7.4 Volve closed cooling over heating

[jili]

having an issue with my 7.4Volvo marine engine(2000)
I have a slight overheating issue.
Temp should run at 175, it is running at 195.
I have replaced the impeller, the old one was fine.
I noticed the plastic fill tank for the anti-freeze had some black
particles in it. I removed and cleaned this tank out and put fresh
anti freeze in it. It still ran hot. Also the plastic tank is all dirty again.
Something is breaking down somewhere.
Any ideas what is causing this? could it be the heat exchanger?

Thanks, jim

 

[tpenfield]

Re: 7.4 Volve closed cooling over heating

Welcome to iBoats, Jim . . .

The heat exchanger may be getting clogged as evidenced by the dirt particles in the reservoir. Maybe time for some back flushing of the exchanger and engine block.

I have a closed cooling system on a Merc 7.4 and it runs up to 175 maximum. So, 195 is pushing it.

 

[Scott Danforth]

Re: 7.4 Volve closed cooling over heating

do a system flush on the fresh water side, and flush out the raw water side. do not forget to back flush the power steering cooler. those plug first.