Yanmar coolant change and flush

[Fredd]

Looking for some advice on changing the coolant in my Yanmars as I have never done this before .
The existing coolant is there over 10 years and is the old green colored one and I was going to change to the newer pink yanmar coolant . The last owner did his own servicing and I've no record of him changing it ,but there is receipts showing it was done in 2006 by a previous owner so I think it is well due a change .
I was originally going to drain the system and flush with De-ionized water and fill with the new but I was wondering if I should use a cleaner in the system first .
Is a regular automotive radiator cleaner ok ? I was thinking of this Radiator Cleaner or is there something more specific for marine engine systems.
I wasn't having any issues with engine temp and the engines are running fine , it's a pair of 4lh 's in a Broom 35 .

 

[VicS]

Looking for some advice on changing the coolant in my Yanmars as I have never done this before .
The existing coolant is there over 10 years and is the old green colored one and I was going to change to the newer pink yanmar coolant . The last owner did his own servicing and I've no record of him changing it ,but there is receipts showing it was done in 2006 by a previous owner so I think it is well due a change .
I was originally going to drain the system and flush with De-ionized water and fill with the new but I was wondering if I should use a cleaner in the system first .
Is a regular automotive radiator cleaner ok ? I was thinking of this Radiator Cleaner or is there something more specific for marine engine systems.
I wasn't having any issues with engine temp and the engines are running fine , it's a pair of 4lh 's in a Broom 35 .

If changing from a conventional, low silicate type of antifreeze to a long life, OAT type the recommended procedure is to clean the system with an oxalic acid flush, then drain and neutralise.
(Others will know better of course. )
The alternative is to stay with current type.
Unless an OAT type is recommended for your engine I would continue to use the conventional type . This is what is usually recommended.

Change at two yearly intervals in future even if using the long life OAT type because contamination with salt water is always a risk.

 

[VicS]

If changing from a conventional, low silicate type of antifreeze to a long life, OAT type the recommended procedure is to clean the system with an oxalic acid flush, then drain and neutralise.
(Others will know better of course. )
The alternative is to stay with current type.
Unless an OAT type is recommended for your engine I would continue to use the conventional type . This is what is usually recommended.

Change at two yearly intervals in future even if using the long life OAT type because contamination with salt water is always a risk.

The oxalic acid flush procedure was described by RJJ in November last year

I did the acid flush last season. If you can do a coolant change, you can do an acid flush. I'm sure it's expensive but only because it would involve rather a lot of sitting-around-drinking-tea time.

If you pm me I can send you the Volvo official instructions and ratios but essentially:

- Empty the old coolant
- Fill with oxalic acid and run up to temperature; then drain off once cooled
- Fill with bicarb solution and run up to temperature; then drain off once cooled
- Flush two or three times with fresh water; run up and drain off each time. you can keep going until the water runs clear if you like.
- finally fill with the new coolant.

For better or worse, I didn't drain the calorifier.

As stated, the two types (yellow and green in Volvo colours) don't mix at all. If changing from one t'other, you must acid flush. Being so clever, I've forgotten which one I put in last year, so will probably end up doing it all again in a years' time.

Dont mix the two antifreeze types unless you are using one which is suitable for mixing with other types

 

[Momac]

Why flush with deionised water when tap water will do .
If the existing coolant looks a good colour it probably hasn't been in there too long.

 

[RichardS]

Why flush with deionised water when tap water will do .
If the existing coolant looks a good colour it probably hasn't been in there too long.

If the tap water is hard I would also tend to avoid it as some of it is always left behind after draining although I agree that it is a very minor issue. Soft water would be fine. More that one flush will probably be required and the cost of buying deionised water would put me off although I might use it just for the final flush.

I have endless supplies of tumble dryer condensate which is ideal but not everyone is so blessed.

Richard