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BMC 2.2LTR Leaking water pump


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Hi guys a bit of advice needed for a mechanical learner here, I have a raw water cooled (from a mud box) 2.2 ltr BMC diesel engine and the water pump has developed a constant drip when the engine is turned off after an hour ish of running. This "drip" is now quite bad and about a litre dripped out over night from the pump and a old hose (now fixed). Now i can see a loose  rubber O ring that in the pump (between the cast bits) that seams wrong, my other theory was the impeller inside the pump? or possibly the thermostat? there my three guesses what dose every one think? My main worry is in the tray i placed under the pump to catch the water there seams to be some trace of coolant (blue/greeny colour) which could of  possibly come from a loose hose which i have now tightened  and that drip seams to have stopped and could have been a separate issue??. Any way i now need to put more water and anti freeze in the bowman can i use standard 50/50 blue anti freeze and coolant from halfords? or do i need something different. Cheers

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The exact design of that raw water pump varies so to be a little more positive about what pump you have I need to know if it is direct raw water cooled or indirect raw water -heat exchanger cooled.

In general there is a gap in the body casting that contains a rubber thrower - this is what I think you are calling a loose rubber O ring except it is more like a rubber washer.

There should be absolutely no way for blue water to get there unless its a heat exchanger boat and there is a leak inside the exchanger but as you do not mention continually topping up the fresh water part of such a system I feel this is unlikely.

The shaft in the pump may be running in the pump body or it may be running in ball type bearings. In either case thee needs to be two oil seals. One to keep oil in the engine and stop it leaking down the shaft ad the other to stop water leaking from the impeller chamber. The rubber washer is to spin either oil or water away from the shaft.

If the shaft is running in the pump body then in all probability the body is worn oval so you are now unlikely to stop it leaking. If its running in bearings then new bearings and two new seals should sort it. The pumps with shaft running in the body tend to have a grease cap on top, insufficient use of this leads to the wear I describe above.

If you are really lucky and as long as the shaft has no significant radial play then just a pair of seals may be all it needs. With such old engines you may find the seals have worn a groove in the shaft. If so the new seals may not last long and a new shaft it probably the best way forward

Edited by Tony Brooks
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5 minutes ago, Tony Brooks said:

The exact design of that raw water pump varies so to be a little more positive about what pump you have I need to know if it is direct raw water cooled or indirect raw water -heat exchanger cooled.

In general there is a gap in the body casting that contains a rubber thrower - this is what I think you are calling a loose rubber O ring except it is more like a rubber washer.

There should be absolutely no way for blue water to get there unless its a heat exchanger boat and there is a leak inside the exchanger but as you do not mention continually topping up the fresh water part of such a system I feel this is unlikely.

The shaft in the pump may be running in the pump body or it may be running in ball type bearings. In either case thee needs to be two oil seals. One to keep oil in the engine and stop it leaking down the shaft ad the other to stop water leaking from the impeller chamber. The rubber washer is to spin either oil or water away from the shaft.

If the shaft is running in the pump body then in all probability the body is worn oval so you are now unlikely to stop it leaking. If its running in bearings then new bearings and two new seals should sort it. The pumps with shaft running in the body tend to have a grease cap on top, insufficient use of this leads to the wear I describe above.

If you are really lucky and as long as the shaft has no significant radial play then just a pair of seals may be all it needs. With such old engines you may find the seals have worn a groove in the shaft. If so the new seals may not last long and a new shaft it probably the best way forward

Hi tony thanks for getting back to me so quickly ill send you a video of what iam looking at. i believe i have a heat exchange system, its a bowman tank with a fresh water and antifreeze mixture filler cap on top. i think the contamination was coming from a loose hose so ill top up the tank and see if after running the engine later theirs any antifreeze mixture in the tray. 

IMG_2657.JPG

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1 minute ago, Tony Brooks said:

It is a heat exchanger system and the pump is one with bearings in it.

I can not see enough of the area above the pump but I would say whatever the blue thing above the pump is it does not seem to be sitting square - that could well be a leak area.

