Brake system vacuum system leak - need help finding it

Hi all,

I have a 2005 Passat B5.5 1.9TDI. I'm experiencing some brake issues exactly as discussed in this thread:

https://forums.tdiclub.com/showthread.php?t=162913

I lose vacuum boost after a few brake pedal pumps, so i've deduced that there is a leak somewhere. Unfortunately I can't hear any air leaking into the system, but I have found a 'loose' hose where the vacuum hose meets the vacuum pump. There is visible play where this hose meets the metal housing of the vacuum pump so I thought this would be a good place to start.

In order to investigate, I cut off the factory pressed clip with the intention of measuring the short section of hose so i could replace it. The whole piece can be bought online but the harder vinyl hosing which goes towards the brake servo seems in good condition so I only wanted to replace the small piece of rubber hose right next to the vacuum pump.

However, after removing the clip I realised that the play is actually from however the hose is connected into the vacuum pump. It seems like the hose is clamped onto a metal insert. I reattached the hose with a clamp and left it.
Can someone tell me if this is normal/a problem? If it's an issue and a likely source of my vacuum leak, how can I tighten it up?

Unfortunately having trouble uploading photos - the pics website is not recognising my login details so I can't upload a photo, so here's 2 links to them:

https://photos.app.goo.gl/TJT3y2TJjRvBWNfcA
https://photos.app.goo.gl/kumDEaEkaUsdoRS7A

Thanks in advance!

that hose connects to the tandem pump and where it connects the hose is usually soft, the pump provides brake boost. I always replace the hose and coolant flange under the pump. One of the members found a ball Bearing inside the pump which became frozen, result, no boost

Here is a thread in which the original poster complained about the same issue on a 2012 Jetta. He connected a vacuum gauge to the system and found out the connection between the vacuum pump nipple and the hose is leaking when he moves it. I would just wash the hose and the nipple in a solvent and reassembled with a small amount of silicone, then let it cure for 24 hours, and be done with it.
http://forums.tdiclub.com/showthread.php?t=503628

OK great, thank you.

I feel like dissembling the vacuum pump to check for frozen ball bearings might be a job too far for me. But I'll happily clean up and reattach the hose.

Can anyone tell me how that hose is connected to the pump? I tried pulling it to no avail, I should just pull harder?

Also, could you recommend a silicon product to use? I work in construction so to me silicone is caulk sealant, which I definitely wouldn't use in an engine bay?

I believe the hose is just slipped over the nipple, but I cannot confirm that as I no longer own the Jetta I used to drive. It may really be that you aren't pulling hard enough. As for the selection of silicone - I do not know what is available in France, but here in the US, the most commonly used brand of silicone compounds for automotive applications is Permatex. They come in several colors, depending on the applications. What you need is something that has good resistance to oil because that is the only medium the silicone will come into contact with in that location. Those caulks you are using in your profession are formulated to resist ozone, water, molds and other environmental conditions, so they may not be the optimal choice for your need. A 100g tube of quality automotive silicone should not cost more than $5.