Engine Cooling System Flush.

[Pete G]

I feel I am well advised to flush out the engine before refilling with coolant. I do not know how the cooling system has been treated prior to my ownership in terms of what has been put in it. I don't just want to run clear water through it to flush out the loose muck.
The radiator has been cleaned out so it is just the lump which I would like to feel more confident about.
There are many products on the market which claim to do the job but I have not been able to find any reports here by anyone who has used any of these products, although Forte's flush has been recommended. There seems to be a lot of snake oil.
I can't help feeling that there must be some generic chemical which will de-crud the interface between the coolant and the hot metal with the engine in one piece without dissolving the essential bits.
I have the idea of building a rig which will circulate said "Magic Flush" through the system (with radiator removed) using a central heating pump.
The rig bit is easy but won't achieve much without the "Magic Flush". Does anyone know of such a substance that will shift the build up of the hard muck with which the V12 is familiar?

[christopher storey]

The best flushing agent is citirc acid, which can usually be bought in powder form from a pharmacy . Dissolve it in some water, and add it to the cooling system for a few days, with the engine being warmed up a few times, and then flush thoroughly with a hose . You will be suprised what comes out!

[abowie]

Go to a radiator place. Get it done professionally.

[PeterCrespin]

Hello Pete. Still in Congleton?

Try a plumbing or water treatment place. Their scaling problems make a V12 look like child’s play.

One issue is that the 12 is all-alloy, including the pump. This is good news in some respects but it is less resistant to home-brew mistakes than iron. The problem is not just getting the chemistry right but the reaction conditions. Significant scale takes time to dissolve and heat helps too. Trouble is, the only guide you have is what comes out and that’s not very informative once the first crud clears up.

If you want to do more than a basic flush you need to see the waterways and scale deposits to judge progress. Bare blocks can be treated to come out like new - especially iron ones. But you don’t want to be too aggressive on a running all-alloy engine.

Flushing with the rad out of circuit is good and for the rest I’d do as Chris suggests or buy bulk from a plumbing supplier. We’ve got some good chemists here who may chip in.

[jagwit]

The best flushing agent is citirc acid

I believe my car is suffering from scale by virtue of pushing out coolant 2 min after being switched off with temp gauge anywhere between M and L of normal and I've been wanting to either pull the heads or apply chemical treatment, so I'm all ears....

What would be the recipe for mixing the citric acid solution? (I presume as much of the regular coolant should be removed first??)

[MarkRado]

Mercedes recommends: 1kg of citric acid (powder, for baking purposes) for 10 l of water for some of their classic engines (see google). Drain sytem, refill with acid/water mixture, run engine (idle) for 10 min, drain and thouroghly flush, then refill with antifreeze mix.
I did it on my 1998 XJ8 a few years ago, but drove some miles with the acid mix in hope for a better effect. Water temp was noticeably higher, so no good idea in hindsight, but nothing damaged up to date.

[Pete G]

Thanks folks for the info./advice. The consensus appears be to use citric acid powder in solution although I am still concerned what dilution to use. 1 kg of acid per 10l of water sounds very aggressive if it does the job in 10 minutes, maybe Mercedes engines don't scale up to the extent that Jag v12s(aluminium) are reputed to do or maybe the metals used in their construction is different.
Christopher - how much acid powder would you add to the 20l capacity of the engine?
Perhaps I should start off with what seems to be a weak solution and keep adding powder until something worthwhile is excreted, it's a bit like kidney stones really!
Peter - I looked into central heating descaling products, Fernox DS40, on paper at least, looks the part. I shall contact Fernox to get their opinion on using it in my situation.
Yes, still in Congleton, or close to in Church Lawton. I've just fitted the AJ6 exhaust you sold me when we were still young!

[christopher storey]

Peter : I have to say I've never used anything like 1kg of citiric acid at a time ! I would advocate the approach you have suggested , of starting with say 250g/ 0.5 lbs dissolved in a litre or so of hot water, and leaving it in for a day or two with the coolant having been thoroughly circulated.( It tends to go very green ) If you are not satisfied with the result, up the ante on a 2nd attempt . Incidentally, citric is a very weak acid and is very unlikely to do any harm as far as I remember . If our organic chemist Simon is lurking, he can no doubt give a definitive opinion on it

[Pete G]

Thank you Christopher for the further advice. To be clear in my mind are you suggesting that I dissolve 250g in 1l of water and then make that up to 20l to fill the system i.e. 250g to 20l of water? I don't think you are suggesting a dilution rate of 250g to 1l 'cos that would require 5kg of acid in 20l of water to fill the system, or are you?
I can't run the engine so I propose to build a rig which will circulate the solution from a 5gal drum using a central heating pump in at the top of the engine, out at the bottom with the thermostats and radiator removed. I can leave that running for as long as required or until the liquid runs out of the spark plug holes if I overdo the strength.