'08 X2 MCX Saltwater series manifold overheat

[NoSubstitute]

Looking for some ideas for a possible fix. I have an '08 X2 with the MCX and the closed cooling system. Last season, I had a problem with the exhaust manifold elbow (plastic composite) melting. It was near the end of the season, so I replaced it with an iron elbow to get me through the weekend and took it to the local MC dealer to get it fixed. They determined that there was air in the system, and took off the heat exchanger and raised it above the manifold to get the air out of it. They did the winterization at the same time, I didn't get a chance to verify the fix. I got it out this season and the first day it lost about an inch of fluid from the reserve tank in one day. I topped it off to the cold line the next morning, and by the end of the day, approx 3 hours motor time, it was down again by about the same amount. Topped it off again and added a little more and took it out again. This time, after about an hour, it started blowing steam all over the inside of the engine compartment (same as last year) as the elbow melted again - so not fixed. The temperature gauge read around 165 and there were no alarms.

I'm in Michigan, so the dealer doesn't work on the CC systems very often, and I'm looking for some advice to help resolve the problem. Any suggestions?

[NoSubstitute]

Would the kit from Bakes that helps the cats/exhaust run cooler on a fresh water system work for a closed cooling system?

[CruisinGA]

Sounds like you may have a leak in the system, #1 suspect is the exhaust #2 heat exchanger. I would pressure test and isolate components until you narrow down the problem.

[NoSubstitute]

Thanks for the suggestion. I called the tech today and he said they filled it up with anti-freeze and lake tested it and it didn't over heat. I told him the gauge never shows that it over heats, it's just that manifold that gets hot. I asked if they had pressure tested it and he said no. In Michigan, the Mastercraft dealer just doesn't see saltwater series boats. Can anyone suggest a reputable Mastercraft tech that works with closed cooling systems on a regular basis?

[trunderw]

I'll claim ignorance on the closed cooling portion but I know the EXT Cat I have on my 08 MCX had a recall due to hot spots. Several times it melted a hole in the exhaust hose, fortunately the recall did fix it. Perhaps it manifests differently in the closed loop models?

[NoSubstitute]

Talked to the MC dealer and they topped off the antifreeze and burped it and said it was ready to go. Picked up the boat last night and drove it from the launch to the dock which is about two miles. By the time I got to the dock, the new elbow already had melted a hole in the side. The temp gauge never got above 165.

I took the exhaust manifold off thinking that it must be plugged. I ran water through it from the hose, and it appeared to have good flow with no restrictions. I was really hoping that it would have been the problem so now I'm at a loss. Does anyone have a flow pattern for the coolant? I put a clear hose on a new elbow and started the boat thinking it should have coolant flowing through it immediately but nothing appeared. Should coolant flow through the exhaust immediately or does it have to get to operating temp before it circulates?

[osmonet]

Take a look at this post on burping procedure.

https://www.mastercraft.com/teamtalk/showthread.php?t=28195

[forcel0]

Once mine overheated enough the melt the plastic all the coolant hose had stretched and had very small leaks. Borrow a coolant pressure tester from autozone or the like. Pressurize and wait a couple hours to see if it's holding pressure if not once it started to pressurize and get hot the coolant boils off in a runaway senerio. My vote is a leak somewhere in the coolant side of the system. The other culprits are raw water side impeller or blockage at the trans cooler screen.

[NoSubstitute]

Osmonet, thanks for the tip on the burping procedure.

Sunday, I got the engine up to operating temperature, and once the gauge hit 160, the coolant began to flow through the exhaust manifold (still have the clear hose on). Let it run for a few minutes, and everything seemed good. It was too rough to take the boat out, so I'm not sure what the status is now.

I called the MC dealer Monday morning to explain what happened after I launched it, and they agreed to pick it up for no charge and take a look at it again. I talked with the tech and explained in detail what has been happening, and he said that what I described was different than what the issue was that was explained to him, and now has a better understanding of what the problem is. We'll see if he comes up with anything.

The thing that really baffles me is the engine temp gauge shows 160-165, so it's not overheating. If the impeller or water pump was bad, the engine would be overheating as well. I've melted 4 elbows on the port side, but there haven't been any issues on the starboard exhaust side.

