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4-slot rubber hard line clamp on AAZ by Otis2 on 13 Jan, 2026 00:01
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Hi there.
I recently picked up a 4-slot hard line clamp for my AAZ engine, which had been missing it for some time.
In an ideal world, to resist cracking, I understand this engine needs 3 clamps: two 2-slot clamps, and one 4-slot clamp.
I had no problem up to now using a pair of 2-slot clamps for the lines to cylinder 1 & 2, and to 3& 4, but tonight I decided to add the final missing clamp.
It did not go well.
After loosening all the nuts for the hard lines and playing with them for well over an hour, the closest that I could come to having all 4 lines fit into the 4-slot clamp, was a position that forced the hard lines for cylinders 1 & 2 (or A and D on the pump if you prefer), to be damn near 2 cm away from where they should fit into the delivery valves on the pump.
I suppose I could bend and force them into that position to connect, but that would obviously work harden them.
I suspect that doing that would make them more likely to crack than if I just skipped the 4-slot clamp altogether.
Can anyone comment on the relative risk of running only the two 2-slot clamps and skipping the 4-slot clamp altogether?
I'm trying to decide whether to bend the lines to use the clamp, or leave well enough alone.
I am sure the best solution would be to replace the lines, but I don't even think these are available new for an AAZ engine any more. And a used set may be in worse shape than these ones anyway.
I will post a link to two photos on my Google drive that show where the lines have to go with the 4-slot clamp in place, and then where they would "like to go" with the clamp just resting loosely on top of them.
Thanks!
https://drive.google.com/file/d/1hhR_i8kSEYgjHZCNicDZOaoj51z6AC8R/view?usp=drivesdk
https://drive.google.com/file/d/1GH84B4cUhVEenfDwXyF1Uhi9E9OnpMf4/view?usp=drivesdk -
#1 by sgnimj96 on 13 Jan, 2026 07:34
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You'd have to bend it perfectly or the stress of fitting it in the clamp
defeats the purpose. This site says there is variations in AAZ pipes?
https://brickwerks.co.uk/news/vw-aaz-injector-lines/
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#2 by Otis2 on 13 Jan, 2026 13:50
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Thank you, I didn't realize anyone was reproducing these now!
Those look different to the shape of mine, and I guess at least two of mine are bent.
So I guess I'm in for a completely new set from them, since they are designed to fit with each other.
"In for a penny, in for a pound", in this case quite literally. -
#3 by fatmobile on 13 Jan, 2026 15:04
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Your lines look good and I'm seeing the brickworx links to be out of stock. I'm not sure where you'd get a new set.
I would probably put some rubber hose around the lines and maybe use a hose clamp or weave some wire to kind of hold them together.
Nice if they look all lined up but I don't think it's necessary. -
#4 by Otis2 on 13 Jan, 2026 23:44
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Thanks fatmobile.
I will indeed button everything back up as-is. Bending them to accommodate that 4-slot clamp introduces the potential for a very bad ending.
I emailed Brickwerks, and those hard lines are a completely new product that has not come into stock yet, but hopefully will be in stock within a few weeks.
I asked them to reserve a set for myself.
In the old car hobby, I have found that you have to buy re-pop gear when it becomes available, not just when it is convenient. -
#5 by sgnimj96 on 14 Jan, 2026 20:31
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I like fatmobiles idea about using custom rubber hose or something. You could even carefully
wrap silicon tape around a fuel line to make a rubber cushion, pia, but custom fit.
For me, rubber hose or silicone tape and zip ties comes to mind (I'm such a cheapskate)
Looking at the ALH fuel pipes, they only use 2 sets of 2-line rubber clamps, located about in
the middle of the length of the pipe.
https://www.amazon.com/Diesel-Injector-Lines-Volkswagen-1989-2004/dp/B08Y5YRHY1
Also, just a thought, the extra rubber clamps on the IDI pipes may be mostly for holding the
4-pipe assembly in position for removal and installation.
Edit: ChatGPT disagrees-
Q: Are the rubber securing clamps on diesel (IDI) injection metal lines put there to prevent the lines from cracking or just to hold the pipes together when removing them?
A:On IDI diesel engines, the rubber-lined securing clamps on the steel injection lines are there primarily to prevent cracking and failure, not just to keep the lines together during removal.
What those clamps actually do
1. Control vibration and resonance (main purpose)
Injection lines see very high pressure pulses (often 1,500–3,000+ psi).
Each injection event sends a sharp pressure wave through the steel line.
Without restraints, the line can resonate and flex at specific RPM ranges.
That cyclic flexing leads to work-hardening and fatigue cracks, usually right near bends or fittings.
The rubber in the clamp:
Damps vibration
Prevents metal-to-metal contact
Reduces stress concentrations
2. Maintain correct relative positioning
The lines are shaped and spaced very deliberately.
Clamps keep them from touching each other or the engine, which would:
Transmit vibration
Wear through the line over time
Create noise and fatigue points
3. Secondary benefit during service
Yes, they do help keep the lines grouped when removing/installing them,
But that’s a convenience side effect — not the design reason.
Important service notes (very relevant on IDIs)
Do not omit the clamps when reinstalling lines.
Do not substitute solid clamps (rubber isolation matters).
Do not mix up line positions — even slight reshaping can preload stress.
If a line has been bent “just a little,” it’s already compromised.
On many IDI engines (Ford 6.9/7.3, VW IDI, Mercedes OM-series, etc.), running without the proper clamps will eventually cause a line to crack, sometimes surprisingly quickly.
Bottom line
➡️ They are there to prevent vibration-induced fatigue and cracking.
Holding the pipes together during removal is incidental, not the purpose. -
#6 by Otis2 on 27 Feb, 2026 12:02
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Thank you for the link, @sgnimj96.
The Brickwerks hard lines came into stock recently, and I bought a complete set.
I'm very pleased, they fit perfectly together using all three stock VW clamps.
I just bled the system and ran it for an hour, no leaks.
I will keep my old lines as spares, but with the clamps in place properly now, I doubt I will have cause to need them.
Highly recommended product.
Photos of old lines beside the new ones, and the new ones in place on my AAZ engine:
https://drive.google.com/file/d/1IAT4M_9vRNXVDvNX9E2YE6dDbwbUsCYl/view?usp=drive_link
https://drive.google.com/file/d/17qoKb5Br5zj6RMgTHPeiwDm7qt1Qwe2c/view?usp=drive_link -
#7 by ORCoaster on 27 Feb, 2026 16:43
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Ahh this explains a lot about our hoarding behavior;
"I have found that you have to buy re-pop gear when it becomes available, not just when it is convenient."
I see stuff on Marketplace or CL and I just have to have it!!!! Not that I need it right now, but I am sure I will in a year or 5.
I did actually have the chance to replace a fuel line that had a micro hole in it, and it was pissing on the top of the engine and causing that cylinder to run poorly. Bad pop-off pressure is the cause.
It took me all of five minutes to walk into the shed, bring out a replacement line, and install it. My son was watching me at the time and had to shake his head. Who has replacement parts like that in their shed? He asked. I said all of us do. Because it is the way!!!!
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#8 by fatmobile on 27 Feb, 2026 21:46
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Yep, some parts for these are getting hard to find.
Glad to hear you were able to find a supply of new ones, worth the wait.