How to bleed mercedes r129 500sl cooling system

Discussion in 'Engine' started by BAZ-500SL, Jul 5, 2017.

  1. BAZ-500SL

    BAZ-500SL Hardcore MB Enthusiast

    Jul 2, 2014
    Ello guys a quick question how do I bleed the cooling system for air in my r129 500sl it's a 1990, TIA
  2. Auto-mobile

    Auto-mobile Hardcore MB Enthusiast

    Oct 1, 2011
    2x c43 Amg clio 172 turbo 314bhp
    Sit in the car with the heater on full, hold the revs 2500-3000 rpm until you have heat through the vents, Mercs rarely have airlocks.
  3. Zonergem

    Zonergem Member

    Aug 31, 2016
    2015 Audi A6 C7 Avant (daily), 1992 R129 500SL (precioussss), 1989 C124 300CE (project)
    There's a very long thread on Benzworld about an overheating early 500SL up in Scotland.

    Hot running V8 conundrum - Mercedes-Benz Forum

    Someone, who sounds like he knows his stuff, posts this, on page 9

    "Get a good mechanic who understands the 500SL properly and who also understands the significance of air locks on the 129.066 engine.

    This engine is the most tricky of 129 range to refill with new coolant apart from 600. Fill expansion tank up to top of clear plastic where it meets black plastic. Remove overflow pipe to lower tank. Fill up to underside of filler. Leave filler cap off. Run engine at high idle and squeeze top rad hose regularly. When engine starts to get hot, turn cabin heater up to max. Top up coolant if it falls below top of white plastic. Run for 20-30 mins when fully hot, blipping throttle to clear air locks. Turn off engine AND DO NOT REPLACE FILLER CAP UNTIL TEMP IS BELOW 60 deg C. Replace overflow pipe.

    Driving a 500SL with an air lock inevitably leads to overheating and a blown head gasket!"

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