Cooling problem

[concentrik]

Hoping for some advice on a BMW D35 with cooling probs. The arrangement is:

seawater inlet> strainer > engine water pump> gearbox cooler > oil cooler > engine block

There is no water from the exhaust outlet.

Disconnecting the output of the engine water pump - gushes loads of water under pressure, more than a garden hose.

Disconnect output of gearbox cooler (it's just a simple tube running through the base of the box) and again, loads of water under pressure.

But disconnect output of engine oil cooler - just a trickle.

The output of the oil cooler goes to the cylinder head cooling block (it's all direct, sorry, should have said) so barely a trickle is getting to the engine proper and the exhaust elbow.

I suspect the oil cooler is blocked but wonder if the cooler has some kind of thermostat to restrict water flow to a trickle - 'till the oil gets hot? Doesn't seem likely as the exhaust is hot right away. When it was working correctly the cooling water appeared at the exhaust outlet almost right away.

All ideas welcome......

 

[TradewindSailor]

You don't say whether the engine is raw water cooled or uses coolant. I don't know your engine but I suspect it is cooled with coolant and then that is cooled with the raw water (seawater).

If this is so then it is most likely that your heat exchanger is blocked. This will have a number of cooling tubes inside. You need to open in up and make sure the tubes are clear .... or indeed if the waterways are blocked with such things as an impeller blade off your raw water water pump .... in which case you need to renew your impeller too.

Hope this helps.

 

[concentrik]

More of a 'how does an oil cooler work' question now

You don't say whether the engine is raw water cooled or uses coolant.

Thanks TWS, it is direct cooled so there is no heat exchanger for the cooling water. There IS a heat exchanger for the oil and that's my question really....

the seawater is pumped to the oil cooler first, then goes to the engine block - there is barely a trickle of seawater coming out of the oil cooler even when there is loads of pressure at the inlet of the oil cooler. Something in the oil cooler is stopping the flow of water, so my question is - is it meant to do this? If so it is preventing ANY water getting to the block and exhaust elbow until it decides to allow water to flow. Or are the little tubes just blocked?

If the little tubes are blocked is it OK to use something caustic like drain cleaner to clean them?

 

[superheat6k]

Even on a direct cooled engine I would expect seawater from the exhaust immediately, so a blockage looks most likely and your own checks already seem to provide this diagnosis.

The oil cooler would be my first investigation. Before dismantling I would try to soak it in situ with a de scaler. Rydlyme is the best apparently, but not cheap. I use B&Q domestic de scaler powder 2 sachets for £5, works a treat, but mine weren't heavily blocked ( in the plumbing section by the radiator treatments).

Also have you ever suffered a shredded impeller - if so bits of rubber debris could be blocking the flow, and nothing will dissolve this, you have to get in and physically remove the stuff.