I had a length of 19mm hose (Gates) and managed to get them over the matrix pipes (heated in boiling water and some soap).
Or pre-stretch it a bit with a 13mm socket (½" drive) which is outside dia 19mm and 22mm at the drive side.

Well, as you've done it Tony, it obviously can be done, but I'm not up for the degree of shoving/ twisting required. My suspect O rings would definitely not thank me for it. I'm treating those solid pipes to the matrix with ultimate gentleness. I'll be patient and wait for the 100mm of 22mm bore pipe that I need, to turn up in a day or two from the bay.
Pirtek locally would have sold me a metre for £30 plus. None of the local motor factors have it.
I've been known to be a bit mad with the cash occasionally, but £30 for 4 inches of pipe? Not even me!

In that you are very right Mark, sometimes my imagination brings me to solutions which not always are the safest.

At last! Hose arrived, cooling system re-assembled. Time for pressure/ vacuum test and refill now...

Do-over time! Whilst digging into the centre console/ under dash to remove bodged in wiring and replace gear selector cable, found a telltale drip under the heater matrix O ring.
Bugger- so I did disturb it, despite being hyper careful putting on new hoses.
Oh well, at least I had most of the bits off to get to it anyway..

Time to get the dash out and bottom it :)
I'll try not to sound too smug or something else will drop off....

Reckon whether 19mm pipe will fit over 22mm pipe will depend on brand of pipe. I have various types of coolant pipe and find the better branded / thicker walled stuff tends to be less flexible than cheaper stuff. Would think if you've got to force pipe so hard to stretch, that can't be great in terms of potential future failure point either.

A lot of vehicles that use 19mm heater hose have a small section that flares out to maybe 22mm where it connects to engine / firewall fittings, could simply go to a scrappies and cut some from a relatively new engine bay to save that £40 (for a metre of hose, really?), this would be a solution to 22mm to 19mm pipe in 4 inches if that's a problem, though I suppose you'd have to weigh up pros and cons / longevity with the stuff I refer to being only thin walled. Does the 22mm pipe need some adaptor to 19mm anyway?

Simon

Now you've got the drip, just take the dash out, free up the heater box flaps, and whack an audi heater core in... then it's 19mm pipe straight thru to to engine connections.

Martyuk wrote:

and whack an audience heater core in...

Predictive text strikes again..... Or, rather than spend a fortune on 22mm hose, why not buy a replacement genuine hose that flares out to 22mm at the end and chop off the end 4 inches?

Edited... yep.. stupid predictive text.

I'm thinking I'll go with the audience heater core :)
Now have lots of 22mm hose- bought off the bay, but...
...getting the old pipes out was such a faff I don't want to go through that again!
O rings were solid, rectangular and crusty and would have completely failed soon.
Now to have a hunt for the Nissens part number for the Audi, which I know Marty posted on here somewhere...
Gottit 70230. Should be here Wednesday.
Gives me tomorrow to sort starter motor on blue one, which clicked for the last time when trying to drive back from workshop. Had the deep joy of taking old one off, outside workshop, in the dark. Thread came out with top bolt. Now 2 disabled P38s and a walk home :(

Did I mention the toasty hot air in The Duchess?
Without the cheque book symbol the HEVAC Unit looks bare with just AUTO and two temps illuminated. :smugface:

Seriously, for the piece of mind - you won't regret using Marty's heater core mod. But you might swear at the centre rail that fits in front of the heater box...

But you might swear at the centre rail that fits in front of the heater box...

Why's that?

Because it can be a bit of a bitch to get out, and more so to get back in again....

But it is doable without too much bending of the dash... I slacken off the 13mm nuts on the studs in the footwells (closest to the centre of the vehicle) to give a bit more wiggle room.

Just make sure you have the wiring looms in the right place on reassembly, because trying to get them past the center brace is curse inducing - and best avoided if possible...

But that being said, it sounds more difficult than it is most of the time!

My sympathies, Orangebean. Been there, done that. Must pay homage to the long Posidriv # 2 (screwdriver)!

Re centre rail, I find the easiest way to get it out is to take the skuttle panel off, and unbolt the top part of the metal framework on the passenger side. That gives plenty of flex room to get the bar out. Getting it back in is a little harder, for whatever reason, but just line stuff up on the drivers side and have someone hang off the framework on the passenger side whilst you slip the cross piece in place.

I may have to eat my words re matrix, I don't think these o-rings will ever seal on mine.
How well does it fit in the heater matrix slot?

Slots in like a glove. The rib in the centre of the heater box needs to be removed as the end tanks on the audi core are a little bit bigger than the RR one - but easy to do if you have the heater box apart to free up the flaps, or if you aren't splitting the heater box then generally a couple of taps with a sharp chisel does the job.

The Nissens cores come with some sticky backed foam, which a wrap of that around both ends seals up the box pretty well and stops it from moving in the box. 4 x 5/6mm holes drilled in the flange at the opening end and a couple of cable ties keeps it from coming out.

When you have the heater box out, actually fitting the core is probably quicker than it's been for me to type this up!

I'll second Martys views on the Audi fit. Easily done. Bit of easing metal aside. You may need lots of lube to get hoses through bulkhead grommets or maybe I just had thickwall tube.