[Vwdiesel] ALH vacuum pump

S P SHERMAN spsherm at msn.com
Wed Jun 16 11:29:15 PDT 2010

Symptoms are loss of "power" brakes after long coasting times at idle. Brakes seem fine at higher engine/car speeds, but if you coast a long way say in a parking lot, the brake pedal will be hard, and no power assist. Since the symptoms appear to go away as soon as the engine is run at higher rpm for a bit, I've been assuming it is a vacuum leak somewhere that is significant at low rpms but overcome when the rpms are higher. 

I've checked the hoses and they seem OK, but might be a hard to find split...

From: tadc at europa.com
Date: Wed, 16 Jun 2010 11:00:51 -0700
Subject: Re: [Vwdiesel] ALH vacuum pump
To: spsherm at msn.com
CC: vwdiesel at vwfans.com

Loose nipple on the pump is normal... at least mine does it.  

What symptoms lead you to the vacuum leak conclusion?

When my 01 Golf developed intermittent loss of boost, it turned out that the fat hose coming off the pump had split right along the hose clamp.  It wasn't immediately obvious from looking, but when I would get "on it", the engine would move enough to open up the split and dump all the vacuum, causing loss of boost control.  

Another likely possibility is the hard plastic hose going to the brake booster.  Mine was split along the backside at both ends and probably leaking pretty good, but it wasn't obvious until I took it off.  That hose is also $$$ to replace with OEM, but I just used a similarly-sized rubber hose, and it seems to work fine... however others have argued that it "could" collapse and cause loss of brake boost.  

On Wed, Jun 16, 2010 at 10:42 AM, S P SHERMAN <spsherm at msn.com> wrote:

My '00 Golf has a vacuum leak somewhere. I've done a quick inspection of the vac lines with no obvious culprits. One thing which I found that seems suspicious is that the  nipple on the vac pump itself is loose (the one the main vac lines goes on); it rotates and has some wobble where it enters the case of the pump.

My question is, is this normal? Shouldn't the nipple be tight on the pump body? And if it is not right, does this nipple screw into the pump body or can it be tightened again?


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