Cooling System Maintenance
Bill Buckwalter '98 1.9

Jack the car up first Jack the car up first
The objective here is to get the car far enough off the floor to make crawling under it with a drop light and catch pans easy. It is important to be safe and to have the car level for complete coolant drainage.
Z3 dipstick detail Z3 dipstick detail
Note the coolant hoses and coolant shut off valve were removed. This opens up that quadrant of the engine bay for easy viewing toward the back driver’s side of the engine.
happy idiot
happy idiot
My wife stopped in to call me to dinner and went back and got her camera. Note there is enough room in the engine bay for the 4 cylinder engine and a fat ass. It also makes working back along the firewall much easier. From this position one can see and work on the hoses connected to the back of the head.
Coolant manifold location, view from top Coolant manifold location, view from top
This shows the inlet hole in the block for the plastic coolant manifold, located at the bottom end of the chop stick. It needs to be cleaned of all residue before installing the new manifold and O ring. Be sure to grease the O ring, it is a tight fit.
Accessory removal, side view Accessory removal, side view
This illustrated the standing room in front of the engine and how removing all the gingerbread on the front of the engine opens up things for access. Note the blue tape labels.
Accessory removal, front view Accessory removal, front view
Note the top half of the intake and the power steering pump with bracket were unbolted and set aside. This was to avoid removing the throttle linkage and power steering hydraulic lines, minimizing the work of adjusting the throttle linkage and coping with power steering fluid on reassembly. The 4 cylinder motor in this car has the room to facilitate these kinds of short cuts. Just have plenty of soft rags or towels handy to sit things on in order to not scratch paint. Some mechanic’s wire (or coat hangers) comes in handy too for holding things off to the side.
Z3 Coolant manifold Z3 Coolant manifold
This is the manifold that has the history of cracking. There is another one on the front of the engine that is reported to not have the same problem. After twisting and turning this one to fully seat the O ring in the block I used thread lock to hold the two bolts in place that go through the brass rings in the flange plates along the bottom of the manifold. Note the rear brass ring sits in a slot. I figure that allows for thermal expansion, so I cranked the bolts down tight.
hose inventory match hose inventory match
As an amateur enthusiast I cannot stress enough the significance of verifying all the right parts are on hand before starting the job. Make a project out of it. Look at them carefully, and when you extract a part from the car, compare it to it’s new brother. Note I left the short “S” hose on the heater coolant valve assembly. This was to help me assemble things correctly with minimal puzzlement. Plumbing gets a bit convoluted back there by the firewall.
From: "Shawn Fogg"
Date: September 19, 2006 9:48:55 AM EDT
Subject: RE: [z3rides] Re: 1997 Z3 Heater Hose Help!!!!

I would also add to make sure it is actually the heater hose that is leaking before you start this job.
In BMWs infinite wisdom (???) the fitting that that hose attaches to at the back of the engine is made out of plastic. That can and has broken on some 1.9l causing coolant leaks back there which are a royal PITA to fix.
There is a second hose attached at the rear of the engine as well. If you are going to be working back there consider changing it out as well 'just in case.'
And if you pull the intake manifold there is at least one more hose under it you might want to think about changing out too. And a longish plastic coolant fitting.
Hell for the guy who designed those parts in plastic should be an eternity spent swapping out those parts on 1.9ls. Esp. the one at the rear of the block.........
(The parts that worry me the most on my car are those plastic coolant parts......)

Reading Shawn's note, I now agree, if that coolant manifold on the back of the engine is plastic I would change it too. And I bet it is a bear to change. 
I have been told BMW's plastic attachment parts were part of the "green" effort. They facilitate ripping a motor out of the car as part of a brutally efficient mechanized recycling process. That being the case, I bet that puppy on the back of the motor is plastic too.....and with my luck mine will fail somewhere out there where the road comes to a point at both ends and the nearest wrench belongs to a guy who thinks BMW is a British thingie.
I am going to look into that as part of my next coolant change, scheduled for next year after a trip to Florida in May.
Thanks for the information.
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