No water in exhaust after thermostat replacement

[Mattwebb]

Hi folks, thanks for your help in advance. My engine is a BMC 1.5 indirect raw water cooled, Bowman exchanger in a GRP Broads Cruiser.

I switched thermostats the other day from 82 to 74, replaced the coolant and understood that I wouldn't be able to change the impeller as I'd hoped as I was a tool short to release the water pump off the engine mounting. Started her up and the water pump belt wouldn't move, probably because of leaked coolant onto the belt. Dried it off and got it all moving BUT, there's no water coming out of the exhaust (previously it looked pretty satisfying). Can anyone explain how working on the pressurised circuit has caused a blockage (air, impeller blade, silt?) in the raw water circuit, and is there anything I can do while waiting for the water pump/impeller to be looked at? Cheers.

[Tony Brooks]

I think that the RAW water pump looks like the ones with a packed gland under a big nut just behind the pulley and the shaft runs in the pump body, so if the body is worn it may well suck air down the shaft, rather than raw water. I can't be sure, so really need a better view of the pump, side or top view. If there is a grease cap hidden behind the pulley then it is likely to be as I say, so fill the cap with stern tube grease and tighten down, and try running again. If it is a packed gland, then tighten the big nut a little.

 

I am assuming that you have checked the raw water inlet strainer/mud box and ensured nothing has been sucked into the hole in the hull.

 

If you have an inlet strainer, make sure the cap is properly sealed to the body, especially if the strainer is above the water line. Otherwise, the pump can, and will, suck air under the cap.

 

That blue hose on the top (outlet) of the pump looks to me as if it could be kinked and thus restricting the water flow.

 

If you have been boating in very mucky water, then the inlet side of the raw water heat exchanger tubes can get blocked. but to check, you will have to drain some of the coolant. Take the two rubber end caps off and poke through with a length of wire or straightened coat hanger.

 

If the impeller has shed a blade, then it could well be stuck in the blue hose somewhere.

 

Finally, a pair of rare but very puzzling possibilities. If the exhaust is blocked then exhaust back pressure can build up sufficiently to stop the raw water pump delivering water, the pressure bends the blades down. This can be caused by the exhaust hose delaminating inside, the mixing elbow furring up, and in the odd case a rag put into the exhaust for the winter not being removed when recommissioning.

 

Edited to add:

 

There should be no way simply changing the thermostats or doing anything else to the engine coolant (fresh water) system can cause problems for the raw water, unless there has been some accidental damage to the raw water system like a squashed pipe.

Edited August 3 by Tony Brooks

[Peugeot 106]

Now that is a comprehensive reply!

[Tony Brooks]

1 minute ago, Peugeot 106 said:

Now that is a comprehensive reply!

 

Not as comprehensive as it could have been if the OP had chosen to give us some background as to why the thermostat was changed. If it was simply to reduce the calorifier temperature then it adds nothing, but if the OP thinks it will stop overheating then that would tend to suggest a pre-existing raw water problem. If the OP had told us what gearbox is involved and if the boat has engine oil cooling, as a sea boat may well, then there are two more things to consider - depending upon where in the raw water system they are located.

[Peugeot 106]

Let’s just hope he lets you know how he gets on. It must be disappointing when they disappear into thin air

[DD.]

I really hope it's not disappointing. This kind of info is worth it's weight in gold to people looking through threads. Even a couple of years later.

 

So to me this is what makes this forum a great find for me 

[Tony Brooks]

5 minutes ago, Peugeot 106 said:

Let’s just hope he lets you know how he gets on. It must be disappointing when they disappear into thin air

 

Yes, but one comes to expect it. I don't think they realise their responses will help others.

 

I also don't think they realise the question is not resolved until their problem is solved and reported to the forum, even if we did actually explain how to sort it out. This is why I applaud those who come back and tell us the results.

Edited August 3 by Tony Brooks

[Mattwebb]

Hi Tony, thanks for your reply. I was changing the thermostat to reduce the calorifier temperature, and to see how a cooler stat affected the running, as I'm about to start some river cruising. (Previous stat was tested in a pan of water and seemed to begin opening in high 70's).

Before the change I had no concerns with the raw water system, aside from the impeller being well overdue for replacement, but as I say, flow was strong from the exhaust.

No mudbox but strainers are clear and plenty of water is coming in - and it goes straight to an oil cooler. I'm not sure of the gearbox make, but can provide photos on Tuesday. I'll also check for greasing options on the pump and have a root around in the heat exchanger.

All a bit of a mystery ATM....

 

[Mattwebb]

And before I'm shot down in flames for taking 24 hours to reply - I checked every single topic on all 28 pages of the BMC area of this forum before asking for help - so as not to waste anyone's time.

[MrsM]

No-one will shoot you down in flames. Tony merely pointed out how useful it is when posters report back. And that it is somewhat frustrating when they don't. 

[Tony Brooks]

18 minutes ago, Mattwebb said:

No mudbox but strainers are clear and plenty of water is coming in - and it goes straight to an oil cooler. I'm not sure of the gearbox make,

 

The oil cooler tells me that it is probably a hydraulic box and as the oil cooler comes before the pump it will be worth taking the rubber caps off the oil cooler to ensure the input side is not full of muck. If the oil cooler is an all-in-one copper body with no rubber end caps then reverse flush it and see what comes out.

 

Re the water pump.

