drain ALL coolant with Rad. change?

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put in a new radiator today but only drained that fluid (and what dribbled out of the block of course).  It's all back together now but I'm wondering if I need to drain the block coolant (by the back plug) before filling it all up again?  The fluid is all good too, not old.  I guess I'm concerned about airlocks and bleeding if I don't drain.  Of course, if I don't have to so much the better.

booker

'92 E34 Touring 525 TDI

Edited by bookerfatz

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bookerfatz Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 19-June-2009 Location: France Status: Offline Points: 99	Post Options Post Reply Quote bookerfatz Report Post Thanks(0) Quote Reply Topic: drain ALL coolant with Rad. change? Posted: 24-June-2010 at 17:11
	put in a new radiator today but only drained that fluid (and what dribbled out of the block of course). It's all back together now but I'm wondering if I need to drain the block coolant (by the back plug) before filling it all up again? The fluid is all good too, not old. I guess I'm concerned about airlocks and bleeding if I don't drain. Of course, if I don't have to so much the better. booker '92 E34 Touring 525 TDI Edited by bookerfatz
	Booker 2002 E39 5 series Touring

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Andrew Rolland Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Go away rain Joined: 19-August-2004 Location: Scotland Status: Offline Points: 6579	Post Options Post Reply Quote Andrew Rolland Report Post Thanks(0) Quote Reply Posted: 24-June-2010 at 18:33
	No you should need to drain the block unless you want to do a full coolant change. You will get air locks if you fill too quickly and don't bleed out the system. It's a pig on the E39 petrols but it can be done, similar I would guess applies to your oil burner. I replaced the thermostat on my E39. I drained down the system via the drain on the rad. I didn't touch the block drain plug (scared of shearing it or stripping it). When I removed the water pump a considerable amount of water then left the cylinder head thru the hole that the water pump was in. All the time the rad drain plug was open, which meant that water was still being held in the head even though the lowest part of the system was open to atmosphere. Heater valves were open also. I would never re use antifreeze, it doesn't cost that much and the more you replace it the more chance you have got of ensuring that the old stuff is getting removed. Andrew
	Be exclusive and drive a Petrol 5 Series! Current '13 62 F10 535i MSport Auto Previous '04 04 E60 545i SE Auto '03 53 E60 545i SE Auto (Stolen) '98 S E39 523i SE Auto

jetsetwilly2000 Members Profile Send Private Message Find Members Posts Add to Buddy List Really Senior Member II Joined: 10-December-2003 Location: Cambridgeshire Status: Offline Points: 701	Post Options Post Reply Quote jetsetwilly2000 Report Post Thanks(0) Quote Reply Posted: 24-June-2010 at 20:51
	Actually the coolant system in the E34 is described as self-bleeding, and certainly I've never had any trouble with it. I've done the rad on my 540 and I didn't do more than drain down from the rad and then top back up. Should be the same for yours.
	E90 M3 DCT, E46 330d Touring, VW T5 wannabecamper Previous: Disco 3 TDV6, 2x E34 540i6, E34 535iS

bookerfatz Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 19-June-2009 Location: France Status: Offline Points: 99	Post Options Post Reply Quote bookerfatz Report Post Thanks(0) Quote Reply Posted: 25-June-2010 at 10:00
	thanks guys! Will give it a go... good tip about the old antifreeze as well.
	Booker 2002 E39 5 series Touring

Andrew Rolland Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Go away rain Joined: 19-August-2004 Location: Scotland Status: Offline Points: 6579	Post Options Post Reply Quote Andrew Rolland Report Post Thanks(0) Quote Reply Posted: 25-June-2010 at 13:19
	If the expansion tank is the highest level in the system you should be o.k. with filling, i.e. avoiding air locks. The E39 6 pots have the expansion tank halfway down the rad. Go figure! Let us know how you get on. Andrew
	Be exclusive and drive a Petrol 5 Series! Current '13 62 F10 535i MSport Auto Previous '04 04 E60 545i SE Auto '03 53 E60 545i SE Auto (Stolen) '98 S E39 523i SE Auto

bookerfatz Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 19-June-2009 Location: France Status: Offline Points: 99	Post Options Post Reply Quote bookerfatz Report Post Thanks(0) Quote Reply Posted: 25-June-2010 at 15:06
	got it topped off and she's running good. I'll take her out tomorrow for a good run in this nice hot weather but I think it's fine without bleeding. Nice design that! The only little 'bug' that happened though was that the new rad sits in the 'hole' a little looser then the original. I'm not sure why the wiggle room is there as they measure the same. Strange. I didn't get it from BMW though but from here for half the price:<http://www.mecatechnic.com/Radiateur-d-eau~Pieces- pour-BMW-serie-5-E34~Moteur-et-boite~Circuit-d-eau~FR-E34-MO T-EAU-RAD.htm>. It's actually those clips at the tip that hold it in (and down) where the problem is so maybe that's it. It's not a biggie though. I'm just going to have to find a way to 'shim' it I guess. Shouldn't be a problem though. I do not want the radiator jumping around there that's for sure. It needs to be snug. Thanks again for the helps! Booker
	Booker 2002 E39 5 series Touring