LS3 Overheat warning, what's going on?

[MWJ68]

1 hour ago, justgary said:

You should not need to rely on a heater to have your engine cool properly

Agreed. However, if there is a restriction in a cooling line that feeds the heater, and thus the return ,it appears to cause the overheat. When the heater is removed from the equation the system works fine.

[csleaver]

The heater circuit is an integral part of the cooling system on the L98 and LS3.  If it is blocked off or if there is no water flow from the "to heater" to the "from heater" fittings the motor can overheat.  I'm not sure why there would be a flow issue if the pump is working, but a restriction in the heater hoses or heater core, or an issue with the pump wiring, connectors or relay may cause an intermittent flow problem with the pump.  I have seen melted electrical connections cause the pump to not always work properly.  The long run of hose to the heater core requires a good working pump to keep the water flowing through the system.  It looks like you have the system figured out, and testing everything right.  Sorry I couldn't be more help.

[MWJ68]

20 minutes ago, csleaver said:

The heater circuit is an integral part of the cooling system on the L98 and LS3.  If it is blocked off or if there is no water flow from the "to heater" to the "from heater" fittings the motor can overheat.  I'm not sure why there would be a flow issue if the pump is working, but a restriction in the heater hoses or heater core, or an issue with the pump wiring, connectors or relay may cause an intermittent flow problem with the pump.  I have seen melted electrical connections cause the pump to not always work properly.  The long run of hose to the heater core requires a good working pump to keep the water flowing through the system.  It looks like you have the system figured out, and testing everything right.  Sorry I couldn't be more help.

Ha! Couldn't be farther from the truth!  You are a constant source of excellent knowledge! The fact that you agree with my assessment so far gives me what I need to continue. I plan on doing a series of tests on the heater circulation pump both in and out of the boat circuit. If that checks out I'll start on the supply and return lines to see if theres some type of intermittent blockage or restriction. 

Thanks again!

[formulaben]

Have you read this post and thread?  It also mentions Indmar Service Bulletin SB 2012-3IN which I would think your model year already has incorporated into it, but worth checking to make sure.

 

[MWJ68]

15 hours ago, csleaver said:

The heater circuit is an integral part of the cooling system on the L98 and LS3.  If it is blocked off or if there is no water flow from the "to heater" to the "from heater" fittings the motor can overheat.  I'm not sure why there would be a flow issue if the pump is working, but a restriction in the heater hoses or heater core, or an issue with the pump wiring, connectors or relay may cause an intermittent flow problem with the pump.  I have seen melted electrical connections cause the pump to not always work properly.  The long run of hose to the heater core requires a good working pump to keep the water flowing through the system.  It looks like you have the system figured out, and testing everything right.  Sorry I couldn't be more help.

This now gets more confusing but I'm making progress isolating the issue. I hope...

Today I hooked the boat up again as designed with the bypass removed and the entire heater (lines and pump)  included in the circuit. = Boat overheats (shut it down at 190)

Then I re-installed the bypass (3 inches long and 3/4 diameter "U" line) at the block with the heater (lines and pump) removed from the circuit. = Boat returns and stays at 158.

Before I continue, I'll explain the heater circuit from and returning to the block. I have a 5/8 fitting and line out from the block to the heater circulation pump, then the 5/8" line continues to the heater core, then a 3/4" line returns from the core back to the block into the 3/4" fitting on the block. (note the circuit contains a 5/8" line to the heater)

Then I removed the "U" bypass at one end and added a 5/8 diameter line 3 foot long line and attached to the block. (So I didn't change a thing other than adding 3 feet to the bypass) granted the line diameter is a little smaller but not much) = boat overheats. This really surprised me. Granted the line is a smaller diameter but thats the size of the line to the heater in the circuit. 

This latest finding suggests to me the block itself has a flow problem. I would think the block should have enough pressure to push water through 3 feet of line without the heater circulation pump in the circuit. 

