Coolant over flow bottle does not drain when engine cools ?-gctid407161

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HI all,

Just trying to figure out why my port side coolant overflow bottle will not fill back into the engine when the engine cools down ... I thought I had a coolant leak as every time before I start the engine I open the cap and the coolant was low on that engine ... so I top it up and look for a leak, but none were present ... so for 2 or 3 trips there is no coolant appearing in the bilge ... I just noticed that the overflow bottle was getting fuller each time and then, of course, it will eventually overflow into the bilge ...

BTW ... 1990 - 3288 with 150 hinos ( 135 with turbos ) ... Any thoughts why it is not flowing back into the rad ?

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Have you checked the tube running to the overflow bottle? Is it or the tube from the radiator cap plugged? That would allow for a full bottle which overflows since each time you refill the coolant and you only see coolant in the bilge after the overflow. Is the overflow bottle above the level of the cap with a little of the tube below the cap level?

Hope this helps,

Richard

[dktool Guru Find all posts View Profile Close dktool]

Most likely a bad cap, it's not working in both directions as it should.

Swap it with the one on the other engine and see if the problem goes to that engine, or just replace it and see what happens.

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Be sure o/f bottle is well vented both for pressure and suction.I have had it happen where o/f bottle cap seals tight on suction and wont allow coolant to escape back to engine.

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Thanks to all ... I'll check all of the above out ... I assume the tube is not blocked as it is filling the bottle ... ( or are there 2 tubes ) I will have to check that again as I don't think so ... I guess I must observe the cool down ... Kinda like watching paint dry ... well I can always clean my bilge again !

CHeers

Bruce

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All of the above but when my coolant recovery bottles quit siphoning it is usually because of an air leak, I've found cracked hoses and/or one of the ends not sealed (usually at the pressure cap). Also check the tank fitting for the cap, the material is thin and the tangs can bend so the cap doesn't seal tight.

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Check also where the cap seals on the upper portion. I had a car that did that and the housing was corroded and when the engine cooled it would draw air instead of coolant back in. Also the check valve on the cap it could be stuck shut or plugged. That is the small metal disk on the bottom. Most people don't realize how many pieces or in a radiator cap. Either swap or replace the cap and monitor. If all else is good it could the signs of a internal leak to the combustion chamber. You may need a combustion gas test done on the cooling system. A tube with a special chemical is put over the coolant neck where the cap goes and gases drawn through the fluid if it changes to yellow or green from its normal blue color exhaust is getting into the cooling system. I would hope that isn't your problem though. If changing the cap doesn't help you can have mechanic do a block check or you can purchase a block check kit from Napa or other vendor and check it yourself. Its not really difficult if you follow the instructions.

[talman Founding Member Find all posts View Profile Close talman]

Make sure yours is the one that supports a relief tank. Some are 'one way.' They only 'relieve' the HE, not allow refill.

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I had this identical problem that turned out to be a bit severe. Hopefully this isn't your problem, but if none of the suggestions here work for you then consider this.

Every time I ran the boat, the level would increase in the overflow as well. Turned out, this was because there was a small crack in the cylinder head between the combustion chamber and coolant chamber. The force of the combustion gasses pressurized the cooling system, ultimately forcing coolant into the overflow. The overflow bottle never went down because that coolant had been displaced by the combusion gasses. To confirm if this is your problem, you can buy or rent (many auto parts stores have this) a hydrocarbon tester that fits over the opening of your heat exchanger. It "sniffs" the air inside while the engine is running to detect if combusion gasses are present. If they are, then you have a crack in the head, or possible a leak in the head gasket.