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Isuzu 55 Marine Engine Coolant Emptying...


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Afternoon all,

 

I've recienntly been away with a friend, he had a bit of a problem with his engine that i'm struggeling to get my head around...

 

For the first few days his engine ran absolutly fine, as it had done for the past few years.  All of a sudden, whilst appraochng a lock, the high temperature alarm went off, & engine was turned off within about 30 seconds.  Pulled the engine hatch, steam everywhere... A few mugs of tea later we saw that a coolant pipe had popped off the gearbox oil cooler.  Examined the pipe, all looked good, re attached with its hose clamp, refilled the coolant, bled the skin tank using the bleed screw, got the engine to temperature, gave all the pipes a good squeee looking to any more air, it all looked good so carried on.  It ran perfectly for the rest of the day, probably another 4 hours of running.....

 

The next day it ran for a few mins before the high temp alarm went off again, opened the engine hatch, steam everywhere, a few cups of tea later, examined the engine.... No pipes had come off but there was no water in the engine... Again filled the coolant, bled the skin tank, got engine up to temp, squeezed pipes, engine ran perfectly for the rest of the day....

 

The following morning, we check the coolant before starting, it was empty again....  refilled and bled, ran perfctly for the rest of the day... this repeated for the next 6 days...

 

It looks like all the coolant is ending up below the engine, I've been all over the engine but alas, cannot find a leak...

 

Does this sound fimilar to anyone, am i being really stupid and missing something simple...?  My current thinking is the headgaskget is leaking pressurising the coolant and forcing it out of the overflow...??

 

Thanks

 

Dave

 

Setup is: Isuzu 55 Marine Diesel circa 2000 / 2005, skin tank & calorifier...

Edited by Quattrodave
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Ha, good thought, i like your thinking there... Its fine, we've been eating and drinking & showering on that boat most of the week.  I would assume we'd have noticed if the calorifier had an internal leak.  I'm pretty sure the coolant is ending up under the engine... 

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Prior to the first bout of overheating had you topped the system up? I had a boat that was very tempremental and if the header tank was above a lowish level it would overheat and dump all the contents into the bilge. I had to fill to a precise level for it to behave.

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18 minutes ago, mrsmelly said:

Prior to the first bout of overheating had you topped the system up? I had a boat that was very tempremental and if the header tank was above a lowish level it would overheat and dump all the contents into the bilge. I had to fill to a precise level for it to behave.

 

Hang on, i'll ask...

 

No it wasn't topped up before we left on day 1.

Edited by Quattrodave
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How old is the boat and what hull spec? If you can't find any leaks then it is possible that the skin tank has rusted through, so coolant is leaking into the canal, especially when the cap is on and the system pressurised, but that does not explain the coolant under the engine.  I would clean out the engine n drip tray so you can see it was historical or it's filling up again.

 

Have you found and checked all the core plugs?

 

Engine water pumps tend to be beasts when they start to leak. They are totally unpredictable when and how they will start and stop leaking. Look for  rusty/antifreeze coloured stains down the front of the engine below the top pulley, torch and mirror often required.

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3 hours ago, Bod said:

What colour is the end of the oil level dip stick?

Black = good

Gray = bad

 

Don't know, i'll double check at the weekend.

 

3 hours ago, Bod said:

Is there coolant in the area under the engine?

Does the bilge pump run unexpectedly?

 

Yes, coolant is in the rather large driptray under the engine.  No the bilge pump doesn't run unexpectedly

 

3 hours ago, Tony Brooks said:

How old is the boat and what hull spec? If you can't find any leaks then it is possible that the skin tank has rusted through, so coolant is leaking into the canal, especially when the cap is on and the system pressurised, but that does not explain the coolant under the engine.  I would clean out the engine n drip tray so you can see it was historical or it's filling up again.

.

Boat is a 2005, not sure what the hull spec is.  Thats a good thought but, as you say, a lot of coolant is ending up in the large driptray under the engine.

 

3 hours ago, Tony Brooks said:

Have you found and checked all the core plugs?

 

Engine water pumps tend to be beasts when they start to leak. They are totally unpredictable when and how they will start and stop leaking. Look for  rusty/antifreeze coloured stains down the front of the engine below the top pulley, torch and mirror often required.

 

I think i've found all the core plugs but will double check at the weekend.

Yes, i've had leaky water pumps before, i'll double check there...

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  • 9 months later...

UPDATE:

 

After far too much time I've eventually got round to doing some work on this engine.  I was pretty sure the had gasket had gone and the coolant was being pressurised by one ot more cylinders.  I cut the bottom out of a large fizzy drink bottle and wedged the bottle neck into the engine coolant filler neck, basically to act as a bug funnel. Topped this up with water and started the engine.... wow, massive bubble just kept coming up through the make shift funnel and it would not bleed or slow down.... Now convinced the head gasket was faulty I ordered all the parts up to do the job.  Removed the head, actually not a bad job, nice engine to work on.  Ah ha!!! A few areas of the headgasket didn't look in great condition, sent the head off to be skimmed, apparently wasn't far out at all.  Cleaned everything up & re assembled the engine as per workshop manual.  Engine started pretty much first time, was rather pleased with my self and packed up for the night. 

