Coolant Changes Color

[myocean]

We have two more or less new Volvo engines in our catamaran. (worked now 100 hours)
One is fine, the other one now shows a different color of the coolant (Type LR-25) which is normally blue-green. It has now changed to a dirty green (a bit brown). This engine has in the past repeatedly lost coolant and we think this was lost at the connections to the hot-water boiler which is connected to the engines coolant circuit. (We found coolant in the boilers bilge but now this is thought to be fixed)
What can be the reason for the different color? Can this be a leakage between hot water in the boiler and coolant? However our experience is that coolant and water separate from each other which should be visible in the engines coolant reservoir.

[George P]

Just thinking out loud from a similar situation I had.
I would consider possible corrosion in the coolant system.
Or, did you add a different type of coolant when you topped off? Less so today but some coolants don't mix well and can react with canges in color and become thicker.

[John A]

There is a possibility that, in overheating the engine, a pinhole has developed in the head gasket of one of the cylinders causing oil to intrude into the coolant.

[az_r2d1]

It could be a blown head gasket due to overheating ?
Change the coolant out and see if it returns.
How much coolant is it losing?

[jstevens]

Sounds a bit like oil in the coolant. How is your oil cooler plumbed? Is it cooled by raw water or the engine coolant? Does the oil show any sign of coolant? If any of the above is "Yes", then I'd change the oil cooler.

John

[Geoff54]

Oil in ethylene glycol/water coolant tends to emulsify and turn milky. Just to be sure, put some in a jar and shake vigorously – if it doesn’t emulsify, it’s probably not oil getting in the coolant. Also check the oil for coolant in the oil.

I would suspect corrosion, in which case the question would be whether it is occurring or residual from your previous problems. I would back flush the system thoroughly, fill with fresh coolant and then use a hydrometer to test & record the SG. Can you bypass your water heater and subsequently reconnect? That will allow you to see if it is coming from there. If it does reoccur, retest the SG to see if the coolant is being diluted with fresh water or maybe salt water from the heat exchanger, which is leading to corrosion.



Good luck!

[barnakiel]

I also think this may be corrosion. Seen same story on Westerbeke gensets.

b.

[Outwest34au]

Combustion leak.
Get your hands on a colour change dye setup and it takes 1 minute to check to confirm at the radiator/ header tank.