# Hard brake pedal at low speeds after vacuum pump overhaul



## msr (Jan 24, 2011)

I have a 2009 Tiguan 2.0 TSI and replaced the seals on my vacuum pump today to sort a bad oil leak. The job was pretty straightforward and the seal kit included 3 o-rings and the gasket between the pump and the head. Everything seemed to be fine until I pulled up to park and after pushing the brake pedal a couple of times it went hard and the brakes almost didn't work. If I drive off it's fine again after the revs get up a bit but the same thing happens if I pump the pedal at low speed.

I've tried pumping the pedal with the engine off, then hold and start the car and the pedal doesn't go down. I think this suggests a faulty booster but it's a bit of a coincidence! I've checked all the vacuum hoses are secure, the only one I had off is the one at the back of the vacuum pump. I can't see anything out of place and if I get someone to pump the pedal I can't hear any leaks under the bonnet.

Does anyone have any idea what I might have done wrong? I don't think the vacuum pump can be fitted the wrong way, there's a channel on the camshaft it has to line up to. 

When I opened the pump itself to replace the main o-ring there was a small part that dropped off the rotor(?) inside, it wasn't attached with anything, it just slid on the end. I put it back and checked it was the same as the other side. I suspect if this was wrong the pump wouldn't work at all though.


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## Thy_Harrowing (Dec 7, 2014)

Correct, there is no way you could have put the vacuum pump back on wrong. Likewise, if you had a vac leak you'd have other symptoms so that's not it either. I'm not really understanding what you're trying to say with the following quote though:



> When I opened the pump itself to replace the main o-ring there was a small part that dropped off the rotor(?) inside, it wasn't attached with anything, it just slid on the end. I put it back and checked it was the same as the other side. I suspect if this was wrong the pump wouldn't work at all though.


Can you try to explain that more?

Otherwise, are you saying that the brake pedal is hard only after you've parked and *engine off* or after you've *pumped the brakes several times*... because neither of those things are abnormal If the pedal isn't any harder when the engine is on with normal application of brake pedal and if it isnot hard at any point while actually driving (even if pumping the brakes rapidly), then I'm not so sure you actually have any issue. If you're positive something is different and you're not just inventing an issue since you did related work, then maybe I'm just not picking up what you're putting down. Maybe the symptoms and before/after behavior need to be discussed more in that case.


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## msr (Jan 24, 2011)

Thy_Harrowing said:


> Can you try to explain that more?
> 
> Otherwise, are you saying that the brake pedal is hard only after you've parked and *engine off* or after you've *pumped the brakes several times*... because neither of those things are abnormal If the pedal isn't any harder when the engine is on with normal application of brake pedal and if it isnot hard at any point while actually driving (even if pumping the brakes rapidly), then I'm not so sure you actually have any issue. If you're positive something is different and you're not just inventing an issue since you did related work, then maybe I'm just not picking up what you're putting down. Maybe the symptoms and before/after behavior need to be discussed more in that case.


I'll try! To replace the biggest o-ring I had to open up the pump itself, this required removing 2x T20 screws. A rotor is probably not the correct term, if you look at this image you'll see what I mean :- 

https://cdn.shopify.com/s/files/1/1489/0528/products/front_seal_logo_large.jpg?v=1511980995

Those little seals at either end of the black part just slide in, one fell out when I opened the pump but looking at the picture now I don't think I could have put that back in the wrong way either.

I removed the vacuum line from the pump again on Friday to check the o-ring on the port, then tightened the screw on the port as much as I could and reinserted the line. There was definitely an improvement after doing that. Now the issue is mainly when reversing, if you push the brakes even lightly more than a couple of times the pedal becomes hard and it's an effort to make it stop. Not so bad going forwards, you have to pump the pedal maybe 5 times at low speed to get the same issue. This is just when maneuvering slowly, there are no issues when driving at and braking from higher speeds.

I'm positive it wasn't like this before, I'm considering taking it all off again, opening the pump and refitting just in case. It only took about an hour...

Apologies for the delayed reply, I didn't have email notification switched on.


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## msr (Jan 24, 2011)

I removed the pump again earlier, opened it, checked everything and put it back together. I'm confident that everything is where it should be but the issue remains. The parts inside my pump are all metal, not plastic like those in the photo. The pump turns smoothly when turned by hand.

The oil leak was pretty bad before I replaced the seals. Now that there isn't an oil leak could the increase of vacuum have caused an issue elsewhere? What's the next weakest link? Failing check valve?

