Eric_Oz_S2

I'm draining the radiator to replace the coolant. I have removed the plug on the bottom of the radiator, but it has only drained around 3 litres of coolant. What is the trick to get the rest out (air vent is open) - or is that all you can drain?. On the S2 there is no block crankcase drain plug. I was going to replace the plug, fill with distilled water, run and drain again before filling. My concern is I won't be able to get 4 litres of coolant in the system.

Mark944na86

Getting the coolant out of the heater block can be a pain. Removing the hose from the WP to the bottom of the radiator gets some more out. But when I flushed/replaced my coolant, I ran the descaler in the system with the heater on for about 30 mins or so, then did a series of flushes with distilled water until it was running out clear, running with the heater on to get the flush through the heater core as well. Made a couple of trips to the supermarket to get more water IIRC.

Eric_Oz_S2

Ok - got a whole 4 litres out.

Jfrahm

I use a wet vac, works great.

Luis de Prat

I would never use those drain plugs on the radiator. They're plastic and can break, leaving you high and dry. When I replaced the coolant on my 951 I drained the system by dsconnecting the lower hose to the radiator, as per Clark's Garage.

Get ready for some extensive bleeding after refilling the system. It will take several attempts!

Eric_Oz_S2

Plug didn't break this time.

Bleeding didn't take long - just opened up the top vent every few minutes and left the cap off.

Mark944na86

I suspect the problem some people have had with the plastic plugs is not so much due to the weakness of the plug itself, but probaby due to overtightening. There is an o-ring, and if that isn't sealing properly due to age, the temptation would be to overtorque.

I've used it many times without incident, but then I'm careful with the torque.

And even if it breaks, it's no biggy. A small chisel or similar can be used to grab the broken part and back it out. Plastic is certainly easier to work with than steel in this regard.

As regards bleeding, I also don't find it's as hard as some people say. I do pretty much as Eric has done, and find that any small remaining amount of air remaining in the system will find it's way to the overflow tank, and a bit of a top up might be required after a few days driving. I know when it's properly bled when the temp gauge stays solidly on the first line once warmed up.

One other useful trick I've found with bleeding the heater is to put a zip tie on the heater control valve holding it open independently of the vacuum control. It saves having to run the engine until it heats up and then turning the heater on to get the valve to open. An inelegant but effective approach for the impatient.

Luis de Prat

I think you've just been lucky. 18+ year old plastic can become brittle and disintegrate just upon loosening the plug, just like it does on so many other applications in these cars. I think generally speaking, with people having cars in such varying climates, that it's much more sound advice to suggest draining from the lower radiator hose.

Come to think of it, you're both referring to your S2s.

Bleeding the cooling system in the 951 is a whole 'nother ball of wax, believe me. It's more convoluted with the added turbo cooling circuitry, and stubborn air pockets form that take a lot of persistence to eliminate.