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Bryan Schumacher

Switching From Closed Cooling To Fresh Water

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Bryan Schumacher

Gang,

2007 Moonsoon 340 VLX

ext/cat exhaust manifolds

I've had nothing but issues with my closed cooling system and antifreeze coming out of the overflow. Tried different things over the years, but still have issues. I never boat in salt water, so other than the winterizing, it's more of a pain that its worth. I would like to switch back to fresh water cooling, but have a few questions on how the hoses should be run.

I purchased the thermostat upper and lower housing from skidim. There are 4 ports: block circulation pump (large port), water inlet from transmission cooler (1.25" port), and two more ports that go to the exhaust manifolds (1" ports I think). With the closed cooling, the exhaust manifold hoses went to the exhaust manifolds and came back to the antifreeze tank so there were 2 hoses going to each manifold. My question is:

Do I just plug the lower hole on the exhaust manifold by the big exhaust elbow and only connect to the top port on each exhaust manifold? Also, the holes in the front of the exhaust manifolds were plugged from the factory (usually there is a drain hose connecting both manifolds together there). Should I put that drain hose back in? Do the manifolds need to be connected together, or is that just an easy way to drain the system?

Thanks for any and all help!!!

Bryan

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Bryan Schumacher

I think I found what I need to do. I have the wrong thermostat housing. I finally found a pic of what it should look like, and it has 6 ports, not 4. Hopefully I can get the correct one ordered.

381936.jpg

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99response

Regarding the second question the manifolds do not need to be put together with the drain hose, it is just a nice way to drain them down at the end of the year. Also saves some mess because the disconnect is down in the bilge.

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FIC

I personally wouldnt switch from closed cooling , the engines last longer and run better, on a raw water system the engine expansion from the front of the block to the rear is very different and tends to fatigue head gaskets and crack heads, Ive always run closed cooling and put over 1500hrs or more and never had my engines apart only normal oil changes and service. Just my 2 cents worth.

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Nitrousbird

I would also stick with the closed cooling. Perhaps have a pro look over the motor and figure out what is causing your issues.

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Bryan Schumacher

I would also stick with the closed cooling. Perhaps have a pro look over the motor and figure out what is causing your issues.

I would love to stick with closed cooling, however ever since the boat was new, there has been an issue with coolant overfilling the overflow tank. I bought the boat used, and knew of the issue, so I'm not blaming anyone. However, I always have to keep filling the tank, and at some times, it gets low enough to set off the overheat alarm. The original dealer tried all sorts of things including a new radiator cap the first year, etc. But no matter what they tried, after awhile, the coolant would be low again. I even installed an overflow tank about twice as big as the stock one, and it helped a little with how long I could go before adding coolant, but didn't solve the problem. To be honest, I'd rather have a fresh water cooled engine without issues than a closed cooling engine that I have to check each time I run it.

Any suggestions?

P.S. Closest Malibu dealer is 400miles away... so taking it to the dealer isn't an option. :)

Edited by Bryan Schumacher

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Manga Boats

Are you able to either send me a picture of your heat exchanger and pipes or post it on here please.

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FIC

Is the overflow system a return system, which means the hose from the heat exchanger will go to the bottom of the overflow instead of the top, this allows the coolant to return to the exchanger as its cooling down so it never gets low.

Also have you performed a preassure check on the exchanger to make sure there are no leaks?

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Bryan Schumacher
Are you able to either send me a picture of your heat exchanger and pipes or post it on here please.

I will post pics tonight. Everything is removed and inspected. I have not done a pressure test yet, but if I can get this problem solved and keep the closed cooling, I certainly will.

Is the overflow system a return system, which means the hose from the heat exchanger will go to the bottom of the overflow instead of the top, this allows the coolant to return to the exchanger as its cooling down so it never gets low.

Yes, it does have the hose going to the bottom of the overflow tank to suck coolant in once things heat up. That's the problem. It will suck in the coolant fine but when the engine heats up - the overflow tank will then totally fill up and coolant will come out the top port of the overflow tank no matter how big the tank is. (I upgraded from a little over a quart tank to a gallon tank to make sure it had enough room for overflow and still have the same problem.) There are no other noticeable leaks in the system. At one point I had a problem with one of the plastic hose barbs on the exhaust manifold leaking, but replaced that with brass parts to fix the issue. Was planning on doing that to all of them.