[SkiDog]

I'm having to replace mine on the port side too. My original elbow just basically wore out I think, and broke off in the manifold. My dealer is 6 hours away so I had to Riggernig it to get me by for the weekend. I found parts at lowes, but quickly found out they were not high temp rated. Went thru about 3 of those setups. and the temp never went over 160. Finally I got smart and used a brass fitting and its held up after a weeks worth of boating. My new elbows came from the dealer on Monday, but I haven't installed them yet. I've noticed too, that I'm using more coolant than I should be. But I cant figure out where its going. None in the bilge.

[MC197indy]

NoSubstitute ,

Based on your engine not overheating and running at normal operating temp, To me it sounds like you are having the issue with the Water flow to the cats. The replump kit would be the fix, Im just not sure on the closed cooling, how your water flow is vs the non closed cooling.

There has to be a replumb configuration for it.

Your cat is getting so hot it is melting the gains elbow.

@ that location, Indmar went to aluminum elbows on the newer engines, ( on my 2011 197) but still use the plastic style on the front of the cats.

https://www.mastercraft.com/teamtalk/showthread.php?t=67725&highlight=replumb

[NoSubstitute]

Based on your engine not overheating and running at normal operating temp, To me it sounds like you are having the issue with the Water flow to the cats. The replump kit would be the fix, Im just not sure on the closed cooling, how your water flow is vs the non closed cooling.

There has to be a replumb configuration for it.

Your cat is getting so hot it is melting the gains elbow.

@ that location, Indmar went to aluminum elbows on the newer engines, ( on my 2011 197) but still use the plastic style on the front of the cats.

MC197indy -
Thanks for the response. I've seen that kit and asked the MC tech about it. He doesn't think Indmar made a kit for the closed cooling systems and I've searched and can't find anything either. I was thinking that there might be a problem with the CAT as well, but the engine seems to run fine - if the CAT was plugged, I would think it would stumble or cough occasionally. I visually inspected it when I had the manifold off, and it looked pretty clean. I'm planning to use a laser thermometer to check the temperatures of both manifolds this weekend and see if there are any hot spots.

The aluminum elbow would be great to fix the burning through of the composite elbow. Any idea on a part number?

[CantRepeat]

MC197indy -
Thanks for the response. I've seen that kit and asked the MC tech about it. He doesn't think Indmar made a kit for the closed cooling systems and I've searched and can't find anything either. I was thinking that there might be a problem with the CAT as well, but the engine seems to run fine - if the CAT was plugged, I would think it would stumble or cough occasionally. I visually inspected it when I had the manifold off, and it looked pretty clean. I'm planning to use a laser thermometer to check the temperatures of both manifolds this weekend and see if there are any hot spots.

The aluminum elbow would be great to fix the burning through of the composite elbow. Any idea on a part number?

lol I was typing this as I read your post.

Not a fix but a suggestion.

Get one of those IR temp guns and check how much difference there is between the side that melts and the side that does not.

I think switching to the aluminum elbow is just a band aid for a bigger issue. I would really want to know what is causing this issue.

I wish I could help more but I've never owned a closed cooling system MC.

[forcel0]

Mine never showed overheating at the gauge either until enough coolant cooked off for it to actually over heat. The path of coolant on mine and probably yours is heat exchanger -> engine water pump -> engine (block, heads, etc.) -> coolant temperature sender -> manifolds -> heat exchanger. On mine the heat exchanger was doing the job of bringing the coolant back to temp, keeping the engine cool past the sender and then going to the manifold and overheating there. Once you have air in the system from a small leak somewhere it collects in the manifold and allows them to get over 220 degrees boiling the coolant as it comes through. this eventually forces it to boil back and out through the coolant reservoir. If the dealer is going to handle it I'm sure they'll figure it out but if you're going to keep looking at it I would definitely pressure test the system to make sure you don't have any leaks as a starting point. Point and shoot temp gauge is also helpful because it allows you to see the manifold temp. My gauge would show a rock steady 160 degrees which the engine was the issue was the manifold was creeping well above 220. I know an improved design is to tap hose barbs into the top of the manifold that tees into the crossover and goes back to the reservoir, this allows the system to self burp.

[NoSubstitute]

I know an improved design is to tap hose barbs into the top of the manifold that tees into the crossover and goes back to the reservoir, this allows the system to self burp.

Thanks for the suggestions and the image file. In looking at the coolant lines, my system doesn't have a connection between the two manifolds and the lines that flow from the top of the manifolds flow directly back to the Heat Exchanger. I like the idea of a self-burping setup. If I were to T them together, (it looks like you are using a cross-flow in the drawing), where does the line terminate? Do you plug it after it burps?