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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15635
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a Volvo Penta 2003T with 700 hours on it. It

Customer Question

Hello I have a Volvo Penta 2003T with 700 hours on it. It starts easily, and idles beautifully. It can run up to 2,000rpm under load or 3,200 with no load and is perfect. BUT if I exceed 2,000rpm under load then it overheats. This developed quite suddenly when under way. The shaft is free to turn by hand and alignment has been checked. There is no smoke from the exhaust. The engine is freshwater cooled. The seawater filter and pump have been checked - no damage to impeller, good water flow through exhaust. Oil and water are clean. The temperature used to stay just below 80 degrees centigrade, but now rises to the expected 82 very quickly, before rising if the engine is run hard.
One clue is that a block tester shows combustion gases present in freshwater. My first thought was head gasket, but the system does not seem to become over pressurised.
Any ideas would be very welcome! Thanks.
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.

Hello my name is ***** ***** am I speaking with.

How old is the actual impeller, and when was the last time it was changed?

Have you changed the thermostat yet?

Customer: replied 2 years ago.

Hi Jason, I'm Simon. The impeller was about 1 year old, had no damage, but has been changed for new anyway. Have not changed thermostat - more concerned about combustion gases in cooling system. Somehow the system has picked up my wife's email address, so she has just received your query. I did type my email address, which is the same as hers, except sim at the front instead of ang. Thanks.

Expert:  Jason replied 2 years ago.
Which block tester are you using, are you using the dye type where you suck gasses up through the dye?
Customer: replied 2 years ago.

Yes, that's correct. Glass tube, blue fluid, turns yellow.

Expert:  Jason replied 2 years ago.
Just to make sure. You are just sucking gas up that are in the heat exchanger, you are not sucking up antifreeze through the dye, correct?
Customer: replied 2 years ago.

Correct. Tester applied to expansion tank and air drawn from there; but interesting that antifreeze can change the fluid colour. However, bubbles appeared in the tester, the fluid level did not increase. I might have to leave PC in a moment, so next response might be tomorrow.

Expert:  Jason replied 2 years ago.
The only thing I would do is try your tester on another engine that is not having any problems, for example your car, just to make sure there isn't an issue with the dye. But if the dye doesn't change color on the car engine, but does on the engine, there is a very minor head gasket leak. Does that make sense?
Customer: replied 2 years ago.

Hi, I have checked the tester, and it is fine on good engines, and changed colour on one that had a known head gasket problem. I would have expected any leak with a diesel to produce much more pressure in the system, so wondered if there was anywhere else that could leak, or any common issues with this model of engine?

Expert:  Jason replied 2 years ago.
As far as every day items go on this engine the only thing that would cause it is the head gasket. It's more than likely just a pinhole in the head gasket, and not a full blown tear.If you had a further question on the isssue feel free to ask. If not, Just incase you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. Please let me know if you run into any problems or errors when trying to do it. Questions do not lose out, so if you have to come back tomorrow or next with follow up questions to this you still can even after doing a ratingIf I do not hear back from you I thank you in advance and good luck!Jason

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