Vacuum Pump or brake booster ?

Okay, (2003 beetle alh)so the brake pedal gets very stiff after a few uses. I hooked up a vacuum gauge and it shows the vacuum dropping off rapidly after the brake pedal is released and it slowly builds back up to about 25hg. Now if the pedal is pressed hard and released repeatedly by about the 4th release the vacuum gauge is near zero and the pedal is a stiffy. The vacuum will slowly build back up and I can repeat the process. I hooked up the vacuum gauge to the tee off of the main booster line and have both n18/n78 disconnected and plugged. If I shut off the car it will hold vacuum (30 mins and no change)

This to me leaves two items, the booster or pump. Is there a way to test either ? I did the same test on my golf and the vacuum never dropped, and when I created a leak and plugged it up the vacuum recovered twice as fast and to 30hg.

The vacuum pumps dont crap out very often.
Check the hard plastic tube that goes from the vacuum check valve to the booster. They are notorius for cracking right at the barb fitting they attach to.

If there was a leak, wouldn't it have lost vacuum while sitting, engines off ?

Bkcorso said:

This to me leaves two items, the booster or pump.

Click to expand...

There is a third item, a vacuum leak you haven't found yet.
Test each branch the same way you tested so far, after the N75 and N18 and then test them.
Sorry if you already did this.

Well those items are blocked off from my current testing. I'm trying to remove as many variables as I can to help isolate the problem. If the problem disappeared after removing both N18/N75 from the system then I would continue with testing down those avenues.

Roger that.
It's time to just isolate the vacuum pump and see if it gives full Vacuum.

It could be that the nipple on your vacuum pump is loose allowing air to enter when the engine is running. When the engine isn't running there isn't any vibration to vibrate the nipple and cause air in leakage. You can check if the nipple is loose by gently pulling up and down on the rubber hose/nipple going into the pump. If you have movement, you know there could be potential for air in leakage.

As a preventative maintenance item and as part of your trouble shooting effort, I would go ahead and remove the black rubber line from your vacuum pump nipple. Remove the vacuum pump, and clean the nipple area really well with brakeclean or similar spray cleaner. Once the area is clean, use a ball peen hammer to gently tap around the cast aluminum that holds the nipple in place. This should stabilize the nipple mechanically. Once that's done, clean the nipple area again really well, and apply some UltraGrey RTV to the nipple base. Once the RTV cures you will now have a mechanically stabilized and leak free nipple connection. This may or may not fix you issue, but is certainly worth doing especially since these TDI's are aging. You will also need a new vacuum pump to head seal when you remove the vac pump FYI. Let us know how it goes.

..

I have the same problem you describe, i also think that the nipple on the vacuum pump is the culprit as i have heard it leak before... There was a whistle noise coming from the engine bay, i wiggled the hose and it disappeared.

The new replacement pumps come with a solid nipple, so it's not a problem to glue it... I've also heard that the seal from the oil filter is a perfect replacement and is thicker than the one for the pump


Sent from my BlackBerry 9300 using Tapatalk

cr4zy3lgato said:

I have the same problem you describe, i also think that the nipple on the vacuum pump is the culprit as i have heard it leak before... There was a whistle noise coming from the engine bay, i wiggled the hose and it disappeared.

The new replacement pumps come with a solid nipple, so it's not a problem to glue it... I've also heard that the seal from the oil filter is a perfect replacement and is thicker than the one for the pump


Sent from my BlackBerry 9300 using Tapatalk

Click to expand...

I'm not sure if the new vac pump nipples are of the same cast as the rest of the vac pump body or not now. I know the old ones were two piece as far as the vac pump nipple goes. Over time, the aluminum that was pressed down around the nipple base gets loose from engine vibration etc. and causes air intrusion usually reducing the maximum vacuum output seen by the brake booster, and other controlling solenoids. A new vacuum pump is seldom needed as the old ones can be refurbished to meet original design output. You are correct, the separate vacuum pump halves do have an "O" ring type seal that can be replaced. They become brittle and plastic like over time. The BRM engines oil filter housing "O" ring can be used effectively as a replacement. The vacuum pump contains two distinct seals-one that seals the two vacuum pump halves together(BRM "O" ring), and the "P" shaped gasket that seals the vac pump to the head.

