Volvo 4.3 overheating

Greetings,

I just joined this forum and I also just purchased a boat. It's a 1990 Carver 2767 Santego. We like the boat but when we took at out a few days ago the starboard engine overheated. The engines are Volvo 4.3 model 431A. They have the closed freshwater system installed.

I tried a new thermostat, but it still got hot so I swapped the thermostat from the port engine to the starboard engine. Still getting hot, and port motor works fine.

I pulled the impeller and it looked fine.

I pulled off and inspected the circulation pump. It looked fine and spun normally. I put it back on the motor.

So I've ruled out the impeller, the circulation pump and the thermostat.

At this point I'm suspecting the sea water pump. How can I test this? My first thought was to mark an impeller blade and run the motor to make sure it's spinning. Is there anything else I can do to test?

Is there anything I should be looking at?

Dean

Re: Volvo 4.3 overheating

I pulled the impeller and it looked fine.

Click to expand...

So, when you say it "looked fine", did all the vanes straighten out within a few minutes? If not, it's not fine. Did you install a new gasket when you looked at the impeller?

Re: Volvo 4.3 overheating

Yes, the straightened out right away. I did not replace the gasket?

Re: Volvo 4.3 overheating

Have you backflushed the heat exchanger? Are the manifolds also freshwater cooled? Salt water boat?

Re: Volvo 4.3 overheating

I've not touched the heat exchangers. They are cooled in the closed system with antifreeze.

Re: Volvo 4.3 overheating

When I pull the plug on the back of the heat exchanger and put my finger in there, I can feel a bunch of debris. This was the same on both of them on the starboard motor. I will check my shop manual, but do I need to remove those to flush them out or do I just run fresh water into the inlet hose with that drain open?

Dean

Re: Volvo 4.3 overheating

I also opened the impeller port and marked a fin. I turned the motor over without starting and noted that it moved. This suggests that the raw water pump is spinning.

The fresh water cooling system is a San Juan Engineering.

Dean

Re: Volvo 4.3 overheating

Fish_Molester said:

I've not touched the heat exchangers. They are cooled in the closed system with antifreeze.

Click to expand...

They have raw water and antifreeze in them. You can flush the raw water side by running a hose into the raw water exit side of the exchangers, flushing the debris back out the raw water intake side.

After rereading your posts, are you confusing the heat exchanger with the exhaust manifolds???

Perhaps you could post a pic of your engine to help identify what you've got.

Re: Volvo 4.3 overheating

Fish_Molester said:

This was the same on both of them on the starboard motor.

Click to expand...

Both? Engines don't have more than one heat exchanger usually..

Re: Volvo 4.3 overheating

I fought overheating problems in my 4 cyl volvo for 3 or 4 years.
Finally a guy came along and told me I had too much antifreeze in my heat exchanger.
I thought he was crazy
The book says 50/50.
I took out quite a bit of antifreeze and added water.
Lo and behold...no more overheating problems.
Just a thought,
I was way over 50/50

Re: Volvo 4.3 overheating

I ended up replacing the impeller and problem solved. Thanks everyone for sharing your ideas.

Dean

Re: Volvo 4.3 overheating

I guess it's too late for my suggestion, now that you have solved the problem.

But a common problem on older Volvo V6 & V8 is that the exhaust risers over time gets clogged with rust, where the water exits. And this will lead to an overheating engine.

I have experienced this several times.