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2002 Malibu VLX - Overheating


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Greetings, just recently bought my Malibu used from an Owner in VA. Took the Malibu out a few times and it performed great. However, this past Sunday, I notice that the engine was over-heating. There was steam coming from the engine, and an alarm going off. I knew something was wrong, so I tried to hurry and dock the boat but when I throttle it, I was only able to go about 10 mph (figure this was normal to prevent the boat from further damage). The boat is now out of the water and stored.

Now we just experienced a lot of rain this weekend here in Charlotte. I normally keep the boat in a open storage facility. I notice that storm-water accumulated in the boat before I took it out this past Sunday.

Could it be that the storm-water may have damage the cooling system somehow? I'm thinking the engine was submerged, and a sensor or fuse must of got damaged. Anyone know if this is possible? If so, where should I look and what to replace?

Could the water intake be clogged from debris? I also heard that I might need to replace the impreller? Any advice will help. Thanks!

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take a look at the impeller (replace it if you don't know when it was last swapped out or if it's missing fins, etc.) then take a look the input side of the transmission cooler for accumulated debris.

if the engine was wet take a look at the oil (level and condition).  water in the oil will make the fluid look milky.

take a look at the transmission and vdrive oils for water intrusion, too.

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Yes, when the alarm went off, I stopped the boat. I let the engine cool down before I turned it on again. I was stuck out in the middle of the lake.

Thanks Tvano. I checked the oil and it looked good. I'll check the other fluids. I already ordered me an impeller. Arrives this weekend. I'll circle back if this fixes it. Thanks again.

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  • 2 weeks later...

Hey guys, I could use some more advice. What I've done so far:

  1. I check the hoses of any leaks. All hoses seem fine. No leaks. I could replace the hoses but not sure this is the problem.
  2. I checked the water intake (under the boat). Clear of debris.
  3. I took out the transmission cooler. There was little debris, not much. But I cleaned it out good.
  4. I took out the thermostat completely. I have one ordered, but I wanted to see what it will do without a thermostat. Water seems to be circulating and coming out the back of the boat, but it's not much. Engine still is running hot.

When I completely these items, I ran the boat (with the flusher) for about 15 minutes. The engine still gets hot. Water is coming out from the back of the boat, but I don't think it's enough. I still think that something is clogging the cooling system.

I was going to drain the oil, to see if there was any water intrusion. Might as well change the oil. I can look into the transmission & v-drive oil; but this should not cause the engine to overheat if it's in idle?

I'm going to check the hoses & connections one last time. I didn't see a sea strainer, don't think mine has one. What about the heat exchanger? 

I appreciate the replies. I'm really determined to get this fixed before handing it over to a mechanic, so please help me out.

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You mentioned a heat exchanger.  If you have one, then you have closed cooling (probably half closed since the manifolds are usually cooled with raw water).  The exchanger will look like a fairly large black cylinder with a radiator cap on the top.  If you don't have one, no big deal, you just don't have closed cooling.  If you do have one, you should have seen coolant (antifreeze) when you pulled the thermostat.  

Running on your garden hose may not provided enough water to effectively cool the engine, depending on your local water supply and delivery pipe size.  The only true test is running it like a real boat.

Anyway, I was just talking to a friend at the ski lake who had finally figured out is overheat problem with his MC.  Turns out that the raw water inlet hose was just loose enough to allow air to get sucked in.  He fixed his problem by removing all of the raw water hoses and making sure that each connection was solid before he moved to the next one.

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Thanks Gary. No I didn't see any antifreeze. I didn't think I had a heat exchanger. I've had another mechanic tell me that I might have 2 thermostats? Could someone tell me where the other thermostat could be if I had another one? The thermostat I pulled out was right above the water pump. I had someone else tell me that I have two impellers? I don't think so, but please help locate them if I do. The impeller I replaced was at the back of the boat (on the timing belt).

I'll check the hoses and connections again. If I can't find the problem, I'll replace them all.

Thanks for the reply. I'll let you know of the results.

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Hey guys, just want to follow up with ya.

So I think it was a bad connection with one of the hoses. I took off the hoses and flush them out. Looked cleaned. And then I re-attached them. I observed the temperature and it was working the way it's suppose to. Must have had an air leak near the connection. So weird how something this small can make a huge difference!

Anyways, thanks for your input. I hope this forum will help someone with similar issues.

  • Like 2
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2 hours ago, Carlos said:

Hey guys, just want to follow up with ya.

So I think it was a bad connection with one of the hoses. I took off the hoses and flush them out. Looked cleaned. And then I re-attached them. I observed the temperature and it was working the way it's suppose to. Must have had an air leak near the connection. So weird how something this small can make a huge difference!

Anyways, thanks for your input. I hope this forum will help someone with similar issues.

I'm glad to hear that you got it working.  Air is much less viscous and massive than water, so it will move into a tiny hole long before water will move through a big pipe.  As you found out, it doesn't take a very big air leak to cause a lot of problems.

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  • 3 years later...
On 6/24/2019 at 8:37 AM, Carlos said:

Hey guys, I could use some more advice. What I've done so far:

  1. I check the hoses of any leaks. All hoses seem fine. No leaks. I could replace the hoses but not sure this is the problem.
  2. I checked the water intake (under the boat). Clear of debris.
  3. I took out the transmission cooler. There was little debris, not much. But I cleaned it out good.
  4. I took out the thermostat completely. I have one ordered, but I wanted to see what it will do without a thermostat. Water seems to be circulating and coming out the back of the boat, but it's not much. Engine still is running hot.

When I completely these items, I ran the boat (with the flusher) for about 15 minutes. The engine still gets hot. Water is coming out from the back of the boat, but I don't think it's enough. I still think that something is clogging the cooling system.

I was going to drain the oil, to see if there was any water intrusion. Might as well change the oil. I can look into the transmission & v-drive oil; but this should not cause the engine to overheat if it's in idle?

I'm going to check the hoses & connections one last time. I didn't see a sea strainer, don't think mine has one. What about the heat exchanger? 

I appreciate the replies. I'm really determined to get this fixed before handing it over to a mechanic, so please help me out.

ive also got a 2002 malibu vlx. im trying to replace my thermostat but i cant tell which one it is because of the age of it. does anyone know which thermostat i need and what goes with it and where can i  buy one!? thank yall!!

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On 4/16/2023 at 11:05 PM, EricLeo said:

ive also got a 2002 malibu vlx. im trying to replace my thermostat but i cant tell which one it is because of the age of it. does anyone know which thermostat i need and what goes with it and where can i  buy one!? thank yall!!

I think your engine (monsoon) should be the same as my 2001 VLX and i just changed my thermostat and gaskets out last week. Here are your part numbers:

765007 Gasket

S551004 Gasket

985009 Thermostat 160*

I got all my parts for a Malibu dealership and was about $60

  • Like 2
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