How to change coolant in a Mercruiser 496 Mag

[ricklonna]

I want to change the antifreeze coolant in my 2005 merc. 496 mag engine with the closed coolant system.
After draining coolant from block by removing plugs and replacing them, do you just add coolant to the reservoir or do you have to run the engine at idle while adding coolant?
I'm not sure how the air gets dispersed in the engine when new coolant is added, as I know this could be a problem if the air is not removed.
Thanks

 

[Don S]

Re: How to change coolant in a Mercruiser 496 Mag

Make sure the engine is level or the front up a litttle to keep air from being trapped in the engine, then just fill the system through the pressure cap. Not sure if your model has a reservoir built into the heat exchanger or a separate one. Just be sure you are not trying to fill through the overflow reservoir.
Here is the OEM system, #22 is the cap you remove to fill.

 

[ricklonna]

Re: How to change coolant in a Mercruiser 496 Mag

Thanks for the info.- now I'm not sure how to drain the heat exchanger?
Does it drain by just removing plugs on engine block, or is there something else I need to do?
Thanks again.

 

[Don S]

Re: How to change coolant in a Mercruiser 496 Mag

Here is info from the service manual for changing the antifreeze.

 

[HT32BSX115]

Re: How to change coolant in a Mercruiser 496 Mag

Thanks for the info.- now I'm not sure how to drain the heat exchanger?
Does it drain by just removing plugs on engine block, or is there something else I need to do?
Thanks again.

When I did mine, I used DEXCOOL (pink/red/orange etc)


If your's had DEXCOOL in it, make sure you refill it with the same or similar type AF.....OR be sure to flush the system THOROUGHLY!

You do not want to mix "regular" AF with DEXCOOL or other "longlife" AF.

 

[piratelew]

Re: How to change coolant in a Mercruiser 496 Mag

once the hex heads bolts are pulled and the coolant is drained is there any fluid trapped anywhere else. The reason for the question is that over the season l lost coolant and added water to make my return trip. Just want to make sure I do not have water trapped any place. Any insights would be great

 

[Don S]

Re: How to change coolant in a Mercruiser 496 Mag

Welcome to iboats pirate, but you need to start your own thread, not hijack someone elses thread.

 

[jjs2000ss]

Do you have a copy of this manual how to change this? i do not know where to drain the coolant. Can someone help?

 

[Bt Doctur]

Unless you can speak with the Angels you wont get to speak to DonS He passed on
The best thing to do is start your own thread with your specific problem