Mysterious noise from my JP - any ideas?

[frangar]

I reckon JP's know when they are on a tidal stretch or a scary bit of river and make odd noises just to keep their owners on their toes....I know mine does....it also has the odd cough just to make my heart beat a bit faster.....

 

Cheers

 

Gareth

[starman]

There are two copper discs,each a bit bigger than the size of a 2p coin, if my memory serves me correctly, which are held in position by weak-ish springs. These are the valves which open and close as the piston in your water pump goes up and down. I have a JP2 in my boat, and every now and again I get this tapping noise from the engine room, which I'm pretty certain is coming from these valves hitting their seats. Of course, when you're steering the boat, it's not the easiest thing to duck into the engine 'ole at the merest whim to have a listen. This noise can happen at any time and under any operating condition but more often when running hard. On my engine, I have blanked off the bilge pump part of my water pump, and I've often wondered if it's this that is causing the pump to make this noise, by causing extra suction on that part of the pump. It scared the hell out of me when I first heard it, but after 20 years of hearing it on and off, I'm a bit blase about it now. Of course, if I'm wrong.....................Can anyone help me? I've got a strange knocking noise coming from my engine.........

It's as good a theory as any! And I agree with Gareth, they do something every now and then just to keep you on your toes. (Ours overheated for the first time ever the day before we were crossing the Wash - air lock in the skin tank - so to say the least I was twitchy out there in the sea.)

[monkeyhanger]

It's as good a theory as any! And I agree with Gareth, they do something every now and then just to keep you on your toes. (Ours overheated for the first time ever the day before we were crossing the Wash - air lock in the skin tank - so to say the least I was twitchy out there in the sea.)

I had problems with air in the skin tank for quite a few years. I got into the habit of opening the air bleed on the top of the silencer for a couple of seconds every time I passed through the engine room- it used to leave a lovely rusty pattern on the ceiling if the revs were too high. Everyone who "knew about old engines" told me to get rid of the piston-type water pump,as the only way to cure the air/potential overheating problem. Sometimes, as I'm sure you know, after being told countless times "you can't fix that" you get in the frame of mind that you just want to prove them wrong. So I fixed it. I fitted an automatic air bleed valve on top of the silencer in place of the tap -solid brass, polished up nicely so it looks like it's always been there, and a 3/8 copper pipe tapped into the top of the skin tank, and taken up to the top of the header tank via a swan neck, to remove any air which reached there. The end result is no overheating and a maximum of 3 seconds gurgling noise from the header tank when I stop the engine ( instead of at least five minutes as it was previously) Now I only need to check the water level in the header tank every couple of days, not every couple of hours as I had to before.

Edited August 31, 2014 by monkeyhanger

[steamraiser2]

The piston type water pumps are notorious for leaks and introducing air into the cooling system. We don't think they are at all suited to the average skin tank cooling system. We always recommend an upgrade to a Jabsco type pump to our customers. Most of those who decide to retain the original pump come back afterwards for a retrofit. Says it all really.

[monkeyhanger]

The piston type water pumps are notorious for leaks and introducing air into the cooling system. We don't think they are at all suited to the average skin tank cooling system. We always recommend an upgrade to a Jabsco type pump to our customers. Most of those who decide to retain the original pump come back afterwards for a retrofit. Says it all really.

I think it depends on your attitude. If you opt for a vintage engine, you can't expect to open the doors, put the key in the ignition, and off you go. I'd suspect that most people who have a vintage engine( I can only speak for JPs) accept that you have to oil the rockers, sometimes bleed the fuel pump, and put up with the fun and games associated with the piston water pump. It's all part of the fun associated with owning an ancient lump of iron .If you find it all too much, go for a Kubota!

[Timleech]

The piston type water pumps are notorious for leaks and introducing air into the cooling system. We don't think they are at all suited to the average skin tank cooling system. We always recommend an upgrade to a Jabsco type pump to our customers. Most of those who decide to retain the original pump come back afterwards for a retrofit. Says it all really.

 

I fitted a JP2 with ram type pump to a narrow boat using a sort of 'hot well', a substantial tank formed between engine beds and hull side with the top effectively 'open', so far as I know it's never given any bother. Takes a lot of antifreeze, though!

 

Tim

[flatplane8]

There are two copper discs,each a bit bigger than the size of a 2p coin, if my memory serves me correctly, which are held in position by weak-ish springs. These are the valves which open and close as the piston in your water pump goes up and down. I have a JP2 in my boat, and every now and again I get this tapping noise from the engine room, which I'm pretty certain is coming from these valves hitting their seats. Of course, when you're steering the boat, it's not the easiest thing to duck into the engine 'ole at the merest whim to have a listen. This noise can happen at any time and under any operating condition but more often when running hard. On my engine, I have blanked off the bilge pump part of my water pump, and I've often wondered if it's this that is causing the pump to make this noise, by causing extra suction on that part of the pump. It scared the hell out of me when I first heard it, but after 20 years of hearing it on and off, I'm a bit blase about it now. Of course, if I'm wrong.....................Can anyone help me? I've got a strange knocking noise coming from my engine.........

