Overheated Engine

[Lord Farringdon]

Hi Guys,

I have recently had the stern leg serviced although I dont think that had anything to to do with the overheating I experienced this weekend.

I slipped down the fairway and headed out past two entrance markers. I throttled up to about 1800
rpm and 7 knots while waiting for the engine to get to operating temperature before getting up on the plane. I
noted the temperature rise to 95 degrees but was surpised to see it continue to rise passed 100 c. I handed
the helm to my wife and grabbed my temperature gun and noted a temperature of 110 degrees at
the engine. At this point the temperature gauge was rapidly rising to the stop on the right hand side of the gauge and when I looked back to the engine, the coolant header tank had started to relieve pressure with steam and coolant
spraying out. I immediately shut the engine down.

We were maybe 200 metres of the rocks with a southerly blowing us to shore. I dropped the anchor and was
considering a PAN call but given that it appeared the anchor was holding fast I was satisfied we had time to
consider our situation.

After some analysis of the seawater filter, impellor, and sea water intake hoses I was able to establish that the impellor had been running dry but that whatever the blockage was, it had now gone away and I was able to start the engine and return back cautiously to the marina, with the temp remaining within limits. My assessment is that it was something blocking the stern leg intake.

The boat has suffered overheating before and in prevoius ownership had to have a disintergtrated imprellor replaced. I have experienced a previous event where the temparture was above limits but then stopped before getting too serious. Now this event last weekend which had we not been smart with the anchor may have found us bashed against the rocks and in some considerable distress.

This can't be normal. Is blocked intakes a common occurence or I have got somethin more sinister going on?


Terry


Terry

 

[OldSkool]

Terry,
The Volvo KDA 300 engine is pretty resilient to overheating. First signs of a cracked head due to overheating would be compression in the coolant tank. A test of the coolant for exhaust gasses can confirm this. In the Volvo engine overheating will typically cause # 6 piston to gulled or scrape the cylinder wall. This will cause the engine to drag when trying to start. We commonly see starter burn out with this as many overheat the starter trying to spin the engine fast enough to start it. Most Volvo's need between 150 - 180 rpm to start.

All that being said, if you were able to restart the engine and have not seen any of the above or increase engine heating again, you may have “lucked out” as we say.

If at any time you see fuel in the coolant then the injector cups may be bad. With the injectors developing 21,000 LBS of pressure on injection the combustion is greatly increased and over time may cause injector cup leakage. I must say that the KDA 300 has had a very good service record on this count.

Your engine is a super/turbo charged engine. It develops about 285HP at 3,800 RPM. It weighs in at around 1,200 lbs and has peak torque of 417ft lbs at 3,500 rpm.

If anyone has anything to add or correct please do so. As a Volvo guy we sometimes get real techy so let me know your real world experiences if they differ from mine.

 

[BonBini]

Bill: sounds from your description the KD 300 share similar injector seating with 3100 series Cats. Don't know the material a Volvo uses, but Cat uses a copper cup.... Also your mention of no six failures leads me to believe the coolant water must enter the block at the front like a straight six car engine. Not trying to turn this into a comparison, just found it interesting.

Terry: with any engine you can't get away with too many overheating situations. Especially with light weight/high out put packages. Seems the first thing that gets weakened is the head gasket fire ring. Second would be cylinder scoring. The fact that you were on the ball watching the engine temp was a good thing for sure. Us Cat guys use two different test to look at these areas. A bubble test for combustion gasses in coolant system. Blow-by test for damaged cylinders. A third test we use is for injector cup seat integrity, a bubble test on the fuel system.

Hope things go well for your boat...

 

[OldSkool]

Bill: sounds from your description the KD 300 share similar injector seating with 3100 series Cats. Don't know the material a Volvo uses, but Cat uses a copper cup.... Also your mention of no six failures leads me to believe the coolant water must enter the block at the front like a straight six car engine. Not trying to turn this into a comparison, just found it interesting.

You are correct on both counts.

Because the injection PSI and compression has drastically changed we see some copper cup failures due to compression deformation. This has been documented on both Volvo and Cat engines. Like Cat we have gone to an improved design cup to eliminate the deformation. (PS. I’m an Ex-Cat guy). :grin:

Even with increased cooling number 6 is still the last to get the coolant. I don’t know if that will change as the engine has no issues if the coolant system remain in good operating condition.