 

1 minute ago, Tony Brooks said:

It is a heat exchanger system and the pump is one with bearings in it.

I can not see enough of the area above the pump but I would say whatever the blue thing above the pump is it does not seem to be sitting square - that could well be a leak area.

cheers tony the blue thing is a separate tube from the mud box carrying raw water, not connected. i think its safe to say its a problem with the bearings or seals in the pump so am gunna top up the fresh water tank with an approx of what i lost last night, and see if any anti freeze mixture comes out after running, i hope that will trouble shoot the possibility of a cracked coil in the heat exchange tank? if it drips clear tonight i guess ill be ok for a week till i get to a marina right?

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Where is the pump relative to the water line on the boat. If below then turn off the sea cock and the drip should stop. If its above it will drip until any raw water in the higher parts of the engine have drained.

If it only drips AFTER topping up the cooling system header tank then it is a heat exchanger problem but I would want to see the heat exchanger before I can suggest what it might be. There is not a coil inside but a bundle of tubes in brass end caps. How the end caps are sealed between raw water and coolant depends upon the design of the heat exchanger so that is why I need to see it.

If its dripping raw water then remember you are filling the bilge and the drip might get worse. If its the coolant and you do not keep it topped up then the engine will overheat with all that may lead to. As long as you understand that and act accordingly it should be fine - my boat has a  dripping seal in a simmilar pump since last summer and its fine as long as I keep it topped up with antifreeze mixture.

 

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2 hours ago, Tony Brooks said:

Where is the pump relative to the water line on the boat. If below then turn off the sea cock and the drip should stop. If its above it will drip until any raw water in the higher parts of the engine have drained.

If it only drips AFTER topping up the cooling system header tank then it is a heat exchanger problem but I would want to see the heat exchanger before I can suggest what it might be. There is not a coil inside but a bundle of tubes in brass end caps. How the end caps are sealed between raw water and coolant depends upon the design of the heat exchanger so that is why I need to see it.

If its dripping raw water then remember you are filling the bilge and the drip might get worse. If its the coolant and you do not keep it topped up then the engine will overheat with all that may lead to. As long as you understand that and act accordingly it should be fine - my boat has a  dripping seal in a simmilar pump since last summer and its fine as long as I keep it topped up with antifreeze mixture.

 

Thanks Tony I think I've got my head round it, the shut off valve from the mud box is lower than the pump so I recon it's raw water left in the pipes above. There's no sign of antifreeze mixture now so tightening that hose must have been the culprit. After running for 1 and a half hours the pump has stoped dripping but it tends to start after the engine has cooled down again (Mabey a heat expansion thing) Iam not sure what the engine running temp is supposed to be I was gunna get one of them cooking probe thermometers and tie it to the header tank to try and get somthing more accurate than touching it lol, what u recon? Also I can see the copper pipes inside the tank your talking about when I take the filler cap off how full should that tank be? I can't see any mixture in there, but I did top up with a approx amount of what dripped out before I started the engine up again. Apologies for all that and thanks for your help. I'll send more pictures of the tank and surrounding pipe work tomorrow if you want? Cheers. 

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Typically the header tank, which is also the heat exchanger and possibly the exhaust manifold as well, is topped up to about 1" below the bottom of the filler neck when COLD. this is to allow space for the coolant to expand when heated. NOTE TO OTHERS - this is not correct for tank cooled boats.

If you overfill it all that will happen is some coolant will be blown out as it heats up.

If the engine is not boiling with clouds of steam and water spurting from the filler cap it is almost certainly running at an acceptable temperature. Temperature alone rarely causes leaks. 

Lip seals work by pressure forcing the lip against the shaft. As the engine heats up the cooling system shoudl become pressurised, that will help force the seal lip against the shaft. As it cools down the the pressure drops so a worn lip may start leaking again. It all sounds consistent with a worn seal but with the raw water shut off valve shut with the engine stopped the drips should stop once the raw water in the pipes has drained out.

You have been loosing antifreeze so check the strength, the vital thing abuout antifreeze is that it helps to prevent corrosion inside the engine..

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