 

The next day I used the make shift funnel again to bleed the coolant system, muchmuch better this time, no air continually bubbling through it!  Engine running to temperature with no issues, bled the calorifier, no apparent issues, engine still running fine.... just can't get any hot water.... Sooooo after a bit of head scratching and a fair amount of testing the coolant pump only seems to be pushing water through the calorifier when engine is over 1200 rpm... Even then its an unsteady trickle...

 

Have I got a lazy coolant pump... could a lazy coolant pump have caused the head gasket to fail...???

 

Thanks

Dave.

 

Edit:

If anyone has got an isuzu 55 with a calorifier, would you be good enough to take a pic of the take off and return engine side please, thanks.

Edited by Quattrodave
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I have seen a piece of junk from inside the water jacket  wear all the impeller vanes off a water pump........so this may be with yours....take it off and check.

Edited by john.k
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21 minutes ago, Quattrodave said:

 

Edit:

If anyone has got an isuzu 55 with a calorifier, would you be good enough to take a pic of the take off and return engine side please, thanks.

 

I've sent you some pictures attached to a PM. Is that what you need? 

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1 hour ago, Alan de Enfield said:

 

 

This is 'like an impeller but smaller" .....................

 

 

20210828-105753.jpg

 

Hang on Alan. It is very unlikely that an Isuzu on a skin tank would use a rubber impeller pump unless it was a "Fred in a shed" marinisation. I think JohnK is talking about debris from inside the block wearing the metal/plastic centrifugal impeller on the engine water pump.

 

Before I commented on the OP's problem  would want to know where the calorifier take off pipe is fitted on his engine. If it is on the skin tank side of the engine thermostat I am not surprised he has that problem.

 

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25 minutes ago, Tony Brooks said:

Before I commented on the OP's problem  would want to know where the calorifier take off pipe is fitted on his engine.

 

 

Just to clarify, it's not a Jabsco type pump with a rubber impeller, it's the factory engine coolant pump.

 

The calorifier is connected (as far as I can tell from the manual) to where the heater matrix would be which is not skin tank side of the thermostat.

 

Image curtesy of blackrose but engine in question is exactly the same, photo is much better than mine:IMG_20220604_115245.jpg.d904c21a3a548892fb230a9395f00751.jpg.d04ca1c21235d8cd1c85c8bd2e807b7f.jpg

 

25 minutes ago, Tony Brooks said:

 If it is on the skin tank side of the engine thermostat I am not surprised he has that problem.

 

Tony, what do you say that, not arguing or disagreeing, just intrigued?

 

Thanks

Edited by Quattrodave
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 If the smaller of those two hoses in the image is the take-off to the calorifier then that is fine. I suspect the larger one is the return from the skin tank. If that is so I ask myself why the different hose diameter. Lets suppose nothing else is going on then you should get the full pump output through the calorifier while the engine is warming up, probably from tickover upwards. This is because the engine thermostat is closed and the calorifier is the only path for the output of the water pump( see * below). As the thermostat opens an increasing amount of flow can bypass the calorifier and flow via the skin tank. However by then the calorifier should be hot.

 

If the calorifier was taken from the skin tank side of the thermostat then the bulk of the flow from the pump MIGHT find it easiest to flow through the skin tank and ignore the calorifier - hence my comment.

 

* below: I don't know the Isuzu engines in detail, but I think they conform to the above. They probably have a small port that allows some water to flow from the water pump through the engine when the thermostat is close to prevent boiling on any inner surfaces that have t deal with more heat than the bulk of the engine. This is known as the bypass port. This does not normally affect calorifier operation. Some engines have a much larger bypass port and a special thermostat that closes this port off when the engine is hot. I don't think the Isuzu is like this. However, if someone fitted an ordinary thermostat in place of the special one you could get your symptoms and possibly overheating.

 

I know you say that you have bled the calorifier circuit, but this still sounds like an airlock or a valve that is partially closed. I would suggest inspecting the calorifier circuit pipes looking for kinks, inverted U bends that can trap air or even a one way valve that is reluctant to open with water flow. If you  have one I would make sure it is a flap valve, correctly orientated, and with a flap that moves easily.

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  • 2 weeks later...

The saga continues....

 

It's done the headgasket again, well I assume it done the headgasket, I have exactly the same symptoms as before huge amounts of air bubbling out of the coolant cap...  I'll be taking the head off again in a week or so but any reason it would have failed again so soon??

 

Genuine gasket set used, head was skimmed, manual removal and tightening sequence  follows to the letter, everything was cleaned, checked and double checked on assembly. 

