Turbo Underboost and Stiff Brake Pedal, thoughts?

Turbo Underboost and Stiff Brake Pedal, thoughts?...SOLVED!

02 Golf, 5 sp
To start off, I've read about every thread on this. I am writing this to make sure I'm on the right track, and hopefully it can be of help to someone in the future once this is solved.
Start at the beginning. Few months ago, everything fine. I could come out after letting the car sit overnight, and I would put a foot on the brake pedal while starting the car, and it would have the "soft" feel of a normal brake pedal. Ie you could tell the system was holding vacuum.
Then, I started getting a hard pedal in the morning after letting it sit overnight. So the system had a small leak. I let it be, as soon as the car would start, vac would build, brake pedal was fine as long as the car was running.
I then did some suspension work and bled the brakes with the help of a member on here.
After this, I developed and audible "click" in the brake pedal at the end of the stroke. Easy to hear and feel, always at the same point in the pedal stroke, but did not affect braking or braking power at all, but my OCD didn't like it.
This week, was driving to work. Completely lost my brakes to a hard pedal on the freeway. Also lost boost. Threw the P1538/1556 codes. The fault to ground I tracked to some frayed wires in the plug leading to the ASV So that's taken care of.
I got to work and pulled the big vac line (rubber and plastic piece) from the pump down to the brake booster. It had cracks, and I had to get home, so I salvaged the fittings and made a home brew version out of some fairly stiff fuel line and worm gear hose clamps. I inspected the nipple on the vac pump, it's got very little wiggle in it.
This worked for about 15 minutes, everything felt good. Then, it was back to hard pedal and not boost. Here's the caveat...if I drive without using the brake pedal on the freeway for say, 2-3 minutes, I can get 2-4 good pumps out of the pedal, and the turbo comes back. After those pumps use up the vac in the system, it's back to hard pedal and no turbo until I drive some more. This process repeats
I've had a set of vac lines from IDparts waiting to be installed for a while. I installed these new lines last night. Took out the check valves and tested them with a mighty vac, even though the symptoms point to a leak before the valves (since brakes and turbo go out together).
I went for about a 30 minute drive, where everything was working better than before (with my home brew line). Even the click from before went away (meaning that may have been related to a vac leak somehow?) Then pedal went hard during the drive, and the pattern of 2-4 good pumps and a working turbo, to nothing started again. This to me indicates a CONSISTENT bleed off somewhere rather than one that is happening because of engine vibrations.
What I found odd is every time I remove my homebrew line and reinstall it, or like when I changed out all the smaller vac lines, I got 20-30 minutes of a working system, then it went back to the 2-4 good pumps on the pedal with a working pedal, to stiff pedal and no turbo after a used up vac, then that would repeat.
So I do have a pump to booster line on it's way from Cascade German, as well as a new grommet to the brake booster.
I'll put this line on and hopefully it solves my issue and the leak is coming from my line I've built.
I'm curious, is it possible that my fuel line (on my home-brew hose) is collapsing under use of the brake and then expanding enough to build vac, then collapsing again under use, and that's why I'm having that 2-4 pattern with the pedal? Can't see it while I'm driving obviously...
Also, if the new IDparts line doesn't work, I'll pull the vac pump and peen the edge over and high temp RTV it. I just replaced the internal o-ring that sandwiches the pump pieces together so I don't suspect it's that.
I also don't think it's related to the N75 valve as even if this was bleeding off, I would have a turbo issue but the brakes are using the in-line check valve so they should still theoretically work correct? When all this goes down, I lose brakes and turbo.
Just want to pick your guys' brains, appreciate it!

I am not reading all that, but the line between the vac pump and booster is probably cracked, happens a lot. In general you have an air leak, check around the ball in front of the engine as well, its a reservoir.

steve6 said:

I am not reading all that, but the line between the vac pump and booster is probably cracked, happens a lot. In general you have an air leak, check around the ball in front of the engine as well, its a reservoir.

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Thanks for the attempt a solution, but without reading, you'd know everything about the pump to booster line, the symptoms I've ran into, the solutions I've done, etc.

I know it's long winded, but I don't give all this information for people not to read. I provide as much detail as I can so that questions don't have to be asked unless there is something I blatantly missed. This avoids responses that address something I've already covered...

