Overheating KAD32

[barney365]

I've over the last 12 months put a few threads on the site for an overheating KAD 32 engine on my S34. I still experience issues and still looking for a solution.

The Overheating is caused by the pressurisation of the fresh water cooling system pushing coolant out of the coolant expansion tank and then causing overheating.

The problem tends to manifest itself at 2,500 rpm at around 10 knots.

At full throttle all works well, its only when dropping to 2-2,500 rpm when the problem seems to materialise - in fact I have run back from Poole with no issue until I came back into the Solent and brought back the throttle.

Plenty of engineers, fellow boaters and head scratching. Here's a list of whats been done so far ...

New Impellars
New Thermostats
Fresh Water Pump removed and checked
Acid batch oil coolant and heat exchanger
Exhaust riser checked
Turbos checked
Raw water pumps changed over
Inlets checked

.... also have run a detection test to see if coolant pressure contains co2 to indicate head gasket or liner leak but this test brought no results - there seems to be pressure in the system but this does not appear to be CO2

The problem engine is the Starboard engine - the engine heats quicker than the port.

I can run the boat on sea trials and run without issue until usually running back into the marina.

Any advice will be greatfully accepted as I'm at wits end on this.

Thanks to all those who have already supplied advice to date.

 

[david_bagshaw]

Does the engine have an injection advance mech? or all electronic? perhaps the timing is leading to the overheat? One for volvo paul.

 

[dingdongs]

remove main waterpump circulating pump which is driven by the fan belt.make sure all the metal vanes are intact and its still solid on the shaft.only saying this as i,ve seen only 1 vane of 5 left on a landrover 300's waterpump caused by someone dropping a circlip into a hose and it finding its way to the waterpump and break vanes off.gave similar symptoms.

 

[omega2]

Do you draw the raw water in through the leg? I wonder if at that particular speed/revs, there is a "hole" in the sea at the intake area causing a lack of raw water.

 

[volvopaul]

As it happens at" hump speed" water will be present around the leg so no chance of an air pocket id say.

What you have missed is the oil cooler for the steering is on that engine maybe its blocked, maybe you have some old loose impeller blades floating around the intake pipe, I came across this on one particular engine and it turned out to be loose blades tucked underneath the intake of the sea water pump.

As you have done all the tests re head gasket you are happy in the knowledge that the base engine is ok, but have you checked the heat exchanger end cap for debris, the oil cooler for debris and bits of impeller etc, also the sw pump wears on the back plate and can virtually stall when the impellers not spinning fast enough to suck, theres something to be going on with, for now.

 

[Phill]

In automotive applications, we have seen expansion tank caps which weaken and don't fully hold pressure which leads to leakage and then overheating. Maybe worth swopping yours over and seeing if fault moves to other engine.

 

[barney365]

Hi Volvo Paul - have had out and checked, also heat exchanger out twice now and cleaned. Have also swapped out the raw water pump with port engine. The combustion test, although showed no co2 did highlight lots of air pushing out of the cap.

Have also swapped filler caps between engines.

Other thing is I have blown air through raw water intake and with aid of underwater camera checked for any air escaping other than the intake on the leg - nothing.

 

[volvopaul]

There have been some cases where the plastic fresh water pump impeller has fallen off but that only shows up when its really under load, is the gauge actually near 100deg c when the alarm goes off, as it could be just a faulty alarm sender of a glitch in the electrical pack that makes the alarm work.

The only way to source the problem would be for me to carry out a sea trial and test the engine with my infared heat gun for hot spots on the engine whilst under load and at various rpm speeds.

 

[barney365]

Hi Volvo Paul, the overheating is caused by the loss of coolant in the system I think more than actual overheating. The other weekend during trial overheated once back into entrance to Portsmouth but by this time two litres of coolant in the bilge.

 

[dingdongs]

sounds like your putting pressure in the water system from a blown head gasket probably blowing directly to the water gallery instead of an oil one which would show as a milky substance in your oil.may be best to pop the rocker covers and see if all bolts are torqued down correctly or just have a new gasket fitted.if water gets into one of your combustion chambers it will bend a rod and then major expense and an engine pull will be neccessary

 

[volvopaul]

Barney are you now saying that as soon as you run the engine under load water leaks past the cap and you loose 2 litres, id say that would not make it overheat to that extent, but if it keeps pouring out you do either have a head gasket problem, or the fact that the closed water side is not passing through the heat exchanger to be cooled, all this can be tested on a sea trial with the right diagnostic equipment.

Have you done the work yourself or used the services of a marine engineer?

 

[RIN]

Barney
Sorry if I missed it in this or your previous posts but do you actually have an alarm going off? or is it the fact that there is coolant coming out of the filler cap? If the former yes there is a problem. If it is just the latter, I had similar issues if I filled to the correct mark on the header tank. Someone told me that was a problem with KAD32's and since then I have not filled up to the correct mark but just made sure there was water at the bottom of the header tank and have had no more emptying of coolant over the alternator.

 

[barney365]

Hi Dingdongs - what I can't get my head around is that I can run at full throttle from Poole to the Solent - even runs from Portsmouth to Yarmouth on the IOW without problem but soon as I throttle back problem occurs. Also on leak detection kit shows no CO2 in coolant gasses. Mystified

 

[barney365]

Hi RIN - yep alarm goes off

 

[Elza_Skip]

The KAD32 on my previous boat would always run hotter at the revs you describe with the supercharger running, but never overheated, as a previous poster mentioned you have to top up the coolant to the bottom of the header tank to leave plenty of space but you have probably already sussed that.

What about your calorifier, is that on this engine and could this be leaking fresh water into the cooling system as it heats up?

 

[[2068]]

Have you checked the inlet hoses from the outdrive to the transom shield?
These can disintegrate internally.

 

[barney365]

Hi Volvo Paul - multiple engineers, Seastart and advice from volvo technicians. All hit a blank and hence nearly 12 months of the problem.

 

[barney365]

Hi Flower Power - as much as possible without a recent lift out - in all issues the heat exchanger remained at around 17• c.

 

[RIN]

Barney
Just another thought - did you note the temperature on the helm gauge when the alarm went off? Was it over 97C?

I had an intermittent overheating alarm on the port KAD32 for a long time and spent ages trying to track it down and swapping bits from port to starboad engine to try and find out what was going on.

Eventually (with the help of a cheap digital IR thermometer from Maplins) I worked out that the culprit was the alarm switch itself This is not the one on the thermostat housing but on the left side of the engine as you are looking at it. It is impossible to see but if you trace the wire by hand you can find it.

I was not able to find let alone change this myself but thankfully Peanuts from this forum managed to get his hand on it and eventualy remove it with some sort of crowsfoot spanner. I'm sure he will be along soon to say how he did it

It costs around £35 I think

Of course you still have coolant coming out but see earlier post - do you fill to the recommended level or just to the bottom of the header tank.

 

[[2068]]

Hi Flower Power - as much as possible without a recent lift out - in all issues the heat exchanger remained at around 17• c.

That does suggest a circulation problem on the freshwater side of things.

Circulation pump - no play in the pump shaft behind the pulley?
Is this the engine with the calorifier or the one without?
Sounds like you've already checked the other likely things:
- turbo housing
- heat exchanger