MB Coolant Low level warning

The Middlebridge has no coolant low level warning so the following may be of interest.

A low level warning system comprising:-

  • A coolant tank having 2 level probes.
  • A circuit board/ module to suit the level probes.
  • A low coolant sounder (or warning light).
  • Coolant hoses to suit.
  • Bracket(s) to support and secure new tank.

At least two types of coolant tank are commonly available to give low level warning. Those with sensor probes and those with a make/ break switch. Though the latter is simpler to wire in I couldn't find one suitable so ended up with the former (from VW Golf).

Sadly, the current through probes types is very, very weak and needs to be boosted to action a sounder or warning light. From ebay (cost less than a fiver) I bought;

"9-12V Liquid Level Controller Sensor Modules Water Level Detections Sensor AC/DC". At less than a fiver I thought it worth trying.

Link to module from ebay

The module:-

Which I wired thus:-

The module caters for three probes but we need only two, "Common" and "Low Level".

Ignore the AC stuff illustrated in the module diagrams and go straight into our 12V DC.

I used a warning sounder (Piezo) rather than a light because I didn't want to be cutting holes in the dash or adding brackets for a visible light. Also, I incorporated a test switch (normally closed) to conveniently check from time-to-time the circuit is still in good order.

My module, sounder and test switch are all together on a board fixed to cockpit side panel (out of sight but conveniently located to operate the test switch from driving seat).

Take care tank does not interfere with closed bonnet, bonnet stay and alternator.

Hoses! The 'Golf' tank has 16mm coolant connection whereas MB tank is greater so different hose is required. But, engine coolant pump connection is anyway 16mm so now it's conveniently 16mm throughout. Also, MB tank bleed connection is 10mm whereas the VW is 8mm. This good news because the engine thermostat housing connection is also 8mm and now we have 8mm straight hose throughout.

Golf tank installed in MB engine bay

P.S. Do not throw away the original MB tank as they are rocking horse poo scarce. Save it to restore MB to original condition should you later wish.

P.P.S. At less than fiver a pop consider buying a spare module.

May I take this oppertunity to thank Alan Timmis very much for this wicked tip and upgrade.

Cheers Mick