Coolant change on closed system Mercruiser advice?-gctid340236

[Morecoffee]

I want to change the coolant in my Mercruiser 5.0 Alpa 1 Gen 2 closed system. I have never done it and it most likely should have have been done before now. Is there an existing thread on this? I have looked and only found Hino ones, nothing for Mercruiser. Any advice or a link would be appreciated.

Cheers and Happy New Year

[Guest]

It should be pretty simple. Pull a low water jacket drain plug, or a low coolant hose to drain the coolant, and then reinstall the hose or plug. Then put a mix of 50/50 antifreeze to water in the top filler cap. If you can put a bucket under the plug or drain plug to catch the old coolant that would make the cleanup easier.

[2850Bounty]

E/G = ethylene glycol

H/E = heat exchanger

Assuming this is a Half System (engine only):

To fully drain the old E/G from a 5.0L Merc, you must remove the side engine block drain plugs.

Then remove the circulating pump suction hose and empty into a container.

Have the H/E cap open while doing this.

NOTE: The H/E's pencil anode port is not a drain for the E/G side.

The circ pump hose should take care of the E/G side of the H/E.

When re-filling, make sure that your thermostat has the air bleed hole in it.

Best to use distilled water with your E/G.

When fire up for the first time, do as you would with a car/truck.... give time for a bit of heat to just open the stat, shut her down.

Check coolant level... top off... repeat.

One or two Warm/Cold cycles.... and the air should be purged...... and you should be OK.

If you have a WH or Cabin Heater, extra measures are required.

You may also want to have the PH balance tested before you disgard the old E/G and get an idea of what's been going on inside the cooling system.

[Morecoffee]

This was exactly what I was looking for, thank you.