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davidk
07-25-2009, 10:28 PM
"I would appreciate help in diagnosing an overheating problem I have a 1986 Hallberg-Rassy 312 with a Volvo Penta 2003 Saildrive engine. About 2 years ago I had fresh-water cooling installed. Since then the engine has had about 70 hours of light use. Once last summer, after motoring at idle for at least an hour, I heard the over temperature alarm chatter briefly. Since then no problems.

A week ago we went on a river cruise which was mostly motoring. We had no problems for the first 20 hours. We got underway for the last leg and after about 4 hours the over temperature alarm came on. We anchored quickly and let the motor cool for an hour. Getting underway again the over temp alarm began sounding in only a few minutes. We sailed for several hours until we were near a good anchorage. In starting the motor to enter an inlet the alarm sounded within a minute. The next day we we towed to our dock.

To diagnose this problem I fastened thermocouples to the cylinder head (T1) and to the copper tube on the output of the heat exchanger that delivers raw water to the exhaust manifold (T2). I tied the boat to the dock so I could operate it in gear.

Here are the results, which I have also uploaded as a graph:

Time
Conditions and Results

1240
Started engine 1900RPM in gear; T1 rises to 76C and stabilizes, T2 rises to 28C when T1 crosses 74C.
1303
Turned on DC circuits with Alternator at 23A
1325
Dropped to 1000RPM still in gear; T2 drops maybe 2C
1331
Closed off engine comartment
1348
RPM back up to 2000RPM in gear, Alternator 20A; T2 rising steadily during next hour
1433
T1 at 85C, increased RPM to 2500 in gear; T1 climbs rapidly
1436
Over temperature alarm sound with T1 at 96C.
1436
RPM reduced 2000RPM in gear; T1 drops rapidly
1440
RPM reduced to 1000RPM and in neutral; Engine continues cooling
1445
Shutdown with T1 at 85C

There are some things I note:

1) The thermostat spec is for opening at 74C and fully open at 87C. The 74C opening is apparent on T2.

2) The engine oil is clean and at the full line.

3) The cooling system expansion tank is at the full line.

4) Twice during the operation at 2000RPM I collected exhaust water in a bucket, which measured the raw water flow at about 3.6 gal/minute.

5) There was no obvious slipping of the belts.

6) The water temperature in the harbor was 25C, and the raw water output of the heat exchanger was below 30C until the over heating began.

7) I might add that in the leg of the cruise in which overheating occured we had been living on house batteries for the preceding 2 days. I have a high output alternator which was probably charging at 50A while we were motoring at 2000RPM. So this might have driven us into the overload region.

I have uploaded a temperature graph of this test, and I would be very grateful for comments.

Thanks and kind regards, -- David
http://www.marineengine.com/discus/messages/12494/289610.jpgHR312 Engine Temp Test

haffiman37
07-25-2009, 10:45 PM
"A few comments.
Did You properly clean out the engine cooling system BEFORE installing the fresh water system?
Have You changed coolant in the engine since the conversion?
In my Jeanneau 37 I have a temp controlled fan installed that blows INTO the engine room compartment as soon as the temp goes up in the compartment. When You say closing the 'hatch' the alarm goes off, this might be a solution."

davidk
07-25-2009, 11:00 PM
"I am going to talk with the installer on Monday. But I don't believe the engine cooling system was cleaned out first. And the coolant has not been changed since. I wondered about blockage when I saw the raw water output of the heat exchanger only 5C above the input temperature. Do you think maybe I have a blockage in the block or the heat exchanger?

As to the compartment temperature -- that is intersteing. The second run at about 2000RPM was a bit faster than the first -- it's hard to set the throttle precisely. But I also closed the compartment. Before, the companionway steps were off, but after - when the temp was rising - I closed the compartment completely. The only ventilation is that provided by the engine sucking air in from the lazerettes."

