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svnfightsvn

temp issue?

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svnfightsvn

So I was out this past weekend and within a half hour, we start smelling a melting plastic smell and see "smoke" (really steam) coming up from the engine compartment. All gauges looked ok (temp, oil pressure, etc). Turns out that one of the exhaust fittings that allow water to flow from the thermostat housing to the risers broke off. After creeping back to the dock (with the engine pumping hot water into the engine -creating steam- and into the bilge the entire time), I took a close look at the part (made of nylon) and all the threads were gone and it looks like it was melted.

We rigged up a temporary brass fitting so I could get the boat to the ramp and onto the trailer, but on the way there, the exact same thing happened to the fitting on the other exhaust riser. However this time, my temp gauge was reading 120....40 degress lower than normal. The engine felt hotter than 120... Water was being pumped out of the riser and the hose running to the fitting so I know my impeller was working properly.

So now my questions...how could this happen? Could it be coincidence? These pieces are supposed to withstand temps of like 250+. Could I have a bad thermostat ? I would think if the thermostat wasn't opening, the temp gauge would show a higher engine temp, not lower. I can replace these parts easy enough, but I'm worried that this is just a symptom of bigger problem...

F61022FE-C9A5-430B-BE52-E5A147388158_zps

This is the temporary replacement (a couple brass fittings):

AF79D9F2-C0CB-4414-8A4F-76E514C49F6D_zps

Also - I know I can buy replacement fittings here:

http://bakesonline.com/detail.aspx?ID=2514

When I screw the replacements on, should I add some plumbers putty or tape?

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MadMan

I would say there's no way it's was a coincidence. Something was stopping or slowing down water flow at some point and both fittings melted. Could have been something plugging the input, maybe something at the trans cooler, maybe the impeller not being able to pump enough at idle or high rpm.

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svnfightsvn

water was definitely flowing...like I said, I had hot water gushing out of the hose/fitting after it broke/melted off. If it was some type of water flow issue, why would the high temp not register?

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MadMan

water was definitely flowing...like I said, I had hot water gushing out of the hose/fitting after it broke/melted off. If it was some type of water flow issue, why would the high temp not register?

With a lack of water flow, it's possible the exhaust manifold overheated before the engine.

Also, when the 1st one came off, maybe all the water was pouring out that one, so the other manifold overheated then.

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Andrew63

These fittings let go from time to time.

Did you have any tell tale signs of water seeping from the fitting where it screws into the manifold?

If you did, usually some corrosion starts as a result & you get lumps of white corrosion growing inside between the nylon fitting and the alloy manifold. This pushes the nylon thread creating an irregular shape.

When I replaced my fittings I picked up a tap to clean out the corrosion before fitting the new nylon elbow.

I do find it odd that these fittings are not recommended to be brass or bronze yet the fitting up high between the two O2 sensors on a CAT manifold are brass from the factory.

I an inclined to think with the thread tape to seal the thread, a brass fitting like you repair would be a better option for a permanent fix.

What engine do you have?

If the 350 Monsoon with CATs, there was a cooling system upgrade to improve circulation.

http://www.themalibucrew.com/forums/index.php?/topic/47808-new-kit-for-manifold-overheating-on-hh-and-monsoon-cats/?hl=%2Bcooling+%2Bupgrade#entry842325

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minnmarker

KISS principle. Check the impeller. If it is bad then it would not be able to pump much water and the block gets first dibs on water. Engine temp could be normal while the manifolds cook.

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svnfightsvn

These fittings let go from time to time.

Did you have any tell tale signs of water seeping from the fitting where it screws into the manifold?

If you did, usually some corrosion starts as a result & you get lumps of white corrosion growing inside between the nylon fitting and the alloy manifold. This pushes the nylon thread creating an irregular shape.

When I replaced my fittings I picked up a tap to clean out the corrosion before fitting the new nylon elbow.

I do find it odd that these fittings are not recommended to be brass or bronze yet the fitting up high between the two O2 sensors on a CAT manifold are brass from the factory.

I an inclined to think with the thread tape to seal the thread, a brass fitting like you repair would be a better option for a permanent fix.

What engine do you have?

If the 350 Monsoon with CATs, there was a cooling system upgrade to improve circulation.

http://www.themalibucrew.com/forums/index.php?/topic/47808-new-kit-for-manifold-overheating-on-hh-and-monsoon-cats/?hl=%2Bcooling+%2Bupgrade#entry842325

I did not see any water leaking from these fittings prior to the issue. I did see a little bit of white corrosion on the threads of the manifold after I got the boat home. I did clean the threads out pretty good with that brass temporary fitting. According to Bakes, you shouldn't use brass as a replacement because "Replacing these fittings with brass with cause the area around the fitting to act like a zinc because of the metallurgic difference."

And yes - I do have the 350 Monsoon with ExtCATs. I see you did the upgrade? What did it cost?

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svnfightsvn

KISS principle. Check the impeller. If it is bad then it would not be able to pump much water and the block gets first dibs on water. Engine temp could be normal while the manifolds cook.

I will check the impeller but again - a ton of water was being pumped out the broken fitting

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grandude

Replacing the fittings with brass is definitely a good idea, and I definitely recommend the re plumb kit from Indmar. This is an easy install and will help regulate the temp on the engine (keeping the temp below 160 without the fluctuation) and keep the cats way cooler. Prior to installing the kit. The cats don't receive water flow from the thermostat housing until the thermostat opens by reaching about 150+. If the boat has been run hard prior to warming up, the cats can be VERY hot, (melting fittings) etc. not to mention the damage that can happen from dumping cool water on hot metal (cats). The kit supplies water flow to the manifolds from the first start of the engine helping to keep everything cool.

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MadMan

According to Bakes, you shouldn't use brass as a replacement because "Replacing these fittings with brass with cause the area around the fitting to act like a zinc because of the metallurgic difference."

Hard to imagine this is a problem since brass freeze plugs, thermostats are used in marine engines.

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Andrew63

I did not see any water leaking from these fittings prior to the issue. I did see a little bit of white corrosion on the threads of the manifold after I got the boat home. I did clean the threads out pretty good with that brass temporary fitting. According to Bakes, you shouldn't use brass as a replacement because "Replacing these fittings with brass with cause the area around the fitting to act like a zinc because of the metallurgic difference."

And yes - I do have the 350 Monsoon with ExtCATs. I see you did the upgrade? What did it cost?

Re PLumb kit is $120 USD from Bakes

https://www.bakesonline.com/detail.aspx?ID=3433

Hardest part for me to track down down under was those 2 tight elbows.

Apart from these, I used regular hose sourced locally, even though it is red, still designed for this application.

Took about half an hour to fit on the DD, a V drive may take longer due to access

I havn't changed to Brass fittings but thought if there are already brass fittings up where the CATs are why cold you not use them further back along the same allow cast manifold.

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svnfightsvn

Does the replumb kit have enough hose? From what I can tell, the rear thermostat housing hose is supposed to connect to the bottom front of be manifold. The diagram says 13" of hose. Since I have a v-drive, I'll need more than 13" of hose right?

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Jonsey

I had the same problem with my 2010 vlx, it happened when surfing withe the boat listed heavily. My understanding is that the boat needs to be level to get equal amount of coolant to the CAT/ manifolds. I replaced with the original plastic fittings and did the upgrade as mentioned by Andrew63. All the new 5.7's are plumbed this way. My CAT/ manifolds run way cooler and the engine does as well. A definite must do upgrade in my opinion.

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TexasTexas95

Wish I saw all these threads before melting my cats yesterday........

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