Citric acid

[les]

Just looked at my citric acid pack, it’s out of date ! I need more. For block cleaning what grade is better, food grade or what they say general cleaning ? I was inclined to think it’s the former any thoughts please.

[svenedin]

The crystals last almost indefinitely if kept dry so I wouldn't worry about the date just for cleaning engine blocks. Food grade is purer but cleaning grade is fine for descaling a block. The made up citric acid solution does go off (microbes break it down). I used to use citric acid as a stop bath in photographic work and the made up solution had a short life.

Stephen

[les]

Thanks for that Stephen, I was surprised when I saw the apparent best before date on the pack, it was 2022 ! My main concern was leaving it in the block for a couple of weeks to find it had lost its strength, requiring starting again.

[svenedin]

Thanks for that Stephen, I was surprised when I saw the apparent best before date on the pack, it was 2022 ! My main concern was leaving it in the block for a couple of weeks to find it had lost its strength, requiring starting again.

It should be absolutely fine but one thing to consider is that as the temperature starts to fall it works rather slowly.

Stephen

[les]

Better get cracking then, the weather is changing.

[les]

Acid now in block, there are different views on how long to leave the acid in the block, I’m wondering if there is an active life for it, for arguments sake, if it is left in for say 3 weeks, would it in fact, have done its job in two weeks, the 3rd week having sat there doing nothing having lost its cleaning ability ?

[philthehill]

Les
With your citric acid just use it.
I have had 2 packs of citric acid for some time, there is no use by date on the packet but it still works ok.
It is food grade citric acid and the only constraints are that it should be kept in a cool dark place.
I keep the packs (which are sealed) in a sealed airtight container.
As regards length of time in the block - it will vary with the amount of corrosion in the coolant jacket. If you can leave it three weeks then do so. The longer it is left the better. You can always drain some off and refill with new solution if required.
Phil

[les]

Ok Phil, I had thought of leaving for two weeks, then drain and fill for another two. Thanks for your thoughts.

[59Elva]

Can citric acid be used in an installed running engine? Will it attack aluminum, copper, or brass components? I’ve had plain water in the truck since June. I don’t expect freezing temperatures before November but you never know. I should find some antifreeze soon.

[svenedin]

Yes citric acid can be used in a running engine. It works really well that way as the reaction is much faster when hot. I would only leave it in the system for say two heat cycles and then drain and flush with clean water. It does react a bit with brass but not so much that it is a concern providing it is not left for long periods of time or not properly flushed out. Citric acid was the major ingredient of a proprietary cooling system cleaner that these days has a different formulation. Sometimes these cleaners are blamed for causing pinholes when what has actually happened is they have dissolved the crud that was blocking the pinholes. Citric acid is also a major ingredient in the some rapid type central heating cleaners. Such systems are iron (radiators) copper (pipes) brass (unions) aluminium (boiler heat exchangers). Citric acid cleans any tarnished brass rather well but it can make it a bit pink from leaching the zinc (which is more reactive) from the surface layer.

Stephen