As far as the vac pump nipple is concerned, I personally avoid ridgid glue like epoxy etc. for this application. Once you gently tap the aluminum around the nipple base and solidify it, and clean the area the UltraGrey RTV will seal it really well. The RTV allows flexure of the assembly-so over time when the vac pump nipple base becomes loosened the RTV will allow flexure while still retaining a seal. With that said, others have used JB weld and have had no issues- although over time those may crack and fail. I preffer the flexible joint method myself. FWIW

I went ahead and swapped out the vacuum pump and booster hose from my Golf which was working great and the symptoms did not change one bit, so that leaves me with the brake booster unless I'm missing something very obvious.

Vacuum Pump to Brake Booster Line

Howdy! I need to replace the Vacuum Pump to Brake Booster Line. It looks like it just pulls straight out from the brake booster and has a simple clamp on the other end going to the vacuum pump. Is that correct or is there a trick I need to know about to replace it?
I've already replaced all of the other vacuum lines except the one going to the EGR vavle, pulled the intack and exhaust manifolds with the turbo and cleaned all of them. Still getting a vacuum leak and discovered someone has used some RTV on this line at some point to seal a 1.5 in crack.

d2305 said:

http://idparts.com/catalog/product_info.php?products_id=785

Click to expand...

The vacuum pump to brake booster line is $40 at IDparts. Is that about the best price you will find for it?

Long shot, but something to look at. The o-ring between the master cylinder and the booster...

Sorry to bump this again but just had a very interesting read!

I have this exact problem - not sure if its booster or pump.
I bought a second hand pump and fitted it & still pedal went hard within seconds.

I hear a loud hiss when pedal is pressed (louder than usual, clear leaking sound) which would make me think its booster, however nipple on pump is loose too.

Did anyone find their problem?
Thanks in advance

Bump, curious if problem is nipple on vacuum pump as well.

josh8loop said:

It could be that the nipple on your vacuum pump is loose allowing air to enter when the engine is running. When the engine isn't running there isn't any vibration to vibrate the nipple and cause air in leakage. You can check if the nipple is loose by gently pulling up and down on the rubber hose/nipple going into the pump. If you have movement, you know there could be potential for air in leakage.

As a preventative maintenance item and as part of your trouble shooting effort, I would go ahead and remove the black rubber line from your vacuum pump nipple. Remove the vacuum pump, and clean the nipple area really well with brakeclean or similar spray cleaner. Once the area is clean, use a ball peen hammer to gently tap around the cast aluminum that holds the nipple in place. This should stabilize the nipple mechanically. Once that's done, clean the nipple area again really well, and apply some UltraGrey RTV to the nipple base. Once the RTV cures you will now have a mechanically stabilized and leak free nipple connection. This may or may not fix you issue, but is certainly worth doing especially since these TDI's are aging. You will also need a new vacuum pump to head seal when you remove the vac pump FYI. Let us know how it goes.

..

Click to expand...

Excellent advice.
Just wanted to add.... I first remove and clean pump, then I use a socket that fits over the nipple to crimp/peen the aluminum around the nipple tight again ,one or two firm but not too hard taps with a hammer usualy does the trick.
Then make sure and clean everything with a wire brush and brake clean and JB weld over the joint.

d2305 said:

http://idparts.com/catalog/product_info.php?products_id=785

Click to expand...

That was the culprit on my car. I used two layers of heat shrink over the cracked plastic hard line and it worked very well. However...

maxmoo said:

Excellent advice.
Just wanted to add.... I first remove and clean pump, then I use a socket that fits over the nipple to crimp/peen the aluminum around the nipple tight again ,one or two firm but not too hard taps with a hammer usualy does the trick.
Then make sure and clean everything with a wire brush and brake clean and JB weld over the joint.

Click to expand...

