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Old 19-08-2017, 12:26   #1
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Can I remove thermostat during a coolant flush

Hello all,


We are about to change our coolant. We purchased the boat last fall and do not know what type of anti-freeze the PO used so we plan to drain the old coolant and flush 4x with distilled water before adding the new coolant. We plan to follow Cap Don's steps given in post #9 in the linked thread below but don’t want to spend the four hours.


http://www.cruisersforum.com/forums/...30f-60535.html


Question: To save time, could we remove the thermostat?


It occurred to me the only reason to have the engine reach 180F is to open the thermostat and ensure the coolant flows into the heat exchanger. If we remove the thermostat before the “flush 4x with distilled water part”, could we get away with just running the engine for a few minutes for each flush? Not only would this save the time to heat the engine but it would also save the time to cool down the engine. We would replace the thermostat before we add the new coolant.


I'd very much like to save the four hours, but I'm fairly new to this stuff and don't want to make a huge mistake.
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Old 19-08-2017, 12:39   #2
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Re: Can I remove thermostat during a coolant flush

You can remove the thermostat when flushing the cooling system.
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Old 19-08-2017, 12:44   #3
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Re: Can I remove thermostat during a coolant flush

Ive never used distilled water for a flush. Typically, just city water for the flush and distilled mixed with the coolant for the fill.

Yes, remove the thermostat as you dont need to run so long that scalding hot water builds to open the thermostat.

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Old 19-08-2017, 13:17   #4
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Re: Can I remove thermostat during a coolant flush

Go to Walmart or an auto parts store, buy a Prestone flush kit and install it according to the instructions. Just realize your calorifier hose to your water heater, is exactly the same as an automobiles heater hose and therefore a marine engine and a car engines coolant can be flushed the same way.
Sufficiently diluted engine coolant is not a pollutant like say oil is.
I wouldn't bother with distilled water myself, batteries yes, but not for coolant.
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Old 19-08-2017, 21:53   #5
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Re: Can I remove thermostat during a coolant flush

Do your self a favor, Replace the thermostat with a new one as they dont last for ever and you have it out any way (keep it for a spare) and while at it change your raw water impeller,you may want to check your riser as well??

Your engine will love you for it!!

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Old 20-08-2017, 10:03   #6
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Re: Can I remove thermostat during a coolant flush

Radflush chemicals help remove rust and oil film from inside coolant galleries. Do your first flush with plain water, and run hose until it comes out clear. Then add rad flush and repeat. Supposed to run engine up to temp for best effect. The Prestone Radflush kits works nicely, but the instructions say to cut a hose open, insert flushing nozzle and leave it in place when done. Don't! Pull a hose off the block, put the insert in there and with a little bit of hose reconnect it to the block. Don't like leaving a bit of cheap plastic in place long term, and with two extra clamps that may leak... Considering the cheap price of new rad hose I'd try to replace as much of it as possible during this task, since you likely don't know the maintenance history.
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Old 20-08-2017, 10:23   #7
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Re: Can I remove thermostat during a coolant flush

Drain the coolant, take back to auto store or to toxic waste. Use water proof gloves, avoid getting on your skin, it is absorbed thru your skin. Very toxic stuff.

Remove thermostat, replace housing, flush at least 3 times with distilled water.

After the final drain, put in new thermostat and gasket.

100% of the water won't drain, so:

Add the new anti freeze to the engine measured to be half the volume, then top off with distilled water. Run the engine to temp, allow to cool, then top off again with distilled water.

Check for leaks. Enjoy.
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Old 20-08-2017, 14:57   #8
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Re: Can I remove thermostat during a coolant flush

Quote:
Originally Posted by Rough Magic View Post
Drain the coolant, take back to auto store or to toxic waste. Use water proof gloves, avoid getting on your skin, it is absorbed thru your skin. Very toxic stuff.

Remove thermostat, replace housing, flush at least 3 times with distilled water.

After the final drain, put in new thermostat and gasket.

100% of the water won't drain, so:

Add the new anti freeze to the engine measured to be half the volume, then top off with distilled water. Run the engine to temp, allow to cool, then top off again with distilled water.

Check for leaks. Enjoy.
Coolant is not especially toxic, but .... it is not a pussy cat either!

Most are based on Ethylene Glycol, plus numerous additives for corrosion protection on either Aluminium or Cast Iron. The ethylene glycol is biodegradable, all goes within a few days but it is toxic and will affect liver with ingestion and prolonged exposure.
Most handlers do not worry, but do not suck or blow on a pipe coated in it etc and wash skin after contact.
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Old 20-08-2017, 16:37   #9
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Re: Can I remove thermostat during a coolant flush

Thanks for all the replies,

We will remove thermostat to speed up process. That will make switching back to green stuff less time consuming.

Thanks for the warnings on the coolant. I always wear gloves when I work on the boat after having read the label on some boat cleaning stuff. The warnings on that bottle made me a believer in gloves, glasses, and sometimes facemasks.
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Old 21-08-2017, 12:37   #10
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Re: Can I remove thermostat during a coolant flush

Quote:
Originally Posted by redbeard1 View Post
Thanks for all the replies,

We will remove thermostat to speed up process. That will make switching back to green stuff less time consuming.

Thanks for the warnings on the coolant. I always wear gloves when I work on the boat after having read the label on some boat cleaning stuff. The warnings on that bottle made me a believer in gloves, glasses, and sometimes facemasks.
Be careful not to leave coolant exposed where pets/animals can get to it as coolant has a sweet taste ,pets/animals have died or gotten sick from it – not a pretty sight.
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Old 09-11-2017, 12:45   #11
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Re: Can I remove thermostat during a coolant flush

Hello all,

Just an update on our process. We only did this last week as we decided to wait until we were on the hard in case we broke some tube or seal.

We removed the thermostat with very little trouble. The metal hoses/seals gave us no trouble.

Draining the old coolant took the most time due to our inexperience. The area near the drain-cock is very small and we had trouble trying to aim the flow into containers. Tip – open drain-cock fully. Initially, we turned it several times and thought the small amount of fluid draining was due to debris in the drain-cock. After using a wire to “clean” the drain, we accidentally turned the drain some more and the fluid flow increased dramatically. Tip – open reservoir for venting. This troubleshooting/trial and error took several hours. We finally decided to use a hose on the drain-cock to direct the fluid into our engine bilge (separate from boat bilge). Once the liquid was in the bilge, we pumped it out into containers using a cheap hand pump. The draining of the coolant (ignoring the learning curve) should not take longer than five minutes for each drain.
We flushed 3x with distilled water (by the 3rd flush, the water looked so clear we just didn’t think we would gain anything from a 4th flush, and we were cold – it was in the low 40s).

We calculated the total system capacity – 186 oz (from manual) plus 30 oz of additional hose (our coolant is also used to heat a water tank) - and added the right amount of 100% coolant, topped off with distilled water and we were done.

The old thermostat worked fine but we will replace it. One last tip, if doing this before winter in the north, remember to bring the engine to operating temperature (open thermostat) after the coolant has been added. Otherwise, you will only have distilled water in the heat exchanger.

Thanks again to all for the help.

edit: forgot to add, remember to burp system. We usually wait for at least 30 seconds after last bubble before stopping engine. On the final fill, we waited for a minute or two after the last bubble.
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