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The end of the engine?


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Well, a month or two ago I posted a pic of my engine room. Was looking good! Unfortunately, things have not gone so well.

 

I have a volvo penta 2003T, 1998 model, with a 120S saildrive. The unit has around 10,000 hours. It has had some work done to it in this lifetime, including one rebuild.

 

Prior to those engine room pics, it had had oil in the water. I removed the head, had it crack tested, skimmed, and valves etc done. New head gasket, valve seals etc, all done. Re Assembled it, painted whole engine and engine bay, new lights and a general spruce up. Got it running, a bit more oil in water. Flushed cooling system a few times, seemed fine. Had a few weekends away, all good.

 

BUT the other week, when I was supposed to do my RYA offshore masters practical test, it overheated on the way to Auckland. Had to postpone the test, returned to Gulf Harbour.

 

I took out the heat exchanger, oil cooler and refrigeration heat exchanger. They were pretty clean, but a few bits of shells etc, which I cleaned out, now all spotless.Took out thermostat and boiled it, its opening and closing. Reassembled, water flow from the exhaust looked fine.. 

Tied to the wharf, in gear, 2000 revs , all ok. 2300 revs, water level in the header tank rose, and blows out the header tank overflow. :-(

At this time, exhaust water temp is cool, and the heat exchanger is only hot at the entry end. So, from this, I presume the issue is circulation.

Remove the fresh (closed circulation) connections, and the circ pump. No issues found with the circ pump, but I found a small piece of rubber blocking the turbo bypass cooling flow restrictor. I know that that can cause overheating, so I thought that would be it. Reassemble again. 

Seems ok at the dock. Go out for a test, ok at 2700 rpm, motor for 20 mins. Try WOT, overheats quite quickly :-(

Now I'm thinking maybe the fresh water flow is not actually enough. So, got in the water and cleaned the saildrive intake, I did find an oyster growing in the saildrive - maybe that was it? 

I also removed all the heat exchangers etc again, and on closer inspection one of the water flow guides was a bit bent, allowing some water to escape and flow only across the cap from the inlet to outlet, rather than being forced thru the cooler. Surely those two things were it?

Reassembled again!

Today went for a test. Motored for 40 mins at 2500 no issue. 2700 water level rising... Back to 2500, ok, level back down.  Then motored 30 mins, and it spat out some water :-(

When home, I borrowed a mates IR thermometer, compared it to mine. Mine reads 20 deg lower!

Maybe its the thermostat? Took it out again, boiled it. Supposed to begin to open at 76 deg c, fully open at 88 deg c. It did not start to open until about 82 deg, fully open at about 90. I let it cool, and it seems to be near spec the 2nd time, but very slow to move. Maybe  its not right, so I'll get another, and try that. Other than that, i'm out of ideas. There is a bit of oil in the water again, but it could be residue still, not sure.

Anyone got any other ideas?

Its about 16-20K for a new engine, but at east I can install etc myself.....

By the way, the IR thermometer error seems to have been only a dirty lense... so keep your IR thermometer lenses clean!

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Cant. The thermostat has the sealing ring for the cover. plus, its a bypass system, the open thermostat blocks the bypass, so all the water goes thru the heat exchangers. Without the thermostat, the path of least resistance is the bypass, no heat exchanger

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Have you checked the radiator cap and where it seals, a common problem in older Subarus, they just spit out heaps of coolant that looks to be overheating and erode the sealing ring surface on the radiator as well? I'd try another cap and make sure it sits on the filler mouth area with good pressure, a tricky problem!

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Sad news ... When you did the full power test did the temperature take off almost immediately? and did the header tank dump water straight away or after the temperature surge?  On a separate line of thought has it had a couple of good work-outs since the rebuild a few months back? 

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It actually seems to spit water out without being really hot. Its as if there is an area withing the closed cooling system that is getting hot enough to boil - therefore expanding and blowing the water out of the header tank. The tank is hot, but not so hot you cant touch it.

Yes, when first re-installed, it would run at WOT (circa 3300 rpm) with no issues.

Part of the problem is it seems to be inconsistent - like today it ran at 2500 no prob, then, after the issue at WOT, it wouldn't do 2500 without ejecting water. 

There must be some logic I'm currently missing.....

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I think we are starting to get it a bit worried now ... where do you reckon the piece of rubber came from? could there be more hiding in there - a back flush of the system into a bucket could be worth doing. i once worked on an engine (outboard) that had inconsistent water flow and it turned out to have bits of impeller intermittently blocking the water galleries. It doesn't sound like the head gasket at the moment. A vigorous back flush may shed some light.

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Yeah, done that. Also used a head gasket leak (combustion gas) detection kit on the coolant. Nothing showing.

The rubber I think was a pinched off piece of one the coolant sealing rings used on the unusual copper coolant tubes on these engines. It was small, and the only part it could have blocked was that 3mm hole in the turbo coolant bypass restricter.  

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now that my IR thermometer is going again, tomorrow ill check the temps again, at the thermostat, at the fresh water inlet to the heat exchanger, and both the fresh and salt water outlets. Looking for hot spot...

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Ha Jim, that makes 2 of us! The Circ pump was rebuilt at Muzzas Pumps a few months back. Looks fine, and they are pretty basic. I did wonder if perhaps it was allowing air in through the shaft seals, but that seems pretty unlikely.

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assuming both pumps are doing their job (no slipping key / spline / grub screw ), then considering the checks you"ve already done  it does make you start to think about cracked blocks etc... I'd be keen to see the list of temps taken on the run in case something (hopefully) stands out.

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I had an overheating problem on the yanmar,replaced water impeller as old one had missing blades,fitted new one fine for about 30 minutes then overheating,took off pump inspected impeller and found the bush was turning inside impeller,faulty gluing??

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Crikey IT, that diesel has really been putting you through the wringer.

Easy for me to be philosophical but I have tackled the whole heart lung transplant experience on our princess and although a lot wiser and poorer I can in all honesty say "the storm will pass and the sun will shine".

Try starting a Givealittle page  :thumbup:

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If it’s a cracked block, leaking compression gasses into the coolant, that should show up on the test I did in the header tank. It didn’t. It’s not the raw water pump HT, the flow rate is good. I’ve seen the vulcanising fail on the impellers before, and also the splines...

Ongoing...

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