Here's a pic of my pump in case it's helpful - https://1drv.ms/u/s!AvEMMGITq3yVh9kLqiO_p0ohBV2epA


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## Thy_Harrowing (Dec 7, 2014)

Okay, yeah what you are describing is definitely NOT normal. I just wasn't totally clear form the first post. Like you said, the pump really only goes together one way and it would be pretty hard to mess that up. This is a pretty curious case, especially that it is behaving differently in reverse then in forward gears. I can't think of any explanation or association behind that besides that the gearing ratios of reverse and forward gears is obviously different, therefore the RPMs you tend to be at in reverse are different and your throttle input may be different (circumstantially) when using reverse, therefore the vacuum pressure may be different. Bit of a stretch to connect all those dots but theoretically it all lines up. I can't think of anything else. I don't know of any way in which the car is really "aware" that you're in reverse that would pertain to brake behavior with the booster system directly, so I figure the connection is indirect like how I described.

But that's kind of a tangent... as far as the issue at hand: I agree, I would have to start suspecting the check valves next if we are to assume the pump itself is not where the issue lies. Have you checked what kind of vacuum pressure you are seeing at idle and under different scenarios too? That would be good to know.


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## msr (Jan 24, 2011)

I went out today to do some testing in forward and reverse and I think like you say it's just a revs based thing. I hadn't really thought about it but previously when I was reversing I had already pushed the brake while going forwards. I drive forwards into my car port then have to reverse and move forward again because there is limited space. So slowly forward while pulling up, brake a couple of times, all at idle speed, then engage reverse and brake again before moving forward. So back to today's test, I found a quiet street and if I pump the brake quite hard from 20mph or so it can start to feel like the pedal is getting hard after only 3 pumps. It's much the same if I build up a bit of speed in reverse. When the revs get to 1200rpm it's already back to normal.

I haven't managed to test the vacuum other than putting my thumb over it at idle. I don't have access to a vacuum tester but if it comes to it I could get one from eBay, they're quite expensive to buy locally. I think the pump should be fine though because the brakes work very well when driving at anything other than idle?

Assuming this is the check valve:

https://1drv.ms/u/s!AvEMMGITq3yVh9kbrwXu0-dh7havkA

I removed the pipe it's attached to, the connection at the bulk head was quite difficult to remove so I believe it's making a good seal. The connection on the vacuum pump port wasn't as difficult to remove but still took quite a bit of effort to get it off. The valve appears to be working, I can only blow air one way (again I don't have tools for this so maybe not a good test!). I wrapped some insulation tape around the vacuum pump port before refitting the hose just to make sure it was tight. This didn't make a difference though.

I think the next thing I'll try is removing the pipe that goes to the brake booster to check it for any cracks. The small pipe that goes from the vacuum pump port to the N75 valve appears to be good and there are no leaks when I blow down it.

I'm thinking it must be a leak somewhere? At high revs the pump makes enough vacuum for a small leak not to matter but at idle 750-800rpm or so, it just doesn't create enough for the brakes?


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## Thy_Harrowing (Dec 7, 2014)

I think you’re on the money. It is more likely a small leak of check valving issue than a pump or booster issue, for all the reasons you have noted. Additionally, if it is a leak it must be very small indeed to not but impacting your idle quality at al (or at least I assume it hasn’t since you haven’t mentioned anything like that). Typically vac leaks result in uneven idle and even surging. I would suspect at this point a small leak since that would explain the above as well as why you haven’t found it yet. It could be a small leak where the vac hose actually connects to the brake booster, not a leak in an actual line. 

Unfortunately I am not at all familiar with you vac hose layout, based on seeing your pictures in your other thread. So I can’t give specific pointers. I’m most familiar with the FSI layout, not yours.


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## msr (Jan 24, 2011)

Yes the idle is steady at about 750 rpm. I bit the bullet earlier and bought a cheaper vacuum gauge that I found locally, still twice the price of eBay, but I can't wait over a week for one to arrive!

I did some diagnostics, plugged the tube from the gauge directly into the port on the pump and started the car. It immediately went to 16 in. Hg and stayed there. I'll need to do a bit of searching to see if this is in spec. With the engine still running at idle I unplugged the gauge from the port and then plugged it back in again, this resulted in the vacuum only going to 10 in. Hg and then it slowly built to 12 in. Hg after a few seconds and didn't go any higher. I repeated this test and the results were consistent. If I rev the engine the vacuum builds up, not sure how high it would go but over 20 without revving much.