I posted a picture of 6 pistons on another thread that show the # 6 piston gulled. I’d post it again but me thinks you know what they look like.:thumbsup:

 

[Lord Farringdon]

Thanks guys for the informative resposnes. I can safely say (or maybe happily say) I didn't experience any deformation of the header tank or any starting difficulties. Given the relative simplicity of the system, ie the water comes in the stern drive inlet, up the hose and into the impellor/seawater filter, the problem is either a blockage in the piping system or a blockage of the outlet. If it was the former I doubt it would just go away so my guess is it was the latter and stopping the engine allowed whatever it was to fall away from the inlet. There are a couple questions I'd like to ask you Bill about the KAD 300:

1. How many hours are you seeing these engines (KAD300) do in outdrive configuration before major overhaul, assuming good preventative maintnence?

2. The seawater inlet is critical to the operation of the engine and therefore to safety at sea. It seems to be subject to blockages quite frequently and when it does, engine temperature rises rapidly, especially if on the plane. You will get an alarm but that's because you have an overheating engine, not because you had a loss of seawater flow 2 minutes ago. As Bon Bini says, you can't have too many of these overheating episodes on a lightweight/high output engine like the KAD 300. Is there any kind of flow meter/alarm or such like that can let you know you have an inlet blocakge or reduced flow as soon as it happens rather than having to wait until the motor cooks itself and the coolant alarm goes off?

Really appreciate having a Vovlo tech on these forums Bill. :grin:

 

[melida]

Terry,
Glad you are ok after the alarm went off before hitting rocks.
Not a qualified answer as Bill and Bon Bini wrote, I do always and recommend you to always check your water intake by diving into the sea and keep it clean of algaes,seaweed and barnacles. Also every time in spring/summer maintenance uninstall the hoses where sea water passes through and spray air in them to fully empty the debris.
In my previous boat I had D4-210-DPH and every season I had overheating beacuse of clogged water hoses and cleaned them by myself.
In my current boat since 1,5 years I own it every time before docking or anchoring in a place depth below 2 meters I raise the drive to beach range +10 +15 degrees(dont forget to do not exceed 1500rpm in beach range). This is protecting me from overheating and also I check my sea water hoses which were clean in last year's and this year's maintenance. Raising the drive helped me which I didn't in D4 keeps KAD300 clean.
Also KAD300 has easy accesable impeller then D4-D6 and you should/I do uninstall the cover plate and check the vanes of the impeller which are easily cut by barnacles, and replace even one vane is cut but not torn yet will ristrict the water flow in high rpm.
Hope your overheating caused by this simple trick not that complicated things mentioned by Bill and BonBini.
Best regards.
Melida

 

[OldSkool]

KAD 300:

1. How many hours are you seeing these engines (KAD300) do in outdrive configuration before major overhaul, assuming good preventative maintnence?

2. The seawater inlet is critical to the operation of the engine and therefore to safety at sea. It seems to be subject to blockages quite frequently and when it does, engine temperature rises rapidly, especially if on the plane. You will get an alarm but that's because you have an overheating engine, not because you had a loss of seawater flow 2 minutes ago. As Bon Bini says, you can't have too many of these overheating episodes on a lightweight/high output engine like the KAD 300. Is there any kind of flow meter/alarm or such like that can let you know you have an inlet blocakge or reduced flow as soon as it happens rather than having to wait until the motor cooks itself and the coolant alarm goes off?

Really appreciate having a Vovlo tech on these forums Bill. :grin:

Terry,
The KDA300 should go between 3500-4000 hour before rebuild. Again, as you stated, there are many variables that will shorten or extend that time. The D6 which replaced the KDA300 is rated at 5000 hours.

If you take the recommended usage of 300 hours per year on a KDA300 you have 12-13 years of operating time before rebuild. The sad thing is that most engine surcome to poor maintenance before their full potential is reached.

As for the flow meter, I can see the worth of such a sensor but I'm not aware of any for the application. I will research and get back to you.

Hope this helps.

 

[Lord Farringdon]

Thanks Bill. Very helpful. I'd certainly be interested in anything you find out about a flow meter/sensor.


