Xantia: flushing the radiator & cooling system.

Hi there,
I have an L-reg Citroen Xantia 1.9 turbo diesel and want to change the water in the radiator. It has been over-heating, but topping up with water, running
the engine and adding more water seems to have alleviated that problem. However another thread on alt.autos.citroen <http://tinyurl.com/h6ypm this week indicates I should bleed the cooling system when I top up the water-bottle.
The water already in there seems to be pretty disgusting and my father, who has years more experience of car-maintenance than I do, can't recall ever having seen anything like it. He has described himself as fairly shocked when he "saw the brown muck at the radiator-cap and that deposited where overflow had blown out of the system". There's lots of rusty-brown floating scum in the cooling system's water tank, and the water just seems quite disgusting.
I think that ideally I should drain the cooling system completely & refill but the problem is that I can't even drain it!!
On the Xantia there is a tap at the bottom of the radiator for draining; 60 degrees of turn it seems to be its full travel, yet no water comes out when it is fully open. Could this be because I didn't have the bleed vents (described at <http://tinyurl.com/l88ld & <http://tinyurl.com/q3og2 ) opened, or is it more likely to be because the tap itself is full of crud?
Obviously if there's a blockage in the tap then - although in the long-term I'd hope to fix that - I can get around it by disconnecting one of the radiator hoses, and drain the system that way. What I'm wondering if there's any treatment I can do for a system in which the water has become as nasty as that in mine - it's the rusty-browness of the water that concerns me. Is Rad-Flush (tm) any good for this, or is there some other treatment? I always figured most stuff like that is snake oil, but I'm loathe to ignore what appears to be corrosion floating around within the engine block's cooling system.
Stroller.
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It's possible you have a blown head gasket, especially as you mention that the gunge has been blowing out of the overflow. That doesn't normally happen on a healthy engine- the coolant should be fairly clear and only come out of the overflow if the expansion tank has been overfilled or if the engine became extremely hot for some reason.
With the engine cold, and with the heater on 'hot', disconnect the bottom radiator hose and reverse flush the system with a hose pipe until it runs clean. A proprietry radiator cleaner solvent will no doubt help. Once the system has been refilled and bled, keep a very close eye on the expansion tank for bubbling or blowing out the overflow. If you notice a problem it'll need professional (or experienced DIY) attention.
Morse
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Morse wrote:

My apologies for not being clear. I'm not sure that the gungey water is "blowing" out of the overflow - I think it may only be running out of there when the expansion tank is being filled. Initially when I topped up the water only a little would enter the system, and only running the engine would allow it to do so. Undoubledly this was because I wasn't aware of the bleed vents at the top of the Citroen's cooling system and the correct procedure for refilling.

Thank you. I'll follow your advice.

Is there any in particular which is recommended? Or do they all do much the same thing?

These would indicate a blown head gasket, right?
Thanks for your help,
Stroller.
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Stroller ( snipped-for-privacy@bigfoot.com) gurgled happily, sounding much like they were saying :

<waves>

Not exactly unusual.

Yup. That's most likely.

Certainly the best bet.
Then, when it's drained, get a hose pipe in there and flush both block and rad out - first "with" the normal flow, then "against" it, then back to "with". You should start to see the water coming out fairly clean.
*Warning* - You may find things start to leak that didn't before. If the crud's blocking the rad drain, think what it may be doing to any pinhole leaks... If the rad's anything other than very healthy looking, externally, it might just be as easy to change it.
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Adrian wrote:

Dumb question: which direction is "with the normal flow" that I should start with, or do you just mean "flush in aternatate directions"?
I had thought to remove the hose which is connected to the bottom of the radiator, as this is easy to access once the car is on the ramp and, being near the blocked drain tap, would appear to allow most water to drain from the system. I might hazard that hot water enters the top of the radiator and exits the bottom when cooler, so flushing with the flow would mean that I stick the hosepipe into the cooling system hose that I've just disconnected. Sound good? Or should I be looking to flush with the garden hose in more than one place?
Stroller.
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Stroller ( snipped-for-privacy@bigfoot.com) gurgled happily, sounding much like they were saying :

Check which one gets hot first - top or bottom hose.

Indeed.
Yup.
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prudent to mention that all modern engines need anti-freeze added all year round and if you have been running just plain water then your cooling system will be rotting from the inside out!
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radar wrote:

In my defence I've only owned the car about four months.
What symptoms will an engine display, if the previous owner has run it without anti-freeze for some time?
Assuming the engine is not yet FUBAR (and it seems to run alright) will flushing it now and replacing with fresh water & anti-freeze stave off any further damage? Or may it have already deteriorated terminally?
Stroller.
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You may well have a HG issue never the less, but you must clean out the cooling system so you can then refill it with no airlocks and monitor it from there.
Get the upper and lower rad hoses off at the radiator so you can get a good flow out through it and rinse out the crap as best as possible with a garden hose.
Getting it clean will mean draining and refilling it several times, so set aside a whole morning. I always use either a spot of liquid diswasher detergent or washing soda on a mucky system with no oil contamination. You;ll need to run the engine upto working temperature afew times so the thermostat opens and you can flush out the block too.
I have the luxury of a hot water garden hose which vastly speeds up the operation as you dont have to wait ages for the engine to warm up, and if you can rig one up its a god send.
Having used the detergent, perhaps twice, and got it clean, flush it out with water afew times, then carefully refill taking proper note of the bleed screws and half-a-coke bottle when refilling the system.
Tim..
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