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dm001681

LS3 Overheat warning, what's going on?

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dm001681

I have a 2015 LSV23 with the 409.  My marina (not a Malibu dealer) performs the winterization and oil change at the end of every season.  This year when I got the boat out of winter storage and put it in the water for the first time after starting the motor I noticed the water houses that should have been connected to the motor were not.  My marina reviewed their work and reconnected everything.  I then took the boat out and the boat performed as it has the first two seasons, no issues.

Now, the second time out after starting the motor immediately after launching the engine temp climbed to over 200 just sitting at idle by the launch.  Once I put it in gear and got better water flow the motor cooled down into the 160's however I continued to get an overheat warning.  I monitored the temp carefully and under way the temp stayed there however if I slowed back to idle/neutral the temp would climb a bit.

I took the boat home, put a hose buddy attachment on so I could start it in the driveway to test.  The impeller appears to be working correctly and I'm getting good flow of water.  Temp climbed to 169 when I shut it off as I wasn't comfortable with that.  Port side manifold was definitely hotter in the driveway though, not sure if that is indicative of a particular problem.  I did also look at the impeller to see if there was anything clogging it and it was clear.

Thoughts?  And thanks!

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BlindSquirrel

Did you remove the impeller and look at it or just the cover? I bet running it dry while the hoses that should have been connected caused it to destruct. The symptoms you describe of it cooling down while moving and staying somewhat cool on the hose are such of an impeller that is not working properly. Both of the times it is "getting good flow" the water is being forced in. There are several ways to remove it ..... there is a pricey tool, or I have great success with 2 paint can openers on either side to pry it out. If you don't want to remove it, you can also undo the hose to the transmission cooler (shaped like a beer can, if the 2012's have one), it will be full of rubber pieces from your exploded impeller.

Edited by BlindSquirrel

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BlindSquirrel

Here is one that looked good when inspected with just the cover off.

impeller1

But was not so good upon inspection and was causing the engine to overheat when not underway. 6 of the 12 fins were damaged, so it does not take much.

impeller2

 

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MadMan

Whenever this kind of thing happens, I first try to figure out if it's truly getting hot or just instrumentation (faulty sensor, gauge).  You could use an IR thermometer , or simply install a mechanical temp gauge to verify.

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MWJ68

I was with dm001681 when this happened. We looked at the impeller with the cover off but did not pull it out. From the exterior it looked fine. At no time has the engine been run dry. 

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sic0048

Also, keep in mind that most temp sensors only work when there is water moving past them.  If you impeller fails and there isn't enough water going through the system, the temp gauge is probably inaccurate and not showing the actual temp.  In fact, it is very common for the gauge to read a completely normal temp (like 160) because that was the temp right before the impeller failed and then there is no water moving past it to make the sensor read the higher temps.

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MWJ68

We can check the impeller but when we first started the boat with the boat buddy sealed and water turned on to a easy low flow, we started the boat and the pump immediately sucked the water in the hose hose and collapsed the hose, we immediately increased the water to the hose and then continued the check. I would think if the pump has enough suction to collapse the hose (heavy duty garden hose) then that certainly indicates adequate suction to draw water to the entire engine. 

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csleaver

The Indmar 409 L96 6.0L has a reverse flow cooling system and air can get trapped in it and cause overheating at idle.  So on standard cooling models around that year (with no coolant or heat exchanger) there is a air bleed tube that has a hose that goes to a small through hull fitting on the transom near the port exhaust flapper.  If that hose, fitting, or tube gets clogged, the motor will run hot at idle, even with a good impeller and nothing else clogged in the cooling system (like weeds in the trans cooler).

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skurfer
1 hour ago, csleaver said:

The Indmar 409 L96 6.0L has a reverse flow cooling system and air can get trapped in it and cause overheating at idle.  So on standard cooling models around that year (with no coolant or heat exchanger) there is a air bleed tube that has a hose that goes to a small through hull fitting on the transom near the port exhaust flapper.  If that hose, fitting, or tube gets clogged, the motor will run hot at idle, even with a good impeller and nothing else clogged in the cooling system (like weeds in the trans cooler).

Always wondered what that hose was for! Now I know! 

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MWJ68
9 hours ago, csleaver said:

The Indmar 409 L96 6.0L has a reverse flow cooling system and air can get trapped in it and cause overheating at idle.  So on standard cooling models around that year (with no coolant or heat exchanger) there is a air bleed tube that has a hose that goes to a small through hull fitting on the transom near the port exhaust flapper.  If that hose, fitting, or tube gets clogged, the motor will run hot at idle, even with a good impeller and nothing else clogged in the cooling system (like weeds in the trans cooler).

