High idle is probably caused by vacuum leak. Check to make sure the o-ring from the block breather elbow tube is still there...mine wasn't...
On a side note, if I may, what connects to the bottom of the SJP on the '04+ if it's not the PCV?

[Charles.waite]

High idle is probably caused by vacuum leak. Check to make sure the o-ring from the block breather elbow tube is still there...mine wasn't...
On a side note, if I may, what connects to the bottom of the SJP on the '04+ if it's not the PCV?

Fresh air from the Intak manifold.

[Jenn]

6 Years later...this thread rocks! Thank you!!

[varundev11]

6 Years later...this thread rocks! Thank you!!

Hi Guys..A londoner looking for help...My Audi A4 2.0 Automatic Petrol 2003 was diagnosed with the error code P1479 and P1137, I took the car to Audi and they did the smoke test etc and confirmed that the brake vacuum pump itself was faulty. Now I am in a fix to know what the exact part code of the pump is, would a general 8E0 927 317 work? or this model has a specific letter at the last.

I will be grateful to know.

Thanks
Varun