I'm not a novice with these engines, I do know about the reservoir and what it is, but these are not prone to leaking. I'm stepping through the troubleshooting right now, but given my symptoms listed above, I haven't seen another post similar

This sounds like a vacuum leak somewhere that you haven't found yet, or it's the "home brew" line from the vacuum pump to brake booster. I'd question the "very little wiggle" out of the vacuum pump exit. It should have none. You may be leaking vacuum there. It sounds like the system is able to build vacuum under some circumstances, but other times it loses it faster than the pump can replace it.

I'd first replace the line from the pump to the booster. And if the nipple on the pump is loose at all I'd either try and seal it up or replace the pump. I'm betting this will solve the problem, assuming the other vacuum lines are intact and the N75, check valve, and N18 are OK and plumbed correctly.

I’d guess the nipple on the back of the vacuum pump is loose

It seems you're certainly on the right track. I know we have one check valve up near the N75, but recently someone mentioned a check valve associated with the brake booster. Do these have that?

I was talking about the check valve near the N75. It's all on the same system.

IndigoBlueWagon said:

This sounds like a vacuum leak somewhere that you haven't found yet, or it's the "home brew" line from the vacuum pump to brake booster. I'd question the "very little wiggle" out of the vacuum pump exit. It should have none. You may be leaking vacuum there. It sounds like the system is able to build vacuum under some circumstances, but other times it loses it faster than the pump can replace it.

I'd first replace the line from the pump to the booster. And if the nipple on the pump is loose at all I'd either try and seal it up or replace the pump. I'm betting this will solve the problem, assuming the other vacuum lines are intact and the N75, check valve, and N18 are OK and plumbed correctly.

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Thanks Indigo!
To your points in blue...

I'm wondering about the line I made as well. Before the line nothing would work at all. After the line I'm getting that consistent 2-4 good pedal strokes with a working turbo, followed by no turbo and a hard pedal, then that process repeats itself over and over consistently.

The nipple really doesn't have any play. I can "spin" it but it's tough. Lateral wiggle isn't really there. Maybe it's enough to cause the symptoms I'm seeing. Seeing that originally the system "let go" all at once, I wouldn't think that the joint at that nipple would completely fail. I've seen youtube videos of the pump nipples that are bad, and mine is no where near what those videos show. But it's in the path for me to check if the replacement OEM line doesn't solve the problem

As far as the check valves (N75 and N18) they are plumbed in correctly. I removed the entire vacuum assemble as one unit, all in tact, labeled, and replaced one line at a time. I would be more prone to one of these units being bad IF the check valve in line on my home brew setup wasn't working, but I pulled vac on it and it held. If that check valve from the pump to the booster failed, then bleeding of the system would affect the brakes and turbo. Seeing that I have brake and turbo failure at the same time leads me to believe that it's a system issue ahead of the N75 and 18 units. Those components would either be the pump nipple, reservoir, line and/or check valve. The line/check valve will be ruled out of the equation tomorrow when I get it

Thanks for everyone else responses as well. This was a very scary situation when this let go on the freeway!

IndigoBlueWagon said:

I was talking about the check valve near the N75. It's all on the same system.

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Oh you're talking about the ying-yang check valve (black and white).
Yeah I verified this was holding vac as well. Yes they are all on the same system, but if the check valve on the hard line from the pump to the booster is doing it's job, a failure of the n75 (turbo) n18 (asv) or the ying yang check valve should't effect the brakes

BobnOH said:

It seems you're certainly on the right track. I know we have one check valve up near the N75, but recently someone mentioned a check valve associated with the brake booster. Do these have that?

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That is the check valve integrated into the hard line/rubber hose that connects between the pump nipple and the booster. When I made my home brew line to get me home, I pulled that line and checked it when I got home and that valve was working

Unfortunately the USPS can't figure out how to deliver parts from Portland OR, to Olympia, WA, without going through Seattle first (way north of where I live) so unfortunately I have to wait another day to update on the potential solution. I will ensure to post up what I do and results

Update

So the hard line from the booster to the pump got to me on Saturday and I was able to bounce between working on the car and the motorcycle.

Installed the hard line assembly from Cascade and a new brake booster grommet, which ended up not solving the problem. The weird thing was once I reconnected everything, the 2-4 pedal strokes and working turbo for a short time, followed by stiff pedal and no turbo, well this test it was more like 1 pedal stroke and a brief time with the turbo. The turbo always lasted a bit longer than the brakes off what little vacuum was being made.

Anyway, I pulled the vac pump, and split it just to make sure there was no damage to the internal o-ring (which there wasn't). The pump halves weren't leaking anything either. I had ordered 2 o-rings when I did this before, so I replaced the one in there.

