High Temps - Closed Cooling System Ateriosclerosis...

BAYOU_PILOT

New Member
Oct 9, 2017
28
Miami, Fl
Boat Info
2004 Sundancer 340
Engines
8.1S Mercruisers...
V-Drives...
Hi Everyone,

I've experienced unusual high temperatures over the normal lower rpm regimes for this engines (it is between idle and 2000 rpm) making a lot of trips trying to figure out what could happened...

In the meantime, I've made a complete service of 500 hs> coolant levels were normal, no leaks, changed impeller, Oil, filters, sparks, fuel water separator, etc.

When the engine reaches 3000 rpm +, it starts slowly increasing temp till alarm rings...

Once opened to check the thermostat and so, we found this...

Never Use a wrong coolant...
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Now we're in cleaning process, we'll keep in touch...

L.
 
probably was a mix, with a wrong coolant (I can guess brand due to its colour...:()

and maybe no winterizing since the boat born and actually lives in south Florida.

I'm still waiting the cleaning process to reassemble and try it..
 
Bayou my daughters ex mixed coolent in her car. It took several flushes to get the jelly out. They even tore the engine down and washed it out. It will take more than once to clean it all out and it will need to be done often. We now do hers every oil change.

Good luck with the motor
 
Hi Brian, Yes, in fact it seems to be the same problem.

After trials on tuesday evening, everything is normal. Crossover was cleaned, Heat Exchanger too. And of course the hoses as well.

I drain the engine to make a fresh water flush, but in this case it was not necessary. Engine was clean and the jelly concentration was on those two parts.

We noted that pink "jelly" sticked on the crossover started to eat its aluminium... probably due to wrong coolant incompatibility used with this material.

Many Thanks for the support !

L.-
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Last edited:
how do you flush the coolant? what is the best way? i added some west marine coolant which is NOT dexcool - (only on gallon) and then i disconnected the hose to the pump and got a green/pink mix out. Then i got dexcool and added some. engine ok at high RPMs but not lower RPMs - on the lower RPMs i get a slightly higher temp.
 

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