Coolant Change Drain - Webasto ThermoTop EVO

[JoeC]

Hello.

I am draining the coolant on my Webasto ThermoTop EVO as the blue coolant is 3 years old and time for a change along with a flush. I have had the boat for 1.5 years and not changed it before but an Eberspacher engineer reckoned that all I need to do is drain from the drain point on the lowest radiator whilst taking the lid off the expansion tank and opening the valves and bleed points on all radiators. When I asked him how much refill I would need he guesstimated maybe 40 litres. Refill is a case of constantly topping up the expansion tank with pre-diluted 25 (coolant) / 75 (deionised water) and bleeding the radiators - the Webasto should auto bleed itself.

 

On draining I have maybe got out 15 litres which seems not a lot to me. My boat is 60 feet long, 4 radiators and 2 fin rads and the Webasto is connected to the calorifier. Is there more to the draining than what I have done above? Is there a bleed point or something on the Webasto that I need to go to?

 

EDIT - I have just found two drain valves in the engine bay that are connected to the IN and OUT pipes of the Webasto unit. Do I need to drain BOTH of these?

 

Thanks in advance.

Joe

Edited May 30, 2023 by JoeC

[JoeC]

I've opened both of the drain points in the engine bay and nothing came out. I opened up all three drain points and the system is still not draining anymore. Putting it back together to fill up with tap water to run for a while as a flush before refilling with antifreeze and de-ionised water.

[cuthound]

On 30/05/2023 at 11:44, JoeC said:

Hello.

I am draining the coolant on my Webasto ThermoTop EVO as the blue coolant is 3 years old and time for a change along with a flush. I have had the boat for 1.5 years and not changed it before but an Eberspacher engineer reckoned that all I need to do is drain from the drain point on the lowest radiator whilst taking the lid off the expansion tank and opening the valves and bleed points on all radiators. When I asked him how much refill I would need he guesstimated maybe 40 litres. Refill is a case of constantly topping up the expansion tank with pre-diluted 25 (coolant) / 75 (deionised water) and bleeding the radiators - the Webasto should auto bleed itself.

 

On draining I have maybe got out 15 litres which seems not a lot to me. My boat is 60 feet long, 4 radiators and 2 fin rads and the Webasto is connected to the calorifier. Is there more to the draining than what I have done above? Is there a bleed point or something on the Webasto that I need to go to?

 

EDIT - I have just found two drain valves in the engine bay that are connected to the IN and OUT pipes of the Webasto unit. Do I need to drain BOTH of these?

 

Thanks in advance.

Joe

 

When  I drained the central heating system on my 60 foot boat one large double rad, one single rad and a double half height rad plus heated towel rail I got 25 litres out of it.

[MtB]

The thing is, every boat is different and no-one here has seen the OP's boat, so no-one can tell them how to do it, which is in turn why there are so few answers.

 

This is aside from the apparent pointlessness of changing the fluid in the system anyway! 

 

 

[JoeC]

@cuthound  Thanks for your information.

 

@MtB  I appreciate that all boats are different and your comment can be said for almost any question that people ask. However, I see it as those comments are information and learning points that help me to decide how I want to proceed. As for it being a pointless task then that is your opinion and I have my own. But thank you.

[Awayonmyboat]

The biggest point to remember is water only drains downhill. So make sure you are draining the lowest points of all circulating loops. On my boat that means draining the radiators (which are on one side of the boat) the bathroom towel rail (which is on a long loop on the other side) and the Webasto itself. 

 

Whilst it is fair to say all boats are different, as a point of reference mine which is a 58' fairly standard reverse layout with radiators along the length of the boat took 27 litres when I filled it after installation. It is plumbed with the recommended 22mm pipe for the main runs, obviously if your system uses 15 mm throughout that would use quite a bit less.

[MtB]

42 minutes ago, Awayonmyboat said:

The biggest point to remember is water only drains downhill.

 

The second biggest point to remember is water sometimes refuses to drain out of open drain cocks unless air can get in at the top of the system.

 

So open any and all air vents or the water can 'hang' in the system, held in by atmospheric pressure. 

 

 

[blackrose]

Since it's the anti-corrosive properties of antifreeze that expire first (after 2 or 5 years for most standard blue and long life red coolants respectively), an alternative to completely draining engine and heating systems is just to add a bit of Ankorsol.

 

https://www.morrislubricantsonline.co.uk/ankorsol-anti-corrosion-fluid.html

 

It's the lazy way of doing it, potentially avoiding some mess and I can't really see any downsides. It just extends the lifespan of your antifreeze but I don't really know at what point the antifreeze properties of antifreeze are reached?

[JoeC]

Thought I would give an update as it may help others.

 

I drained the flush water out of the system (still coming out blue) and I'm still getting about 15 litres out. As people have mentioned there could be a mixture of reasons why no more water is coming out - pipes not fully downward pointing to the drain point, bow end where the drain plug is being higher than the back of the boat, fresh water tank not full so bow sticks upwards, small bore pipes, calorifier laying horizontally and many more.

I think there is a 'drain' mode in the Webasto via engineer tools and software (which I don't have) which would give a full drain but I'm OK with the way I'm doing it, albeit taking longer to do but I have the time.

