GPSguru Posted December 30, 2020 Share Posted December 30, 2020 4 hours ago, Saintly Fish said: The expansion bottle on the cooling system of an engine is there to catch coolant if over filled and it expands ? Yes or No? If yes, why does it have a min and max line etched on it? If no, is it a top up reservoir ? And if it is a top up reservoir and the level drops, where is the coolant going, if not found in the bilge? If you have a closed circuit cooling system then there will be a pressure cap somewhere in the system, but it might not be on the expansion bottle (as an example, some cars have them on the Rad) ............. I assume that you have a closed circuit cooling system, and it is cooled by a raw sea water heater exchanger ? As a heating engineer you will know that water (or coolant) expands when hot, therefore somewhere is needed for that expansion to go , hence the min / max level ......... on other engines min / max would be cold / hot ............ It you are seeing a drop in coolant level on a closed circuit system, then you have a leak and the leak will be worse when the system is up to pressure (i.e. the engine and coolant is hot) ............. generally it is just a weep from a pipe, but in some cases it can also be a head gasket failure ............ or in the case of Mercrusiers with the 1.7L Vauxhall derived engine, a cracked head. Firstly look around the cooling system pipes for discolouration around pipe clamps etc, as that is a sure indication of a weep ............... also run the engine up to temp and again look for any wetness on the cooling system pipework .............. Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 30, 2020 Share Posted December 30, 2020 13 minutes ago, GPSguru said: If you have a closed circuit cooling system then there will be a pressure cap somewhere in the system, but it might not be on the expansion bottle (as an example, some cars have them on the Rad) ............. I assume that you have a closed circuit cooling system, and it is cooled by a raw sea water heater exchanger ? As a heating engineer you will know that water (or coolant) expands when hot, therefore somewhere is needed for that expansion to go , hence the min / max level ......... on other engines min / max would be cold / hot ............ It you are seeing a drop in coolant level on a closed circuit system, then you have a leak and the leak will be worse when the system is up to pressure (i.e. the engine and coolant is hot) ............. generally it is just a weep from a pipe, but in some cases it can also be a head gasket failure ............ or in the case of Mercrusiers with the 1.7L Vauxhall derived engine, a cracked head. Firstly look around the cooling system pipes for discolouration around pipe clamps etc, as that is a sure indication of a weep ............... also run the engine up to temp and again look for any wetness on the cooling system pipework .............. But the reservoir on his engine is unpressurised, so can only be a catch tank I.e. the flow is only one way (out of the pressure cap valve and into the tank) not two way like in a pressurised expansion tank situation. GPSguru 1 Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 If you are loosing coolant with no visible staining my first port of call would be your heat exchanger, as the cooling circuit runs a higher pressure than the raw water side it will leak into the sea water side and go out via the spray head in your exhaust. Or wherever the raw water discharges, if the leak is big enough you may get the rainbow effect on the surface of the water but usually a small crack in the tubes is enough to drain the level down over time and be virtually undetectable. Only way is to pressure test the exchanger. But first make fully sure you have no air in the system or external leaks Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 Also assuming you don't have a charge air cooler on this engine? Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 (edited) Sorry for multiple post, having zoomed in on your picture with the red circles I can explain a bit more, the small circle is showing your cooling system pressure cap, this is set to relief at a given pressure say 1.5 bar. The black pipe coming off and going to the expansion tank is there so that if the cap reliefs it will discharge the coolant into your expansion tank instead of spraying it around your engine bay. The expansion tank is designed to catch it, under the cap is there a stack pipe that runs down and would be under the coolant level? Edited December 30, 2020 by Scotch_Egg2012 Quote Link to comment Share on other sites More sharing options...
GPSguru Posted December 30, 2020 Share Posted December 30, 2020 10 minutes ago, Andy135 said: But the reservoir on his engine is unpressurised, so can only be a catch tank I.e. the flow is only one way (out of the pressure cap valve and into the tank) not two way like in a pressurised expansion tank situation. So . the 'bottle' , not 'expansion bottle' , is on the 'blow off' outlet from the pressure cap ? ............. if so, is that a special cap (similar to the older petrol Fords) that blows off into the bottle and then sucks the 'blown off' coolant back in once the system has cooled and the coolant has contracted ? Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 2 minutes ago, GPSguru said: So . the 'bottle' , not 'expansion bottle' , is on the 'blow off' outlet from the pressure cap ? ............. if so, is that a special cap (similar to the older petrol Fords) that blows off into the bottle and then sucks the 'blown off' coolant back in once the system has cooled and the coolant has contracted ? Looks exactly like that Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 30, 2020 Share Posted December 30, 2020 5 minutes ago, GPSguru said: So . the 'bottle' , not 'expansion bottle' , is on the 'blow off' outlet from the pressure cap ? ............. if so, is that a special cap (similar to the older petrol Fords) that blows off into the bottle and then sucks the 'blown off' coolant back in once the system has cooled and the coolant has contracted ? I was wondering whether it might suck back, but without Fishy taking a pic of whatever is under the cap we're all just speculating. @Saintly Fish, new pics please! GPSguru 1 Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 1 minute ago, Andy135 said: I was wondering whether it might suck back, but without Fishy taking a pic of whatever is under the cap we're all just speculating. @Saintly Fish, new pics please! I'd be amazed if there is not a tube running down into the coolant in the tank GPSguru 1 Quote Link to comment Share on other sites More sharing options...
