To find leaks you may need to get a Flashlight with a strong beam and a Mechanics/Dentist type Mirror so you can see it.

It has been unusually cold out here in S CA and I have found 2 cases on My House where the Faucets that did not leak during the day were found dripping a bit in the Morning. Tighten the valve more stopped it.
I think that was because the rubber washers shrunk a little in the cold. Old inelastic Hoses could also shrink.

There is 3 Hoses. The Upper Radiator Hose, the Lower Radiator Hose and the Bypass Hose wich is only about 2.5 inches long.

When I first got the Car in 2007 the Bypass Hose area was seeping. I decided to change all 3 of the Hoses.

For the Bypass Hose I also removed the Upper Housing it was attached to. I did not have issues with breaking Bolts that is common when removing any of the Coolant System Bolted on Parts.

However, what I found is that I had deep corrosion/pitting under the Hose with the pitted areas being full of that powdered corroded Aluminum. Being sort of a powder it of course leaked in the case of the Bypass Hose.

I wire brushed out all of the white corroded area and or scraped it down to the bare Aluminum, degreased with Brake Cleaner and filled in the low spots with the long curing JB Weld as it can take the temp.

In order to contour it I taped over it.

After it cured and the tape was off I had to fill in some recesses with more JB Weld. When that cured I filed and sanded it down so the Hoses would seal.

Where the Upper Radiator Hose made contact with the Thermostat Housing was also pitted but not as badly.

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84 300D, 82 Volvo 244Gl Diesel