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Rusty coolant why and what flushing agent to clear.
Bluemoon - 29/4/16 at 06:37 AM

Hi All,

The coolant in my 1.8 CVH is rusty , I have flushed the system twice in the past (forward and reverse flush with hose until water runs clear), but the rust comes back within a short period of time. It's now due a coolant change and I want to sort the issue, what is the recommend flushing agent? There seems to be a lot out there and I am sure some are snake oil... cheap alternatives considered (critic acid?).

The cooling system has Steel block Aluminium head, Aluminium radiator, some copper pipe work with some solder, silicone and rubber hoses.

What might be causing the rust? at the moment I think it's just the poor state of the cooling system in the donner car (I suspect they have used water to save ££££).

Could head gasket cause the issue (No sign of oil in coolant or coolant in oil, just rust in coolant, but I do loose coolant from time to time!)?

Regards,


Dan

cliftyhanger - 29/4/16 at 06:48 AM

You can de-rust the system, but fresh clean steel/iron will rust in minutes.
If you want to get rid of rust, an acid is good. Possibly phosphoric acid once you are sure the system is free of crud, as that will form convert any surface rust to a passive/inert surface. Cheap cola is a source of dilute phosphoric acid....
A good rinse and then, as you have a mixture that includes copper and solder, blue antifreeze at at least 50% concentration. A mate of mine (ex drag racer) uses neat blue antifreeze, though that has some disadvantages in terms of cooling, the system in his 47 year old engine (daily driver car) is spotless.

nick205 - 29/4/16 at 08:43 AM

I've always used the clean water/hose flush and a generic rad flush product, have never suffered a rusty coolant system. As above, steel blocks and/or heads may be more prone to rust though.

v8kid - 29/4/16 at 11:29 AM

quote:
Originally posted by cliftyhanger
Cheap cola is a source of dilute phosphoric acid.....


That's v handy to know

Cheers!

joneh - 29/4/16 at 11:31 AM

How about a waterless coolant? I gather there's been a few discussions on the merits etc in the past.

Might be worth a search on here first.

DJT - 29/4/16 at 12:27 PM

Mine went rusty as I'd used steel tube for hose joiners. Replaced with proper aluminium ones and the problem disappeared.

cliftyhanger - 29/4/16 at 03:59 PM

quote:
Originally posted by v8kid
quote:
Originally posted by cliftyhanger
Cheap cola is a source of dilute phosphoric acid.....


That's v handy to know

Cheers!


It is very dilute, but should be adequate to get a coating on teh iron/steel. Best use diet stuff.....

britishtrident - 29/4/16 at 04:35 PM

quote:
Originally posted by joneh
How about a waterless coolant? I gather there's been a few discussions on the merits etc in the past.

Might be worth a search on here first.



Water less coolant is really just a glycol antifreeze concentrate ( it can be either Ethylene or Proplene Glycol) with anti-corrosion additive package adjusted to keep the PH at the right alkalinity --- really not a good move.
The sweet spot for glycol anti-freeze mixture lies in the range 40/60 to 60/40

britishtrident - 29/4/16 at 04:40 PM

There is likely a huge ammount of rusty sludge in the block, not easy to get out with the engine in the car.

theconrodkid - 29/4/16 at 05:50 PM

washing soda crystals,same as used with electrolisis worked for me,put it in the engine and run it for a bit

Brian R - 29/4/16 at 07:21 PM

quote:
Originally posted by britishtrident
There is likely a huge ammount of rusty sludge in the block, not easy to get out with the engine in the car.


Indeed. We had similar issues when building up an old crossflow. Stripped it including taking all the core plugs out. Dug the worst out with a screwdriver and fired a steam cleaner in every available orifice to free up the rest.

Surprising how high it had built up around the cylinders. Would have more than likely caused cooling issues too.

britishtrident - 30/4/16 at 07:27 AM

quote:
Originally posted by theconrodkid
washing soda crystals,same as used with electrolisis worked for me,put it in the engine and run it for a bit


That was the old school method for 100 perecent cast iron engines trouble is washing soda attacks alumininium.
Citric acid is cheap from ebay a very good rust remover.
Anything added as a flushing agent has to be flushed out.
In normal use the PH of the cooling system needs to be mildly alkaline for corrosing protection a PH of 9 to 10 for old style green antfreeze and round 7.1to 8 for OAT coolant.

[Edited on 30/4/16 by britishtrident]

sprintB+ - 30/4/16 at 08:10 AM

Bit late with this, but, I have a friendly central heating guy. With his advice I used boiler cleanser, Sentinel X400. It is safe on all metals and rubber. So I added it, left it in there for 3 weeks, ran the car nearly everyday and flushed it out when hot. Next thing was a central heating flushing pump, lots of water and chemicals moving at a high volume but a low pressure, the pump has a reverse facility, couple of adaptors and ran it for an hour, frightening what it removed and very pleased with the results. I've just completed a V8 Rover engine build and have arranged to hire this pump again. Chemicals easily available off the shelf at Wickes etc.