Volvo Penta D1-20 overheating sometimes, now every time

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vasouman

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Hi, we have a Volvo Penta D1-20 installed 12 years ago, and used just 1200 hours. I have no idea how it was maintained since I just recently bought to boat. We experience some overheating problems. Usually in wavy conditions, or when heeling, it will quickly sound the overheating alarm. On the other hand, it may run 48 hours in calm weather without any problems. This was untill today, when it started sounding the alarm after approximately 30 minutes of work at about 2000rpm. What has mostly happened in between was that a month has passed since the last used the boat, and last thing we did was to opened and cleaned the salt water filter, without testing the engine much after that. Today, We opened and cleaned the salt water part of the heat exchanger. Couldn't open the back cap, so cleaned it only from the front. There was some salt blocked pipes, impeller is intact. We thought air may have filled the exchanger, so we moved the expansion tank higher then the heat exchanger, as originally it was slightly lower (don't know if that should be so, but I believe it should be higher), and tried to bleed the air by running the engine and occasionally slackening the cap and squeezing the hoses, but it overheated again after 40 minutes. All hoses are warm, so I suppose thermostat is working. When we tighten the cap, coolant level in expansion tank drops and does not rise (it was warm already, so I supposed it is due to pressure getting restored. At first we thought we just need to fill in lots of coolant, but seems that it's getting too much. Already filled 3, or 4 liters or so. I'm afraid we might be loosing coolant, but haven't detected a leak yet, or greasy exhaust water. Weirdest thing is that it worsened after just sitting in port for 1 month. What would you suggest?
 
Could be coolant leaking into the exhaust elbow at the rear of the heat exchanger.
The rear cap of the H/E is removed in a similar manner to the front. It can be stubborn to detach, a soft-faced mallet helps. If you can get it off you will be able to discern whether or not there has been a breakdown in this area, allowing coolant to leak into the raw water.
 
If you already added 3 or 4 litres of coolant, there is obviously a leak in the coolant system and that will inevitably lead to overheating. The coolant must be in the bilge, in the engine sump, or going out with the exhaust water. If it's not in the bilge or the sump, then it's in the sea and you have to strip down the heat exchanger.

Richard
 
There was a previous thread on this subject. The upshot was that, intermittently, in certain conditions, (engine revs, etc.), bubbles form in the top of the heat exchanger , causing an airlock, the cure for which was to raise the height of the coolant reservoir.
Alternatively, there is a leak at the back of the H/E, alowing coolant to drain into the exhaust. There is discussion of this here: http://www.ybw.com/forums/showthread.php?478674-Volvo-D1-20-leaking-coolant-into-elbow-How-to-weld
 
Last night I filled the expansion tank with coolant and left it open overnight. I the morning it was all gone. We opened the engine today. Removed the head, heat exchanger and lots of other stuff. Cylinders were filled with coolant, no salt water as far as I can tell. Air intake in the head was wet, so I suppose coolant came in with the air. All gaskets look good, cylinders also. So far, I have no idea where the coolant came from. Perhaps a crack in the head, although I don't see anything sispicios for now. It has to be something really bad, so that coolant can enter the engine even when not under pressure.
I'll have to bring the parts to somebody experienced and see if we spot something. I'll try to keep in touch, but it wont be untill after a month or two when I'll be ready to try to assemble the engine back

Vasil
 
vasouman said:
Last night I filled the expansion tank with coolant and left it open overnight. I the morning it was all gone. We opened the engine today. Removed the head, heat exchanger and lots of other stuff. Cylinders were filled with coolant, no salt water as far as I can tell. Air intake in the head was wet, so I suppose coolant came in with the air. All gaskets look good, cylinders also. So far, I have no idea where the coolant came from. Perhaps a crack in the head, although I don't see anything sispicios for now. It has to be something really bad, so that coolant can enter the engine even when not under pressure.
I'll have to bring the parts to somebody experienced and see if we spot something. I'll try to keep in touch, but it wont be untill after a month or two when I'll be ready to try to assemble the engine back

Vasil
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Did you drain the coolant before loosening the head?
 
We didn't drain it. But we removed the glow plugs and turned the engine by hand. It was spiting out coolant from the plug holes
 
As you've got the head off, get it pressure checked and that will tell you whether the problem lies In the water jacket or the heat exchanger. When we had this problem with a Penta it was the expansion tank casting, corroded through to the exhaust headers.
 
Hi, We had very similar problem with our Volvo 2003T and I have recently wrote on this forum how we managed to repair it for good.
Volvo had some plastic restrictor inside the water cooling pipe work that is not even on they technical drawings. As soon as we cleared that, all working perfectly.
 
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