Overheating Yanmar

[whiplash]

My Yanmar 4JH2-DTE overheated on sunday and coolant came out of the expansion tank.
The engine is 7 years old but i have only had the boat 2 years and it had 150 hrs on it when i got it and now has 310 hrs.
I have never changed the coolent since i got it.
I was planing to drain and flush the system with Radflush and then refill with new coolant. Also i`ll check to make sure the thermostat is working.
The raw water side seems to be pumping ok but i`ll check the impellor.
If this fails to cure the proplem then i was thinking of taking apart the heat exchanger to see if its blocked up with crud at all.
The coolant in there seems to be a brown colour
Any ideas where else i should be looking or what it might be ?
I just hope it`s not the head gasket!!!!
Looks a real pig to work on.


Alan

[kerry]

i m8 hows things . appart from engine . i guess this is an inboard engine . is or was there a small flow of water in the header when its run if so then the pump is ok then the thermostat does it open when its submersed in boiling water ? its usually the case when thermo gone preasure builds up in the pipe work then blows the pipe or the joint. if head gasket gone your oil will be like baileys cream . so check oil first if ok then u can chill .
regards kez

[whiplash]

I won`t be able to check anything untill i`m at the boat next Wednesday.

Alan

[kerry]

is there any belts on the engine check them too

[squidlips]

check the thermostat first,then look at the heat exchanger to make sure it is not blocked.also make sure the coolant is being circulated by the engine water pump.at 300 hours your engine is hardly run in.
if you need to do major repairs it would be easier to remove the engine from your boat,than to struggle in the space you have there.

[monkeynuts]

hi m8
i see 100s of these little fellas and they are a very good engine on the whole, so dont hit the panic botton yet
it normaly somethink dead small making things looks bad

question?

after refilling the anti freeze did over heat again

if so did over heat with load on it or does it still do it at tick over ?

as for brown anti freeze=
yanmars do make the anti freeze go brown quickley, nature of the beast and thay should have it changed around 150-200 hours or once a year but make sure you use the right stuff(cant spell it but il right it down tommorrow)

if you had no more problem and got home at norm temp
it could be the PHANTOM bag witch my have been sucked up while running and soon as you turn off its gone and you never know any more about it,
but still check the impeller

starting with the impeller is a good shot as iv seen a good hand full of impellers de-bond them selfs and at higher revs thay just dont pump the water needed to keep it cool and eventaly pack up compleatly,, thay also can go soft which will do the same thing at higher revs

next i would say at 7 years the heat exchanger needs cleaning regardless of hours , infact lower hours are worse for blockages in the exchanger(310 hours in 7 years is low), make sure you rod out every tube inside to remove salt deposits and wash the out side off in a acid bath if posable or boiling hot water and wire brush to remove the crap you see in you anti-freeze which seems to stick like shite to a blanket

next if you engine over heats at tick over with no load after this, you will have to check the termo stat(or id just put a new one in any way after 7 years )

il pm you my number and if you need any help give me a ring and il try to talk you though

i would hope its not head gasket but a way to tell if head gasket is gone (if you anit got a presure kit) is=

your engine will knock like hell when 1st started and run rough after, once warm care fully remove the rad cap with a cool wet rag(be very careful, it f***in hot) some hot water will come out and it should then setle unless its blown to bits(in which cas eit will probaley have not started), next rev the engine up and see if any bubbles come up (this will be quite obvious)
if the is no sign of bubbles the gasket/ head should be ok

[whiplash]

Cheers Monkeynuts, i`ll go through all that next wednesday.

Thanks
Alan

[whiplash]

Well I got stuck in today and first thing I did was change the Impeller, the old one seemed fine but after a year it was due to be changed soon.
Next the thermostat was removed and checked and was found to be operating at the correct temperatures so it was replaced with new gaskets.
I then drained the fresh water side of the cooling system, refilled and then flushed with cleaner and aftter refilling with new coolant took it for a test run.
Done about 8 miles near flat out and not a problem shown, engine purring like a kitten.
I did find a drain Cock leaking a bit so that may have been the reason for the overheating but not sure. Also possible that somthing blocked the sea water inlet for a bit and caused the overheat.
The Water that came out the system when flushing came out dark brown
so it was a good thing it was flushed and refilled with fresh coolant.The head gasket worries look ok at the moment.
Thanks for all that helped me with the problem. It looks like I`m back in action.

Alan

[monkeynuts]

no problem m8 ,sounds like the plastic bag sindrom at the moment then (not boat angler know why thay should not chuck shite in the water)
give us a shout if you get any more probs