alexincornwall
Active member
My relationship with our Perkins M50 is a little strained at present so I’m hoping some clever forum members might be able to throw a few ideas at our quite unusual problem and help us to get back on track.
Earlier this year I noted that we were leaking a little coolant from the front of the engine and into my clinically clean bilges. The leak was minor, perhaps a teaspoon ever 10 hours. Suddenly, things got a lot worse and reached a point where we were losing over a litre per hour. The next time I arrived to the boat the seals had let go completely whilst the engine was shut down. Fairly easy diagnosis - water pump seal failure. It looked like the original 30-year-old part so it had had a good innings.
There’s a global shortage of genuine Perkins parts so we bought a non-genuine unit from a regarded engine spares business. Pump purchased, inspected (looked good), and professionally installed - pulling apart the timing belt and pulleys isn’t for me, especially given that our engine bay space is incredibly awkward at this end of the unit.
Sadly, it appeared that we’d bought a duff and the pump immediately leaked from the drip hole but at a manageable rate of around 250ml every 12 hours of running. Our engineer was happy with installation so we all concurred that it was simply bad luck. We bought a second from the same seller and went through the motions again. Guess what? Leaked again. Same place, same volume of coolant loss, and same interesting pattern of coolant loss. I’m confused, our engineer is scratching his head and the parts seller thinks it highly, highly unlikely that we’d have bought two duds in a row - I can see his point.
Here’s what’s happening:
- Engine fires up - no leak
- Around 20-30 minutes from start-up (Perhaps 10 minutes after reaching running temp), coolant begins to drip into bilge at its fastest rate from the drip seal. Let’s say a drop every 10-20 seconds.
- Engine continues to run at a constant 82ish degrees - never overheats
- Drip continues at higher rate for around 90 minutes
- Then subsides to slow drip
- Around 3 hours of running and the drip is virtually gone
- Approx. 250ml coolant mixture in the bilges
Identical symptoms for both new pumps.
Here’s what has been done:
- Pressure tested the second pump installation - no problem
- Checked the RTV gasket on both installations - all good (we can see coolant staining around drip seal of the first pump so no doubt that it’s coming from there)
- Compared and replaced radiator filler cap to ensure correct operation of pressure release
- Confirmed that we’ve not overfilled the system (though would expect any overfill to escape via the cap overflow - we don’t have a header tank)
- Confirmed that we’re not losing coolant from the overflow
- Confirmed that the coolant we’ve lost is clean and contains no notable rust or debris
Any ideas? Have I simply struck bad luck twice in a row or is there something that we’re missing here? Is there any way that the pressure in the system would cause the pump to leak before the rad cap released from fluid from the overflow?
Earlier this year I noted that we were leaking a little coolant from the front of the engine and into my clinically clean bilges. The leak was minor, perhaps a teaspoon ever 10 hours. Suddenly, things got a lot worse and reached a point where we were losing over a litre per hour. The next time I arrived to the boat the seals had let go completely whilst the engine was shut down. Fairly easy diagnosis - water pump seal failure. It looked like the original 30-year-old part so it had had a good innings.
There’s a global shortage of genuine Perkins parts so we bought a non-genuine unit from a regarded engine spares business. Pump purchased, inspected (looked good), and professionally installed - pulling apart the timing belt and pulleys isn’t for me, especially given that our engine bay space is incredibly awkward at this end of the unit.
Sadly, it appeared that we’d bought a duff and the pump immediately leaked from the drip hole but at a manageable rate of around 250ml every 12 hours of running. Our engineer was happy with installation so we all concurred that it was simply bad luck. We bought a second from the same seller and went through the motions again. Guess what? Leaked again. Same place, same volume of coolant loss, and same interesting pattern of coolant loss. I’m confused, our engineer is scratching his head and the parts seller thinks it highly, highly unlikely that we’d have bought two duds in a row - I can see his point.
Here’s what’s happening:
- Engine fires up - no leak
- Around 20-30 minutes from start-up (Perhaps 10 minutes after reaching running temp), coolant begins to drip into bilge at its fastest rate from the drip seal. Let’s say a drop every 10-20 seconds.
- Engine continues to run at a constant 82ish degrees - never overheats
- Drip continues at higher rate for around 90 minutes
- Then subsides to slow drip
- Around 3 hours of running and the drip is virtually gone
- Approx. 250ml coolant mixture in the bilges
Identical symptoms for both new pumps.
Here’s what has been done:
- Pressure tested the second pump installation - no problem
- Checked the RTV gasket on both installations - all good (we can see coolant staining around drip seal of the first pump so no doubt that it’s coming from there)
- Compared and replaced radiator filler cap to ensure correct operation of pressure release
- Confirmed that we’ve not overfilled the system (though would expect any overfill to escape via the cap overflow - we don’t have a header tank)
- Confirmed that we’re not losing coolant from the overflow
- Confirmed that the coolant we’ve lost is clean and contains no notable rust or debris
Any ideas? Have I simply struck bad luck twice in a row or is there something that we’re missing here? Is there any way that the pressure in the system would cause the pump to leak before the rad cap released from fluid from the overflow?
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