Replacing coolant on 2000 Z3 Roadster

Looking for the simplest way to pefrorm this task. Hoping there is one.

Can I simply drain system from below (collecting old fluid), and then add clean water to system from above with the drain plug still removed and the engine running (heat on)? I was told that this would be sufficient. Next step to replace drain plug and fill with 50/50 mixture until full (approx 2 gallons).

As always, thanks in advance. This forum is an invaluable resource.

Scotty

There are many threads here on this topic. You should look through some of those. Near the top of the page, on the right, is a button labeled "Search this Forum." Click that and type something like "coolant". That will help.

Rather than just replacing the coolant, you should consider replacing all of the plastic parts including the water pump, water pump pulley, thermostat, thermostat housing, radiator, reservoir, and hoses. These are getting old and brittle, can fail catastrophically, and can quickly destroy the aluminum engine.

The way to change the coolant is to drain the radiator and drain the engine using the plug on the exhaust side of the engine by the number 2 cylinder. It's a messy job and coolant will run everywhere. Put down cardboard first. Have on-hand a new crush washer for the engine drain. Then fill the system with 50/50 coolant/water.

Then you have to carefully bleed the system. That is done with the front of the car high, engine warm and above 1000 rpm, heater on. Squeeze the top hose to help expel the air. Again, there are detailed instruction available by searching.

Running the engine with the drain plug out, even while adding water, is very very risky and unnecessary. If insufficient coolant is available, the engine will be destroyed. There will also be water trapped in the engine block that will dilute the coolant that you will add. It is best to drain the radiator and block then refill and bleed the system.

Blacklane,
Thnx so much. I am always amazed at how people with knowledge of these cars are willing to go out of their way to share it, and help others like me. Much appreciated.

Quick question:

Can I reach the drain plug without raising the car too much?

Supposed to reach 47 degrees here today, and I hope to take advantage of the sunny weather.

Best,

Originally Posted by Blacklane

... Rather than just replacing the coolant, you should consider replacing all of the plastic parts including the water pump, water pump pulley, thermostat, thermostat housing, radiator, reservoir, and hoses. These are getting old and brittle, can fail catastrophically, and can quickly destroy the aluminum engine....

This is on my list, but maybe in a year or two, as my 1997 only has 33,000 miles. I went into RealOEM and made a spreadsheet of the part names, numbers and typical prices, and for my 1.9L it came to $1,079:

BELTS
Ribbed V-Belt, alternator, pump
Ribbed V-Belt, AC compressor
Adjusting (tensioner) pulley

COOLING SYSTEM REBUILD

Radiator
Brass bleeder screw
Coolant
Fan shroud fasteners
Radiator
Gasket ring for temp. switch
Radiator cap
Expansion tank
Gasket ring under exp. Tank
See
Radiator/tank combo (BavarianAuto)

Water Pump & Thermostat
Water pump
O-ring for water pump
Thermostat w/housing
Axial gasket for thermostat

Hoses
Upper radiator hose - right
Upper radiator hose - left
Lower radiator hose
Hose on top of plastic heater pipe
Hose on end of plastic heater pipe
Double hose on plastic @ rear head

Plastic Connectors
Plastic connector pipe on block
O-ring for block connector
Plastic Y connector on head
O-ring for Y connector

Manifold
Lower intake manifold gasket
Upper to lower intake man. gask.
Block coolant drain crush ring

To SDFarrell: Yes, you only need to raise the car high enough to get your head under it to see where the drains are. The drain on the side of the block is pretty high. The drain in the radiator is pretty low.

To vintage42: this I a pretty good list. I can't tell from your descriptions, but be sure to replace the two plastic fittings on the 1.9 engine. One is in the back and is hard to see. For my job, I also added an aluminum thermostat housing and aluminum water pump pulley. I would also add the plastic fan to your list, although I converted mine to an electric SPAL fan and mounts from Fanman.com.
You might also need the two radiator clips, which are easy to break, and the four rubber radiator mounts, which may have deteriorated.
I replaced all of my belt tensioners and idlers which for the 2.8 with AC is 2 tensioners and one pulley. The 1.9 is different.
You will probably need new hose clamps, particulary the small ones which are one-time use.
You might need a fan holding tool and wrench. (Remember, it's left-hand thread).
Finally, I replaced my block drain plug with a magnetic one from e-bay, but that probably makes no difference. I just bought it along with a magnetic oil pan plug.

Originally Posted by vintage42

Plastic Connectors
Plastic connector pipe on block
O-ring for block connector
Plastic Y connector on head
O-ring for Y connector...

Originally Posted by Blacklane

... I can't tell from your descriptions, but be sure to replace the two plastic fittings on the 1.9 engine. One is in the back and is hard to see....

They are on the list. The plastic fittings are actually tubes called connectors, connecting heater hoses to the block and head. Thanks for the other info.

Originally Posted by Blacklane

I would also add the plastic fan to your list, although I converted mine to an electric SPAL fan and mounts from Fanman.com.

I think you mean www.the-fan-man.com

www.fanman.com is a ceiling fan company.

Coolant should be changed every 3 - 4 years, no matter the mileage.

Which reminds me, I need to do this on more than one car.