Overheating KAD32

Peanuts

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One day we will get this one sorted - hopefully!

As you have mentioned nearly all of the items have been checked, was this done by removing the items and inspecting or by a type of in situ check.
As the engine sometimes works OK I don't think it is an item that is causing the problem but more of an interconnecting one, eg pipework.
The way I look at these types of problems is sometimes it is easy to overlook the basics, so on that note I would start at the water intake on the outdrive, if need be remove the 's' type hose to make sure it is not collapsing in any position. The I would flexi endoprobe from the transom water inlet up to the oil cooler, checking for damaged internal pipework and debris, once reaching the oil cooling checking for restrictions. Of course most people won't have flexi endoprobes so I would be dis-connecting the water pipe from the oil cooler and inserting a hose pipe with water on pushing it in until it appears at the transom, this will ensure that part is clear. I would then check the actual oil cooler (as VP mentioned in post 5). Then I would check the pipe work between oil cooler and pump/strainer. That area is now 100% checked.

The reason for this overkill is for a reason, I remember once we had a problem that had us baffled, it involved the pressure not being released from an item, units were changed until there was nothing left to change, apart from the pipe work, everything looked OK, nice shiney braided flexi-hoses. We x-rayed one of the flexi-hoses and there was the problem, the inner part completely deformed, the pressure from the pump could push it's way through but did not have the force to release once the pump was off. Even when we knew where the problem was no-one could see any damage on the outside, so what I am saying is don't assume - check it.

I look forward to the next installment of your on-going problem.
 

david_bagshaw

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.......When not under load I dont lose coolant or overheat

Have you tried fast running, to heat it up then run in neutral on that engine at the failing rpm, and with the other engine , hopefully able to runat sufficient speed in gear to reach the same knots. to hopefully rule out water flow problems, equally what happens if you run at that rpm on the one engine ingear, underway of course.
 

barney365

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Hi Peanuts & David

Thank you for all the pointers - I'm down at the boat this weekend so will try the recommendations - will advise back.

Thanks

Paul
 

Squiffy

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Hi,

just a thought as I had a similar problem with slight overhaeting at low revs but fine at higher revs.After the Marina engineer had wanted to change various parts in some sort of scattergun approach,I was in the engine room and heard a slight hissing noise immediately the engine was switched off.On investigation it was the seawater strainer which had avery small piece of dirt in the lid which was allowing air into the system.At higher revs there was sufficient "draw" to conceal this.After cleaning the lid seal and re tightening the problem disappeared - not something anyone had suggested to me at the time.

Maybe?
 

barney365

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Hi All

Armed with my infrared thermometer, wow what a worthwhile piece of kit, I spent Saturday in the enginebay with notepad and pen.

To start off the level in the coolant tank was to the line, when I throttled the engine the level dropped quite drastically, when brought back the revs the level came back.

Brought the engine up to 80oC and first thing worthy of noting was the raise in the level in the coolant tank.

Raw Water Pump 18oC
Top of Thermostat housing 66oC
Bottom of thermostat housing 72oC

Into the heat exchanger 42oC
Out of heat exchanger 16oC

into and out of turbo unit 16oC

Exhaust riser and block 76oC

What did happen is the level in the expansion tank continued to rise until started to spill through cap.

At this point I revved up the engine to around 3 k revs the increase to begin with pushed the coolant through the cap before then dropping right back to about an inch from the bottom and here the level stayed and also temp on dials dropped below 80

Took temps again

Raw Water - 18oC

Top thermostat 76oC
Bottom Thermostat 81oC

into Heat exchanger 62oC
Out of Heat Exchanger 16oC

Into and out of Turbo 16oC

Exhaust Riser and block 82oC

I also tested gasses with my leak detection kit - blowing gas through but no discolouration

Does this indicate anything ?

The more I try things the more confused I become .........
 

volvopaul

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Hi if it's pushing water out at such a low temp it can only be expansion, as it not even near boiling point. To test another way for head gasket or as I sometimes call it "making water" I do the rubber glove test by clamping a latex glove over where the cap fits, if it continues to fill with air it can only come from compression gas, but I'd also pressure test the heat exchanger incase it's sea water entering the system. Have you tried anew cap , is the matingface on the tank ok where it meets the seal of the cap. Might be worth pulling the fresh water pump off to check vanes or if the impeller spins on the shaft.
 

Peanuts

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Hi
Glad to see you are having fun with your thermogun, they are great aren't they? I am engine running most of the day but will try to look at the figures tomorrow but I have to say I always run my KAD's with about 1 " of coolant in the tanks otherwise they just kick it all over the place.
 
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dingdongs

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post 12 and 47 mention keeping the coolant at near bottom of expansion tank.if you try that for a while you may see results and if you keep an eye on your instruments and levels when at these particular circumstances occur when throttling back coming into port you may no longer have fluid over the floor.give it a try at least!!!
p.s.did you compare temps to the other engine?
 
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barney365

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Hi all

Armed with rubber gloves I have just tried Volvo Pauls idea of gloves on the filler. To start off with it looked like the glove was going to be sucked into the unit when getting revs up to 3k . I then brought back the revs and the glove started to expand, soon filling with coolant. Had to turn off the engine before it decided to blow - VolvoPaul I take it that's a conclusive result ?
 

barney365

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Further update - with the glove in place the inflating of the glove manifests when the revs drops and the supercharger kicks in - can this extra pressure of air into the engine create enough pressure to push through the head gasket ......
 

andy59

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Just a thought but have you pressure tested the freshwater cooling side and is there anywhere that inlet air pressure made by supercharger can get into cooling system ?
 

RIN

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Can we just dispense with issue of the water level in the header tank? Can you confirm you have tried running with a low level of water in the header tank - just over the bottom - and you still get the problem?. I have just reread the posts and didn't spot where you tried this.
 

volvopaul

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Before you go ripping the head off id still start at the freshwater pump as its still expansion with the glove test, are thre any bubbles in the coolant at just off idle in the header tank? if not then I doubt its headgasket, more expansion due to poor circulation.

As for the sc, that will put a positive pressure on the inlet manifold theninto the engine but compression pressure is far higher which in turn is headgasket failure.

You could have a copper injector sleeve o ring gone pushing comp pressure into the cooling system.
 

Peanuts

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Hi Barney - once again

Although I am on a weeks break (on the boat of course) I am still pondering about your engine problem, what I cannot get out of my head is that it is not a consistent problem. What I am getting at is that although there have been many suggestions, for example the injector sleeves, would that problem not be there all the time? Also the fact that you are running with leak detection fluid that does not show up a leak. What I am getting at is the problem is varible, (spelt wrong?) sometimes it's there, sometime not. If say it was a head gasket it would be there all the time. So what is the problem - don't know.

However, have you run the engine without the thermostats? or did I miss that post!
 
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