I did have a leak at the vac pump nipple too. I used brake cleaner to clean it up, scuffed it with a wire brush, and dabbed on gray RTV. Worked like a charm and I had plenty of vacuum.

I'm reviving this one cuz it's great advice. I found the vacuum pump nipple to be loose on my car. I tapped the aluminum with a hammer to snug it up and put some black RTV around the fitting. I'll see how it holds up.

josh said:

I'm reviving this one cuz it's great advice. I found the vacuum pump nipple to be loose on my car. I tapped the aluminum with a hammer to snug it up and put some black RTV around the fitting. I'll see how it holds up.

Click to expand...

Josh, any update on your repair?

mrrhtuner said:

Josh, any update on your repair?

Click to expand...

I'm not Josh, but I did the same repair last winter with the vacuum pump nipple on my 03 Golf. I've put 46,000 kms on the car since then and it has been fine.

It extends the life of the pump, and only costs you a tiny bit of RTV. Wouldn't hurt to change the vacuum pump seal while you have it off of there for the repair...they're cheap.

Rembrant said:

I'm not Josh, but I did the same repair last winter with the vacuum pump nipple on my 03 Golf. I've put 46,000 kms on the car since then and it has been fine.
It extends the life of the pump, and only costs you a tiny bit of RTV. Wouldn't hurt to change the vacuum pump seal while you have it off of there for the repair...they're cheap.

Click to expand...

Thanks man,

Mind me asking, where did you tap the vacuum pump at?

Was it in this red section?

mrrhtuner said:

Thanks man,
Mind me asking, where did you tap the vacuum pump at?
Was it in this red section?

Click to expand...

Yes, that is correct. I put the pump in the bench vise (with soft jaws) with the nipple pointing straight up. Using a hammer and punch, I tapped that aluminum rim IN towards the nipple in 4 places. The nipple becomes nice and tight. Then clean the area with brake cleaner, and apply RTV silicone to seal up the remaining gap. I taped it off...to be neat and tidy...lol, and then put a good layer of RTV on it.

The only thing you have to be careful with is, don't punch the lip too close to the edge or it will crack the cast aluminum. Just be kind of gentle if that makes any sense.

Hope that helps.

Let's get to it.

Does anyone have a number for normal vacuum range?

Other day I saw some type of redesign on the pump of our cars. It actually had a threaded nipple vs the pressed in or whatever you would call the originals. My car we sealed it up with silicone on the outside and all is well. I've always read 25 is a good number to have for vacuum on our cars. Don't know what the design spec is in optimal conditions.


Sent from my iPhone using Tapatalk

where can i get the o ring for the pump. Thinking about replacing that while im in there.

03 TDI

joncfinney said:

where can i get the o ring for the pump. Thinking about replacing that while im in there.

03 TDI

Click to expand...

Just about any site-supporting vendor here will have them. Probably not much at the dealer either. Pretty much should replace it whenever you remove the pump: leaks from here can get kind of messy.

is there some sort of interval this seal should be replaced or dont do it unless it is actively leaking?

AnotherPerson said:

Other day I saw some type of redesign on the pump of our cars. It actually had a threaded nipple vs the pressed in or whatever you would call the originals. My car we sealed it up with silicone on the outside and all is well. I've always read 25 is a good number to have for vacuum on our cars. Don't know what the design spec is in optimal conditions.

Click to expand...

Where did you see this?
Link please.

Rich W.

Vacuum Pump O-Ring

joncfinney said:

where can i get the o ring for the pump. Thinking about replacing that while im in there.

03 TDI

Click to expand...

If you are speaking of the o-ring that is between the two halves of the pump, the oil filter o-ring from a BRM is the perfect size. The size is a 74mm x 3mm. A new o-ring from an ALH is 75mm x 3.5mm and is too thick, I did not try a used one as mentioned above. Due to the fact there is "no rebuild kit" available people used to just throw them away; my vacuum pump was down to 11" of vacuum, I replaced the o-ring and the vacuum went right back up to the 24"-25" vacuum range.

The nipple on mine was a bit loose as well but I tapped it tight before I changed the o-ring and for me it made no difference vacuum-wise.