merc 5.7 over heating help

[bolo78910]

merc 5.7 close cooling system, was running great took it out to fishing ground today. runs great for about 30 min then the gauge start climbing from 180 to 190 then it about to hit 200 i shut it down. we sit on the anchor for about an hour to let it cool down, re start and the guage start climbing again with the antifreeze over Flo tank just spilling boiling over. at this time we call the towboat us , when we got back to the dock we install a new raw water pump start the engine, the risers felt cold and nice, the manifold felt hot, foget to mention we took the thermostat out on the water , so with this new raw water pump install we are running without a thermostat . ok so at idle the temp start rising again i put in nutral and hold the rpm at 2500 the guage fel like a stone to 120 as i stated the thermostat is not in right now, i will install a new one tomorrow .


ok guys raw water pump is new, could it be my circulating pump shot?? or maybe a head gasket?? or it need that thermostat ??


full close cooling system only the risers get raw water.

also it has a belt driven raw water pump. thanks for any info guys.

 

[bolo78910]

Re: merc 5.7 over heating help

fagot to tell yall the big hose that goes to the circulating pump was collapsing at the 2500 pm in nutral.

 

[bolo78910]

Re: merc 5.7 over heating help

gess there isnt much help here anymore, any way guy replace circulating pump new thermostat, and it still over heating at idle , pull the dip stick and found milk shake, gosh that hurt. oh well

 

[bolo78910]

Re: merc 5.7 over heating help

bump

 

[Bt Doctur]

Re: merc 5.7 over heating help

Sounds like a bad head gasket blowing gas into the cooling system

 

[bolo78910]

Re: merc 5.7 over heating help

thanks bt doctor, seems it is now locking up . hopefully we might save it.

 

[Bondo]

Re: merc 5.7 over heating help

Ayuh,... Sorry to hear it bolo,... And sorry I missed your posts,...
The forum has been Flyin' for the last month or 2...

I'm guessin' headgasket, or restricted H/E,... the collaspin' hose...

 

[bolo78910]

Re: merc 5.7 over heating help

thanks bondo for jumping in, tonight i went back , took the spark plugs out on the starboard side in number 2 cilinder out came antifreeze , i then crank the engine over to spit the rest out, it did. port side has no anitfreeze in the plug holes. ok now i took the risers off and behold antifreeze is settle at the bottom of the manifold a nice little puddle . so my gess is a crack manifold.

now please help answer these few ??? guys would a crack manifold dump antifreeze in the oil????

could it be when the temp goes up to 200 degree it mess the head gasket up??

or maybe the intake manifold is crack ??

last with both manifolds off i will perchase new ones in the morning, should i just install them and keep my fingers cross.???

or i should just rip the heads off???

i will also back flush the heat exchanger.


thanks guys hope i could get some answer tonight.

 

[bolo78910]

Re: merc 5.7 over heating help

today i took about three gallion of antifreeze from the oil pan, can that much gets in from that one bad manifold??

 

[bolo78910]

Re: merc 5.7 over heating help

as bondo said this forum is on fire , never seen a thread dissapear so fast.

 

[Bondo]

Re: merc 5.7 over heating help

can that much gets in from that one bad manifold??

Nope,... No way,... You've got another Leak somewhere...

drain, then pressure test the cooling system with compressed Air...
You'll Hear the leak, then follow the sound...

 

[bolo78910]

Re: merc 5.7 over heating help

thanks bondo , couldnt get any reply so i just rip the whole engine apart.

took the heads off and the gaskets are fine.
the heads show no cracks as far as the eye can see .
intake look good but just beause it is old i order a new one.

notice, that morning before we head out to the fishing groung, i did switch the engine of while it was in nutral idling at 20,000 while warming up.

at that time the engine goes into dizeling mode for a few seconds.

could the dizeling dump water in the engine that way.

so far i drain the oil pan what a mess milk shake who wants lol

now that i gets bondo reply we should have pressure test cooling system before we took it apart. so how about when we put everything back we run the pressure test before we start the engine???


thanks bondo for coming all the way back to give me these repplys

 

[Bondo]

Re: merc 5.7 over heating help

could the dizeling dump water in the engine that way.

Ayuh,... Dieselin' will fill the cylinders, but it still has to pass the rings to get to the base...
Just like the manifold thing...'n it would be Salt, not antifreeze...

Is the motor still in the barge,..??
Is your plan to put it back together with just fresh gaskets,..??
Is there a trip to the Machine Shop planned,..??
What temp does this antifreeze Test too,..??
How Cold did it get last winter,..??