Volvo Penta MD2020 Coolant Issue

[Ads_Cunni]

Hi Everyone

So I'm fairly new to the sailboat world and I'm dealing with a few issues on a 1998 Bavaria 32 with a Volvo Penta MD2020.

When I bought the boat the coolant was fairly dirty so I thoroughly flushed it and cleaned the heat exchanger, since refilling i'm having an issue with the coolant resovoir seemingly pressurising when it's cold so when I removed the coolant cap it hisses out air and sometimes some coolant and then refunds it's normal fill level.

There no expansion reservoir on it just a tube going down to a bottle to collect and this doesn't seem to fill when the engine is hot so I'm quite confused as to how it seems to be pressurising!

Any ideas?

Thanks in advance.

Adam

 

[Boater Sam]

Do you mean that it pressurises very quickly when running from cold? If so the head gasket is likely gone.

 

[Ads_Cunni]

Do you mean that it pressurises very quickly when running from cold? If so the head gasket is likely gone.

No so basically when it's left for about a week without being run and then I go to do the pre run checks on the coolant it seems to have an air pressure build up which isn't enough to open the over pressure cap but still hisses out a lot of air and some coolant with it then the level drops back down to the normal fill level

 

[nevis768]

The coolant reservoir as you call it is the expansion tank, but the coolant rarely expands much on mine. It usually sits at the same level. I'm not quite sure what you mean? If the engine has run it will leave the coolant tank pressurised. Exhaust elbow issues can affect the coolant.

 

[pete]

It's a long shot but If you have pressurised water to the taps and a slight leak in the hot water colorifier inside the tank, with the pump on it could pressurise your engine cooling water even when it was cold but where the air is coming from?

 

[Ads_Cunni]

The coolant reservoir as you call it is the expansion tank, but the coolant rarely expands much on mine. It usually sits at the same level. I'm not quite sure what you mean? If the engine has run it will leave the coolant tank pressurised. Exhaust elbow issues can affect the coolant.

Yeh so mine doesn't actually have an expansion vessel higher up above the engine, the over expansion just goes down a tube and collects in to a plastic bottle so it's very unclear on my engine how much expansion actually goes on, ideally I need to fit a separate expansion vessel like most tend to have but I haven't got round to that yet.
Its quite an unclear question I understand and I've tried my best to explain it but basically I have no problems when the engine is hot, it's when the engine is cold and I do my pre start checks, when I remove the coolant cap it hisses out air and spits out some coolant which I would understand it the engine was hot but it's stone cold at this point. Very confused sorry

 

[Ads_Cunni]

It's a long shot but If you have pressurised water to the taps and a slight leak in the hot water colorifier inside the tank, with the pump on it could pressurise your engine cooling water even when it was cold but where the air is coming from?

Thanks Pete, it's a good point but my calorifier was disconnected by the previous owner due to a worn hose so it's not actually connected at the moment.

 

[cpedw]

An alternative long shot - is the hiss caused by air going in - a slight vacuum has developed when the engine cooled? Difficult to reconcile with coolant spitting out though.

 

[nevis768]

Yeh so mine doesn't actually have an expansion vessel higher up above the engine, the over expansion just goes down a tube and collects in to a plastic bottle so it's very unclear on my engine how much expansion actually goes on, ideally I need to fit a separate expansion vessel like most tend to have but I haven't got round to that yet.
Its quite an unclear question I understand and I've tried my best to explain it but basically I have no problems when the engine is hot, it's when the engine is cold and I do my pre start checks, when I remove the coolant cap it hisses out air and spits out some coolant which I would understand it the engine was hot but it's stone cold at this point. Very confused sorry

If the previous owner removed the T piece type of expansion cap which allows coolant into the reservoir presumable he has put a different cap on? This may be the problem, those caps also allowed a small plastic tube to be fitted to release coolant when over pressurised, it often releases through that cap when the cap seal is worn. I replaced my seal due to this issue. I think I would replace the expansion tank and replace the calorifier, or else block the clarifier off another way allowing use of the expansion tank.