Overheating

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Wobbo

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Volvo Penta Kad32 been going great guns then recently we've been noticing water in the bilge.
I put some luminous dye in the fresh water and it was leaking out the header tank.
Did a 30mile run this morning fine, just the usual small leaking into the bilge...then this afternoon after chugging up the river and then giving it the beans it shat itself big time. Luminous green water pumping out the header tank and temperature gauge on red alert in a very short space of time.
Have had troubles with overheating in the past which was a bunged up oil cooler but after stripping that off it seems ok.
Thermostats appear good.
No air locks.
Impeller on raw water is good.
No sign of water in oil
Any suggestions????
Cheers
 
If the heat exchangers have not been cleaned out recently then they will need a flush with hydrocloric acid ( supermarket if you are in Spain e1 for 1.5 lt or eBay in U.K. )

Remove or replace engine anodes as it dissolves them
 
The only few times I have had overheating on the river has been due to something picked up on the intake. After stopping the engine and letting it cool all has been well.
 
pickup elbow on the outdrive?
If its the alloy type they rot and break after a few years.
Temps all ok at displacement speed as it's underwater but once on the plane then air rather than water is sucked into the cooling system and BINGO overheat.
 
Should have said this is a RIB. Got it back on the trailer and ran it in a tub and raw water side runs fine. Checked the elbow just inside engine bay where it picks up as we had the remains of a shredded impeller once but all clear. Nothing in the strainer.
 
An obstruction on the intake may have fallen off.
Check the raw water pump is not worn internally . The brass face may be replaced inexpensively.
 
I had a problem a couple years ago where air was being sucked into the raw water pump from behind through the shaft and bearings. Not enough to stop the pump working at low speeds but at high speeds would suck in enough air to create an air lock. Didn't seem credible at the time but once again VolvoPaul was spot on the money.
Annually I get another issue with similar symptoms. Barnacles and fouling grow in the intake ports of the leg. It doesn't take a lot of them either before they hit critical mass. As you are on a trailer this is probably not the case, but if you left your RIB on a mooring even for a couple weeks you'll be surprised how quickly the little critters can invade and grow enough to do this.
 
jrudge said:
If the heat exchangers have not been cleaned out recently then they will need a flush with hydrocloric acid ( supermarket if you are in Spain e1 for 1.5 lt or eBay in U.K. )

Remove or replace engine anodes as it dissolves them
Click to expand...
Got that off and it's clean as a whistle..
 
tico said:
pickup elbow on the outdrive?
If its the alloy type they rot and break after a few years.
Temps all ok at displacement speed as it's underwater but once on the plane then air rather than water is sucked into the cooling system and BINGO overheat.
Click to expand...
I shall check it out thanks
 
Have you recently filled the coolant expansion tank?

Certainly on early Kad42, the tank was under sized and would chuck out coolant for fun.

Could be as simple as a coolant cap is knackered too.
 
BruceK said:
I had a problem a couple years ago where air was being sucked into the raw water pump from behind through the shaft and bearings. Not enough to stop the pump working at low speeds but at high speeds would suck in enough air to create an air lock. Didn't seem credible at the time but once again VolvoPaul was spot on the money.
Annually I get another issue with similar symptoms. Barnacles and fouling grow in the intake ports of the leg. It doesn't take a lot of them either before they hit critical mass. As you are on a trailer this is probably not the case, but if you left your RIB on a mooring even for a couple weeks you'll be surprised how quickly the little critters can invade and grow enough to do this.
Click to expand...
Hmmm I shall look into the pump.
I have pulled out a hose which goes from the exhaust elbow to the outlet in transom,behind the leg. It has a bend but it's collapsed so much it might be restricting flow. I'm not much of a mechanic and I can't get my head around why fresh water coolant will explode out of the header tank if the raw water system is not working correctly. They are not connected ? My,only slightly more qualified mechanic mate assures me it matters.
We are barnacle free but I know what you mean. We've had trouble with them when we kept the boat in the water.
 
FARSCO said:
Have you recently filled the coolant expansion tank?

Certainly on early Kad42, the tank was under sized and would chuck out coolant for fun.

Could be as simple as a coolant cap is knackered too.
Click to expand...
We have been filling it regularly as it's been leaking but only to the halfway mark. Did have an issue with overheating once before which turned out to be bunged up oil cooler but before we sussed that out we changed to a new header tank and cap...I think we ended up with 3 new caps so have been swapping them about recently!
 
Wobbo said:
Hmmm I shall look into the pump.
I have pulled out a hose which goes from the exhaust elbow to the outlet in transom,behind the leg. It has a bend but it's collapsed so much it might be restricting flow. I'm not much of a mechanic and I can't get my head around why fresh water coolant will explode out of the header tank if the raw water system is not working correctly. They are not connected �� My,only slightly more qualified mechanic mate assures me it matters.
We are barnacle free but I know what you mean. We've had trouble with them when we kept the boat in the water.
Click to expand...

If the hose is old and soft then the vacuum draw of the pump can allegedly cause it to collapse starving the raw water feed. I have not experienced this myself but it sounds plausible enough and others have reported it. May be worth changing any old and "gone soft" rubber intake hoses.
 
Wobbo said:
We have been filling it regularly as it's been leaking but only to the halfway mark. Did have an issue with overheating once before which turned out to be bunged up oil cooler but before we sussed that out we changed to a new header tank and cap...I think we ended up with 3 new caps so have been swapping them about recently!
Click to expand...


Our Kad 42 doesn’t like the antifreeze any higher that halfway between low and half ie “quarter tank maximum “ took me ages to work this out couldn’t realise why I kept having to top up ,since only putting 1/4 tank antifreeze the level never budges all season
 
On my ka32s the coolant is in the low mark on the reservoir one cold engine and stable.
If you are not seeing hight temp on the gauge sounds like you simply need to adjust the coolant level.
 
Restoration man said:
Our Kad 42 doesn’t like the antifreeze any higher that halfway between low and half ie “quarter tank maximum “ took me ages to work this out couldn’t realise why I kept having to top up ,since only putting 1/4 tank antifreeze the level never budges all season
Click to expand...
Aye..there is another thread for an overheating Kad32 on this forum I read through and I did note they don't like to be filled to the mark.
When you fill up do you bleed the air out somehow to avoid airlocks? I fill up through a hose at highest point by the turbo, not sure if I should be doing something else!?
 
MartynG said:
I intended to write .... on the low mark on a cold engine
Click to expand...
Yes I'm definitely giving this a go. Restoration man said same thing. I Can't get down until the weekend. Did start stripping bits off and poking around in hoses last Sunday on my way to the oil cooler which was the cause of trouble last time so I'll reassemble and see what happens.
How do you fill up with coolant!? Through top of turbo?
Thanks for all the replies ?
 
MartynG said:
On my ka32s the coolant is in the low mark on the reservoir one cold engine and stable.
If you are not seeing hight temp on the gauge sounds like you simply need to adjust the coolant level.
Click to expand...
The temperature shot up really quickly so we stopped, lifted the engine box just in time to see all the coolant pumping out the header tank.
 
I just top up via the expansion tank then crack the small coolant return line union on the turbo whilst running to bleed.
 
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