Any thought on my finding?

Lastly, if I remove the lines from both fittings at the block and let the engine run ( water pouring out of the "to heater" side and dribbling from the "from heater" the boat temp actually drops quickly ( down to 120's) This didn't make sense to me either. If a flow restriction restricting water returning to the block, (lack of water into the "from heater" fitting) is causing the overheat, then if I remove the bypass altogether and no water is returning to that fitting I would think the temp would also go up, but it goes down quickly. This makes no sense.

Next I will run the same bypass with the extra 3 feet but I will install the circulation pump in the circuit and see what happens.

 

[MWJ68]

18 minutes ago, MWJ68 said:

Next I will run the same bypass with the extra 3 feet but I will install the circulation pump in the circuit and see what happens.

With the bypass and extra 3 feet Plus the heater circulation pump installed = the system runs normal 158 degrees

I suppose its possible the flow issue with the extra 3 feet is enough that the circuit pump is required.

Another off the wall question: As was stated in the first post of this thread. This boat was winterized from a non Malibu dealer and actually had a few lines not reinstalled after the process. I've looked at the boat and all lines seem to be connected to the proper ports. In fact most are obvious and couldn't be reconnected improperly due to fitting and line size. The only two I see that could have been swapped are the thru hull line and a V-Drive line. Both are right next to each other and use the same size and type hose. But I suspect if they were actually swapped the cooling system would try and run in reverse flow and would immediately overheat. Thoughts here?

The way its connected is: the thru hull line is a soft hose that runs around the starboard side of the motor and connects to the impeller housing. The V-Drive line runs half way around the starboard side of the engine and then converts into a hard pipe that runs to the impeller housing. So if they were reversed the impeller would be pulling from the V-drive and pushing to the thru hull.

Edited October 7, 2018 by MWJ68

[csleaver]

I think GM does not recommend more than about 2 or 3 feet of total hose run on the heater circuit without using a circulation pump on the L96.  I haven't tried running a motor with the heater hoses removed, so I don't have an explanation for the results you got.  I have had problems with heater water flow when the heater core or hoses are higher than the motor. 

I saw a 5.7 GM in an Axis with a heater mounted at the top of the observer storage area that would not blow hot air until a circulation pump was installed, but the 5.7 motors don't overheat from lack heater coolant flow.

I worked on a 2013 Malibu with the monsoon 409 L96 a couple years ago that had an intermittent overheating issue, and after several tests, I had to remove the cylinder heads, clean out the passages then replace the head gaskets and bolts to get the coolant temperature under control.  I have also found that coolant temperature can vary when running the boat on a flush as opposed to running it in the water.  I've had boats that overheat on the motor flush, but do not overheat on the water.  And sometimes a bad sea pump seal or loose hose can prevent the cooling system from priming on the water, but it will run fine on the hose.  But, I think I've gotten a little of topic.

I would recommend running new heater hoses, as low as possible, with smooth bends to prevent kinking; make sure your heater core is mounted as low as possible; check the harness connections, relay, fuse holder, ground and power connections for the circulation pump.  If it overheats, bypass the heater core by connecting the two hoses together, to take it out of the equation for your next test.  I know you have done a lot of testing, so if you have already checked this stuff, please disregard.

[tvano]

off the wall q, not sure if it will help:

is the heater a factory install running a heatercraft Y on the suck side?

that heatercraft Y limits the amount of hot water returning to the suck side of the pump.

without that limiting factor i'd wonder if too much hot water returning to the cold side of the coolant is making the block too warm.

[MWJ68]

1 hour ago, tvano said:

is the heater a factory install running a heatercraft Y on the suck side?

that heatercraft Y limits the amount of hot water returning to the suck side of the pump.

I'm not familiar with a "Y" in the heater system.

1 hour ago, tvano said:

without that limiting factor i'd wonder if too much hot water returning to the cold side of the coolant is making the block too warm.

