Isuzu 35, raw water hydraulic lock

[maverickcoddiwompler]

Hi folks, has anyone had an raw water cooled Isuzu 35 hydraulic lock with raw water before? Any ideas how the water is getting in? Is there a gasket between the heat exchanger and the block? TIA

[Tony Brooks]

If it has a heat exchanger it is NOT direct raw water cooled, its indirect or heat exchanger cooled. For the best response accurate information is needed.

 

The raw water circuit on neither system can airlock or hydraulic lock as such but the raw water pump (rubber impeller type in your case) can fail, pipes can block in elbows, air can be sucked into poor hose to metal joints and the raw water inlet can be blocked. On wet exhaust boats (another thing we do not know) rarely a blocked or partially blocked exhaust can stop the raw water pump pumping.

 

both types of raw water cooling have a raw water inlet somewhere in the hull. On a narrowboat this is often a mud box but on more recent builds it may just be a hole in the hull feeding a strainer.

 

The cooling heat exchanger is normally part of the exhaust manifold so there will be a manifold gasket between the exchanger and cylinder head  but this has noting to do with water. I am not 100% sure abut Isuzu but I would expect ALL water connections, both raw and antifreeze mixture, to flow into the exchanger by hoses.

 

You ask how the water is getting in - what do you mean, raw water into the boat, raw water into the exchanger, or antifreeze mixture into the heat exchanger.

 

I think you may do well to try to  clarify what the symptoms are, at the moment you have only given your diagnosis of the symptoms and that could well be incorrect, in fact I think the hydraulic lock thing is wrong. It may also help if you post a few images of your  engine and surrounds.

 

EDITED TO ADD: I could write a long piece based on my guesses of what you mean with lots of "if this then thats" in it but the thing seem so vague to would take too long for me.

 

Edited April 18, 2021 by Tony Brooks

[Tony Brooks]

If you mean the piston(s) has hydraulic locked rather than the cooling system then it will probably be a cracked head, blown head gasket, or cracked cylinder that may of may not be fitted with a liner.  The chances if water getting in from the exhaust manifold cum heat exchanger are not very great but possible. That again will be caused by a crack or corrosion hole.

 

Some Isuzus don't have a conventional inlet manifold and they also have no air cleaner. If water poured onto the right place on the cylinder head that might allow water into the cylinders.

[Eeyore]

Possibly related to your previous post about overheating, so maybe a head gasket. Did it hydraulic to a stop whilst running, very bad; or did it simply refuse to turn over when you came to start it? The brass pump that you removed for access to the belts has a rubber impeller inside. The rubber impeller is a consumable item, and as such should be renewed annually, this is the manufacturers recommendation. You didn't come back to the forum to update on the overheating issue, were you able to restore the raw water supply?

[Tony Brooks]

14 minutes ago, Eeyore said:

Possibly related to your previous post about overheating, so maybe a head gasket. Did it hydraulic to a stop whilst running, very bad; or did it simply refuse to turn over when you came to start it? The brass pump that you removed for access to the belts has a rubber impeller inside. The rubber impeller is a consumable item, and as such should be renewed annually, this is the manufacturers recommendation. You didn't come back to the forum to update on the overheating issue, were you able to restore the raw water supply?

 

Ah, so another one who may well think we all remember everything they post. From memory the post you refer to was some time last year so you have a good memory.

[maverickcoddiwompler]

Hi guys, my apologies for not updating on my last post last year, I was just happy to clear the blockage and get going again. That was solved by simply removing the stopcock on the other side of the mudbox, poking the blockage through with a coat hanger and hurriedly replacing the stopcock as the canal poured in!! Fun times!

[maverickcoddiwompler]

Today, I removed the glow plugs and raw water poured out of them, blew them out, replaced plugs and restarted. RCR arrived and determined that the was a small airleak in the exhaust/cooling system that allowed the raw water to slowly siphon back through and enter the exhaust ports at the pistons. He tightened all jubilees (which all had slack in them) told me to close the aforementioned stopcock to stop any further raw water to be siphoned back (I now know I should be closing this every night as good practice anyway!) and I need to replace the o ring on the lid to the box with the raw water cage filter in. 

Hope all that makes sense to you tech guys and thanks again for the quick and detailed feedback, every day is a school day!!! B

Edited April 18, 2021 by maverickcoddiwompler

[Tony Brooks]

1 minute ago, maverickcoddiwompler said:

Today, I removed the glow plugs and raw water poured out of them, blew them out, replaced plugs and restarted. RCR arrived and determined that the was a small airleak in the exhaust system that allowed the raw water to siphon back through the system and enter the exhaust ports at the pistons. He tightened all jubilees, told me to close the aforementioned stopcock to stop any further raw water to be siphoned back (I now know I should be closing this every night as good practice amyway!) and I need to replace the o ring on the lid to the box with the raw water cage filter in. 

Hope all that makes sense to you tech guys and thanks again for the quick and detailed feedback, every day is a school day!!! B

 

Yes it makes sense if its correct. Typically, the raw water enters the  exhaust at an elbow so it flows downwards and as long as the engine is running it blows the water out of the exhaust outlet. If the exhaust elbow on the engine is below the water and the outlet is at or under the waterline  like on many yachts then as you say the exhaust can fill with water and that is why such boats can be fitted with a vacuum break to prevent back syphoning.

 

However, if you have to spin the engine without it starting it has been known for the raw water pump to fill the exhaust so it can back flow into the engine ports.

 

At present, I can't see how raw water could get into the exhaust ports on a typical narrowboat because they would be slightly above the waterline but it all depends on levels and layout. 

 

Anyway, hope it all works out and thanks for the feedback.

[Bee]

Crumbs, that shouldn't happen. Hard to say why that happened without looking at the whole thing but keep a very close eye on it. Hope the small air leak was not in fact an anti siphon device. Water will not siphon if there is an air 'leak' at the top of the system.

[Eeyore]

I refer you back to my previous post regarding the pump impeller, which if stationary doesn't allow water to flow through it, unless it's very worn or missing a vane or two. By all means close the valve, but please, please put a notice next to the ignition switch!!!

Missing vanes usually find there way into the end of the gearbox heat exchanger before the smaller parts migrate into the main heat exchanger within the exhaust manifold, so you'll need to remove a few pipes to check for bits.