What is the nipple size of the fitting at the block by the oil filter that goes to a moulded hose that goes into the firewall to the heater? TIA

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Metric

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

What size metric?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Its about 16 or 17mm, closer to 5/8" rather than 3/4".

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

Thanks. I measured the steel pipe at the aux coolant pump to be 0.720" which is 18 mm. I assume the nipple on the engine is also 18 mm. A brass Pex tee from Lowes is 0.665" which is 16.9 mm. I am going to use the Pex tee and 5/8 hose to tee into the coolant system for my vegi conversion. Do you think I'll have trouble getting 5/8 hose onto the pipes and nipples?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

i think you need to measure your friends nipple size first to determine what size of a heater to get...

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

I think about a 1 1/4 size nipple is adequate. wait, are we talking cars again???

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1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"