Cheers


Terry

 

[Lord Farringdon]

Ok, a little more on this one guys. As part of my maintenance pogram I have just replaced oil and coolant. While messing around with this and starting and stopping the engine to warm the oil and to check renewed oil and coolant levels, I was very conscious of the overheat situation I had just experienced. Before starting the engine first time, I took off the seawater filter cap in order to check the filter. As usual, the flat cover plate underneath the cap was difficult to get off but once it lifted, I saw all the water in the seawater filter drain down below the impeller. I could see the impeller was now dry just like it was last weekend when the overheat problem happened at sea. So this says that up until I removed the sea water filter cap, the impeller was primed but afterwards, it was not. With this in mind, I started the engine and with a temperature gun checked the pump housing. In noted a temperature of 18 deg C rising to 24 deg C. I placed my hand on the cover plate and it was warm to touch. With the engine still going, I 'cracked' the seawater filter cap which resulted in a spewing forth of sea water. I closed the cap and took the pump housing temperature again. It was now 16 deg C and didn't move for the remainder of the time the engine was on.

So there is my problem. I have been checking the seawater filter every time before I start the engine and every time I must have been spoiling the prime and introducing an airlock. I supect more vigoruos application of throttle in the past has been sufficient to 'self prime' the pump, but is this normal?

The bottom of the impeller sits just at water level depending on load and wave movement. I know this because I removed the impeller cover plate when I had the overheat problem at sea and, I have just replaced the impeller as part of this cuurent maintenance cycle and to eliminate that part as the problem. The old impellor looked fine with all the fins in good order.

So, what could be the problem. Is the impeller supposed to allow water back past it if the seawater filter cap is opened or should it be water tight?

Sorry about the long post.

Regards

Terry

 

[melida]

Terry,
What you wrote about opening the flat cover plate and water goes down below the impeller is normal. The direction that water goes down is the water intake hose and it makes 90 degree angle to while reaching to impeller.
I also check and clean inside the filter of oyster and seweeds and never faced airlock both in my KAD300 and previous D4-210.
You should check the raw water intake hoses and clean them. When the engine starts first creates vacuum to pull the water any debris/algae/seeweed would sit at the 90degree point below the pump restrict the water flow.
Also confirm visually (when you close the tap and cap and the temp gun shows sewater pump temp normal) the water is discharged through the outdrive and is there any leak in the raw water hoses port side of the engine.
Hope this helps.
Best regards.
Melida

 

[Lord Farringdon]

Thanks Melida. It is helpful to know that you experience the same drop in water and drying of the impeller after you remove the cap from the seawater filter. Your post also helps because I was starting to wonder if there might have been a certain 'water tightness' about a good impellor that would not have allowed this to happen and that might have indicated I had a bad impeller or setup in some way. It makes perfect sense since we all know that water will find its own level. I wonder if Richard experiences the same thing with his dual KAD300's?

So the problem is narrowed down to to why the impeller won't self prime even after replacing with a brand new impeller?

To answer some of your questions Melida, Prior to messing around with this current problem, there was no sea water in the bilge, just fresh water from rain entering through some poor sealing on the engine room vent covers. Of course 'cracking' the seawater filter with the engine running and replacing the impeller has changed all that but not because of any unkown causes. So I am confident I don't have any raw water hose leaks. I certainly can't see any. If there were any leaks in the system I would expect air to replace water and the seawater filter to be empty when I opened it. But that is not the case.


If water was leaking past pump seals and into the engine than presumably I would see water in the oil. That is not the case either. In fact the oil I extracted during the oil change was in pretty good condition. I think the previous owner had only recently replaced it.

You suggest a blockage in the raw inlet hose. Hmmm, that would certainly make the impeller have to work hard to self prime. I recently had the stern drive removed and part of the leg servcing included cleaning out the inlet and associated piping. There were some crustaceans but not much. But, I haven't been able to completley remove the inlet hose to check for blockages closer to the impeller.

How do you check that seawater is passing out the exhaust on the DP-G? The leg is tucked well under the swim platform and in any case it is under water?

Boy, I wish there was such a thing as a seawater flow meter that could be fitted to these engines. That would make life so much easier!

