Volvo Penta Service Bulletin 26-0-29: Coolant Replacement

[nigelmercier]

While researching the different types, I discovered a Volvo Penta bulletin that stated you needed to flush with oxalic acid if going from conventional to OAT. Not sure about the other way around.

http://www.google.co.uk/url?sa=t&rc...2XNIUmcw51owYSA&bvm=bv.47534661,d.ZWU&cad=rjt

I'm about to buy new coolant, but I'm not 100% sure which type it is, I would like to flush the engine anyway.

In the above file it says to refer to Service bulletin 26-0-29 for instructions. I believe this involves draining the coolant, filling with a solution of Oxalic acid and running the engine for 20 min, then draining and filling with solution of Sodium Bicarbonate, again running engine for 20 min (to neutralise the acid), then water flush before filling finally with coolant.

However, I don't know the concentrations to use, so has anybody got Volvo Penta Service Bulletin 26-0-29?

 

[nigelmercier]

... I don't know the concentrations to use...

I decided to investigate further myself. I had read "[Oxalic Acid is] available in 16oz. containers, which gives the right mixing ratio with water for the typical car cooling system with 3-4 gallons capacity." 16oz = 450g, 4 gallons = 18 litres, so I settled on a concentration of 250g Oxalic Acid in 10 litres of water. I also did an experiment to see how much Sodium Bicarbonate was needed to neutralise 5g of Oxalic Acid, although I can't find my pH papers, it's about twice as much: 10g. Of course it only has to neutralise what is left in the waterways. I will assume 5% is left, so I need 250g x 2 x 5% = 25g.

I thought I was doing really well, I filled up with the acid, ran the engine for 20 minutes, then waited another 20. I figured it must be reasonably cool by now...

Here's a tip. When you have an engine block full of hot acid, do not under any circumstances assume the pressure has dropped. If you take off the pressure cap too early, you will spray said hot acid all over yourself, your tools, the engine, the floor...

Ask me how I know

 

[typhoonNige]

Ouch! In your situation I would have used my professional experience as a chemist and oceanographer - and jumped over the side! Oxalic acid is not all that corrosive, even when hot, but not good for showering IMHO. If you haven't done so yet go and shower and wash the affected clothes.

 

[VicS]

I decided to investigate further myself. I had read "[Oxalic Acid is] available in 16oz. containers, which gives the right mixing ratio with water for the typical car cooling system with 3-4 gallons capacity." 16oz = 450g, 4 gallons = 18 litres, so I settled on a concentration of 250g Oxalic Acid in 10 litres of water. I also did an experiment to see how much Sodium Bicarbonate was needed to neutralise 5g of Oxalic Acid, although I can't find my pH papers, it's about twice as much: 10g. Of course it only has to neutralise what is left in the waterways. I will assume 5% is left, so I need 250g x 2 x 5% = 25g.

You dont have to experiment to determine how much sodium bicarbonate you need........ you were taught how to calculate it when you were aged about 13 or 14.

C₂O₄H₂ + 2NaHCO₃ → C₂O₄Na₂ + 2H₂O + 2CO₂​

There fore 1 mol ( 90g ) of oxalic acid requires 2 mol (168g) sodium bicarbonate to neutralise it.

so 5g will require 9.33g ... 10g will leave a comfy small excess of bicarb.

However oxalic acid is usually supplied as the dihydrate (RMM = 126)

5g of the dihydrate will therefore only need 6.7g sodium bicarbonate to neutralise it. 10g will be a significant excess

 

[typhoonNige]

You dont have to experiment to determine how much sodium bicarbonate you need........ you were taught how to calculate it when you were aged about 13 or 14.

C₂O₄H₂ + 2NaHCO₃ → C₂O₄Na₂ + 2H₂O + 2CO₂​

There fore 1 mol ( 90g ) of oxalic acid requires 2 mol (168g) sodium bicarbonate to neutralise it.

so 5g will require 9.33g ... 10g will leave a comfy small excess of bicarb.

However oxalic acid is usually supplied as the dihydrate (RMM = 126)

5g of the dihydrate will therefore only need 6.7g sodium bicarbonate to neutralise it. 10g will be a significant excess

All very well and impressive in a GCSE sort of way, but in a real world situation like this uncertainty comes in to play. The uncertainty in the estimate for the amount of acid remaining in the system (a rough estimate) is high so I reckon Nigel has it about right.

Another use for oxalic acid on the boat! Better start saving my rhubarb leaves.

 

[VicS]

All very well and impressive in a GCSE sort of way, but in a real world situation like this uncertainty comes in to play. The uncertainty in the estimate for the amount of acid remaining in the system (a rough estimate) is high so I reckon Nigel has it about right.

Another use for oxalic acid on the boat! Better start saving my rhubarb leaves.

The idea was that a quick back of fag packet calculation like this gives some idea of the quantity of bicarb necessary to neutralise the oxalic acid estimated to be left when the system is drained.

There is only about 0.5% oxalic acid in rhubarb leaves and probably not much more than half of it present in a water soluble form. So supposing you want about 120g, to make a litre of solution, even if you can extract it efficiently you will need to start with about 40 or 50kg of leaves.
You should have plenty of rhubarb to eat, give away or bottle.

I'll have a few kg to bottle.

 

[nigelmercier]

.... you were taught how to calculate it when you were aged about 13 or 14...

Yes I know, but it's been a long time. You do this stuff every day, but it would take me longer to re-learn how to do it than to do the experiment. Thanks for the details though, I thought this would get your interest.

As it did in fact take (almost) 10g, does this mean I don't have the dihydrate form of Oxalic? I assume the other form would be anhydrous, which I would have thought would be unstable and revert to dihydrate anyway.

 

[Haven't-a-Clue]

Bluddy hell Vic, I wish I'D had a teacher who could've been bothered to make sure I understood this, instead of just leaving me to guess (and fail). Any reccomendations for a book that assumes the reader knows nothing, to, say, O level standard? I'm not stupid (IQ 134) but couldn't grasp the basics.

edit: Why couldn't I do this as a reply with quote, FFS?

 

[oldvarnish]

You dont have to experiment to determine how much sodium bicarbonate you need........ you were taught how to calculate it when you were aged about 13 or 14.

C₂O₄H₂ + 2NaHCO₃ → C₂O₄Na₂ + 2H₂O + 2CO₂​

There fore 1 mol ( 90g ) of oxalic acid requires 2 mol (168g) sodium bicarbonate to neutralise it.

so 5g will require 9.33g ... 10g will leave a comfy small excess of bicarb.

However oxalic acid is usually supplied as the dihydrate (RMM = 126)

5g of the dihydrate will therefore only need 6.7g sodium bicarbonate to neutralise it. 10g will be a significant excess

Very much enjoyed that. Took me right back.

 

[nigelmercier]

edit: Why couldn't I do this as a reply with quote, FFS?

IQ not high enough