Hey fellas, what is that horizontal black metal tube along the firewall in the W123 300D? It's about three feet long and about 3/4 inch diameter.

I dropped my car off for a state inspection and mechanic said that tube looks like it's leaking coolant. I didn't think that tube had any coolant in it. I'd go look at it but I'm 200 miles away lol.

I figure the coolant has come from somewhere above or forward of that tube and dripped or blown onto it.

But the I realized I had no idea what that tube does.

Thanks!

Jim

You might have them take a pic and email the pic to you.

There is some tubes for the Heater on the Fire wall but I don't recall them being 3 feet long.
There is a tube that is long that goes to the Aux Water Pump but it runs on the rignt between the Fender Well and the Engine.

Own the W123s there is at least 3 different climate control setups so yours may be different then mine.

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84 300D, 82 Volvo 244Gl Diesel

Are you talking about the sway bar?

Maybe one of the heater core lines is dripping on to the sway bar.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

There are two metal lines running along the firewall, neither is three feet long. The lower, longest, one goes from the mono valve to the heater.

Is he referring to the torsion bar being drained on from the cowl? That is three feet long.

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83 SD

84 CD

That was my gut feeling too when I read the first post.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks, everyone - yeah it's probably not three feet long. I was just misremembering.

I bet it's that tube between 281 and 290 on the exploded view.

I wonder if I can replace it with PVC or if I have to go buy a special part?

Jim

Should be able to replace with anything that can stand heat and antifreeze.

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83 SD

84 CD

Just buy a piece of heater hose that will span the entire distance from the heater control valve to the line going through firewall. No need to get fancy and introduce an additional source of leaks.

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‘84 300TD “Mountain Goat”
'62 300d Adenauer-350 Chevy - "Max"
'15 VW Passat TDI
'16 Dodge Ram 3500 - Cummins w/6-speed
'68 Mustang fastback
'55 T-bird
‘63 Studebaker Hawk

The ac suction line is three feet long...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

"I wonder if I can replace it with PVC or if I have to go buy a special part?"

Engine coolant can get up to 260F at 15psi w/o overheating. PVC and/or CPVC pipe will not withstand those temps. Just use heater hose as per KK's suggestion.

On my 240d, I removed & cleaned the battery holder and saw what you are describing, one end of it terminated below the battery case and ran above the tran to the driver side.. There are heater hoses just above it that prop leaked on it like you said. I saw it and thought it added some structural strength is all I could think of..

So in the end the coolant leak turned out to be the radiator plug lol. The mechanic who told me it was leaking from that tube, well, let's just say he got it wrong. I still don't know what that tube is, though! From memory, it's black metal tube about 3/4" diameter running from under the battery to under the power brake rig.

Sway bar for sure

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

Anti-sway bar, not a tube, though it could be hollow. Sounds like your radiator drain plug just wasn't tight, or needed a new O-ring.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Yeah the o-ring was bad. I got another plug off the internets for two bucks.