Does this suggest my pump is faulty or is it normal to be this low at idle? When you start the car the revs are momentarily higher than idle before dropping down which must push it up to 16 in. Hg. 

Are there are tests I should try?


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## msr (Jan 24, 2011)

Oh and to add insult to injury the car is still leaking oil, no evidence of it around the pump or pooling on the transmission where it was previously but it is dripping on the ground on the same side


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## Thy_Harrowing (Dec 7, 2014)

Once the idle rpm lowers a tad and rests around 750rpm you should have ~20Hg vacuum. So assuming that gauge is accurate and assuming it was completely sealed where you plugged it in and all those sort of things that would be critical to accurate readings, then it would appear that you have low vacuum from the pump. However, try hooking the pump up to a vacuum source coming from the intake manifold and see what it reads. It’s been a LONG time since I had factory lines or indeed a factory intake manifold, and plus I have an FSI, so I can’t remember enough or give you a good indication of exactly where/how to hook up. There should be a vac line coming from the mani to meet the line coming from the vac pump though, I think.

Had you thoroughly cleaned up all the oil that had previously leaked before you changed the vac pump seals. Are you positive this oil dripping is new oil not oil from before?


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## msr (Jan 24, 2011)

I've tried taking readings at a couple of other places and I remembered when I had the engine cover off that I removed the hose going from the PCV to the inlet manifold while removing the vacuum pump. I thought I was going to have to remove the fuel line that goes to the high pressure pump that's attached to the vacuum pump. Anyway, on close inspection, the front of the PCV looked a little damp from oil. I replaced the PCV a couple of months ago and hadn't used the new pipes that came with it (not genuine) because the old ones looked good, as did the o-rings. So I replaced the PCV to inlet pipe and took it for a run. It felt like there was an improvement but I can't be sure, the pedal still gets hard, maybe not to the same point it did before though. 

I thought a picture might be helpful to show where I took the readings, I'm not sure if this image will work, here is the link if not: https://1drv.ms/u/s!AvEMMGITq3yVh9lKTGHUX9E32EUhRw










At the top right is the port on the vacuum pump where I get only 10Hg today after warming the car up. If I hook it up to the pipe circled in the middle of the photo I get 20Hg, the needle on the gauge vibrates a tiny amount constantly but stays at 20Hg (+/- a tiny amount). The engine didn't like it when I unplugged that hose connection so I suspect that's why the needle on the gauge is jittery. The hose with the arrow on the left goes to a connection near the coolant bottle. It's a steady 20Hg at that connection as well. I'm not sure what this tells me!

From the pump the larger hose goes to the brake booster via the check valve seen in this photo: https://1drv.ms/u/s!AvEMMGITq3yVh9lJAoShP_oQPwz52Q










The smaller pipe is the one I wrote 'To N75' on. It seems to go from the N75 to what I think might be a solenoid of some sort, not sure. The pipe I disconnected in the middle goes to something below the manifold that I can't reach but it looks to be in good condition. 

Regarding the oil, I cleaned up the transmission, cylinder head around the pump and completely cleaned the under tray last week. The transmission is still clean: https://1drv.ms/u/s!AvEMMGITq3yVh9lMhX-PfKXKTJE7cA










However I dropped the under tray earlier and it looks like this: https://1drv.ms/u/s!AvEMMGITq3yVh9lNXvmuZDMu1gRUBA










That's pretty much how it looked before I cleaned it last week. The part just right of the centre with the pooling oil sits in about the right place for oil to be leaking down from the vacuum pump. Or the rear main seal  If I shine a torch up there's oil residue at the back of the engine, probably that could have come from the leaking pump that I didn't manage to clean up. However for there to be this much oil in such a short space of time (< 100 miles) then I think it would need to be pooling on the transmission to be coming from the pump? Maybe I should replace the gasket between the pump and head anyway, it may not have liked being removed that time I checked everything over. I've left the tray off to hopefully get a better idea of where it's coming from. 

Thanks for your help and suggestions so far, much appreciated.


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## Thy_Harrowing (Dec 7, 2014)

> I've tried taking readings at a couple of other places and I remembered when I had the engine cover off that I removed the hose going from the PCV to the inlet manifold while removing the vacuum pump. I thought I was going to have to remove the fuel line that goes to the high pressure pump that's attached to the vacuum pump. Anyway, on close inspection, the front of the PCV looked a little damp from oil. I replaced the PCV a couple of months ago and hadn't used the new pipes that came with it (not genuine) because the old ones looked good, as did the o-rings. So I replaced the PCV to inlet pipe and took it for a run. It felt like there was an improvement but I can't be sure, the pedal still gets hard, maybe not to the same point it did before though.


