Changing out heat exchanger - start up process

Discussion in 'General Maintenance/Repair Questions' started by frosh coach, Jun 30, 2020.

  1. frosh coach

    frosh coach Member

    197
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    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
     
  2. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Yes, cap off
     
  3. frosh coach

    frosh coach Member

    197
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    Im assuming I can run it until it comes to temp and then place the cap on.
     
  4. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    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.
     
  5. frosh coach

    frosh coach Member

    197
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    thank you!!
     
  6. frosh coach

    frosh coach Member

    197
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    worked perfectly, thank you again
     
  7. northern

    northern Well-Known Member

    Jan 17, 2007
    West coast Vancouver to Alaska
    380 Aft Cabin 1989 GPS and Charts by Nobeltec
    Twin 454 strait shaft
    What was the condition of the one you took off. Did it leak?
     
  8. frosh coach

    frosh coach Member

    197
    Apr 20, 2011
    Long Island Sound, New Haven CT
    1994 300 Sundancer
    1989 230 Cuddy (SOLD)
    Twin Mercruiser 350 FWC, Alpha 1 Gen II
    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.
     

Share This Page

Show Sidebar