 

One thing that's playing on my mind, the manual never mentioned re-torqing the head bolts after x amount of time...  many years ago I was taught to torque head bolts, get engine hot, let it cool then re-torque... problem is I can’t remember how you re-torque.   Just test the torque on each one, slacken and re-torque, or loosen by a quarter turn and re-torque...??

Edited by Quattrodave
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I don't want to alarm you, but this is starting to sound all too like an overheat problem we had on a BMC 1.5. After a couple of head gasket replacements and a head skim we put an illuminated 40 watt bulb down each bore (pistons out) and found a faint line that turned out to be a crack.  How easy would it be to remove the water pump and blank the hole, seal all the hose connections bar one and then do a pressure test on the block. (some water pumps will leak if exposed to higher than design pressures). May also be worth pressure testing the wet exhaust manifold in case that has cracked or corroded through.

 

I am a bit surprised the manual says torque the head down. These days I would have expected stretch bolts that use a protractor thing to decide when they are tight.

 

Does the Isuzu need liner protrusion to seal. It would not be the first time over enthusiastic block face cleaning has removed the liner protrusion.

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Thanks guys,

 

Tony: hmmm good thought, might be difficult to seal everything, what sort of pressures would i need to test to?

 

Yes manual specified a sequence first torque setting, second torque setting & final 90 degree.  Now here is where its gets a little sketchy, we didn't use new head bolts... The reasoning, genuine suppliers had the top end gasket sets but not head bolts, they we're available to order from Isuzu.  The suppliers had them listed as 'head bolts' not 'stretch head bolts' they them selves were surprised at this and couldn't tell me if they were actually stretch bolts or not, they concluded they were not stretch bolts.  The last reason was they were asking £28 per bolt!! With a 6 week lead time!!!!!

 

I didn't see any sign of a liner protrusion, unless it's been machined off many years previous.

 

Tracey: yes previous one defiantly did, I do hope this one does too....

 

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4 minutes ago, Quattrodave said:

Tony: hmmm good thought, might be difficult to seal everything, what sort of pressures would i need to test to?

 

I would want to do it at twice the running pressure that could be 15 psi, so 30 psi and leave it there overnight with paper towel under each "seal point" to indicate accidental leakage. Also make a small allowance for temperature alterantion.

 

A bung in short hoses with a jubilee clip around them should be OK for the hose connections and try the water pump in situ because if it has a decent lip seal it should not leak.

 

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45 minutes ago, Quattrodave said:

Thanks guys,

 

Tony: hmmm good thought, might be difficult to seal everything, what sort of pressures would i need to test to?

 

Yes manual specified a sequence first torque setting, second torque setting & final 90 degree.  Now here is where its gets a little sketchy, we didn't use new head bolts... The reasoning, genuine suppliers had the top end gasket sets but not head bolts, they we're available to order from Isuzu.  The suppliers had them listed as 'head bolts' not 'stretch head bolts' they them selves were surprised at this and couldn't tell me if they were actually stretch bolts or not, they concluded they were not stretch bolts.  The last reason was they were asking £28 per bolt!! With a 6 week lead time!!!!!

 

I didn't see any sign of a liner protrusion, unless it's been machined off many years previous.

 

Tracey: yes previous one defiantly did, I do hope this one does too....

 

I have refitted existing stretch bolts on lots of engines for many years. If they show signs of overtightening and have a definite "neck" anywhere then they need chucking. Other wise I have always just torqued them down, greased, and retorqued at least 3 times on cold assembly and retorqued after a short time running hot by cracking back a bit and retorquing to a wee bit over the manufacturers figures for luck.

Never had any problem doing this on any engine, iron, aluminium or a combination.

The price that they want for bolts is terrible, they are not so special that this is justified.

You could always try to buy plain ordinary bolts of the correct size but I would bet that they are an odd size just to stop you doing this.

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There are various threads on here about the Isuzu 55 engine and head gaskets blowing. It seems to only occur on engines that have skin tank cooling and not on those fitted with a marine mannicooler/heat exchanger. I suspect that your underlying problem is down to overheating of the engine. These engines are not normally fitted with a temperature gauge so your running temperature could be too high without the alarm going off. As you said there is poor circulation to the calorifier I would suspect overheating to be the cause due to poor or restricted circulation.. Possibly check the water circulation pump first as you are taking the head off anyway. It could be a build up of scale/rust in the engine and skin tank on its own or in combination with a blockage of the water passages in the block or head. Skin tanks performance degrades over time with internal corrosion and build up on the external surfaces. Wash out the skin tank and engine and add corrosion inhibitor/antifreeze  when you refill.

air collecting in the head depending on the cooling arrangement could also be causing the issue.

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20 years ago, the better half, had a car that over heated for no apparent reason, no amount of normal looking at, found anything amiss.

Desperation removed the water pump, the light shone brightly!

All the vanes in the pump had corroded away, the poor spindle was doing it's best, but without the vanes, the water didn't move.

Any over heating in a modern engine, would have me removing the water pump to see the condition of the vanes.

 

Bod

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