advice wanted on flushing cooling system

messerschmitt owner · Post by **messerschmitt owner** » Wed Jun 22, 2011 9:05 am

My BX needs a coolant flush - and replacement - any advice and hints before I tackle this rather mucky job?

Post by **Tim Leech** » Wed Jun 22, 2011 10:14 am

Best way is to remove the bottom hose, and if possible to take out the entire radiator and back flush it. When refilling, remove the metal screw at the opposite end of the radiator to the filler to allow all the air to be pushed out. (quite easy)

I always use 50/50 antifreeze to water mix.

messerschmitt owner · Wed Jun 22, 2011 10:38 am

Tim

thanks - I was going to reverse flush the rad as it there is obviously sediment in there - 50/50 sounds about right too.

Having done a HG on an XM - 16 hours labour - I have no intention of doing the BX if I can help it.

Campbell

Post by **Tim Leech** » Wed Jun 22, 2011 10:46 am

Taking the rad out is a doddle so back flushing is a good idea, just the row of 10mm bolts accross the top to remove the radiator locating panel, undo the hoses and out it comes.

Its worth noting though some of the hose clips are the type that can only really be used once (dont know the technical term, ligarex?) so worth having some new traditional ones standing by!

Post by **mat_fenwick** » Wed Jun 22, 2011 10:57 am

If it's any consolation, the BX HG would be less than 16 hours!

Depending on how much you wanted to do, it might be worth removing the thermostat and back flushing the engine via the top hose. And if you really wanted to go to town, you could disconnect the heater matrix and flush that separately also. I've often got a surprising amount of muck from the matrix, perhaps because it's commonly forgotten/ignored.

messerschmitt owner · Wed Jun 22, 2011 11:03 am

matt

you can see all of the head on a BX, without having to remove the engine or twist it on the mounts - and there's no turbo to remove so, all in all, much simpler.

However, it does overheat in traffic - and the contents of the radiator are rusty so I desperately need to flush it and clear the crap from it.

I have a box of jubilee clips at home - I discovered a long time ago that when one needs a few nuts or bolts or clips, it is cheaper to buy a big box and never have to buy them again for a few years.

That's my top tip for anyone with a decent motor factors or screwfix locally - buy in bulk.

Campbell

Post by **mat_fenwick** » Wed Jun 22, 2011 11:27 am

I'd certainly recommend doing the flush given the condition of your coolant, but wonder whether the (main) problem lies elsewhere. Logic suggests that if it only overheats when in traffic, the cooling system is adequate providing it gets enough airflow, and it it was a circulation problem to overheat when the engine is under load, regardless of airflow. Is the fan working correctly?

Agreed about buying in bulk - not only is it cheaper but what price can you put on having what you need at 4 o' clock on a Sunday afternoon?

Never worked on an XM, but by all accounts it sounds like a pain of a job! Let's hope you don't have to do it on the BX though - in my (limited) experience you seem to get away with an engine overheating at idle more so than one overheating under load.

Post by **Tim Leech** » Wed Jun 22, 2011 11:35 am

Malcolm

You could fit a BX diesel fan switch whilst the radiator is removed as it cuts in a few degrees less than the petrol. My 19TZi gets quite warm in stationary traffic and regularly gets over 90 degrees before than fan kicks in, oddly the 16TRS (which has a temp gauge) never gets over 90.

I may take matts advice and remove the heater matrix and give it a flush BUT the heater on the TZI is amazing, and can melt paint at 10 paces

wonder if having A/C and being an auto would make any difference?

messerschmitt owner · Wed Jun 22, 2011 12:41 pm

mat_fenwick wrote:I'd certainly recommend doing the flush given the condition of your coolant, but wonder whether the (main) problem lies elsewhere. Logic suggests that if it only overheats when in traffic, the cooling system is adequate providing it gets enough airflow, and it it was a circulation problem to overheat when the engine is under load, regardless of airflow. Is the fan working correctly?

Agreed about buying in bulk - not only is it cheaper but what price can you put on having what you need at 4 o' clock on a Sunday afternoon?

Never worked on an XM, but by all accounts it sounds like a pain of a job! Let's hope you don't have to do it on the BX though - in my (limited) experience you seem to get away with an engine overheating at idle more so than one overheating under load.

Matt

the fan cuts in quite a lot and I doubt it is the thermostat that is causing any problems as the water in the rad is quite warm quite quickly - I think it's just full of sediment - I'm not losing any water, and have no bubbling in the rad, or excess pressure and the oil is lovely and clean. What I'm finding is that on a run the temp is below the orange light level but that if sitting in traffic, it will some on and flicker off as I blast myself with the heat of a thousand suns (well, at least the heater matrix isn't blocked off and the fan controls on the dash work), and I'm hoping a good flush will clear it enough to keep the temp down properly. On a run, it is absolutely fine but in town and not moving it will heat up enough to go into the yellow.

mnde · Post by **mnde** » Wed Jun 22, 2011 2:40 pm

Hi Campbell,

I thought I would add to this thread my experience of doing a coolant flush on my BX16. The coolant hadn't been changed for a while, so I thought I'd flush the system as a precaution.