Probably not a factor if the difference was minimal enough to be questionable altogether, I think we can ignore that or circle back to it later if needed.




> If I hook it up to the pipe circled in the middle of the photo I get 20Hg, the needle on the gauge vibrates a tiny amount constantly but stays at 20Hg (+/- a tiny amount). The engine didn't like it when I unplugged that hose connection so I suspect that's why the needle on the gauge is jittery. The hose with the arrow on the left goes to a connection near the coolant bottle. It's a steady 20Hg at that connection as well. I'm not sure what this tells me!


The hose your circled and the one on the far left are EVAP hoses. That is a contained system separate of the brake booster vacuum system hence the disparity in pressures. Forget those hoses.




> Regarding the oil, I cleaned up the transmission, cylinder head around the pump and completely cleaned the under tray last week. The transmission is still clean: https://1drv.ms/u/s!AvEMMGITq3yVh9lMhX-PfKXKTJE7cA
> 
> 
> 
> ...



Okay, yeah you definitely still have an active leak and if it were coming from the pump I suspect it would be pulling on the transmission to some extent as well. I suggest you take out the battery and battery tray so you can really get your head back there along with a good large inspection mirror to thoroughly inspect the underside of the pump and pump-to-head seal for any sign of oil before completely ruling it out. But more than likely the pump is not the culprit based on the info so far. If this were and FSI this would be an easy diagnoses because the FSI is common to have either the cam chain housing or the valve cover itself leak on those sides, down over the back of the block straight down to the splash shield like I suspect your leak is; but the thing is the TSI platform isn't particularly well known for either of those leaks. It's certainly always possible and worth inspecting though.

Tracking oil leaks is a pain. If you wanna track it down yourself you have no choice but to get real serious about taking parts out of your way to be able to reach ALL areas with any sign of oil and clean them thoroughly, then inspect them immediately after fairly brief driving to catch the oil in the act. Buying an oil with die, or adding some die, that reacts to blue lights is a good way to trace such leaks after thoroughly cleaning the oil that did NOT have die in it from the area first.


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## msr (Jan 24, 2011)

Thy_Harrowing said:


> The hose your circled and the one on the far left are EVAP hoses. That is a contained system separate of the brake booster vacuum system hence the disparity in pressures. Forget those hoses.


Can you see any other locations on the engine picture that I could tap into or can you suggest a name of a component that uses vacuum so I can track it down in parts diagrams and take readings there? The only two hoses coming off the vac pump are the one that goes to the booster and the other to the N75. There is also the high pressure fuel pump attached to the vac pump. If the pump itself was bad then there would maybe also be fueling issues/misfire?



Thy_Harrowing said:


> ...because the FSI is common to have either the cam chain housing or the valve cover itself leak on those sides, down over the back of the block straight down to the splash shield like I suspect your leak is; but the thing is the TSI platform isn't particularly well known for either of those leaks. It's certainly always possible and worth inspecting though.


When I first bought the car there was a low oil pressure warning the next day, long story short the VW main dealer found oil leaking into the timing cover and replaced the cam housing seal to repair. After the repair there was still a leak and when I took it back to VW they pointed me to the vac pump and wanted to replace the whole thing to repair the leak. I believe there is still oil leaking from the timing cover because I can see some evidence of it there, but I'm not sure it could make it across to where the leak is now. 

After removing the tray and wiping the oil underneath I took it for a 3 mile or so drive and then put clean card under. Checked this morning and the oil has leaked just to the right of the black bracket in the photo: https://1drv.ms/u/s!AvEMMGITq3yVh9lTAg2r7unPEq2GAg












Thy_Harrowing said:


> Tracking oil leaks is a pain. If you wanna track it down yourself you have no choice but to get real serious about taking parts out of your way to be able to reach ALL areas with any sign of oil and clean them thoroughly, then inspect them immediately after fairly brief driving to catch the oil in the act. Buying an oil with die, or adding some die, that reacts to blue lights is a good way to trace such leaks after thoroughly cleaning the oil that did NOT have die in it from the area first.


I am going to need to track this down seeing as it's so bad but the brake problem will need to take priority. I really regret buying this car, it's been nothing but problematic since day one. Not what I expected from a FVWSH, one owner car, with 110k miles.