Thanks Melida.:thumbsup:

 

[Lord Farringdon]

Maybe this is the answer. I did some research self priming pumps and came up with these little pearls of wisdom from the follwoing site:

http://www.gongol.net/knowledgebase/selfpriming/


"A "self-priming" centrifugal pump overcomes the problem of air binding by mixing air with water to create a fluid with pumping properties much like those of regular water. The pump then gets rid of the air and moves water only, just like a standard centrifugal pump.

It is important to understand that self-priming pumps cannot operate without water in the casing. "

and,

"Recirculation of water within the pump stops when pumping begins. The next time the pump is started, it will "self-prime" -- that is, it will be able to once again mix the water and air in the casing to create a pumpable fluid until the pump is fully primed again."

and,

"A self-priming centrifugal pump must have water in the casing in order to operate. You cannot pull any self-priming pump right out of the box, turn it on, and expect it to pump. If it's full of air, it won't prime. "Self-priming" refers to the pump's ability to repeatedly turn an air/water mixture into a pumpable fluid -- NOT the ability to create a vacuum (literally) out of thin air. In fact, you should never try to run a self-priming pump without water in the casing. It's dangerous and will often lead to seal failure."


On this basis, if I open the raw water filter, the water drains to below the impeller casing and so won't prime.

Why does it go down so far?

Well, I guess the boat sits too far out of the water or the engine is mounted too high in the boat.

If the overheating is caused by running a dry impeller, then why does overheating only occur sometimes?

Because the water level is JUST below the impeller casing, a combination of wave action and full throttle advancement sloshes enough water and air to charge the impeller casing and to start priming.

Does this sound like it could be my problem?

Terry

 

[melida]

Terry,
To test, if the sea water is leaking to bilge is easily seen over the rust on the generator/alternator/charger (which one is called in your country) just below the impeller housing. When I bought the boat first there was some rust over it and mech replaced the gasket inside the impeller housing and painted the generator. Also over the hose (below impeller housing carrying sea water from intake) there must be white sea water residue/shade if the sea water is leaking from the pump.
If these symptoms are not seen on your engine, then don’t worry about water leak.
Did/does the engine reach and stay at 85C/185F operating temp in and over cruising speed?
If there is no temp increase so your engine won’t overheat in normal circumstances. So have to find why the air lock occurs.
On the other hand, as you know sea water enters from sea water intake in front of the drive’s lower unit left and right side then passes through the drive (via the hose goes through impeller housing) first cools down the steering pump/servo pump oil (ATF) (very close to stern, just below the starter) than the hose makes 90 degrees angle below the generator and reaches to impeller pump. After circulating in the sea water filter bowl water goes to aftercooler via a separate hose by making downturn. This circulation follows after cooling the air in the aftercooler reaching to heat exchanger and oil (engine) cooler than mixes with exhaust gas at the exhaust elbow and discharges via another hose through outdrive.
http://i998.photobucket.com/albums/af108/melida315/volvo%20penta%20C4%20prop%20set/DPG.jpg
In this picture where red mark is the sea water intake and there is also right side. The yellow mark is the exhaust and sea water discharge.
While your engine is running and there is air lock check visually “bubbling/waving” water around the outdrive. This means your engine is intaking and exhausting sea water. If still overheating than urgently consult a VP tech.
If KAD300 had EVC instead of EDC than we must have the display and could see every kind of engine parameter event the unnecessary, so keep look after to our engine as a baby by watching and hearing.
Best regards.
Melida

 

[Lord Farringdon]

Terry,
To test, if the sea water is leaking to bilge is easily seen over the rust on the generator/alternator/charger (which one is called in your country) just below the impeller housing. Also over the hose (below impeller housing carrying sea water from intake) there must be white sea water residue/shade if the sea water is leaking from the pump.

No sign of any leaks or stains around the impeller casing, alternator or inlet hose.

Did/does the engine reach and stay at 85C/185F operating temp in and over cruising speed?

Yes. Once the the seawater filter cap is 'cracked' water gushes in and the engine operates at between 83 and 90 degrees C according to the gauge. The temperature shows the engine to be a few degrees cooler.

If KAD300 had EVC instead of EDC than we must have the display and could see every kind of engine parameter event the unnecessary, so keep look after to our engine as a baby by watching and hearing.

Yeah, EVC would be great. :smt038But I guess we'll just have to keep a closer eye on the temprature than the scenery.

Thanks Melida.