Saintly Fish Posted December 30, 2020 Author Share Posted December 30, 2020 6 minutes ago, Scotch_Egg2012 said: I'd be amazed if there is not a tube running down into the coolant in the tank There is a verticals pipe Scott yes . Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 1 minute ago, Saintly Fish said: There is a verticals pipe Scott yes . OK so that is an expansion tank not a catch tank. When at temperature the pressure cap will relief and discharge coolant into the tank as it has expanded, there is a vacuum valve in the cap that as the cooling system cools allows the coolant to be drawn back through the cap into the system as it contracts. Was the level in the expansion tank fairly constant after runs before you did the Turbo? Andy135 1 Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 30, 2020 Share Posted December 30, 2020 10 minutes ago, Scotch_Egg2012 said: I'd be amazed if there is not a tube running down into the coolant in the tank And I'd like to see the valve under the pressure cap. I'm curious to see how it could be two way, rather than one way. Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 30, 2020 Share Posted December 30, 2020 7 minutes ago, Scotch_Egg2012 said: OK so that is an expansion tank not a catch tank. When at temperature the pressure cap will relief and discharge coolant into the tank as it has expanded, there is a vacuum valve in the cap that as the cooling system cools allows the coolant to be drawn back through the cap into the system as it contracts. Was the level in the expansion tank fairly constant after runs before you did the Turbo? Yep, agreed. Must be a non-pressurised expansion tank. @Saintly Fish did you definitely fill the system up enough when replacing the coolant after installing the new turbo? Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 4 minutes ago, Andy135 said: Yep, agreed. Must be a non-pressurised expansion tank. @Saintly Fish did you definitely fill the system up enough when replacing the coolant after installing the new turbo? It's an older style of cooling system not used much anymore, nothing wrong with it and all that's needed in thus application, modern Deisels however need a much more efficient system hence we have a proper header tank Andy135 1 Quote Link to comment Share on other sites More sharing options...
Saintly Fish Posted December 30, 2020 Author Share Posted December 30, 2020 12 minutes ago, Scotch_Egg2012 said: OK so that is an expansion tank not a catch tank. When at temperature the pressure cap will relief and discharge coolant into the tank as it has expanded, there is a vacuum valve in the cap that as the cooling system cools allows the coolant to be drawn back through the cap into the system as it contracts. Was the level in the expansion tank fairly constant after runs before you did the Turbo? Yes it was Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 6 minutes ago, Saintly Fish said: Yes it was That'd be my first place to check. Make sure you've no weeps around there it will dry quick so you'll be looking for crystallisation of the coolant. Quote Link to comment Share on other sites More sharing options...
Saintly Fish Posted December 30, 2020 Author Share Posted December 30, 2020 17 minutes ago, Andy135 said: Yep, agreed. Must be a non-pressurised expansion tank. @Saintly Fish did you definitely fill the system up enough when replacing the coolant after installing the new turbo? Well I’m pretty sure I did yeah. Like I say, maybe there was/is a small air bubble that releases the air then pulls in the extra fluid from the tank. Whenever I remove the pressure cap the level is exactly the same just the level in the tank has dropped. Quote Link to comment Share on other sites More sharing options...
Saintly Fish Posted December 30, 2020 Author Share Posted December 30, 2020 1 minute ago, Scotch_Egg2012 said: That'd be my first place to check. Make sure you've no weeps around there it will dry quick so you'll be looking for crystallisation of the coolant. Ok I’ll double check. I did use all new washers and gaskets though. Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 (edited) 8 minutes ago, Saintly Fish said: Ok I’ll double check. I did use all new washers and gaskets though. Maybe a loose pipe clip etc. It would be quite a coincidence to start loosing coolant after the system has been disturbed and not be something taken apart, unless it has an airlock although the older simpler cooling systems suffered less with this. Edited December 30, 2020 by Scotch_Egg2012 Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 30, 2020 Share Posted December 30, 2020 Just now, Scotch_Egg2012 said: Maybe a loose pipe clip etc. It would be quite a coincidence to start loosing coolant after the system has been disturbed unless it has an airlock although the older simpler cooling systems suffered less with this. But as he said earlier his engine room floor is dry... If his expansion cap is going from max to min each time then that volume of fluid should be turning up somewhere if it's leaking? Quote Link to comment Share on other sites More sharing options...
Scotch_Egg2012 Posted December 30, 2020 Share Posted December 30, 2020 3 minutes ago, Andy135 said: But as he said earlier his engine room floor is dry... If his expansion cap is going from max to min each time then that volume of fluid should be turning up somewhere if it's leaking? Don't forget it'll likely only be leaking under pressure (engine running) the turbo will be very hot if it's weeping on a run and if it's leaking round the turbo area it will dry off very quickly leaving just crystallisation. I've seen it many a time on engines no visible wetness just a lot of crystallisation Quote Link to comment Share on other sites More sharing options...
Gordmac Posted December 31, 2020 Share Posted December 31, 2020 If there was much of a leak the system wouldn't really hold pressure. Lower pressure would mean a lower boiling temperature and your leak may be steam rather than water, should be traces of antifreeze where it leaks from though. Other thought is if a significant leak then would it not draw air in the leak rather than fluid in from the tank? Quote Link to comment Share on other sites More sharing options...
Saintly Fish Posted December 31, 2020 Author Share Posted December 31, 2020 55 minutes ago, JonC said: I think the only way to know for sure is to strip the whole thing down and rebuild it. Or buy a new boat. Quote Link to comment Share on other sites More sharing options...
Andy135 Posted December 31, 2020 Share Posted December 31, 2020 33 minutes ago, Saintly Fish said: Or buy a new boat. Definitely. If in doubt, new boat 👍 Saintly Fish 1 Quote Link to comment Share on other sites More sharing options...
suzook12 Posted December 31, 2020 Share Posted December 31, 2020 You got one of them odd Japanese ones, similar to my Nissan terrano, no cap at all on that..... Sounds like you are displacing air from the system bud after the turbo and cooler were done..... Quote Link to comment Share on other sites More sharing options...
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