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## Thy_Harrowing (Dec 7, 2014)

Aside from the sources you've checked already, the only other advice I have it to check vacuum from any intake manifold source. I can only see the main hose going from the intake manifold to the PCV as you described before but is there another one kinda behind that which is going to another point in the intake manifold?

If you can get vacuum from the manifold that should be a good test, but I think what you've tested already is fine.


As for the leak, unfortunately it's going to be really hard for me to help you track it down without physically being there. Oil leak tracking is hard enough in-person, but nearly impossible online dealing with text and pics. The best I can do is give advice on the methodology of tracking at and, to some extent, advice on common leak sources, but I'm not as familiar with your platform.

You say there is a vacuum line going from the HPFP to the vacuum pump??? That is bizarre. I can't think of any reason for that and I am not familiar with that functionality. What engine code do you have btw?


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## msr (Jan 24, 2011)

Thy_Harrowing said:


> Aside from the sources you've checked already, the only other advice I have it to check vacuum from any intake manifold source. I can only see the main hose going from the intake manifold to the PCV as you described before but is there another one kinda behind that which is going to another point in the intake manifold?


I'll check a bit later, I think there is a small hose connection on the underside of the intake manifold but it goes straight into a component that's also under there.



Thy_Harrowing said:


> You say there is a vacuum line going from the HPFP to the vacuum pump??? That is bizarre. I can't think of any reason for that and I am not familiar with that functionality. What engine code do you have btw?


No sorry, what I mean is the HPFP is attached to the vac pump housing, bolted on to the side, not via a vac hose. Thinking about it the HPFP is driven by the cam itself, via a spring system, not the vac pump! Please ignore, I'm obviously not thinking straight.

Engine code is CAW


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## Thy_Harrowing (Dec 7, 2014)

If you want to continue testing vac pressure then disconnect one of the two vac sources on the intake manifold, whichever seems easier/safer, and make sure you have a good seal (which for the larger port may require rigging up an adapter of some kind since it's probably a lot bigger than your vac tester hose).

As for the HPFP relation to the vac pump... okay now that you said it that way I see what you were getting at... but, yeah, you corrected yourself on that before I had to say anything so I'll leave it at that


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## msr (Jan 24, 2011)

I'll need to source some hose to get my tester plugged into the big port and unfortunately I can't access the other one. I could probably get the hose that's down there disconnected but unlikely connected again unless I invest in some long nose hose pliers or similar.

I bought a can of throttle body/carb cleaner earlier and with a cooled engine (and a fire extinguisher nearby) went looking for vacuum leaks. I sprayed every connection that looked likely to be vacuum related and got no change in idle at all. 

So now I'm thinking I could actually have a bad pump. Or booster.


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## Thy_Harrowing (Dec 7, 2014)

Of the two I would suspect the pump at this point


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## msr (Jan 24, 2011)

ok I'll see if I can source a used one.

I made a video earlier - https://youtu.be/q74mZlACq-k

Only 2-3 pumps of the pedal to clear the vacuum.


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## msr (Jan 24, 2011)

Finally got this sorted at the weekend after reading this thread - https://forums.vwvortex.com/showthread.php?5129625-Diesel-Vacuum-pump-rotary-vane-type

Particularly point 4 about the oil and screen. I removed the pump again and thoroughly cleaned it (again) with degreaser. There is now significantly more wear visible, I guess from oil starvation, than there was before. I cleaned the screen and channel last time but it's likely something got in there during reinstall. Either that or something in the oil, the screen was still clear when I removed it but the hole for the oil is pin sized so very easy to block. I didn't put the small screen back in again, put everything else back together and started the car with the gauge on. It's now not possible, well certainly not with 3 pumps of the pedal, to completely deplete the vacuum. It builds very quickly at idle to 25Hg ish. The brakes are back to normal.


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## Thy_Harrowing (Dec 7, 2014)

Wow good catch. I was completely unaware of that aspect of the design of your vacuum pump. All the ones I'm familiar with from other platforms do not have an integrated screen. Had I realized that was a factor at play I may have brought it up. But in any event, I'm glad you finally figured it out. If the pump is now worn from starvation then you'll be wanting to replace that. You'll also be wanting to do an oil change to both visually inspect and also take a sample to send to Blackstone labs just to be certain that the reason the screen was clogged wasn't because of lots of particulates in your oil. Your visual inspection is important to look for visible to the naked-eye particles because the lab analyses are designed to identify things you definitely cannot see with your eye. They break it down to parts per million because they are focused on what's in your oil at levels of microns. Just a cheap way to get some peace of mind usually (hopefully).


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