I decided, to save time, not to reverse flush the radiator. I had heard horror stories of thermostat housing bolts shearing off (!), so I decided not to attempt to remove the thermostat for the purpose of flushing the engine, but instead decided to compromise and use a coolant flushing agent.

(EDIT: I agree that reverse flushing the rad is an easy job if you have the time, so I would recommend it in your case.)

So, I flushed the rad thoroughly through the filler cap only, then replaced the bottom hose and refilled with deionised water and added the coolant flushing liquid, bled through the bleed points etc... Then ran the engine for 20 minutes (I think at a fast idle, as per the flushing fluid instructions) with the heater control on full heat so the mixture would circulate through both the engine and matrix. Then drained and flushed the radiator through again. I refilled with deionised water and antifreeze mix, bled through all the points etc. with engine off, then engine running... topped up, etc.

I used the orange OAT antifreeze that, after some research, I decided would be good for the BX because of the reported benefits: organic corrosion inhibitors, longer service lifespan (5 years - although I still aim to change it after 2), and enhanced protection (apparently the organic acids are kinder to aluminium) and cooling efficiency compared to traditional antifreeze.

Would anyone, e.g. Mat, like to to comment on the effectiveness of my method?

But yeah - be careful if you take your spanners to the thermostat housing bolts!!

Kind regards,

Mark.

Post by **mat_fenwick** » Wed Jun 22, 2011 3:22 pm

I can't offer any advice based on experience, but it sounds like a good thing. Whether it is any more or less effective than reverse flushing with water alone, who knows? I've heard people advise against flushing agents on the basis that you may get leaks afterwards. My personal opinion is that if my cooling system was that marginal, I'd rather find out sooner and rectify!

Good point about using distilled water - I used to live near Gloucester and the tap water was very hard. Had to replace several radiators on cars we bought down there, as they were clogged up with (presumably) limescale. Still, the (noticeable) extra weight helped when weighing the radiators in! Here, we don't have a problem with limescale so have been using tap water with no problems.

messerschmitt owner · Post by **messerschmitt owner** » Wed Jun 22, 2011 3:31 pm

Mat

the hard water is closer to Stroud - where it comes from bore holes - in Gloucester itself, we get ours from the Severn so it is Welsh water really - it ain't hard, thankfully.

We learned a lot about our water when we lost it all for three weeks in 2007 and survived on the bottled stuff.

I'll flush through to the best of my ability. I'm keener just to use water as it's cheaper - lol

mnde · Post by **mnde** » Wed Jun 22, 2011 3:34 pm

I should add a couple of points:

- my BX rad was replaced with a new Valeo item in 2006

- it is also a good idea if you have the rad off to run high pressure water through the cooling fins (perhaps with a good coating with Gunk spray first?) with the proviso that the fins are of course rather delicate.

Mark.

Oscar · Post by **Oscar** » Wed Jun 22, 2011 4:58 pm

Roverman wrote:Malcolm

You could fit a BX diesel fan switch whilst the radiator is removed as it cuts in a few degrees less than the petrol. My 19TZi gets quite warm in stationary traffic and regularly gets over 90 degrees before than fan kicks in, oddly the 16TRS (which has a temp gauge) never gets over 90.

I may take matts advice and remove the heater matrix and give it a flush BUT the heater on the TZI is amazing, and can melt paint at 10 paces wonder if having A/C and being an auto would make any difference?

Mods - Tim's identity has been hacked! He's posting about TECHNICAL stuff and GIVING ADVICE!!!!

Post by **Tim Leech** » Wed Jun 22, 2011 5:02 pm

Oscar wrote:
Roverman wrote:Malcolm

You could fit a BX diesel fan switch whilst the radiator is removed as it cuts in a few degrees less than the petrol. My 19TZi gets quite warm in stationary traffic and regularly gets over 90 degrees before than fan kicks in, oddly the 16TRS (which has a temp gauge) never gets over 90.

I may take matts advice and remove the heater matrix and give it a flush BUT the heater on the TZI is amazing, and can melt paint at 10 paces wonder if having A/C and being an auto would make any difference?
Mods - Tim's identity has been hacked! He's posting about TECHNICAL stuff and GIVING ADVICE!!!!

F*ck off Oscar!

I have owned BX's for over 15 years now and am starting to do more and more spanner wielding these days....