Heat exchanger checking for leaks

[Philip]

I decided to check the heat exchanger on my Beta 20 for the first time yesterday as per the manual guidelines; the channels in the tube stack were clear and the whole assembly was reasonably clean, o rings were ok so nothing more than a check-over needed. The fact that the water temperature had been fine and no leaks prior to checking indicated this. I put it back together and ran the engine at normal revs for about 20 minutes afterwards. To be clear it is an indirect raw water-cooled engine with a sealed coolant system, hence the need for the heat exchanger.

 

My question is would any leaks from the HE have been made apparent within the 20 minutes of test running the engine afterwards? It was all nice and dry after running and the water temperature was fine so, so far so good. But since this was the first time of doing it, I'm not sure if I put it back together properly, specifically I don't know how well the o rings will work now that they've been removed once from the seal for checking and put back on. They fit snugly and smoothly into the groove as before so it looked ok, but as I say I'm a bit unsure. 

 

I'd rather not take the thing apart again unless necessary because it's awkward with the alternator in the way and also with it being aluminium it's a bit delicate against the bolts, so would any problems (ie. leaks) have been obvious within the time I ran the engine for testing?

Edited March 5, 2019 by Philip

[Bee]

Interesting question. Presumably you are also concerned at the possibility of raw water and the coolant mixing as well. I would say that if there are no puddles anywhere then everything is fine. Just keep an eye on levels and the temp. and if nothing alarming happens then it should be ok. Just make sure next winter that the anti freeze is still ok (or just change it anyway to flush rust and sludge out if there is any). Might be a good time to renew the little anode in the system  if there is one as well.

[Philip]

19 minutes ago, Bee said:

Interesting question. Presumably you are also concerned at the possibility of raw water and the coolant mixing as well. I would say that if there are no puddles anywhere then everything is fine. Just keep an eye on levels and the temp. and if nothing alarming happens then it should be ok. Just make sure next winter that the anti freeze is still ok (or just change it anyway to flush rust and sludge out if there is any). Might be a good time to renew the little anode in the system  if there is one as well.

Thanks. Yes I'm going to check the anode next time I'm down, have a spare if it needs replacing. The mixing of raw water and coolant is a concern too but I'm assuming if this happened then it would also show a leak since the raw water would have to get past the seals before it could mix with the coolant? If not the only way to check is to open the filler cap after a while and see if the solution looks a bit murky or with debris.

Edited March 5, 2019 by Philip

[Tony Brooks]

The coolant in the engine will pressurise to something between 4 and 15 psi, depending on pressure cap setting, so unless the raw water side of the heat exchanger flow is into the exhaust any pressure in the raw water system should be almost zero. This means that over time engine coolant should leak into the raw water. On a wet exhaust boat things are more complicated and it will depend upon the back pressure the exhaust system develops and when an exhaust hose collapses or the mixing elkbw furs up that can be enough to bend the wings on the raw water pump and stop raw water flow.

 

I am with Bee, almost certainly fine if the temp and levels    stay as normal.

[Philip]

2 hours ago, Tony Brooks said:

The coolant in the engine will pressurise to something between 4 and 15 psi, depending on pressure cap setting, so unless the raw water side of the heat exchanger flow is into the exhaust any pressure in the raw water system should be almost zero. This means that over time engine coolant should leak into the raw water. On a wet exhaust boat things are more complicated and it will depend upon the back pressure the exhaust system develops and when an exhaust hose collapses or the mixing elkbw furs up that can be enough to bend the wings on the raw water pump and stop raw water flow.

  

I am with Bee, almost certainly fine if the temp and levels    stay as normal.



Thank you. It is indeed a wet exhaust, the impeller was changed not long ago after about 600 hours running, but it was still in reasonable condition. The base plate for the pump was a little worn at the inner rim and was beginning to struggle, so we just turned the plate around rather than fit a new one, it's been fine since.

[Ex Brummie]

58 minutes ago, Philip said:

Thank you. It is indeed a wet exhaust, the impeller was changed not long ago after about 600 hours running, but it was still in reasonable condition. The base plate for the pump was a little worn at the inner rim and was beginning to struggle, so we just turned the plate around rather than fit a new one, it's been fine since.

Turning both the rear plate and the front plate is normal, and is included in the service manual for the Jabsco pumps, IIRC. I've done the same with mine for 30 years.