heat exchanger leaking?

[pandos]

Started my md21b today, first time in 18 months or so, ashore for 4 years... noticed that the antifreeze was missing from the expansion vessel....topped it up with som e fresh water to the mid point.

Started the engine and suddenly the expansion vessel is overflowing... , there was no overheating, there was some heat in the exhaust water.

(engine cooling water via hose pipe)

I deduce that there is a crossover of water in the heatexchanger... does this make sense... presume guys who fix radiators will fix these??

 

[Caer Urfa]

If the amount of water discharge is less than normal from your exhaust discharge then the heat exchanger seems to be on its last legs,OR you may have a blockage in the discharge bend,
also this can also be confirmed if your engine oil is ok any milky signs then you have other problems like a head gasket.

I thought my antifreeze was getting into the engine but all was ok with the engine oil clear ,however in the space of 1 hour I was loosing about a third of antifreeze coolant from the header tank, not sure if you have a bowman heat exchanger or a tubular one, either way you can get new ones BUT check the connections match, OR with the help of changing some pipework slightly will still do the job.

Why pay someone else its not rocket science to change a heat exchanger

 

[pandos]

Water Discharge is fine.

gaining water in the cooling system so it must as a matter of logic be coming from the seawater side..

Oil perfectly clear and no overheating , hot water from calorifier so presume circulation pump operating properly...

I will be only paying to have it repaired if it is not a diy job (never ever paid anyone to do any work on my boat)

The exchanger is tubular, never really examined it's innards, there is a rubber sleeve on one end that looked to me like a repair....

 

[Plum]

Water Discharge is fine.

gaining water in the cooling system so it must as a matter of logic be coming from the seawater side..

Oil perfectly clear and no overheating , hot water from calorifier so presume circulation pump operating properly...

I will be only paying to have it repaired if it is not a diy job (never ever paid anyone to do any work on my boat)

The exchanger is tubular, never really examined it's innards, there is a rubber sleeve on one end that looked to me like a repair....

As i understand it, the seawater cooling system is very unlikely to have enough pressure to force itself into the fresh water/coolant circuit as the freshwater should be under pressure once hot. Run the engine again until it gets hot enough for the thermostat to open then run it a bit longer. Now cover the header tank pressure cap with a big cloth and very very gently start to release the cap trying not to get steam over you. If it hisses you know it was under pressure which tells you there is no leak.

Www.solocoastalsailing.co.uk

 

[Caer Urfa]

Water Discharge is fine.

gaining water in the cooling system so it must as a matter of logic be coming from the seawater side..

Oil perfectly clear and no overheating , hot water from calorifier so presume circulation pump operating properly...

I will be only paying to have it repaired if it is not a diy job (never ever paid anyone to do any work on my boat)

The exchanger is tubular, never really examined it's innards, there is a rubber sleeve on one end that looked to me like a repair....

The rubber inlet and outlet cap connections will have a part number on them and if necessary you can get them from ASAP supplies,
https://www.asap-supplies.com/engin...angers-exhaust-manifolds/replacement-end-caps

Inside the tubular exchanger you will find an inner cooling coil (which can be pulled out) consisting of a number of tubes, sometimes these tubes can get blocked and sometimes depending on age just wear out,

IF there is a leak in the tubes coolant water will slowly join the sea water cooling and discharge out that's why you may not find any signs of a leak.

 

[VicS]

Water Discharge is fine.

gaining water in the cooling system so it must as a matter of logic be coming from the seawater side..

Oil perfectly clear and no overheating , hot water from calorifier so presume circulation pump operating properly...

I will be only paying to have it repaired if it is not a diy job (never ever paid anyone to do any work on my boat)

The exchanger is tubular, never really examined it's innards, there is a rubber sleeve on one end that looked to me like a repair....

It may look Ok but the water injection point is probably restricted and that is causing an excessive pressure in the raw water side and the magnitude of the effect you see effect you see .. Ordinarily there would not be enough pressure to lift the pressure cap although when at operating temperature the coolant will be at a higher pressure than the raw water leading simply to loss of coolant to the raw water side through any HE leak.

 

[VicS]

The rubber inlet and outlet cap connections will have a part number on them and if necessary you can get them from ASAP supplies,
https://www.asap-supplies.com/engin...angers-exhaust-manifolds/replacement-end-caps

Which parts are you calling " inlet and outlet cap connectors" /

 

[pandos]

It may look Ok but the water injection point is probably restricted and that is causing an excessive pressure in the raw water side and the magnitude of the effect you see effect you see ..
.

That might explain why I also saw evidence of water from the antisiphon loop being discharged into the drain.


There was not enough pressure to lift the top, I had it open, but have been reading up on these and from the other posts I suspect there is a blockage in the sea water side with a breach in the seals on the exchanger, so that the impeller pump is strong enough to cause seawater to pass accross into the coolant...

Either way it needs removal and closer examination... but the engine started and sounds ok..so we might sail this year....

 

[VicS]

That might explain why I also saw evidence of water from the antisiphon loop being discharged into the drain.


There was not enough pressure to lift the top, I had it open, but have been reading up on these and from the other posts I suspect there is a blockage in the sea water side with a breach in the seals on the exchanger, so that the impeller pump is strong enough to cause seawater to pass accross into the coolant...

Either way it needs removal and closer examination... but the engine started and sounds ok..so we might sail this year....

An increase i pressure should not cause the anti-siphon valve to open. It is designed to open when the pressure goes slightly negative but if its a bit leaky ( old Volvo one often are) it will leak more i guess.

 

[RichardS]

Run the engine again until it gets hot enough for the thermostat to open then run it a bit longer. Now cover the header tank pressure cap with a big cloth and very very gently start to release the cap trying not to get steam over you. If it hisses you know it was under pressure which tells you there is no leak.

Www.solocoastalsailing.co.uk

On most engines there will be a coolant hose somewhere which you can squish quite easily with your fingers when the engine is cold. As the engine warms up this hose should get hotter and hotter and harder and harder until it's barely squishable. Might be a bit safer than releasing the pressure cap.

Richard

 

[Caer Urfa]

Which parts are you calling " inlet and outlet cap connectors" /

See typical tubular heat exchanger with rubber end caps common on many engines

View attachment 70022

 

[scottie]

Most engines have a happy level for coolant
If you try topping it up then run it up to temp the water expands and blows out the excess then when cooled down needs topping up again
Try repeating but don’t top up and check level again if it still goes down you have a problem
Having a calorifier means more expansion
Do you have an expansion bottle ?
If the engine has been left for 18months you could have air in the system!

 

[VicS]

See typical tubular heat exchanger with rubber end caps common on many engines

View attachment 70022

Yes but I was assuming that the OPs engine has the standard HE as shown in the parts diagrams !

 

[pandos]

Most engines have a happy level for coolant
If you try topping it up then run it up to temp the water expands and blows out the excess then when cooled down needs topping up again

" surely once it has blown out the excess it is at the optimal and therefore does not need to be topped up again!


Try repeating but don’t top up and check level again if it still goes down you have a problem
Having a calorifier means more expansion
Do you have an expansion bottle ? " yes....first line of first post"

If the engine has been left for 18months you could have air in the system! " that was my first thought, but not likely as the system was full when it was shut off[ /QUOTE]

little more to be said except take off exchanger and clean/check... the rubber seals for the ends are the likely culprits..

had never really applied my mind to the operation of the "green tube on the top of the engine"

thanks...