 

1. Did you take the screws out of the end cap, if not, then I am not surprised it won't pump.

 

2. This pump uses one or two oil seals plus (I think) a ball bearings for the shaft. The state of the end plate says it is very old, so when the pump comes off check the shaft for wobble/lift and if it will change the bearing(s) I would also change the oil seal(s). You may find the shaft has been worn into a groove by the oil seal, if it has, I fear you may need a new pump or shaft, a new pump tends to be expensive.

 

I don't consider your question a waste of time

 

 

 

 

[hider]

Why are the 2 mounting nuts partially undone?

 

There seems to be lots of screws missing from the pump back plate and it has already been reversed once, it is very warn on what was the front face.

[Tony Brooks]

FWIW, the pump inlet hose (yellow) in the second photo looks as if it might be twisted and has collapsed. That in itself is enough to stop the raw water pump priming. This may just be an optical illusion.

 

I expect the raw water inlet pipe/hose runs up the port side of the engine fairly low down, could you have stood on it and crushed it while doing the thermostat. If it is hose, does it sit in the engine drip tray and has now perished/softened sufficiently to collapse when the pump sucks.

[Tony Brooks]

Also, if you managed to kick or step on a rigid pipe or a hose that allowed it to disturb a joint anywhere between the raw water inlet and the pump's it may suck air rather than prime. The long "suction" pipe run that included joints for the oil cooler is why when on the fleet we re-piped ours, so there was only one pipe and the two joints on the suction line. The rest were on the pump outlet side. This improved the reliability of the raw water systems.

[Mattwebb]

Thanks for your replies folks. I removed the screws from the water pump backplate, and also slackened the nuts that mount the pump itself. 

I'll be taking a good look around the raw water system tmw, have been away. I can remove the oil cooler caps, remove the outlet from the pump and see if it pumps with engine running, see what's lurking in heat exchanger, and also check for damaged/soft/delaminated inlet pipes. 

Water pump itself will get attention later this week. Can anyone name the manufacturer in the meantime? 

Thanks for your help.

Hi again folks. I've opened up the heat exchanger and oil cooler and found no obstructions, back flushed the pipe from H.E to water pump and this water ended up coming out of the loose outlet of oil cooler. Suggests impeller blades are not stopping water pass through stationary pump. No broken blades found anywhere though. Raw water inlet hose is tired, but not flattening or kinked.

Pump seems very hard to turn manually, possibly seized? Perhaps it's always been this tight. Tony, could either of the red circles in the photo highlight a grease port? I undid the screw and back flush water drained...

Mechanic coming Friday. I didn't mention in first post that last time I was cruising I opened the engine up to 1700rpm or so for a short while as I had just established that the engine wasn't overheating with an infra red thermometer. (Mismatched sender and gauge)

In it's old age could this have been too much for the pump?

I can't find any similar pumps for sale on eBay/Calcutt/asap/Boulters and am wondering if a 12v pump is a viable alternative if this one is beyond repair.

Thanks for your help.

 

[Tony Brooks]

1 hour ago, Mattwebb said:

Pump seems very hard to turn manually, possibly seized? Perhaps it's always been this tight. Tony, could either of the red circles in the photo highlight a grease port? I undid the screw and back flush water drained...

 

A far as I can see there are no greasers on that pump, and I have never seen one like that on a BMC, but there have been a few that have gone obsolete to be replaced by a different design of pump.

 

I suspect yours has one or two ball bearings in the larger diameter part just behind the pulley, plus a lip type seal under a wear plate immediately in front of the impeller and another just in front of the rectangularish hole that you have circled in red. This is a drain hole/tell tail so if the seal in front of the impeller fails, water drains away rather than get into the "packed for life" bearings. It sounds to me as if the bearing(s) may be very much the worse for wear and possibly seizing up.

 

The little screw you also circle is the retaining screw for the cam plate that makes the impeller blades flex to pump water.

 

My advice is to take the pump off so you can strip it on the bench. We know the backplate has been badly worn and reversed, so possibly the wear plate is in a similar state. 

 

Backplate off, impeller out, remove the cam retaining screw and the cam plate.

 

Bang the open face of the pumping chamber onto a block of soft wood (so as not to damage the gasket face on the body) to encourage the cam plate to fall out. You should then see the inner seal, you should be looking at the open face, not just flat rubber.

 

Because I do not know the pump, I can not be sure about the next steps, so take care.

 

If the pulley comes off without a struggle, it may make the next step easier because you could then support the front face of the pump body on a partially opened vice of a couple of pieces of wood.

 

Using a soft metal drift (brass, copper aluminium or even a length of hard wood dowel) drive the shaft out of the bearings.

 

Then you should be able to hook the rear seal out.

 

Turn the pump over onto the soft wood and using the drift to drive the bearing or bearings and the other seal out of the body.

 

Any local bearing or engineering suppliers should be able to match the bearings and seals.

 

Inspect the shaft for a groove worn by the seals, back seal especially. Otherwise, the groove may damage the new seals.

 

As is the favourite of Haines manuals, reassembly is the reverse of the above.

 

 

If it is a main stream marinisation the chances are that it is a Jabsco pump, but it could also be a Johnson pump.

 

As long as you ensure an electric pump delivery is high enough, it should work, but Jabsco certainly have other foot mounted mechanical pumps that will do the job. There is an image here

 

Look at what "The Jabsco Shop" has to offer.

[Mattwebb]

Eventually managed to take the water pump apart, and the plate is a little worn (after being reversed) and the impeller was tired but effective. It primed quickly and seemed to work just like it used to. I'm still baffled as to why it stopped pumping after replacing thermostats, but it's working just fine now. Thanks for you help and advice.