Any chance either of you have a pic of the hose? The only line I see that you describe looks like a oil breather line coming from just below the oil filler neck and runs out the transom just below the swim deck itself and above the port swim deck lights.

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MWJ68

A follow up question: If we pull the impeller and see there are pieces missing, would they be trapped somewhere in the system? Is there a filter something? I confirmed it is a reverse flow system. Line goes from through hull to the impeller pump then directly to the trans- then to the motor. The is no sea strainer on this system.

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ahopkinsVTX
5 minutes ago, MWJ68 said:

A follow up question: If we pull the impeller and see there are pieces missing, would they be trapped somewhere in the system? Is there a filter something? I confirmed it is a reverse flow system. Line goes from through hull to the impeller pump then directly to the trans- then to the motor. The is no sea strainer on this system.

Your trans cooler should have a screen on it to stop debris.

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csleaver

I think the sea pump impeller pulls water from the thru-hull inlet, through the vdrive and transmission cooler then pumps it to the thermostat housing.  Grass or other debris often gets clogged in the trans cooler and failed impeller pieces usually go into the thermostat housing.  If you don't have a strainer, I highly recommend one.  Indmar makes a nice strainer that also has a garden hose flush attachment on it that is very affordable.  Don't forget to check the thru-hull water inlet safety valve.  It should be all the way open, usually with the lever inline with the valve and pointing straight up.

I don't have a photo of the air bleed hose, but it looks like you found it.  It is black rubber, about 1/4 ID, 3/8 OD, and kind of looks like a small fuel hose.  It is connected near the front of the motor on the top of the port intake manifold and goes to the fitting on the port transom close to the port exhaust flapper and underwater light.  When you run the motor with the boat on the trailer using a motor flush, you should see a stream of water come out of the air bleed fitting by the port exhaust flapper within a couple of minutes or less.  If there is a clog, you can remove the rubber hose on the motor air bleed fitting, with the motor not running, and blow air down the hose to the transom fitting and also down the bleed line on the motor.  There is a metal tube that connects the port and starboard cylinder head air bleeds to the transom air bleed hose fitting.  I have, in some cases, had to remove the small bolts to remove the small bleed tube to clean it out with a thin piece of wire.  They have a small oring seal on each side which is often reusable.

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MWJ68
6 hours ago, csleaver said:

I think the sea pump impeller pulls water from the thru-hull inlet, through the vdrive and transmission cooler then pumps it to the thermostat housing.  Grass or other debris often gets clogged in the trans cooler and failed impeller pieces usually go into the thermostat housing.  If you don't have a strainer, I highly recommend one.  Indmar makes a nice strainer that also has a garden hose flush attachment on it that is very affordable.  Don't forget to check the thru-hull water inlet safety valve.  It should be all the way open, usually with the lever inline with the valve and pointing straight up.

I don't have a photo of the air bleed hose, but it looks like you found it.  It is black rubber, about 1/4 ID, 3/8 OD, and kind of looks like a small fuel hose.  It is connected near the front of the motor on the top of the port intake manifold and goes to the fitting on the port transom close to the port exhaust flapper and underwater light.  When you run the motor with the boat on the trailer using a motor flush, you should see a stream of water come out of the air bleed fitting by the port exhaust flapper within a couple of minutes or less.  If there is a clog, you can remove the rubber hose on the motor air bleed fitting, with the motor not running, and blow air down the hose to the transom fitting and also down the bleed line on the motor.  There is a metal tube that connects the port and starboard cylinder head air bleeds to the transom air bleed hose fitting.  I have, in some cases, had to remove the small bolts to remove the small bleed tube to clean it out with a thin piece of wire.  They have a small oring seal on each side which is often reusable.

Great post! Thanks for the info. I'll update this thread when we know more.

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MWJ68

Update: I got the boat back from the local dealer. They isolated the problem to the Heater Core. They said the heater output was just a trickle of water. There are no leaks. They said it was either a bad heater core or a pinched or obstructed water line. They bypassed the Heater and the boat tested fine. My plan is to have them replace the core and check the lines during the winterization. 

BTW, There is no Sea Strainer installed on the 2015. Does anyone have a recommendation on a good strainer to install?

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MWJ68

Update number 2: I've run the boat with the heater supply and return lines and core bypassed by simply putting a "U" line on the engine "to heater" lines. The boat runs great in this configuration, I just don't have a heater. It nearing the end of the season so I tore into stuff today to try and diagnose the issue.

