Bowman blowing

[Benno 1688]

hi all

my 1800 bmc runs fine for about an hour then it starts to over heat I ran with the engine cover open and its blowing water out of the over fow pipe on the filling cap. It appears to have loads of air in the system, any ideas.

 

[bigste]

Sounds more like blown head gasket.

[Benno 1688]

How would I know if it was the head gasket?

[Tony Brooks]

By using a solution that you can buy on Ebay that detects exhaust gas.

 

Assuming its a skin tank cooled boat have you bled the skin tank and manipulated the main coolant pipes to ensure no air is trapped in them?

[Benno 1688]

I have opened the bleed tap until water is spraying out but i have not done the main pipes.

[Benno 1688]

Does anyone know the name of the head gasket test fluid on ebay

[Puddlejumper]

Head gasket gone!!?

[alan_fincher]

Firstly you are not over-filling it, are you?

 

If the Bowman is the only header tank you have, (i.e. there is no external header tank), then it has to accommodate all the expansion of the water as the engine heats up, which, depending on skin tank dimensions, could be a lot.

 

It is normal to start off cold with the level maybe about an inch below the neck of the cap, otherwise expansion will often force water out as the engine heats.

 

Secondly how big is your skin tank, (length, height and "thickness"). this will affect both how well it is able to cool the engine, but also how much water is actually in the whole system that needs to expand.

 

Thirdly, is this water expulsion only whilst the engine is being worked hard, or does it still happen if the engine runs only on idle or low load?

 

Finally who built the boat, as there are some builders who are known to have produced boats with inadequate skin tanks, (but please don't ask me how I know this!).

Does anyone know the name of the head gasket test fluid on ebay

 

You would be after something like this.

 

(I'm not recommending this one - just an example - the first one that I found).

Another search term to try is "Block Tester Kit"

 

Example here

[Benno 1688]

Hi Alanits a springer and yes it is when the engine is worked hard, There is also a calorifer attached does that make anydifferance.Just a thought would the thermostate not working properly cause the same issue.

Edited February 24, 2015 by Benno 1688

[Tony Brooks]

If it takes an hour to bring the calorifier up to temperature then yes, it could be a thermostats stuck shut, especially if it has been subject to excess temperature. It would be worth a check but I thought it less likely because of the time it takes to overheat.

[MtB]

The one hour delay makes me think it isn't a head gasket failure either. I'd expect the problem to be present all the time if cylinder compression was leaking into the cooling system.

 

 

MtB

hi all

my 1800 bmc runs fine for about an hour then it starts to over heat I ran with the engine cover open and its blowing water out of the over fow pipe on the filling cap. It appears to have loads of air in the system, any ideas.

 

 

Is this an assumption based on the cooling water being ejected, or is there a temperature gauge telling you this?

 

What goes the gauge read when the problem begins?

 

 

MtB

[Benno 1688]

The tempreture gauge hits red, im thinking the best place to start is a new thermostat and a new filler cap.what do you think

Edited February 24, 2015 by Benno 1688

[Theo]

Sounds like the best idea.

 

Let us know how you get on.

 

Nick

[matty40s]

As Tony says above, check all pipes and skin tank, bleed and bleed again until you have got rid of any air. Air trapped will lead to your symptoms in the time scale..

[Benno 1688]

Hi thanks for all your comments ive put in a new thermostat and a new pressure cap, and bled it all I manipulated the pipes as suggested and it all seems fine now. Thanks again.