Flushing out coolant system

[TheDampMan]

Hi all
When I checked my antifreeze I noticed the coolant in the expansion tank was a little brown, I think it might be time to flush out the whole system and replace with fresh antifreeze.
Citric acid and vinegar has been posted previously as being a good way to break up any crud in the system?
Any advice/tips on doing this?

[mgcjag]

Hi Steve.....i recently flushed out an xj6 engine where the coolant looked ok i used a product for flushing and actually done it 3 times... draining, filling running etc...i thought it was probably all nice and clean......a couple of weeks i pulled the engine out of the xj6 for use in another build and then removed the water pump and rear plate on the back of the block and was supprised to see how much crud was still in there at a lower level that the actual drain points......i used a jet wash through the openings and removed a supprising amount......Steve

[mark10337]

Quite a strong solution of kitchen / dishwasher descaler, run it up to temp, let it sit for a week before flushing with a high pressure hose. This may have a limited effect on passages that are completely blocked. The descaler can only nibble at the ends of the blockage, rather than softening it along its whole length.