Yes, it's a factory install but there is no "y" in the system that I'm aware of. It is all direct line. Line out to the heater circulation pump then direct to heater(under dash) then direct out from heater to return or "suck" port on the block. In my system (open cooling) I don't think the heater is designed to cool the water. Its sole purpose is to allow the blower to warm air for comfort. Additionally, by bypassing the heating system we are feeding the hot water directly back into the block at full hot temp and the result is the engine temp is normal. 

[MWJ68]

 

2 hours ago, csleaver said:

I would recommend running new heater hoses, as low as possible, with smooth bends to prevent kinking; make sure your heater core is mounted as low as possible; check the harness connections, relay, fuse holder, ground and power connections for the circulation pump.  If it overheats, bypass the heater core by connecting the two hoses together, to take it out of the equation for your next test.  I know you have done a lot of testing, so if you have already checked this stuff, please disregard.

cslever, I tracked all the supply lines and they are free moving with no kinks or sharp bends. Pretty straight shot. I did notice something interesting. Both the engine and heater core both have a 5/8th and a 3/4inch fittings. I would suspect the line running between the 3/4 inch fittings would be a 3/4 inch line. Not so... both the supply and return lines are 5/8 inch lines. The return line (3/4 fittings) has an adapter taking the 3/4 to 5/8 line. This is a factory install and as far as I know its never been touched. But It ran fine for 2 seasons as is..

I think If I do need to change the lines I'm going to run 3/4 on both lines to provide extra room for optimum flow. In addition I'll move the heater down as close to the floor as possible. Its located under the drivers dash behind the sub. Right now Its mounted as high as they could put it.

I checked all electrical lines and no signs of heat damage. I ran the engine multiple times in bypass using the 3 foot line with the circulation pump and it performed well every time. No sign of intermittent pump operation. 

Edited October 7, 2018 by MWJ68

[Rednucleus]

So when you bypass the heater core it works fine. You probably already did this, but have you blown thru the hose going to the core to see how easily air passes?

[MWJ68]

1 hour ago, Rednucleus said:

So when you bypass the heater core it works fine. You probably already did this, but have you blown thru the hose going to the core to see how easily air passes?

Yup, and ran water through with the circulation pump. Flows free. I suspect the circuit pump just doesn't have enough power to push the water all the way to the core and then back to the motor. I'll try larger lines, lowering the heater core closer to engine level and then possibly increase pump size.

I just don't understand why this problem didn't begin until season 3. 

Edited October 8, 2018 by MWJ68

[justgary]

So I was wrong about not needing a heater or bypass on this engine, but my money is still on a bad circulation pump. 

I would expect the suction side to actually suck, not dribble water out. 

[dlb]

3 hours ago, MWJ68 said:

I'm not familiar with a "Y" in the heater system.

Yes, it's a factory install but there is no "y" in the system that I'm aware of. It is all direct line. Line out to the heater circulation pump then direct to heater(under dash) then direct out from heater to return or "suck" port on the block. In my system (open cooling) I don't think the heater is designed to cool the water. Its sole purpose is to allow the blower to warm air for comfort. Additionally, by bypassing the heating system we are feeding the hot water directly back into the block at full hot temp and the result is the engine temp is normal. 

The “Y” https://heatercraft.com/collections/marine-heater-parts/products/low-idle-wyes

this pulls water through the system.  Is is spliced into the raw water intake, prior to the impeller.  Makes all the difference for low speed or idle heat.

[MWJ68]

32 minutes ago, dlb said:

The “Y” https://heatercraft.com/collections/marine-heater-parts/products/low-idle-wyes

this pulls water through the system.  Is is spliced into the raw water intake, prior to the impeller.  Makes all the difference for low speed or idle heat.

Interesting, I'm not sure how this works on my system.. I see I would remove the return line from the block and attach it to the Y. This would increase the "suck" in the return from the heater and increase flow. However< then what do I do with the return line port on the block?

