Changing out heat exchanger - start up process

frosh coach

frosh coach

Member
Apr 20, 2011
237
Long Island Sound, New Haven CT
Boat Info
1997 300 DA,
1994 300 DA (SOLD)
1989 230 (SOLD)
Engines
Twin Mercruiser 350 FWC, 300 HP MPI V-drives
Yesterday I changed out the HX on my 94 Mercruiser 5.7 FWC motor (alpha drive). I filled the exchange with fresh 50/50 antifreeze. My question is when I restart the engine, should (can) I start it with the radiator cap off to allow any air to escape?

Also when my mechanic did the other engine for me last year, I remember him opening a bleeder valve on top of the thermostat housing cover. I think he did that when the engine was running and the cap was on the heat exchange.

thank in advance.

Chris
 
No, let it run for 5 min. and add fluid if it needs it, put the cap on and let it get up to temp. Have fluid in the overflow tank.
 
frosh coach said:
Yesterday I changed out the HX on my 94 Mercruiser 5.7 FWC motor (alpha drive). I filled the exchange with fresh 50/50 antifreeze. My question is when I restart the engine, should (can) I start it with the radiator cap off to allow any air to escape?

Also when my mechanic did the other engine for me last year, I remember him opening a bleeder valve on top of the thermostat housing cover. I think he did that when the engine was running and the cap was on the heat exchange.

thank in advance.

Chris
Click to expand...
What was the condition of the one you took off. Did it leak?
 
northern said:
What was the condition of the one you took off. Did it leak?
Click to expand...
I Had the one on the other engine replaced last year. as it was leaking. I decided To do this engine too. The originals did not have zincs, these do. This was was on its last leg.

Next will be the elbows.
 
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