ZR6 overheated this weekend

[intrlaz]

So we dropped in on Saturday during low-tide and sucked up a decent amount of silt/mud. We did not realize at the time, and had motored for about 10 minutes at idle. I opened the engine hatch to check for leaks in the ballast system I had just installed, and coolant was boiling from the bottle (the engine has closed cooling).

Obviously we shut the engine down to let it cool. I was able to clean mud out of the strainer and get a sheriff to bring some coolant. Added about 1/2 to 2/3 gallon of coolant (not dex-cool unfortunately). The fix worked and we were able to get back to the ramp with no overheating issues of any kind. Temp stayed exactly where it does normally.

Besides flushing the cooling system and replacing with new coolant, is there anything else I should be doing? Engine ran perfect afterward, but does anyone think there could be any major damage?

[jmo]

I would open up your raw water pump and inspect the impeller - running it with no water (aka lubricant) could have damaged it, might want to swap it out while you have it open even if looks okay since it's a $30 part. If the old one looks okay keep it as a spare.

[WakeSlayer]

How hot did it get?

I do not own a closed cooled system, but a buddy does in his SV211, and had a similar incident a couple summers ago. he was very low on coolant and overheated. No harm done, but definitely something that needs to be monitored. I don't think the strainer having junk in it had anything to do with the overheat. They are separate systems.

[intrlaz]

I could be wrong, but from what I understand the raw water is pumped through the strainer and eventually to the heat exchanger. The heat exchanger needs that water flow to cool the coolant, basically acting like a radiator without the airflow. As soon as I got water flowing back through the strainer, engine cooled off nicely and we ran just fine.

I'm not sure how hot it got, but I would guess it would need to be very hot to boil coolant. I don't trust my temp gauge so i like to monitor myself. Didn't really see an vaporized water through the exhaust though

[WakeSlayer]

Sorry, you are right, they do cross at the heat exchanger. Again, I don't own one. On my friends boat I think he had a loose hose clamp or two. He never had the problem last season but only put about 15hours on the boat. I cannot imagine you lost a half gallon in that short of a period though, so I suspect it may have been low in the first place. SHould check your clamps over with a nut driver or ratchet.

[intrlaz]

Just drained about half of the system, but for the life of me I cannot find the block drain plugs. It wasnt hard to find them on my old GT-40. Can you guys help me out?

Is there anyway to flush the system without removing the plugs?

[HS]

Just drained about half of the system, but for the life of me I cannot find the block drain plugs. It wasnt hard to find them on my old GT-40. Can you guys help me out?

Is there anyway to flush the system without removing the plugs?

Should be a diagram in this manual: http://www.pcmengines.com/owners_inf...opperation.php

[intrlaz]

Should be a diagram in this manual: http://www.pcmengines.com/owners_inf...opperation.php

Unfortunately the manual does not point out the exact location.

See the attached water flow diagram. Is there any reason I cant disconnect the fresh water return, start the boat and let it drain while adding water to the coolant fill bottle?

[intrlaz]

In case anyone is interested, I contacted PCM directly to ask about the drain plugs. The guy I spoke to had to get in touch with three different people to find the answer, since apparently they aren't removed very often.

The plugs are not the same size, but both are hex head. One is located just above the crank sensor near the starter, next to a wedge. He said I may need to remove the starter.

The other is large and not really obstructed by anything. It requires a 17mm allen wrench to remove.

I will update when I actually get them out

[intrlaz]

Confirmed that with v-drive orientation starboard plug is 17mm hex head. Pretty easy to remove. Port side I needed to pull the starter. Its only two bolts so not a big deal. It may be possible to get a wrench in there if you get creative with the extensions. I believe it was a 9mm hex.

Hope this post helps someone out

[john_keck]

Thank you! I was looking all over the web for this exact post. I couldn't figure out how to get the other 2 gallons of coolant out. I have a 2006 220 w/ the ZR6 and there just isn't a lot of room to find these (at least with the hard ballast tanks installed).

[DanielC]

Dex-cool antifreeze has been known to cause some problems in GM cars and trucks. It gels, and then plugs passages in the radiator, and heater core, and the only effective repair is replacement. It is thought the problems happen when the coolant gets contaminated with non compatible antifreeze, this happens.

I would suggest you make sure the entire cooling system is flushed completely, and then refill with the recommended coolant. You should also carry the recommended coolant in your boat at all times.