Onto the nipple. I noticed that I could spin the nipple about the axis. Throughout the rotation, there were spots that would "hang up" or be harder to turn the nipple, then one spot was loose. In that spot, I could wiggle the nipple a bit. You could feel as you got to the spot where it was harder to turn it was compressing that internal seal more (I recall seeing a pic of someone on the forum who sacrificed an old vac pump and cut-away half of the nipple section to reveal the internals)

I reconnected everything, the 2-4 pedal strokes and working turbo for a short time, followed by stiff pedal and no turbo, well this test it was more like 1 pedal stroke and a brief time with the turbo.

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I'm thinking that maybe the inconsistencies related to the compression of that seal internally at the nipple? Ie if it was turned a bit differently it leaked differently during the testing?

Either way, I rotated it until I felt that seal getting good compression where the nipple would not rotate or wiggle. I used a chisel and a hammer and peened the edge basically "into" the flat portion that the nipple is attached to, about 16 pl eq. spaced. Just dented the material really. The nipple is solid now. I finished it up with some high temp copper used for exhaust manifold connections because I know that little pump can get pretty dang hot!
Result:



If that doesn't solve the problem I'll take a look at the vac reservoir, but from my understanding that supplies the turbo and ASV and shouldn't effect braking.
If those two don't solve it, I'm going to look at laying a TIG weld around the nipple to vac pump connection, and if that fails, it's onto the brake booster, which I really don't want to deal with.

I haven't got a chance to test yet as the RTV wants 24 hours to cure, so I'll check this afternoon.

Before I replace the Vac Pump...

Alright guys so got home today to test my nipple repair job. Of course, the way my luck has rolled, the now solid nipple that was peened and rtvd couldn't produce enough vac in the system. So with the help of another member, walked through more troubleshooting.

• We verified the new booster line to pump I bought was functioning properly. Ie check valve.
• Hooked a mighty vac directly up to the pump. It pulled vac, but VERY slow. Probably took 25+ seconds or so to build up pressure while running, about 29hg. Seemed stable once it got there.
• Hooked pump-booster line back up to vehicle. Hooked mighty vac up to nipple that supplies n75 and n18 on the pump- booster check valve. Started car. Could not get vac to build on gauge.
• Removed booster end of pump-vac line. Plugged booster end with finger, tried to pull vac from check valve nipple. Could not get it to build vac st all. I know plugging with a finger isn't a good seal....
• Buddy hooked his mighty vac to the check valve nipple of his alh pump-booster line. He pulled full 30ish hg within 10 sec or so... which included drawing vac in the booster reservoir. It took 25+ just for my pump to pull that on a short run of hose to a mighty vac ...
• Booster not hissing at all like it's leaking

.
So, am I the only person here that the nipple fix doesn't work for my vac pump??
Oh I should mention I replaced the internal o ring of the pump halves, 74 x 2.5mm. I bought a set of 2 a couple years ago, no oil leaks coming from halves, no issues with the first o ring.
When I split the halves, the was oil in the vac pump body.
Is it time to bite the bullet? I'm not sure with my peening and rtv job how this pump could have failed, I was very thorough.
Any last insight?

My vacuum pump has started to get flakey at 286k miles. I've struggled through a few of the same issues you've had, but have narrowed it down to that silly pump.

I've observed that if I wiggle the nipple around, it will affect how much vacuum it puts out. I'm also convinced that my worn motor mounts will cause the vacuum to fluctuate as there is stress between that nipple and the brake booster hose when the engine rocks.

I have not tried to RTV my pump yet, but am almost just going to spring for a new one so I won't have to mess with it for another xxx,xxx amount of miles.

djrhetoric said:

My vacuum pump has started to get flakey at 286k miles. I've struggled through a few of the same issues you've had, but have narrowed it down to that silly pump.

I've observed that if I wiggle the nipple around, it will affect how much vacuum it puts out. I'm also convinced that my worn motor mounts will cause the vacuum to fluctuate as there is stress between that nipple and the brake booster hose when the engine rocks.

I have not tried to RTV my pump yet, but am almost just going to spring for a new one so I won't have to mess with it for another xxx,xxx amount of miles.

Click to expand...

In your case It can't hurt to peen and RTV it, and save you $200...

Well, haven't gotten much response here so I called IDparts to see if anyone there had more extensive knowledge about the vac system, as most don't have to dive in as far as I have to find out the issue

Sounds like all my troubleshooting is spot on, these pump internals can wear out. I guess I'm just chalking this up to the internals failing on my vacuum pump.
I ordered a pump from Cascade German since they are only a couple days in the mail from me. Hopefully after how thorough I've been this will solve the problem. Unfortunately my case tends to be as rare as a unicorn.