Do you recall where you got the bleed valve from and what the specification was?

[frangar]

I have fitted an auto bleed to my JP mainly to sort problems I was having with head gaskets...they are ok now (touch wood!) but I have left it on.

 

I just went to my local plumber supplies and asked for an auto bleed valve and got this...

 

 

I had to fit a couple of adaptors to fit the fitting on the expansion box which probably could have been tidier but I really didn't fancy disturbing the fitting that was tight into the casting. The type of valve shown allows it to be sealed unless you unscrew the red cap which means I can keep a check if any air is developing or just leave it off if I have a problem. You can also unscrew the body of the valve if it needs cleaning.

 

Another advantage is when I change the antifreeze any trapped air will go without making a mess.

 

Cheers

 

Gareth

 

Edited to add....apologies for the big pic...was doing it all straight from phone! Found the manufacturer details

 

https://www.flamcogroup.com/uk-en/catalog/expansion-systems-and-accessories/air-and-dirt-separation/flexvent-floatvents/flexvent

 

Hope that helps

Edited September 1, 2014 by frangar

[George94]

Float valves. You can get them at most plumbers merchants for 2 or 3 squids. I have three on my JP.

[monkeyhanger]

Do you recall where you got the bleed valve from and what the specification was?

I'm pretty sure I got mine from screwfix. Have a look at part no :- 76650 Bottle air vent. I seem to recall that this is the size which screws straight in with no adaptor needed. I'm not on the boat at the moment so I can't check for you. The screwfix ones come with a rough cast surface.You can paint it the same colour as the engine, or if you have access to a lathe, it's a 5 minute job to tidy it up ready for the brasso.

[by'eck]

I sometimes hear an isolated knock or two when running at higher revs under lightish load and in low compression. It sounds a little like a pre-ignition knock on a petrol engine. It occurred to me it may be backlash in the gear train, especially since they are straight cut. Any comments?

[monkeyhanger]

I sometimes hear an isolated knock or two when running at higher revs under lightish load and in low compression. It sounds a little like a pre-ignition knock on a petrol engine. It occurred to me it may be backlash in the gear train, especially since they are straight cut. Any comments?

I would't recommend running on low compression with a lightish load.

[frangar]

I would't recommend running on low compression with a lightish load.

I always run in low...loads less stress on cranks at any load....and doesn't smoke apart from when cold or been left idling for a long while

 

Cheers

 

Gareth

[monkeyhanger]

I always run in low...loads less stress on cranks at any load....and doesn't smoke apart from when cold or been left idling for a long while

 

Cheers

 

Gareth

I can see your reasoning----but the makers handbook says always run under high compression unless running hard under a heavy load. I would take" heavy load" to mean in a 70ft boat carrying 25 tons of coal and towing a similarly loaded butty.

Also, from my motor racing days I always understood higher compression to equate to higher efficiency, which must be better. And after all, high comp in a JP is only 19:1, so hardly overstressing the engine I wouldn't have thought.

[by'eck]

I would't recommend running on low compression with a lightish load.

I wasn't recommending it either, but practicalities dictate it will happen from time to time.

 

FWIW Lister recommend using low compression at engine speeds above 850 rpm with no mention of actual engine load.

Edited September 2, 2014 by by'eck

[flatplane8]

Thanks all for the bleed valve info, will look at fitting one of those.

[Timleech]

I sometimes hear an isolated knock or two when running at higher revs under lightish load and in low compression. It sounds a little like a pre-ignition knock on a petrol engine. It occurred to me it may be backlash in the gear train, especially since they are straight cut. Any comments?

 

Possible that occasionally the fuel charge doesn't ignite one one stroke, so there's extra fuel on the next one.

 

Tim

[by'eck]

Possible that occasionally the fuel charge doesn't ignite one one stroke, so there's extra fuel on the next one.

 

Tim

Thanks Tim, that explanation fits the symptoms.

[monkeyhanger]

I wasn't recommending it either, but practicalities dictate it will happen from time to time.

 

FWIW Lister recommend using low compression at engine speeds above 850 rpm with no mention of actual engine load.

I agree.Once in a while, for various reasons, I will run mine on low compression, but my engine wont reach 850rpm (not quite) due to prop size and speedwheel mechanism, so I don't have to worry about high revs. But we're getting a bit "off topic" now.

Edited September 3, 2014 by monkeyhanger