Repacing Antifreeze

[Anniversary SL]

I have to repalce the antifreeze in my 1997 SL500. How do I flush the block and radiator. Where are the drain plugs located on the block. What is the prcedure for flushing. Thanks

 

[Arnie]

Well, as no one else has answered your question, I'll try to give you some pointers.

The drain plugs are usually found on the lower side of the engine block, but I don't know if left or right on your engine. Normally you need a 13mm or 17mm ring spanner or deep socket to open them.

There should also be one at the bottom of the radiator- opened with a short screwdriver in the slot or by hand- near the bottom hose attachment, but if you cant find this one or get to it, you can just remove the bottom hose.

Note you may need to remove the bottom, plastic engine shield panel, to get access to the drain plugs.

It's also a good idea to remove the filler cap, to help the water come out.

Once you have drained the system, you can fill it again with tap water, run the engine for enough time for the thermostat to open (85C) and then drain it again, when cooled a little. Now refil with 40% antifreeze (of a reputable brand for aluminium engines- COMMA do quite a good one with a BASF corrosion inhibitor). Do not use more than 50% as this will impare the cooling, since glycol has a lower thermal capacity than water.

To know how much antifreeze to use, check your engine coolant capacity from the user manual. It will probably be around 10 litres and so you may require a 4-litre container of antifreeze- about £15-£20 for a good one.

If you drain the coolant in to a bucket or tub, you can check to see, from how much water you've collected, whether you've fully emptied the system. But even if you haven't got the last litre or two out, it should not mater, since the system is flushed at least once and any remnant will be very diluted.

Some people suggest that the balance of topping up water should be demineralised (distilled) water, but I'm not sure this is a good idea because this water is relatively reactive and corrosive.

I tend to use filtered water from a BRITA-type water filter jug, which removes 99% of the hardness and leaves no scale.

Once filled, run your engine again to operating temp and check the expansion tank level. If necessary, allow to cool sufficiently and top up.

Done.