Overheating at Idle

[prunjr 0]

I have an 06 Avalanche with about 100 hours. My impellar fried and I replaced it and found all my missing pieces. Pulled hose on transcooler and cleaned it out as well. Came home from my last trip and went to flush with fake a lake. No water flowing at idle but when I rev the engine it flows but still not the same as before. So I pull the seawater pump again and impellar looks fine. Belt is tight. Make 4 more trips and still problem with fake a lake not flowing water at idle when I flush. Yesterday at Tahoe I left boat idling for about five minutes and all of a sudden overheat beeping starts. I look down and temp guage is buried. Remembering fake a lake doesnt flow at idle, I put it in gear and take off and temp came right back down to 175. One of the lakes I visit has some moss, can this clog the cooling system? Or possibly thermostat? Just trying to decide how to troubleshoot and would appreciate some feedback. Thanks

[superdtf 68]

That it cools with RPM's typically indicates engine circulation, not usually seawater pump. Here are the things to look for:

• T-Stat - is it blocked up (this is what I'm betting a six pack on), or does it not open fully?
  
• J-hoses - is there crap in there, or is there some external constriction?
  
• Engine circulator pump -- although these typically start leaking when they fail, and we assume you would notice that. HOWEVER, this is not always the case. My buddy's MasterCraft went through a circulator pump where the vanes corroded away. He was in some weird lakes in CA and also in the ocean.
  
• From there, go to your exhaust (but I'll be very surprised if you don't find your problem before that).
  

[prunjr 0]

That it cools with RPM's typically indicates engine circulation, not usually seawater pump. Here are the things to look for:

• T-Stat - is it blocked up (this is what I'm betting a six pack on), or does it not open fully?
  
• J-hoses - is there crap in there, or is there some external constriction?
  
• Engine circulator pump -- although these typically start leaking when they fail, and we assume you would notice that. HOWEVER, this is not always the case. My buddy's MasterCraft went through a circulator pump where the vanes corroded away. He was in some weird lakes in CA and also in the ocean.
  
• From there, go to your exhaust (but I'll be very surprised if you don't find your problem before that).
  

 

Just what I was looking for, a logical approach to my problem. Thanks and I hope you earn your six pack. The J-Hoses, would this be the hose from t-stat housing to exhaust?

[superdtf 68]

 

Just what I was looking for, a logical approach to my problem. Thanks and I hope you earn your six pack. The J-Hoses, would this be the hose from t-stat housing to exhaust?

No, the bigger ones from seawater pump to t-stat housing and circulator pump to t-stat housing. They are in the shape of "J"'s (at least one of them is, the other is more "J"ish to straightish).

[pjc 0]

To accurately test the cooling system you must have a static water feed, that is with - no head pressure. The "plunger type" fake-a-lake systems add typical pressure from your home water line. Here is a great DiY of a proper system.

 

 

I am going to make one of these soon but, will likely use a plastic, 11 gallon, race fuel, dump can instead of the trash can. I will post photos of the system.

Edited August 10, 2012 by pjc

[superdtf 68]

You are exactly right, but that's the hard way. Here are two that are WAY easier:

1. Put a "Y" on your hose bib, from one side run the hose to your fake-a-lake. Leave the other side open. That's what we did at the dealership for years in order to test the suction of the impeller. You can put another hose on the open side in order to direct the runoff elsewhere if you'd rather not have a swamp at your hose bib.
   
2. Put a "T" in place of the elbow at the thru-hull side of your v-drive. Reconnect your supply side hose, and on the other side install a valve. When you need to run the boat out of the lake, open the valve, attach your hose, and turn on the water; the water drains right out onto the driveway. If your impeller is good, it will begin to draw the water from the side of the "T". I like this one, because I can control the water without leaving the boat, and I don't have to lug anything in/out.
   

Edited August 10, 2012 by superdtf

[pjc 0]

You are exactly right, but that's the hard way. Here are two that are WAY easier:

 

Interesting and thanks!

 

One question though - can you run the motor up in RPM? I am thiking that the static tank of water will provide the buffer needed to deal with the intake volume vreated by a good impeller.

[superdtf 68]

 

Interesting and thanks!

 

One question though - can you run the motor up in RPM? I am thiking that the static tank of water will provide the buffer needed to deal with the intake volume vreated by a good impeller.

yes, no trouble with starving it so far - but we do have very healthy water pressure here.

[chadr 328]

With the hose bib, do you have a hose set up to have female ends at both the source and at the engine? This looks like it would run really well. Also, does it work for you to attach something for winterizing like a container that holds your antifreeze? If not, how do you winterize it?

[superdtf 68]

From the other thread: http://www.centurioncrew.com/index.php/topic/6635-how-do-you-install-a-t-and-ball-valve-to-replace-a-fake-a-lake/

 

I ended up not using a ball valve. If you look at the photo above, the large, blue-handled valve is a gate valve that is "full-port" meaning it opens as big as the pipes. I also liked it because it's only like 2-1/2" long instead of 4 or 5. I ONLY close it when I winterize to suck antifreeze. This image should give you good idea why the gate valve is a nice choice to avoid restricting the flow.

The smaller, green-handled valve is a garden valve that I use to hook up the hose. It's one of the least constrictive valves. I use a double-female hose swivel to hook up the hose. Like this one.

 

So like tonight, I changed the oil. I hooked up the hose, opened the garden valve, and turned on the hose full-blast. The water goes in the garden valve and down the intake tube onto the driveway... until I start the motor, then the seawater pump/impeller "suck" the water in and I can run the motor that way. It's a good test of the impeller and super convenient.

 

To suck antifreeze I do this:

• Run the motor on the hose to get everything up to normal temp.
  
• Shut off the motor and turn off the hose.
  
• Close the large gate valve.
  
• Hook up a length of rigid(ish) tube to the garden valve. I use a piece of curved 1" pex that I crimped a 3/4" FIP fitting and then screwed on the hose adapter. Then the female to female hose swivel connects the valve to the pex.
  
• Stick the other end of the tube into the bucket of antifreeze that I have ready.
  

Edit: Oh yeah, DO NOT forget to close the garden valve. That would be bad. But NOT NEARLY AS BAD as forgetting to OPEN the gate valve.