[MWJ68]

42 minutes ago, justgary said:

So I was wrong about not needing a heater or bypass on this engine, but my money is still on a bad circulation pump. 

I would expect the suction side to actually suck, not dribble water out. 

The problem was discovered in the spring. The fresh water impeller was replaced with no difference. 

I don't think the return port 'sucks" at all. The heater part of the circuit is all pressure driven. There is no 'suck". The only part of the cooling system that 'sucks" water is the intake to the fresh water impeller. Everything in the engine after the impeller is forced water under pressure. So the return port on the block is simply a path for water from the heater to return to the system but this is far downstream from  the fresh water impeller. There is no "suck' there.  If I had installed (which I haven't ) the Y recommended above, that would in fact create "suck". Make sense too you? Please correct me if I'm mistaken.

When I stated the return port dribbled water I was referring to immediately after I disconnected the hose. The water in the block is under pressure so even the return path has water pressure immediately after disconnecting the hose. If I left it running for an extended period of time I'm confident the water would have stopped coming out of the return port. 

[justgary]

The circulation pump I speak of is the one you would call "the water pump" on a car engine.  Unless I'm mistaken, your heater outlet should return directly to the input of the circulating pump.

[MWJ68]

7 hours ago, justgary said:

The circulation pump I speak of is the one you would call "the water pump" on a car engine.  Unless I'm mistaken, your heater outlet should return directly to the input of the circulating pump.

It does not. On my system the heater return line goes back into the block right next to the out Line to the heater. Its not even close to "the water pump" or what I call the fresh water impeller. 

[JasonK]

The circulation pump does not have an impeller that can be replaced. A car and a boat has a circulation pump.

The "Raw" water pump, or also called the "seawater" pump, has a rubber impeller that you can replace. A car doesn't have a "raw" water pump.

Sounds like he also has a "heater circulation pump". An electric pump. Don't mix it up with the regular "circulation" pump.

Let's not mix these up for him.

Edited October 8, 2018 by JasonK

[justgary]

A picture would be helpful. 

True or false:  The engine in question has a mechanical water pump bolted on it, just like a car engine would? 

[MWJ68]

2 hours ago, justgary said:

True or false:  The engine in question has a mechanical water pump bolted on it, just like a car

True, It does and it has a removable rubber impeller. The impeller was changed as part of the problem diagnosis and made no improvement. The heater is not directly connected to this pump, supply or return.

I have a second electric (heater circulation pump) that is in line between the output from the block and the heater core.

Sorry, No pic today. It would be helpful, but the boat is in storage away from my home.

 

[justgary]

9 minutes ago, MWJ68 said:

True, It does and it has a removable rubber impeller. The impeller was changed as part of the problem diagnosis and made no improvement. The heater is not directly connected to this pump, supply or return.

I have a second electric (heater circulation pump) that is in line between the output from the block and the heater core.

Sorry, No pic today. It would be helpful, but the boat is in storage away from my home.

 

That is your raw water pump.  Not that one.  A car engine does not have that pump.  You should have another pump on your engine, exactly like a car would have, exactly in the same place....

[formulaben]

Raw water pump (impeller):

Recirculation pump (normal car engine water pump):

Heater pump:

[MWJ68]

Formulaben,

You nailed it! 

I have pumps 1 and 3. 

However, My Raw Water Pump doesn't have the 3rd smaller port shown in the picture. Just the In and Out! (The smaller port in the pic is threaded and might be a mounting point.

Thanks for posting the pics.

[justgary]

https://www.google.com/search?q=indmar+l96+water+pump&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwinoJLQlfjdAhUQOawKHU2VAGkQ_AUIEigC&biw=360&bih=560#imgrc=b75uhlII7Ue_dM

I really don't mean to argue, but this L96 image clearly shows pump #2.  I don't see how your engine can't have one.