The drain plug on my 90 S4 broke. What is the size and Is this readily available from the local parts store?
If not, Can I put something in temporarily until I order the correct one?
Thanks

 

A regular M8 or M10 bolt (I forget which) can be used in a pinch.

Your local BMW/Audi/VW/etc. dealer will have the same size in stock for cheap.

 

Mercedes part #000 501 01 71

 

Always buy two so you've got a spare.

 

I would like to flush the radiator with distilled water by letting the system run with just that for a couple of days. Then draining it and filling the system up with coolant and distilled water.
Is the distilled water alone corrosive?
Thanks

 

For a flush, I'd just fill with tap water, and add a radiator flushing agent. Then follow the instructions (usually warm up car for 30 mins or similar). Then rinse thoroughly again (including opening the block drain plugs a few times after refilling with more water).

Once you've flushed it, *then* put in the distilled water, with the coolant of your choice (something free of phosphates/silicates/borates).

Flushing with distilled water won't help extract any of the depositions and smaller sediments that collect in the system.

 

I would caution against adding any type of flushing agent to the coolant system,
if you do you will be exposing the head gaskets to whatever cleaner you install and this could be a quick path to replacing the head gaskets.
If you want to clean things out open the block drains, drain out the old coolant,

remove the radiator and back flush it with a hose,
run the hose water through the block,
open the drains and let it drain.

Then install the radiator,
install a new heater control valve and short hose,
as well as a new coolant bottle cap,
and also replace the thermostat and the rear seal and O ring,
refill with 2 gallons of Z O5 coolant and 2 gallons of distillled water

 

The only problem with flushing with a hose is that I have well water. It has been tested and the report said it is very hard water and has iron and copper in it plus it is not filtered. Do not want to take a chance snd maje things worse. Therefore was wondering if filling up with distilled water and driving for a few days and then draining and filling with the coolant and distilled water would be appropriate.

 

Only drawback to distilled water is you've got to buy it vs what's easily available. Distilled water is exactly that: H2O to some purity standard that escapes me. I would not use well water for anything except brewing beer. If you habe enough distilled to flush and run a couple of times, you'll be fine as long as you keep to a nice coolant swap interval.

 

It should be fine to flush it with hose from the well water - just don't let it stay in a hot engine or leave the well water in there for ages - the dissolved iron and copper / hardness will remain in solution unless you heat it up to boiling. Once you've finished flushing - ie lots of volume and water pouring out from all orifices, empty out the sytem, then fill with distilled water to rinse, drain again then fil with coolant/distilled water (Could always use rainwater from a non metallic roof instead).

 

This shop vac method got some grit out of the Van Winkler's radiator.

 

Fraggle,
You are the only person I can think of who would make a reference to beer in a thread about flushing a cooling system! See you on Saturbeerday.

Jerome

 

Be careful with those block drain plugs, snug is all you need them to be lest you end up with this: