Leaking Coolant/PRV Valve

[Ex-Member]

Hi   when I bought my boat the PRV valve drained into the bilge.  The surveyor suggested it should go out of the hull via a skin fitting however, as it has been like that since new, I decided to leave it as is but collect the 'drips' in a 2ltr container. (personally I think this better than going through the hull as at least you can monitor the volume.... but that is for another discussion).   Recently I have been losing coolant and the 2ltr bottle, which used to take days, if not weeks, to fill is now filling virtually overnight.  I have turned the PRV valve several times to remove any c**p/limescale and for a couple of days it reduced the drip but it is now back to high volume.

I am guessing that the two are connected i.e. loss of coolant and increase drip so I plan to replace the PRV during winterisation  unless anyone can advise me otherwise???  

 

Thanks

[Scholar Gypsy]

Um, your hot water,  which is connected to the PRV, should be separate from your coolant circuit which goes through a coil on calorifier. 

Sounds like you may have a leak in the coil of your calorifier, which is  a health hazard as well as antifreeze is poisonous. 

[cuthound]

4 minutes ago, Scholar Gypsy said:

Um, your hot water,  which is connected to the PRV, should be separate from your coolant circuit which goes through a coil on calorifier. 

Sounds like you may have a leak in the coil of your calorifier, which is  a health hazard as well as antifreeze is poisonous. 

I'd agree with this diagnosis.

The hot water which expands out of the calorifier is clear, the coolant will be blue or red in colour, depending upon type, but will be very much diluted by the large volume of fresh water in the calorifier. 

[Scholar Gypsy]

Ps if this were my boat (every boat is different) I would

* close the valve on the cold water supply to the calorifier

* drain calorifier

* run engine for a day

* drain calorifier again and see what comes out, and if it smells of antifreeze. 

[cuthound]

1 minute ago, Scholar Gypsy said:

Ps if this were my boat (every boat is different) I would

* close the valve on the cold water supply to the calorifier

* drain calorifier

* run engine for a day

* drain calorifier again and see what comes out, and if it smells of antifreeze. 

Whilst keeping an eye on the coolant level.

It won't cool the engine very well if most of it is inside the calorifier. 

[Ex-Member]

Ok   thanks  i am trying to follow this.   The previous owner used a clear antifreeze/coolant which you can mix with any colour, either blue or pink, so I spoke with a helpful guy at Wharf Marina and he suggested putting in Morris Blue so I could then check.   The water collecting in the bottle from the PRV is clear & tastes OK  so I am now thinking it is two different problems.  I am not losing a vast amount of coolant, when I check the header tank it is about an inch down so maybe that was a case of it was low and by topping it up it is now just normal expansion  leaving the problem to be the PRV???

[CaptAWOL]

47 minutes ago, Scholar Gypsy said:

Um, your hot water,  which is connected to the PRV, should be separate from your coolant circuit which goes through a coil on calorifier. 

Sounds like you may have a leak in the coil of your calorifier, which is  a health hazard as well as antifreeze is poisonous. 

I agree with this, if you have the PRV spilling straight overboard there is a risk of spraying hot water out and if you do have anti-freeze contamination you'll be killing fish!

[Scholar Gypsy]

4 minutes ago, Numpty said:

Ok   thanks  i am trying to follow this.   The previous owner used a clear antifreeze/coolant which you can mix with any colour, either blue or pink, so I spoke with a helpful guy at Wharf Marina and he suggested putting in Morris Blue so I could then check.   The water collecting in the bottle from the PRV is clear & tastes OK  so I am now thinking it is two different problems.  I am not losing a vast amount of coolant, when I check the header tank it is about an inch down so maybe that was a case of it was low and by topping it up it is now just normal expansion  leaving the problem to be the PRV???

Just a thought. If you overfill the coolant system, then each day it will expand & vent, and then be lower the following morning.

So I would suggest you leave the coolant alone for a few days and see if the level in the morning is the same for a couple of days -- while obviously keeping an eye on the temp gauge of course. In an ideal world you shouldn't really use any coolant for weeks at a time. You can then mark the normal morning level in the plastic expansion tank (if you have one), or note the normal in the metal heat exchanger thingy on the top of the engine (if you have one of those). I have the latter, and normal level is a couple of inches below the lip of the pressure cap.

[ditchcrawler]

1 hour ago, CaptAWOL said:

I agree with this, if you have the PRV spilling straight overboard there is a risk of spraying hot water out and if you do have anti-freeze contamination you'll be killing fish!

If you have antifreeze in your potable water killing fish is the least of your worries, you could be killing people.

[Ex Brummie]

Anti freeze in German and Austrian wines 20 years or so ago, didn't kill too many.

However, with your coolant, as suggested monitor for a couple of days without topping up, it may just settle at a lower level than full. Ref your PRV, switch off your water pump, open a tap to relieve the pressure, close that tap and run the engine and see whether expansion causes a leak. Then open a tap and see what

pressure has built up. Also, you do not say whether you have an expansion vessel. If so, is it pressurised correctly, or is it defunct. If it cannot takeup expansion, then your PRV will leak.

[Tony Brooks]

If it is a perforated calorifier coil, which I doubt, on most boats water would be leaking form the coolant filler cap all the time the pump is turned on. That is unless the pump cut out pressure has been adjusted downwards. Most coolant pressure caps are 15 psi as a maximum and typical pump cut out pressures are at least 7 psi above that.

At present I lean towards simple overfilling of the coolant system.

[cuthound]

1 hour ago, Tony Brooks said:

If it is a perforated calorifier coil, which I doubt, on most boats water would be leaking form the coolant filler cap all the time the pump is turned on. That is unless the pump cut out pressure has been adjusted downwards. Most coolant pressure caps are 15 psi as a maximum and typical pump cut out pressures are at least 7 psi above that.

At present I lean towards simple overfilling of the coolant system.

How does that explain that the amount collected in the container under the PRV  has recently increased, unless the OP has also recently taken to overfilling the cooling system? 

 

6 hours ago, Numpty said:

Recently I have been losing coolant and the 2ltr bottle, which used to take days, if not weeks, to fill is now filling virtually overnight.  I have turned the PRV valve several times to remove any c**p/limescale and for a couple of days it reduced the drip but it is now back to high volume.

I am guessing that the two are connected i.e. loss of coolant and increase drip so I plan to replace the PRV during winterisation  unless anyone can advise me otherwise???  

 

Thanks

 

[WotEver]

9 minutes ago, cuthound said:

How does that explain that the amount collected in the container under the PRV  has recently increased, unless the OP has also recently taken to overfilling the cooling system? 

The two things are not necessarily linked (although of course they could be). The leaking PRV could be down to a faulty expansion vessel. The coolant loss could be down to over-filling. 

[cuthound]

2 minutes ago, WotEver said:

The two things are not necessarily linked (although of course they could be). The leaking PRV could be down to a faulty expansion vessel. The coolant loss could be down to over-filling. 

Very true, but the OP said it is a recent thing that he has been having to top up the coolant, so presumably something has changed,  even if it his him forgetting to stop pouring when topping up the coolant. 

Edited September 13, 2017 by cuthound
To unmangle the effects of autocorrect.

[David Mack]

54 minutes ago, cuthound said:

How does that explain that the amount collected in the container under the PRV  has recently increased, unless the OP has also recently taken to overfilling the cooling system?

If the expansion vessel has ceased to work then more water will be pushed out of the PRV each time the water is heated. It could simply be that the EV needs pumping up, or maybe the diaphragm is perforated.

 

[Iain_S]

I agree with Tony that a perforated coil in the calorifier would lead to the coolant level increasing, and I cannot see how it would lead to water or coolant escaping via a serviceable PRV.  3 Bar is 43.5p.s.i.

 

[Scholar Gypsy]

7 hours ago, Iain_S said:

I agree with Tony that a perforated coil in the calorifier would lead to the coolant level increasing, and I cannot see how it would lead to water or coolant escaping via a serviceable PRV.  3 Bar is 43.5p.s.i.

 

Silly me. I should think harder..

[Ex-Member]

Once again, thanks for all the replies/advice.

I am pretty sure that the coolant problem is solved and that I probably contributed to it. The coolant was low but because the previous owner was using 'Blu Col'  it was clear and because of where the plastic expansion tank is positioned I couldn't really see the indicator level so I think I did overfill it especially as, because I put Morris Blue in, I could see the colour and the excess was dripping into the tray below the engine.  I have taken the advice & given it a couple of days & the level has not changed with no leaks. I have another metal expansion tank (about 20cm sq) which is (I was told) for the Mukuni heater and I think I overfilled that too!!   Steep learning curve but at least I am admitting it and am learning!!

Regarding the PRV  I have tried what the manual says, e.g. repeatedly turning it to release any grit/limescale but I think either the 'seat' has gone or indeed the whole valve. For the cost of a new one I think it worthwhile to change it especially as it will soon be time for winterisation. Although it is still filling the bottle the water is clear and there is no taste of anything.

 

 

[WotEver]

You haven't mentioned the expansion vessel for the hot water. Do you have one? Have you checked its pressure?

Tony

[Iain_S]

1 hour ago, Numpty said:

Regarding the PRV  I have tried what the manual says, e.g. repeatedly turning it to release any grit/limescale but I think either the 'seat' has gone or indeed the whole valve. For the cost of a new one I think it worthwhile to change it especially as it will soon be time for winterisation. Although it is still filling the bottle the water is clear and there is no taste of anything.

 

Unless there is a pressure vessel of some sort, water will escape via the PRV, as the system heats up.

[Ex-Member]

Hi again........  just called in at Streethay Wharf for some diesel and one of the guys very kindly had a look at it for me. He said the coolant is fine, no problems but the PRV is definitely shot. He said that as I will be winterising the boat in a month or so just to carry on and change it then, rather than having to drain the system twice. He also offered to drill a hole through the hull for me on our return journey so I can run it through a skin fitting. So it looks like it should be Ok until then.   Once again thanks for all the help & advice!!

[Iain_S]

Depending on the position of the calorifier, it might be better to plumb into a container. That way provides a check that everything is working as it should. If there is a pressure vessel, or a reasonably sized accumulator and no non-return valve in the calorifier feed, there shouldn't be any water passing through the PRV.

[WotEver]

29 minutes ago, Iain_S said:

If there is a pressure vessel, or a reasonably sized accumulator and no non-return valve in the calorifier feed, there shouldn't be any water passing through the PRV

^^^^^ This. 

[ditchcrawler]

4 hours ago, Iain_S said:

Depending on the position of the calorifier, it might be better to plumb into a container. That way provides a check that everything is working as it should. If there is a pressure vessel, or a reasonably sized accumulator and no non-return valve in the calorifier feed, there shouldn't be any water passing through the PRV.

Maybe he will tell us if he has one

[Ex Brummie]

5 hours ago, Iain_S said:

Depending on the position of the calorifier, it might be better to plumb into a container. That way provides a check that everything is working as it should. If there is a pressure vessel, or a reasonably sized accumulator and no non-return valve in the calorifier feed, there shouldn't be any water passing through the PRV.

An expansion vessel should be able to cope with about 3% - 4% of the system volume. So a 50 litre calorifier would easily be served by a 5litre vessel, allowing for the contents of the pipework.