 

I will do one more flush and then take radiators off as I also want to put foil behind them so the heat goes into the boat and not into the canal. Then I will fill with anti-freeze and deionised water and call it a day.

 

Hope this helps others.

[Tonka]

6 hours ago, JoeC said:

Thought I would give an update as it may help others.

 

I drained the flush water out of the system (still coming out blue) and I'm still getting about 15 litres out. As people have mentioned there could be a mixture of reasons why no more water is coming out - pipes not fully downward pointing to the drain point, bow end where the drain plug is being higher than the back of the boat, fresh water tank not full so bow sticks upwards, small bore pipes, calorifier laying horizontally and many more.

I think there is a 'drain' mode in the Webasto via engineer tools and software (which I don't have) which would give a full drain but I'm OK with the way I'm doing it, albeit taking longer to do but I have the time.

 

I will do one more flush and then take radiators off as I also want to put foil behind them so the heat goes into the boat and not into the canal. Then I will fill with anti-freeze and deionised water and call it a day.

 

Hope this helps others.

Do you not have a wood panel over insulation where the radiators are fitted then

[blackrose]

46 minutes ago, Tonka said:

Do you not have a wood panel over insulation where the radiators are fitted then

 

A proportion of heat emitted by a radiator will always be absorbed by the wall behind and wood won't reflect the heat like foil faced insulation. I put the flexible foil faced bubble wrap type stuff behind my radiators but there shouldn't be any need to take the radiators off the wall to do this.

Edited June 9, 2023 by blackrose

[LadyG]

I topped the Webasto reservoir with yellow coolant, same as for the engine , it's compatible. I won't drain anything till it's necessary, but I wonder why deionised water is needed. My kettle has not furred up in four years.

[ditchcrawler]

5 minutes ago, LadyG said:

I topped the Webasto reservoir with yellow coolant, same as for the engine , it's compatible. I won't drain anything till it's necessary,  How will you know when its necessary? but I wonder why deionised water is needed. Because that is the proper way to do it. My kettle has not furred up in four years.

 

[LadyG]

1 hour ago, ditchcrawler said:

 

I will know it is necessary when it stops working.

[Tony Brooks]

3 hours ago, LadyG said:

I will know it is necessary when it stops working.

 Because the aluminium heat exchanger has developed holes. Check the cost of a new one. new antifreeze every few years or a top up with corrosion inhibitor will probably look a cheap option.

[MtB]

5 minutes ago, Tony Brooks said:

 Because the aluminium heat exchanger has developed holes. Check the cost of a new one. new antifreeze every few years or a top up with corrosion inhibitor will probably look a cheap option.

 

If this is the reason the OP wants to change the fluid, then adding the Morris Ankorsol to the fluid will restore the anti-corrosion properties of the aging antifreeze.

 

https://www.morrislubricantsonline.co.uk/ankorsol-anti-corrosion-fluid.html

 

[Tony Brooks]

4 minutes ago, MtB said:

 

If this is the reason the OP wants to change the fluid, then adding the Morris Ankorsol to the fluid will restore the anti-corrosion properties of the aging antifreeze.

 

https://www.morrislubricantsonline.co.uk/ankorsol-anti-corrosion-fluid.html

 

 

Agreed.

[LadyG]

8 hours ago, LadyG said:

I will know it is necessary when it stops working.

PS will Prestone do?

[Tony Brooks]

1 hour ago, LadyG said:

PS will Prestone do?

 

I assume that is antifreeze and yes it will do if you drain the system and refill at the recommended intervals because if you just keep adding more the concentration of antifreeze will keep increasing and the stronger the mixture the less heat the liquid can distribute around the system. This is why we typically only use a 30% mixture and say 50% is the maximum. Look up the specific heat capacity of whatever "glycol" the Prestone uses and compare that with water.

[LadyG]

40 minutes ago, Tony Brooks said:

 

I assume that is antifreeze and yes it will do if you drain the system and refill at the recommended intervals because if you just keep adding more the concentration of antifreeze will keep increasing and the stronger the mixture the less heat the liquid can distribute around the system. This is why we typically only use a 30% mixture and say 50% is the maximum. Look up the specific heat capacity of whatever "glycol" the Prestone uses and compare that with water.

Ty, it is already di!uted to an extent, will read data sheet.

Edited June 10, 2023 by LadyG

[Tony Brooks]

1 minute ago, LadyG said:

Ty, it is already di!uted to an extent, will read data sheet.

 

That won't tell you the Specific Heat Capacity, but should tell you the dilution rate.

[ditchcrawler]

14 hours ago, LadyG said:

I will know it is necessary when it stops working.

Do you work on the same premise for engine coolant and oil changes ?

[Galoka]

On 10/06/2023 at 07:22, LadyG said:

Ty, it is already di!uted to an extent, will read data sheet.

Prestone just use standard Mono ethylene glycol as the antifreeze component.

The ready to use stuff is a equivalent 50:50 mix. To make a 25%/75% mix as recommended by Webasto, dilute the ready to use stuff 50:50 (so dilute 1litre  of ready to use with 1 litre of water)