View Full Version : AQ D40A fresh water is under pressure and go out on filler cap on thermostat housing

03-17-2009, 07:21 PM
"I have this problem immidiattely when I purchased a boat with two D40A, three years ago. I can drive but I must filling up fresh water every two running hours. All the mechanics told me, that I must take engine out and check the heads if they are cracked. But in mean time I find out that expansion vessel is not working well. If I fill coloured antifreeze liquid in this expansion vessel they not become mixed with water, but is still original green. I see that expansion vessel have three connection pipes. One on the bottom which is connected with hose to circulation pump, one on the midle which is closed by screw and one on the top under filler cap which is connected to thermostat housing under filler cap. I think that expansion vessel can not functioning, because expanded water can not go in expansion vessel because there is already air which can not go out from expansion vessel. I think that hose from thermostat housing should go into midle connection on expansion vessel and upper connection on expansion vessel should stay free for air venting. Please, can someone told me if I have right or wrong? I check the pictures in workshop manual for AQ D40A and there I see that air venting hose from thermostat housing goes to the middle section of expansion vessel. Also on instruction book and in parts manual I can see that this hose goes to the middle of expansion vessel. But on my engines goes to the top pipe of the vessel and also I found some pictures for D40A engines on internet and there also goes to the top of the vessel. I am confused what to do. Please someone answer me what to do.
Best regards to all from thankfully Janko."