Rust in drained water and flushing closed cooling system

[docpaulo]

Here's the situation I have a 2006 mercruiser 5.0 carb that has never seen the water other than muffs. This was an 06 leftover and engine manufactured Oct 05. Purchased 11-06

It was allegedly winterized by selling dealer.

I fired her up this weekend with muffs to flush the engine prior to install of closed cooling system. I collected the water discharge in a big tub and saw no rust just unburned fuel.

I finished installing the closed cooling (full system) -- and during the install drained all 5 blue drain ports (seawater pump, 2 manifolds, 2 engine blocks)

The water from the manifold and pump were clear but the water from the engine block was mostly fine rust particles - brown color...

Question:

is this a bad thing? the rust in the engine block...

how do I go about flushing it more... I haven't filled the heat exhanger yet, should I fill it with water and run the system to flush it before putting on anti-freeze?

Is there a way to directly flush the block and get all that remaining rust out? Can I use compressed air on the heat exhanger cap to force the water out and will it find it's way to the engine block?

Any product I should use to retard or reverse this corrosion?

Am I over-reacting and this is normal?

Thanks for all your help...

(whew...installing that cooling system took longer than the 4 hours the manual mentioned... but glad I did it...)

 

[Boomyal]

Re: Rust in drained water and flushing closed cooling system

I would remove the thermostat, pull the lower water pump hose and pull out the block drains. Stick a hose in the thermostat housing opening and let her rip.

You couldn't have that much corrosion in the block and the flush would clean out any of the loose stuff.

 

[WillyBWright]

Re: Rust in drained water and flushing closed cooling system

And people wonder why I strongly discourage adding closed cooling to a years-old motor. Without antifreeze protection from the get-go, blocks begin to rust with humidity alone. It may take you a few coolant changes before it stops getting polluted. You can filter a lot of that out with a coffee filter, then reuse til it's clean and put in fresh.

 

[enn858]

Re: Rust in drained water and flushing closed cooling system

Dont worry - I had the same problem when instaling FWC on my brand new 2007 Mercruiser 135.

I will change the colant next year - just to be on the safe side - but the rust particles are very small and will probably be no problem. BTW a good antifreeze contains anti corrosion additives - so you dont have to add anything - just fill with a 50/50 mixture of water and antifreeze.

The cast iron blocks will get surface corrosion as soon as they have seen water + air for a few minutes - you can eaven see this on a car engine block if you drain the antifreeze and let it stand for a few hours.

If you dont have a Closed cooling system - this problem will be minimised if you dont drain the block after use - if the block is left with water in it there will be no oxygene to start the corrosion (or at least only the very small amounth the water holds)

I have discovered that since my system is only a "half" system i will leave the seawater in the exhaust manifold after use (summertime only - and i only run in FW) this minimizes the corrosion in the exhaust manifold

 

[Haut Medoc]

Re: Rust in drained water and flushing closed cooling system

You'll be ok....
Do what Boom says first & then:
Drain the block after a couple of times out & strain it like Willy says......
After a couple of seasons you might want to take the exchanger to a radiator shop & have it boiled out.....
You did yourself ( & engine) a favor by going FWC, (especially in salt water)........

 

[docpaulo]

Re: Rust in drained water and flushing closed cooling system

thanks for the input...

Yeah I plan on boating the sound a few times this summer so I figured a FWC now will save me some misery later plust it simplifies storage in between trips.

It's a full system and the hardest part was getting those dry joint gaskets into place (I did it all by myself with o help) and another set of hands would have made it twice as fast.

I'll use cheap anti-freeze (pink) and drain it/filter it end of the season before I go buy the expensive stuff..

Just didn't expect rust to set in that fast... with a full FWC those blocks will never see air again except for a few times when drained and hopefully that will retard corrosion... makes those 3 days of labor start to feel worth it...

 

[Boomyal]

Re: Rust in drained water and flushing closed cooling system

You did the wise thing docpaulo. Any engine that runs in salt should have this. Considering that your engine is carbed, I would seriously think about changing to a 180 deg thermostat.

140's and 160's are nothing but a compromise to help keep salt from plating out in the engine like it would in higher temperatures.

However, absent the salt, your engines cylinder combustion efficiency and cylinder wear (reduced) will be greatly enhanced by running at the 180 deg mark.

Some will say, "why second guess the engineers"? My response is that I am not. The engineers used the cooler stat for the reason above and only the reason above. The benefit of warmer engine operating temperature is no second guess. It is fact.

Just an added note here. At 180 deg we are not talking hot! Your engine, which is fundementally an auto engine was designed to run reliably at 195 deg +.

 

[Don S]

Re: Rust in drained water and flushing closed cooling system

Just a note here guys. A 160° thermostat is all that is used in Volvo and Mercruiser engines with a FWC system installed. The engine will run between 175° and 180°. Don't go running a higher thermostat. Your engine will run hotter, that small engine compartment will run hotter, and the next thing you know you have vapor lock problems.
If you hit 190° with a marine engine, that should be considered a problem.

 

[Boomyal]

Re: Rust in drained water and flushing closed cooling system

I run a semi HiPo 5.0 liter Ford with a San Juan cooling system. I use a 180 deg stat and it runs right on the money. Verified by both the onboard guage and my handy infrared thermometer.

Idle to WOT, it never varies! Even 190 deg, for a modern engine, would not be an issue. As long as it is consistant. The cylinders do not like to be subjected to constantly changing coolant temperatures.

If you do have a hot engine compartment, fuel percolation could become an issue at some point.