I'll update again once I get the new pump installed.

I'm following. I have had the pump nipple leaking and sealed it and everything was good for 6 months. Now it is doing the same thing yours is doing except I have a weird whistle coming from the fire wall sometimes. . Hope you find the problem so I can fix my amusement park ride.

joep1234 said:

I'm following. I have had the pump nipple leaking and sealed it and everything was good for 6 months. Now it is doing the same thing yours is doing except I have a weird whistle coming from the fire wall sometimes. . Hope you find the problem so I can fix my amusement park ride.

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I hate to be a bearer of bad news, but that whistle from the firewall sounds like you have a failing brake booster, leaking vacuum.


It might be an adjustment issue, erratically applying some brake, but if you're not feeling the car dragging when you hear that, and you're not having any issues with the brakes otherwise, probably the booster warning you that it's tired and wants to go home (or to the recycle yard...)

Vac pump should get in today.

Since I replaced all of the vac lines at this point, I was trying to remove the line going to the vac reservoir, and definitely buggered the nipple the hose connects too (snapped it clean off).

So I employed a fix for now. Epoxied the nipple closed then used Copper RTV to fill the rest of the void.

Drilled and tapped the wall for a 1/8" MNPT thread. Fitting needed is a 1/8 MNPT x 1/8 dia barb

Used Green Loctite (620) on the threads of the fitting. This stuff is super HD. They recommend it for things like sled clutches assembly parts which spin up 6-7k+. It's really for press fit bearings to never come out when they are installed. Being OCD, I followed that up with some epoxy at the mating surface of the ball to fitting so I don't EVER have to worry about it leaking. Heck, I might add another fitting and run a gauge from there too.

You can use a homemade pvc cylinder or almost any small vessel that will hold a vacuum, too.

flee said:

You can use a homemade pvc cylinder or almost any small vessel that will hold a vacuum, too.

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I figured I could do that with PVC pipe, caps, and the glue. I used to landscape so used lots of the purple stuff. If this doesn't work I'll give that a try too. I like the DIY options as it's like $5 vs $45

This has been an interesting thread.

The metal nipple on the vacuum pump on the 02 ALH in my Vanagon was leaking oil (and may have been leaking vacuum). Without removing the unit from the engine, I cleaned it as best I could and applied JB Weld. That was at least 5 years ago. No oil leaks and the vacuum system seems just fine. I have a below dash mounted vacuum gauge. Vacuum generally hangs around 23 to 24 inches, depending on elevation.

The nipple on the new pump is much more robust than the OEM design and utilizes a thicker wall and a press fit application rather than just a trapping aluminum wall. That clean oil is just how the new pumps are stored apparently:



I agree this thread has been "interesting" (more like painful on my end) because none of the "go-to" fixes were making a difference. When I talked to IDparts, one of the guys there said that these pumps can wear out internally where the nipple fix won't solve the problem. Not sure if I'll split my old pump or not to see if anything is worn.

There's really no other way to test the functionality of a pump unless you can test it against a known good one on a car, which I did.

Hope this new pump solves the issue and I can move on to the next project. I'll be installing tonight so I'll report back and hopefully put some closure on this thread this evening.

I prefer to put a ring of quicksteel around the loose nipple in a vacuum pump. I haven’t seen one it wouldn’t fix yet

Problem Solved!

ktmkris said:

I prefer to put a ring of quicksteel around the loose nipple in a vacuum pump. I haven’t seen one it wouldn’t fix yet

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I had peened the edge over so it wasn't moving. I chose RTV because that pump gets wicked hot and vibrates ferociously. Figured the RTV would resist cracking.

It only took a new vacuum pump, but the issue is resolved. I started the car up and almost instantly had vac and the brake pedal was back to normal.
Went a drove it around, no hard pedal, have boost back.

So if by chance anyone is as unlucky as me and the nipple repair doesn't work, hopefully they find this thread and troubleshoot what I have...yet faster

So a new vacuum pump fixed it?
Outstanding!

The temperature on or at the vacuum pump is below the operational range of JB Weld or similar epoxies! It takes 600f to begin breaking it down. I helped a guy repair the block (crank case) on a Kohler Engine on his sawmill in 2001. That engine is still functioning today with that JB Weld on it.

If am not mistaken, the nipple has an O-ring that's obviously not replaceable.

Gland you were able to nail the problem.