I'm almost sure the problem lies in the heat exchangers getting air trapped inside them or something along those lines. The heat exchanger lies below the level of the exhaust manifold, so I could see how things could drain when the system gets low on coolant and then allow air to fill the exhaust manifolds. Now if the heat exchanger does have a small leak, it would sure explain things since some coolant would be going out the raw water exit.

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Manga Boats

Sorry need pictures of the pipes attached to the engine not dis-assembled otherwise send me the engine serial number

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Bryan Schumacher

Ok, I temporarily put everything back the way it was for pics. None of the hoses are clamped, but they are in their spots. Here's the pics.

As for the engine serial number: I'm not exactly sure which one is the actual block serial number. The sticker by the starter reveals:

13144

But that also says something about the EXT/CAT - so not sure if that's the engine serial number or EXT/CAT. Other numbers down there were: 417717, and 107MN M607190003.

Hull number is MB2K3398H607

So the way the hoses are hooked up, raw water goes from the lake through the transmission to the impeller then pumps to the transmission oil cooler and finally to the heat exchanger. That water then goes to each metal elbow of the exhaust manifold via a "y" fitting right after the heat exchanger and finally back out to the lake.

The coolant side of things has the big hose from the bottom of the heat exchanger going to the engine water pump. That then splits at the thermostat housing and goes to the bottom port of the exhaust manifold. It exits the top port of the Exhaust manifold and goes back to the 2 inlet ports of the heat exchanger.

It all seems very simple in theory. Wish it worked that way.

engine.jpg

closed-cooling-hoses.jpg

Edited by Bryan Schumacher

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FIC

Have you owned the boat since new , how many hrs, and if you owned since new did this problem exsist from day one?

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Bryan Schumacher

Have you owned the boat since new , how many hrs, and if you owned since new did this problem exsist from day one?

I have not owned it since new, but I knew the previous owner. And yes, there has been issues since day one. The original boat dealer would try things, but after awhile, the problem would resurface. Hence the reason I'm saying it would probably just be easier to remove the closed cooling and go back to raw water. There are somewhere around 700 hours on the boat.

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FIC

Does the raw water intake have a sea strainer, if not has the trans cooler and heat exchanger been checked for debree?

The only reason Im asking is because I have 1250 hrs on a heat exchanger motor and these are the only areas I have seen cause an issue.

Did the dealer change the the thermistat at any time.

It is not normal for the coolant to overflow the container, if it is doing this just changing to raw water cooling is only going to cover for what ever the problem is, like bad flow, thermistat, cracked exhaust manifolds inside, etc.

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Manga Boats

Indmar supply a kit that resolves this issue, the Indmar part number is 495144 - F/W Purge Kit and can be ordered through a local Indmar dealer -check out there website as it could be a Malibu, MasterCraft, Supra or Moomba dealer. BTW your Indmar serial number (sticker by the starter) you supplied is missing a digit and this number should be around the ECU as well or a big white sticker on the oilpan. The issue is that you cannot get all the air out of the coolant lines so when it heats up it expands and blows the water out of the exchanger/radiator cap and so that is why the overflow bottle overflows. The kit changes the way the water flows through the manifolds, increases the flow, provides extra bleed points and relocates the heat exchanger.

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Bryan Schumacher

Manga Boats,

THANKS for your help!!! It is greatly appreciated. I did find the part and it is on order. Hopefully that will solve my issues!!! Unfortunately it wasn't cheap, but beats being stranded somewhere with an overheated engine this summer.

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Chia

Indmar supply a kit that resolves this issue, the Indmar part number is 495144 - F/W Purge Kit and can be ordered through a local Indmar dealer -check out there website as it could be a Malibu, MasterCraft, Supra or Moomba dealer. BTW your Indmar serial number (sticker by the starter) you supplied is missing a digit and this number should be around the ECU as well or a big white sticker on the oilpan. The issue is that you cannot get all the air out of the coolant lines so when it heats up it expands and blows the water out of the exchanger/radiator cap and so that is why the overflow bottle overflows. The kit changes the way the water flows through the manifolds, increases the flow, provides extra bleed points and relocates the heat exchanger.

nice going. That is a top 10 helpful post.

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