Adding caustic soda to water to clean radiator

[MorrisGoa]

Hi,

My 1098cc saloon car has sadly been at mechanic's place & he had filled plain chlorinated tap water to fill the radiator. It had been lying idle for about a year since the car wasn't starting. After locating the electrical fault the car was just started and noticed oil leakage through the timing chain seal.

When the radiator was removed, rust coloured water gushed out.

My mechanic suggests adding caustic soda to the water and running the engine for about 10 minutes before draining. I don't know if this is such a good idea.

Here in Goa there is liquid available called "Red Oxide Metal Primer" used for grill, gates, steel windows, steel structures etc. Should this be added for cleaning.

1. What would you suggest for cleaning?(Please suggest something that modern cars use, since that will be easily available here).
--------------
Another MMOC member had mentioned caustic soda, but didn't elaborate. Here's the link
mmoc.org.uk/viewtopic.php?f=4&t=35659&p ... da#p358373

As was always the case earlier, I intent to add coolant to the water post cleaning.

Many thanks.

[panky]

The only issue with caustic is that it eats aluminium alloys, ie thermostat cover, if it too strong or left for a long time. But if it's only a 10 minute flush then it should be OK but do flush out well with clean water afterwards - and wear gloves and goggles. There are many products available that do the same job, Radflush is one, try your local car accessory shop to see what's on the shelf if you dont fancy the caustic, but I suspect they all contain it.
Red oxide is paint so not a good idea to put it in the radiator

[RobThomas]

"Red Oxide Metal Primer"

That sounds like paint, not a cleaner.

[smithskids]

Never caustic soda, washing soda is good, it is used in old scotch boilers and makes the water feel slimy. Never red oxide paint it will clog up everything. We live in a hard water area and often put bath salts in to soften the water.

[Big Jim]

I am still cleaning mine . After a run I let it cool a bit then drain and refill . I have done it maybe 6 times and it is almost clear now . I would avoid chemical flushes in old cars , It may also damage paintwork , I have used cuastic soda as a paint stripper .

[MorrisGoa]

Thanks all for the quick responses.

I thought I'd provide a bit more information about the radiator. Its top & lower tanks are about 20 years old. However, the cooling tubes/fins are new (1 year old) and were put there by a custom radiator manufacturer. The rust coloured water I guess might be from the engine block too.

@panky: Another owner @'Big Jim' mentions that caustic soda is used as a paint stripper too. I'll wait for a few more replies and consult more people and take a decision. I'm going through paralysis by analysis as owner @smithskids advises against caustic soda and instead recommends washing soda whilst owner @'Big Jim' recommends no chemicals.

@'RobThomas': You are correct. That was an idea given to me. The logic being that it would coat the internals and after drying up would prevent rust. Other owners have advised against it, so it's off the options menu

@'Big Jim': OK. That's the least risky solution as of now

[colin addison]

I would give the rad a good flush out with clean water. Then fill with rain water plus antifreeze. Rain water is soft and doesn't have all the nasty things rads hate. The antifreeze must be the blue variety for old engines, not the newer orange/red type. Antifreeze has anti-corrosion chemicals added.
I have very recently drained water from the top of my rad on the MM and the water is just a pale shade of blue, no sign of rust colouring at all, this about 2 years after a fresh fill.
Colin

[MorrisGoa]

Thanks Colin for the top tip on using the blue antifreeze.

Since the monsoons have just concluded, I'll do the next best thing and take some well water to the mechanic's garage. It has been consumed directly(neither boiling nor filtering) for generations. It's good for humans and has been used with the Morris too .

After giving careful thought to the risks & rewards, I'll flush the radiator, multiple times without adding caustic/washing soda.

[amgrave]

The other thing to remember is the anti-freeze should be changed every two years as it's performance deteriorates over time.

[firehor5e]

I would avoid well water as it could contain some undesirable minerals? rain water is best.

[tortron]

washing soda, aka soda crystals is the one you want. works pretty well