On the 1984 300DT, I'm thinking the interior diameter of the rubber hose going from the auxiliary water pump to the block is 5/8" on the auxiliary water pump side and 3/4" on the engine block side??

I need to replace this hose so trying to find the correct size and fit. All input is appreciated!!

This help?

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Yes, but it doesn't tell the interior diameter. I'm thinking it is 5/8" on the recirculating pump side and 3/4" going into the thermostat (it looks like the thermostat on the drawing....)??

It's $14 at the dealer. Does it really pay to hunt for a generic replacement?
https://www.pelicanparts.com/cgi-bin/ksearch/PEL_search_2016.cgi?command=DWsearch&description=1238329194

(What are the odds that this hose is sized in inches?)

That heater hose for 1985 california is NLA.

The inner diameters of a hose removed from said car measures ~22mm at pump housing and ~15mm at aux pump.

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85 CA 300D

Silicone Heater Coolant Hose 5/8" 16mm. that is the text from an ebay ad. Silicon hose can stretch more than rubber hose. It is likely auto speed shops have it.

There is also plastic or nylon coupling/union that have one size larger and the other end smaller and you would use 2 lengths of hose that are different inside diameters.

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84 300D, 82 Volvo 244Gl Diesel

It is routed that much different that one year?

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Current Diesels:
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