psmestad
08-27-2009, 07:57 PM
"I had the same problem until yesterday, and did the following: Replaced impellar, thermostat and fresh water coolant (service - probably not the problem). Dismounted and cleaned the exhaust exit (found 1 of the 3 water conduits blocked by corrosion/scale plus a poor gasket): Cleaned surfaces carefully and replaced gasket (probably not the problem, but did increase seawater flow slightly). Also replaced the membrane and serviced the vacuum valve - suspect this was the problem. The engine does not overheat in bay at 2500 rpm, but did when running at 5-6 knots (>2000 rpm) at sea, creating (small) underpressure in vacuum valve which lowers seawater flow(?) - reference pressure is just below engine. My 2003 is a 1985, and has worked ok until this year, first time I have opened exhaust, which apart from slight blockage looks good, plenty of metal - but I suspect gasket shoul be replaced every 10 yeras or so. The exit will need cleaning but will last another 50 years. Also have never found any particles on fresh water side - but mine was delivered with fresh water cooling - you should check for rust grains when you drain the fresh water circuit (just run it on clean fresh water for a couple of daya to check). Good Luck"

marksherman
09-01-2009, 01:29 PM
"I have a Volvo Penata 2003 from 1986 and it had overheaing problem where the alarm would sound. after changing out 1. Impeller, Freshwater Pump, checking thermastat. it still overheated but water seemed to be running through. I next removed the Heat exchanger and just cleaned it and all the copper tubbing (noticed 50% reduction due to Mud/rust particles in some tubes)Repalced all rubber o rings on pipes fittings and heat exchanger gasgets. So far so good as it did not overheat at last testing. I found an inferred temp device that allowed instant measurement at any point of the water flow to be very helpful.
good luck"

davidk
09-01-2009, 01:41 PM
"Hello all, and thank you for the advice. The problem is still not solved, but I think it will be soon. I changed the sea water impeller just in case. But in further testing I found the sea water from the exhaust cool to the touch -- about 80F. And putting thermocouples on the fresh water input and output to the heat exchanger measured the input (from the engine) at 200F and the output at 70F when the over temp alarm sounded. So, I think there is not enough fresh water flow (like for Mark). The heat exchanger is at a radiator shop being cleaned. I should have it back together soon and will measure temperatures again. Thanks again to all!"

davidk
09-01-2009, 01:44 PM
Oh -- and I also changed the thermostat before pulling the heat exchanger -- but it was no help.

colinwd
10-17-2009, 12:46 PM
"I expect you have solved this problem long ago. However, I had trouble with my raw water cooled engine overheating though everything seemed in order. In fact the face-plate for the water pump had been work by the impeller and much of the water was merely circulating within the pump. A new face-plate solved the problem."

johndella
11-25-2009, 08:58 PM
"I also have a Volvo saildrive, your problem lies within your heat exchanger, flushing the heat exchanger will not resolve your problem. The heat exchanger will have to be removed and thoroughly cleaned. I found the lower ports in the heat exchanger to be almost totally blocked with scale. Pay particular attention to your exhaust riser which is cast iron (the wisdom of Volvo)constant salt water being passed through the riser is asking for corrosion. I also now use only red coolant recommended by BMW and Mercedes for use with alloy components and have had no problems since."

cragonese
11-26-2009, 11:27 AM
If your engine/s have a fresh water flush check that they are tight. If they are loose they are allowing air into the system restricting water flow which would raise your engine temps.

davidk
11-26-2009, 03:42 PM
"Hello all, and thank you all for your helpful responses. I believe this problem is resolved, or at least understood.
I had the heat exchanger pulled and thoroughly cleaned. That improved the situation somewhat. The temperature still ran at the top of the thermostat range, but did not go to extremes. I ran for several trips with a data logging thermometer on the fresh water in and out of the heat exchanger. On a cruise about a month ago I recorded a sudden spike -- over 10 minutes the temp went from normal to 100C on the pipe from the engine to the heat exchanger, while it dropped to near raw water input temperature on the pipe from the heat exchanger to the engine. This clearly indicated a sudden blockage in the fresh water circuit.
A mechanic pulled the heat exchanger and tubing and found a piece of zinc had worked its way through and lodged in the block at the input to the engine from the heat exchanger. There is a restriction there. He removed that piece. He also pulled an expansion plug from the block and could see a considerable amount of material. He removed as much as possible.
Following this I have run for 10 hours or so with the data logger recording the temperature. The engine runs cooler, there have been no spikes, and the temperature is much more responsive to engine RPM. At the highest RPM the temperature hits the top of the thermostat range, but any decrease in RPM immediately drops the temperature.
Overall, I recommend to anyone having an intermittent problem that a data logging thermometer (eg Omega HH306A $210 or HH309A $300)can observe events which you will not catch with an IR thermometer.
Thanks again and good sailing!"

crzhors
11-26-2009, 07:52 PM
Regular preventive maint. and a $35 Centech handheld IR thermo. A good time investment...