How do you fully drain the cooling system

BX Tech talk
User avatar
NeilGP
BXpert
BXpert
Posts: 145
Joined: Thu Apr 29, 2010 9:16 pm
Location: Bellshill, Scotland

How do you fully drain the cooling system

Post by NeilGP » Wed May 17, 2017 7:49 pm

I bought the Evans Waterless coolant to try out. According to the Citroen & Haynes manuals this should have a 6.7L capacity.
I have removed the lower radiator pipe, disconnected the Choke water pipe, put interior heating valve to Hot, but I have only drained 5L. I added the prep fluid just in case the water level was originally low, but this will only take 5L.

What am i doing wrong?
I don't want to replace the prep fluid until I know I have fully drained the system and waste the waterless coolent.

Thanks
Neil
Neil
A476 RBX
Series 1 BX 16TRS
+ 2015 C4 Flair (boring compared to BX!)

User avatar
Kitch
Over 2k
Posts: 6207
Joined: Sun Jul 03, 2005 9:36 pm
Location: Fareham, Hants
x 49

Re: How do you fully drain the cooling system

Post by Kitch » Thu May 18, 2017 9:28 am

We're an agent for Evans, and do conversions on site all the time. You really need compressed air to get it all out, as there are plenty of little water traps it gets stuck it. The thermostat doesn't help either, as it'll be closed when you're trying to empty everything.

I tend to pull all the lowest hoses off, then compressed air in via all the bleed valves. I converted my 16v yonks ago, and my AX GT and our Saxo both run it too, quite happily. In fact the BX runs no different at all than it did on water (which is a good thing) but has all the benefits of being on Evans.

Don't get too wrapped up in getting exact quantities quoted in the books out of it though, as it might not have 6.7L in there to start with!

User avatar
NeilGP
BXpert
BXpert
Posts: 145
Joined: Thu Apr 29, 2010 9:16 pm
Location: Bellshill, Scotland

Re: How do you fully drain the cooling system

Post by NeilGP » Thu May 18, 2017 7:18 pm

Thanks for the info. I was just concerned of too large a mix of residual water and wasting the coolant. It was not so much the amount of water I drained but the amount of primer fluid I put in, this was only 5L

I will do this at weekend to get the primer fluid out. Luckily the choke coolant feed is directly below the thermostat so saves having to remove the stat. I can put compressed air down this pipe as well.
Neil
A476 RBX
Series 1 BX 16TRS
+ 2015 C4 Flair (boring compared to BX!)

User avatar
Kitch
Over 2k
Posts: 6207
Joined: Sun Jul 03, 2005 9:36 pm
Location: Fareham, Hants
x 49

Re: How do you fully drain the cooling system

Post by Kitch » Thu May 18, 2017 8:50 pm

The prep fluid can handle quite a bit of water. If you boil it after you've drained it out, you can remove most of the water from it. The coolant itself can handle up to 3% water contamination (anymore than that and the benefits start reducing), but on my own cars I disconnect the cooling fan and run them up to about 110degC with the cap off. The remaining water soon finds its way out! For the first few weeks you'll be undoing the cap when it's hot too, and over time the pressure will drop each time you do it. The less pressure, the less water there is.

You only need the prep in there for 30mins or so. Let the fan cut in and out a few times etc. I assume you've done this with the heater valve set to hot?

Just realised I think I was chatting to you last year at the National.

User avatar
NeilGP
BXpert
BXpert
Posts: 145
Joined: Thu Apr 29, 2010 9:16 pm
Location: Bellshill, Scotland

Re: How do you fully drain the cooling system

Post by NeilGP » Sat May 20, 2017 4:30 pm

The air compressor is a neat trick, thank you.
I have now completely flushed and used approx 6L of the main coolant. I will check this over the next few weeks to check for level etc.
I probably did see you last year, but that was a long time ago :)
Neil
A476 RBX
Series 1 BX 16TRS
+ 2015 C4 Flair (boring compared to BX!)

assembled
Confirmed BX'er
Posts: 79
Joined: Thu Jan 05, 2012 2:21 pm
Location: Arendal, Norway
My Cars: 1991 Citroen BX TZD Turbo
1989 Citroen BX GTi 4x4

Re: How do you fully drain the cooling system

Post by assembled » Tue May 23, 2017 10:42 pm

Last time I had to full coolant replacement, I just blew my own lungs out to 1.8TD expansion tank. The things I do for love... This way I drained exactly spec volume.
1992 TZD Turbo berline, aircon, ABS
1991 TZD Turbo berline
1989 GTi 4x4 berline, ABS