Here's what I did:

Per CSlever's post above I verified the bleed air tube is putting out water.

Reconnected heater lines (removed bypass) = still overheats as before and no noticeable flow at the core.

Checked the lines to make sure they are connected as they should be and not reversed.

Checked the circulation pump output (mine has an electric pump that boosts "to heater" line from engine = Flow is excellent (but pump isn't self priming as it shouldn't need to be)

Now I moved the bypass "U" to the heater core itself. So system was connected normally but I installed the "U" bypassing at the heater core = overheated again. So I concluded the restriction is in the supply or return line to the heater core and not in the core itself.  But now it got confusing. It appears the overheat is intermittent, I tried it again but disconnected the return line at the engine and flow looked excellent. I reconnected the line and now it ran perfect. Nothing changed but this time it was working. I let it run for about 5 minutes and it worked great. I shut it down and waited a minute. Then without changing a thing I started it again. This time it overheated....What?

So, Ive discovered its an intermittent problem and the restriction or issue is somewhere in the supply line (including the circular pump) or the return line. Each time I ran it I felt the circ pump and it was running. But when the engine was overheating and I disconnected the return from the engine the return line flow was weak. The next time I ran it and it was not overheating I checked the return line again it was a good solid flow. So one time flow is good, the next its not good.

I'm perplexed and not sure where to go from here.

Any ideas from the pro's?

Edited by MWJ68

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justgary

The heater should not matter at all if your cooling system is working properly. 

Since you have poor flow in the block, it might make sense to change the circulation pump.  Just because you feel it moving doesn't mean the impeller is moving water. 

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MWJ68

Thx Justgary. Poor flow in the block? 

With the bypass installed at the block it works fine. Meaning: I have a "U" pipe installed at he block so the to heater and from heater ports have the "U" installed. So water from the block runs directly back into the block (bypassing the heater) and it works great. So I would say flow from the block is fine. Plus, Ive tested that: With the engine running I disconnected the "to heater" line and it shoots water with force out the line. 

I'm thinking the problem must be in the lines connected to or from the heater or the pump.

To your point though... I did replace the impeller while investigating this at the beginning of the season. Old pump looked great but I replaced it anyway. 

Am I thinking properly or am I missing something your thinking?  I know you guys have lots of experience with this stuff.

Thanks again!

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MWJ68
4 hours ago, MWJ68 said:

Checked the circulation pump output (mine has an electric pump that boosts "to heater" line from engine = Flow is excellent (but pump isn't self priming as it shouldn't need to be)

 

1 hour ago, justgary said:

it might make sense to change the circulation pump.  Just because you feel it moving doesn't mean the impeller is moving water. 

Just to clear things up. In my second update above I referred to the circulation pump. When I said this I was referring to the electric pump that boosts water flow from the block to the heater core. I removed the electric pump from the system and tested it in a bucket and it works well, i.e., throws water from the pump! So unless an air pocket is somehow keeping the electric pump from working it should be good. I would also suspect this wouldn't happen because the block "out to heater" has very good flow out as well and it feeds almost immediately into the electric pump which also tests well in a bucket separately. 

My freshwater impeller was changed as part of the initial investigation. It was replaced and had no damage.

However, Justgary......As you alluded...It may make sense to change the electric pump. As you said, just because the motor is running doesn't mean the impeller is consistently moving water. I'll remove the pump again and test under more scenarios.

Edited by MWJ68
clarification

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MWJ68

Interestingly I checked the V-Drive in and out lines and there is no screen or filter at either port on the V-drive.

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formulaben
54 minutes ago, MWJ68 said:

Just to clear things up. In my second update above I referred to the circulation pump. When I said this I was referring to the electric pump that boosts water flow from the block to the heater core.

Gary is referring to the engine recirculation pump, not your heater pump.  The recirculation (recirc) pump and impeller are 2 completely different pumps.

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MWJ68
3 minutes ago, formulaben said:

Gary is referring to the engine recirculation pump, not your heater pump.  The recirculation (recirc) pump and impeller are 2 completely different pumps.

Agreed formulaben!

Thanks for clarifying that better than I.

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formulaben

Just wanted to make sure we're on the same page!

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justgary
1 hour ago, formulaben said:

Gary is referring to the engine recirculation pump, not your heater pump.  The recirculation (recirc) pump and impeller are 2 completely different pumps.

Yes, what on your car you would call the "water pump."  You should not need to rely on a heater to have your engine cool properly. 

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