Advice please? Failed small diameter coolant hose

[Jeffoir]

Friends,
Could I have some advice please?

The 2013 D4 low coolant warning came on.
lost 2 litres of coolant
after thorough examination, I tracked the source of the loss, to a perished small diameter coolant hose
the perished hose is a short length one on the driver’s side. See photo. You can see the orange coolant in engine block end hose connector.
It runs from a tee-piece on the coolant cross-over pipe, down to the engine block, just below the fuel manifold that delivers to the injectors
MY DILEMA is that the barbed hose tail fittings at each connection point are different diameters
the barb at the engine Block is 21mm diameter
the barb at tee piece is 18mm
a 19mm hose fits one end and is too large for the other end
a 16mm hose has same problem, different ends
DOES ANYONE KNOW WHAT THE SOLUTION IS TO FITTING A REPLACEMENT HOSE PLEASE?
Thank you. 191428

[BradC]

When I ran into a similar dilemma when bypassing the aux fuel cooler radiator I took 2 hose nipples of appropriate size and silver soldered them together. Then just used 2 different sized hoses.

Don't try and fit a single size hose on, it'll end in coolant loss. Either make up an adapter or source an appropriate replacement hose.

[shanegtr]

Silicone Hose Reducer Str (https://aeroflowperformance.com/af9201-075-070-silicone-hose-reducer-str)
Silicone Hose Reducer Str (https://aeroflowperformance.com/af9201-085-075-silicone-hose-reducer-str)

[Jeffoir]

Thank you Brad and Shane,
I ordered the genuine hose part from TR Spares -Sydney. Same day delivery. . 191455
you can see the hose in the red circle in the diagram.

I removed the short hose from the Tee, as replacing the entire cross-over assembly was more work than I wanted to do just now.
the hose ID is formed to fit at each end. It went on perfectly after softening in very hot water. The assembly comes with constant tension hose clips.
topped up coolant and bled the system. All good.
Just driven to Central West NSW. No leaks.
WHAT DID I LEARN?

I don’t know exactly why the hose failed, but I suspect a very, very small diesel weep, some months ago, at the injector manifold closest to that hose, may have contaminated the rubber and weakened it. ??
The root cause of that was the replacement of the head inlet manifolds, as preventative maintenance prior to expedition. The Injector feed is a “crush fit” and needed the smallest extra tightening.
I learnt that this hose damage could not be fixed reliably with silicon tape. The hose had become the consistency of sponge-cake. A repair would fail.
So, to go forward, it had to be replaced
so, for expeditions, check all hoses VERY thoroughly and carry a length of 3/4” hose and the reducer that Shane has posted in previous post #3. Joiner nipple to suit with hose clips. The bottom end hose disappeared on hose extraction. Very small work space
i will buy the special hose clip pliers. $40 Toledo at SCA
All those hoses are 10 years old now. I think a preventative, scheduled replacement may be in order
if diesel contaminated a rubber coolant hose…then replace the hose

safe travels Comrades.
best, Jeff