Yanmar 3GM30F cooling system problem

[Andrew H]

Originally Posted by gamayun

Ah, now I know why I don't live in areas where it freezes!

Andrew, did you check the pump impellor to make sure nothing got damaged during those 5 minutes you had it on? If everything is running but the pump is not sucking, the condition of the impellor seems like a good thing to verify.

I did- a friend mentioned that she once saw an impeller situation where the rubber ring with the vanes had separated from the brass hub, so I took the pump apart again to check that, but it's fine. Impeller spins as it should.

[dennismenace111]

If you're getting an airlock fill the heat exchanger with coolant and run the engine for about an hour or so with the cap off of the heat exchanger! You will see all sorts of bubbles bubbling in the heat exchanger! When the bubbles stop! You're system should be bled! Be prepared to add coolant as the air escapes!

[Andrew H]

Originally Posted by gamayun

Ah, now I know why I don't live in areas where it freezes!

Andrew, did you check the pump impellor to make sure nothing got damaged during those 5 minutes you had it on? If everything is running but the pump is not sucking, the condition of the impellor seems like a good thing to verify.

gamayun- I did check the impeller... it looked fine and spun with the pulley.

[chris mac]

If you do it this way, the antifreeze has only one wat to go. It can't go out through the closed thru hull. If it doesn't go thru the impeller and out exhaust, then it is definitely plugged somewhere in line

Originally Posted by Andrew H

Thanks! That's a good suggestion, I'll do that when I can get fluid to move through the system again.

[AA3JY]

Not unusual to take a full minute or so to see water flow from the exhaust to self prime after placing the water intake hose in a bucket of antifreeze....

[Boatyarddog]

Originally Posted by Andrew H

I'm having a problem with a Yanmar 3GM30F. I had the water pump rebuilt- the bearings were shot. After the rebuild, I reassembled everything, fired up the engine and it worked just fine. Good flow of water from the exhaust, smooth running, no overheating alarm.
I let it run for about 5 minutes, shut it down and replaced the raw water hose with a hose into a bucket of antifreeze. Fired it up again and... nothing.
I tried a few different things, then took everything apart again and examined the pump. It seems fine... the impeller spins when I turn the pulley, no hoses seem to be collapsing, nothing looks different.
I'm stumped- I don't understand why it would work well until being shut down and then just quit.
Has anyone else encountered this? I'd sure appreciate hearing about how I can fix this pretty frustrating problem.

Gallon bucket w/a garden hose attachment plumbed into the bottom of the bucket.
Other end attached to the raw water inlet side, raise the bucket ABOVE the raw water pump, even higher if possible.
Pour the PINK RV ANTIFREEZE ONLY, into the bucket.
Use propylene glycol based antifreeze only, for this!
It'll suck it down quickly, but you should only need a gallon or so.
You'll know it's thru when you see it come out pink from the Exaust ThruHull.
Cheers,
SV Cloud Duster