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Old 10-08-2012, 11:28 AM
robertobaggio20 robertobaggio20 is offline
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Join Date: Oct 2009
Posts: 3,403
Mein Auto: car
This is one area where excellence is neither practical nor possible.

Your engine's cast iron block has a thin coating of rust. This will be there even if you had used and changed coolant at the correct interval since the car was made. This thin layer of rust prevents more rust from settling in on it. Any additional rust that is formed is typically just flakes from this layer which come off and move into suspension and is carried everywhere. Of course, new rust eventually forms where the old rust flaked off in the coolant passage.

The way to remove these rust flakes is to flush the radiator. That is done by simply draining the coolant completely and refilling it. The traditional method was to put a garden hose into the expansion tank and remove the top rad hose and start the engine. Water would go in through the garden hose and out through the top radiator hose. (btw set your cabin heater to full heat and max fan blast.) After 10 minutes, refill with water and coolant, bleed the radiator, then drive.

If you noticed too much rust coming out (a little is not a big deal), then repeat this one week later. Drive during that week. The water will circulate and bring out more of the loose rust from the block to the radiator etc where it can be flushed out once again. If you did not notice rust during the first flush, then you're done.

After that, merely flush the radiator once a year, or when you're completely bored. Well it is fun to do, at least for me, and I usually combine it with a thorough engine wash and cleanup.

Flush the radiator whenever you have to do any work that requires the coolant to be vacated such as changing the water pump, rad hoses, radiator, etc. Coolant needs to be refreshed once every 2 years, and that would be a great time to flush as well.

The so called off-the-shelf radiator flush solutions do not work. Waste of time and money. The only reliable rust remover I found is sold by Cummins, and they generally only sell it to companies that operate their machines not car owners.

Sell off your flush kit. It will not dislodge and remove rust. The only time that rust can be removed from the block is during a bottom overhaul (they don't typically do this during a top overhaul either).

The benefits to a squeaky clean block are negligible over what you've got now, assuming of course that your cooling system is generally clean. When BMW designed our block, they factored in a thin layer of rust in the block's coolant passages.

Unless you deliberately do things like use hard water and add chemicals that promote oxidation, or throw 'nano coolant passage cleaning particles' into the radiator (hey there's a new saleable idea !), rust is not going to make a difference.

They key weaknesses in cooling systems seem to be radiator seals and plastic bits that become brittle and break off due to age, along with worn water pumps and worn fan clutches. The solution to the last two is simple. First, change to a water pump that has a composite impeller. It is lighter than metal and sturdier than plastic. Second, remove the fan clutch after making sure that your aux fan and the aux fan's temp sensor works fine, in both low and high settings. You don't need it, and the reduced load on the water pump will automatically extend its service life....and you don't have to pay for a new fan clutch as well.

Last edited by robertobaggio20; 10-08-2012 at 11:34 AM.
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