Adding pressurised overflow bottle to 300td radiator

1976-1985: 230T, 230E, 230TE, 230CE, 280E, 280TE, 280CE, 240D, 300D, 300CD, 300TD,
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Posts: 4
Joined: Fri 16 Mar, 2018 9:13 pm
Model you own: w123
Region: New South Wales
Location: Newcastle

Adding pressurised overflow bottle to 300td radiator

Post by EddieMurphy » Sat 14 Apr, 2018 3:13 pm

Hi all,

I had a post recently about my water pump falling apart at 100kmh on my 81 diesel 300td w123 and destroying fan and radiator, it has been very difficult to find a replacement radiator in au to fit. I thought I had one sourced and was assured by parts place that it was the correct radiator but upon arrival it seems to be the w126 radiator which requires a pressurised overflow bottle. As it has no radiator cap and an extra hose fitting down the bottom. I can source an overflow from a w126 easily.

So my question is are there any reasons for me not to go this route of retro fitting a pressurised overflow bottle, are there any benefits and how can I be sure to have it at the correct height to ensure that the radiator fills to exactly the right amount and the overflow be accurate?

Also If I shouldn’t do this does anyone know where a radiator for my model can be sourced?

C 111
Posts: 895
Joined: Sat 25 Apr, 2009 10:32 am
Model you own: w123
Location: Melbourne, Vic

Re: Adding pressurised overflow bottle to 300td radiator

Post by tsharkey » Sun 15 Apr, 2018 7:14 pm

Hi Eddie,
I fitted the system you described to my 300TD. Get the reservoir and hoses that run between the reservoir and radiator from a W126 (The need some slight trimming as the W126 is bigger), or order a new set for a W123 from the sponsor. The existing main radiator hoses should fit OK. You can wire in the No Water warning switch if you want, otherwise leave it unplugged on the reservoir. You will need to make a bracket up to hold the reservoir in place, between the SLS oil bottle and top of the wheel arch.

Here is a picture of another of my wagons with this system
OM617A RHD Factory.JPG
I prefer this system as you can see at a glance the water level.
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W123 1981 300TD - Family Kid mover
W202 1998 C250D Factory OM605A Turbo - Partner's daily driver
W123 1982 300CD Retro fitted OM617A Turbo - Mine
W123 1984 300TD 5 Speed Manual, to teach the kids how to drive
W123 1982 300TD Factory OM617A Turbo (Hans) - Project
W123 1985 230TE - Brother's
W123 1985 300D - Sister in Law's
1962 S-Series Valiant (Tho Daimler & Chrysler divorced, still part of the extended family)

Past benzes
W114 1969 250CE - PO put in an M110 transplant and nearly sent me around the bend
W123 1981 300TD - "Matilda" - RIP hit front side & rear but left my brother + niece A-OK

Current Projects
Coupe restoration, Turbo Wagon freshen up

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