ALH injection pump head seal replacement - alternative method


Veteran Member
Jan 9, 2008
Shenandoah Valley, VA
2005 Jetta Wagon; 2005 Beetle; 2004 Jetta; 2002 Golf (three of them); 2002 Jetta Wagon; 2000 Audi TT->TDI; 1999 Beetle

This past week the timing belt tensioner failed on my Audi TT → TDI. I was lucky in that the tension was not completely released and the engine stayed in time. I ordered an ALH timing belt kit from one of the supported vendors and replaced everything.

Over the past year or so I noticed that I was getting some diesel fuel around the injection pump. I figured one of the seals was failing and had already ordered a reseal kit. Since I had the timing belt off, I went ahead and replace the two “cover” seals and the head seal. I’ve done this two times in the past, so I’m familiar with the procedure. This time around the temperature outside was around 30 degrees. I stretched the head seal o-ring over the head and dropped it into the grove. I held the o-ring off the one of the two bolts holding the head in place so I could drop it in to the groove. I did the same for the other bolt.

Unfortunately since it was cold out, the o-ring hadn’t fully returned to shape before I tightened the head back to the body of the pump. As a result, I shaved the o-ring and it promptly leaked all over the place when I started the car up.

I ordered a new injection pump seal kit and thought about how I could better replace the head seal. I read through several posts here on the forum and this one from from AndyBees got me thinking:

See posts 779-780 in the above link

I figured if I used a wire to hold the cam plate assembly in place (like AndyBees did), I could remove the head from the injection pump and put the o-ring on from the other side (so I could examine the o-ring grove and the pump area for corrosion/debris). The small spacer would still fall out of place, but I could do as AndyBees did and hold it in place with Vaseline when re-installing.

First thing I did is I turned the engine over until the Distributor Plunger foot slot was facing up and center in the opening of the injector pump (the cover has been removed). In this position, the cam plate is between lobes and not under pressure. I bolted the wire to hold the cam plate in place using one of the top cover bolts. I then unbolted the head and carefully slid it out of the injector pump body. The shim stayed in the cam plate opening. I removed the shim and set it aside. Here is a picture with the head removed and the wire holding the cam plate in place:

With the head removed, I could easily put the new o-ring in the grove. I used Vaseline to hold the shim in the Distributor Plunger foot while re-installing the head in the injection pump body. Once the head was in place, I removed the wire assembly holding the cam plate and closed everything back up. I used a mighty-vac to pull fuel up through the return line and then bled each injector. I started the car up and checked for leaks. Everything looked good.

If/when I do another ALH injector pump reseal, I’ll use the method above to remove the head from the pump to replace the o-ring

Hope this helps.

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Top Post Dawg
May 27, 2003
Southeast Kentucky
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Eric, thanks for sharing your method of changing the big O-ring.

Jetta 97, I assume you've never stumbled onto one with a stuck O-ring as shown in the link Eric included with his post. That was my first time re-sealing an IP. That IP wasn't leaking, however, the engine (in my Vanagon) was a "hard starter" from the get go with only 129k miles on it. So, as a suggestion from the followers, I resealed the IP. Anyway, not over 100, but I've since resealed a lot IPs and have not found one with a stuck head O-ring.


Top Post Dawg
Aug 12, 2004
north nj
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Can’t see the picture…😕