ALH leaking vacuum pump

**Status update**
So, it would appear that the vacuum pump is NOT the problem at all, but rather, the bearing cap / valve cover interface.
I made sure I had a good coating of Dirko RTV (boraparts recommendation for replacing the oil pan) at that place where I had the sputtering oil, gave it 24 hours to cure, and sure enough - no more leak.
Being that the valve cover didn't leak before....and it leaks with another valve cover I have sitting around....that would mean the bearing cap doesn't have quite enough height to it to properly seal with the valve cover....?
(Brand new head from Franko6 - which I was told over the phone was "OE"....but when I got it, turns out it's an AMC head. )
Or am I missing something?

Did any one try these Viton o-rings?

3mm X 74mm V75 Viton O-ring Black

I have a ALH in here that is only making 12" of vacuum. I guess I will give this a try, before I make the customer spend a whole bunch of money.

You might have a loose nipple. I take a punch and peen the rolled edge in a couple of places then apply a glob of RTV.

The main body o-ring will not impact the vacuum output (output? vacuum?)

runonbeer said:

You might have a loose nipple. I take a punch and peen the rolled edge in a couple of places then apply a glob of RTV.

The main body o-ring will not impact the vacuum output (output? vacuum?)

Click to expand...

Sorry to bring up this old thread, but do you punch the section in red?

Here is a simple drawing showing a section through the nipple. During manufacture, the nipple is set into its hole, then the lip of the hole is rolled over to secure the nipple.

As the engine rocks back and forth during acceleration and deceleration, the booster hose tugs on the nipple. This, over time, pulls the lip up slightly and you get a loosey-goosey nipple. Whatever seal is underneath the nipple will tolerate a bit of looseness, more than that and you get a vacuum leak

The pump needs to be off the car as you just can't get good access with a hammer if it's on the car.

Chuck it in a vise. Don't clap the vise on the area where the o-ring goes, you don't want to mar that surface or you could get a oil leak.

Take a punch and put it on the edge of the lip, parallel to the nipple as per the red arrow. Give it one good whap with a hammer. Go around the lip with the hammer and punch, I do 10 or 12 hits all around the lip.

Thank you Todd, I'm a more visual learner so that helped greatly!

I've been having bad luck resealing these pumps. I'm pretty sure the o-ring I'm using is just a little too fat. Sometimes I put them back together and they only make like 10-15 in Hg. Worse than before.
So I think that the size of the main body o-ring can affect vacuum output.

And as far as peening over the roll on the nipple, sometimes they just end up cracking.

I'm thinking about trying fiberglass here but that seems likely to crack as well particularly if you get the hardener mixed in a little too hot such that you have a brittle resin.

A real solid solution would be to mill out the rolled lip, remove the nipple and the crispy shrinky-dink o-ring on it and then TIG it back onto the body.
Once you have paid someone with these skills, you might as well have bought a new one for $200. Although the pierburg pumps I'm getting look like half the case was cast in a high school class on aluminum casting. Very poor quality appearance. I have yet to buy a genuine VW pump to compare and they list for about $330 which isn't that bad considering you probably have gotten at least 200K miles out of a pump before it starts to fail.

I had the same experience. Maybe the o ring store (linked above by 4 ring king) would have a thinner one that might work.

runonbeer said:

I'm thinking about trying fiberglass here but that seems likely to crack as well particularly if you get the hardener mixed in a little too hot such that you have a brittle resin.

A real solid solution would be to mill out the rolled lip, remove the nipple and the crispy shrinky-dink o-ring on it and then TIG it back onto the body.
Once you have paid someone with these skills, you might as well have bought a new one for $200.

Click to expand...

One of the thoughts I had was to drill a hole in each side of the aluminum neck around the nipple, and thread them so that I could put a couple short stainless set screws in there to hold the nipple tight. I would still be putting the RTV silicone on there as a final seal anyway...so as long as the nipple was tight, the rest should be an OK fix.

What's wrong with plain old RTV around the nipple base? I used it and had no problems afterwards...

Yuri

I've never looked, so I'm just tossing this out in case no one has ever though of this approach- can one tap some threads there and install a threaded nipple (sealed appropriately of course)? Is there just no meat underneath? (might be able to get someone to fab up a better solution? could be cheaper than a new pump)

Or machine a aluminum nipple and weld it in the hole. I have a lathe and an aluminum welder and a "supply" of used or "bad" pumps, so maybe I should tool up.

Send in five loose pumps and get one fixed one back, or just get cash for what you send in? Or something like that.

Richard take one of those nipples out and look at it. I think it has some guts to it that may or may not be important.

If I were going to take the weld approach I'd want to have the rolled portion of the case milled cleanly away. Then it would remain to be seen whether the old nipple could be used or if it would be necessary to create a replacement piece.
If the latter, it may be possible to make it a press fit without required welding.

Then of course we also need to find the suitable size for the o-ring between the case halves.

I'm afraid though that some of these pumps that make weak vacuum suffer from wear on either the inside of the case or on the plastic "vanes" that scoop around in there. This would pretty much render them useless and would compromise the potential core exchange deal. I'm just thinking that since pierburg sees fit to use a new inner case half (albeit poorly built) then there must be a reason why. The outer case half of every pump I've gotten looks like a "recycled" piece.

CoolAirVw said:

I had the same experience. Maybe the o ring store (linked above by 4 ring king) would have a thinner one that might work.

Click to expand...

I have a local source for viton o-rings that I use for my special size BRM turbo inlet seals (which are also probably too fat. Very difficult to install but 100% effective at stopping the oil leak that ruins the heater hoses). Also use them for PD & CR charge pipe seals, ALH EGR seals & pump head seals.

It will be mid January before I'm back in the shop but I'll take an open vacuum pump over there and see if one of their techs can help select the correct size.

runonbeer said:

Richard take one of those nipples out and look at it. I think it has some guts to it that may or may not be important.

Click to expand...

probably a one way check valve, but I could probably build that into the nipple.

Well I have a bit of an update but I'm not exactly thrilled about it.

The good:
a 74mm x 2.5mm seems to seal up the case halves better than the 74x3 did. 3mm was too fat. Pump makes good vacuum with a 2.5mm o-ring in it.

The bad:
The loose nipple is still a problem and there isn't much you can do about it. Can't really weld it because the one way valve inside is plastic and it would just melt.

The ugly:


I used some bondo. I also did a second pump with regular fiberglass mat and resin. They're both ugly. I'm not sure if this stuff will just crack or melt or catch on fire or what.

I put the bondo pump on a customer car and I"m going to put the resin/mat pump on my car. The bondo is definitely faster than the resin but only by a couple of minutes and I could probably cut the mat in a smarter way to make it easier. I basically cut a bunch of ~1" strips and punched a hole in them then laid them over the end of the nipple.



Not sure if I really want to keep walking down this road.

I have some more pictures but the tdiclub pic server is being weird and I don't have time to mess with it right now.

My sample size is substantially smaller than yours, but... RTV seemed to work on my car...

Yuri

Wondering, runonbeer, how durable that o-ring is and what it is made of. Tried the BRM (IIRC) oil filter o-ring and that lasted about 20 miles if that. Got a pump here on the shelf needing an o-ring.

I used 100% silicone on the 0 ring and tightened it back up,but won't
be able to tell if it worked till the swap is done. The nipple on my pump is super wobbly also,I would think that "Quick Steel" would work great.

Quick steel/JB Weld etc usually just cracks. The bondo and fiberglass have a fighting chance because of the reinforcement. It's like rebar in concrete. Like I said, I'm not in love with the idea. Just trying something.

O-ring is viton. "V75" compound. The same material as the pump head seals I use. The 3mm seal is too thick. Doesn't allow the case haves to fully close against each other.

And yes I have used RTV also. Semi-satisfactory results with that

Peanut butter! Um, no, that wasn't it (the first thing that came to my head here- well, I'm hungry maybe that's why). Any chance that furnace duct tape, the real stuff, could be employed in any of this? I know that that stuff is stickier than all get-out and that it does a really good job of sealing. How one molds it is whole nother issue.

Honestly, since this seems to be something that's difficult to resolve, I'd just look at buying a new one and be done with it. It lasted some 200k miles, 200 for a replacement it's that terrible. Sometimes as cheap TDI owners, we must spend the money saved on parts

mrrhtuner said:

Honestly, since this seems to be something that's difficult to resolve, I'd just look at buying a new one and be done with it. It lasted some 200k miles, 200 for a replacement it's that terrible. Sometimes as cheap TDI owners, we must spend the money saved on parts

Click to expand...

Well, that's just the thing though...it's not really difficult to resolve. I did the center punch trick with the vac pump on my 03 Golf, and then sealed it up with a skim of RTV, and it's been fine. I've since put 55,000 kms on it, and the nipple still isn't loose.

I'll admit to being cheap...on some things. I'd just hate to spend $200 on a replacement vacuum pump when all that is wrong with the old one is a loose nipple that can be fixed pretty easily.

I will be fixing the vacuum pump on my Beetle this weekend. The nipple in that one is really loose.

You can buy a new pump but as I said before with the aftermarket pumps the inner half of the case is poorly cast. My helper has a peirburg pump on his motor and it leaks.
So if you're going to spend money on a brand new one, I'd buck up for a genuine pump. That is definitely the best fix.

The o-ring store in Lewiston, ID has the 2.5mm by 74mm viton v75 o-rings (no minimum order) to reseal the vacuum pump. Indeed, it seems to fit quite well and the halves seat together perfectly. So far no leaks and vacuum is 24" Hg. We shall see how long it will lasts.

boertje said:

The o-ring store in Lewiston, ID has the 2.5mm by 74mm viton v75 o-rings (no minimum order) to reseal the vacuum pump. Indeed, it seems to fit quite well and the halves seat together perfectly. So far no leaks and vacuum is 24" Hg. We shall see how long it will lasts.

Click to expand...

Is that local to you? if it holds fine I'd love to order a few or try to find some locally.

Keep us posted.

boertje said:

The o-ring store in Lewiston, ID has the 2.5mm by 74mm viton v75 o-rings (no minimum order) to reseal the vacuum pump. Indeed, it seems to fit quite well and the halves seat together perfectly. So far no leaks and vacuum is 24" Hg. We shall see how long it will lasts.

Click to expand...

Just out of curiosity, why did you need to reseal the pump? Did it start leaking or did you take the pump apart for some other reason?

mrrhtuner...you should be able to buy them locally without any trouble. I may grab a couple myself for the VW spare parts bin...as soon as I find out why they're needed. If they fail at some point, then fine, I might as well have 'em.