Where is the thermostat on my BMC 1.5

[Vicki Kanninchen]

Hi, can anyone help me work out where the thermostat is housed on my BMC 1. 5?

 

My engine has been intermittently overheating- I've checked the filters on the raw water inlets and bled the system and it hasn't resolved the issue- and there's still water coming out of the exhaust. 

 

The boat runs fine for about half an hour (until the calorifier has heated the hot water tank?), then the temp gauge invariably starts to creep up accompanied by an increasing amount of steam from the exhaust. Running the hot water tap sometimes brings the temperature back down temporarily.

 

Occasionally the engine will run for hours without the temperature gauge moving above normal, and a couple of times, stopping the engine and restarting has cured it.

 

I'm thinking it might be an issue with the thermostat, and wanted to take it out and test it.. But having spent hours trawling the internet, I've found plenty of pictures of the thermostat itself, and diagrams of where it's located on other engines that look nothing like mine, but nothing showing where mine would be housed. 

 

I've had completely different advice from various other boaters which has left me more confused than I was before (there's a difference of opinion as to whether what I thought was my heat exchanger is actually just a header tank...). I would be extremely grateful if anyone could point me in the right direction... 
 

[Stilllearning]

I think it may be under the large flat plate that one of your neighbours has tentatively identified as your header tank. To be precise, under the three nuts at the back end of the plate.

A sideways on photo of what is under the plate/tank will confirm, I haven’t looked at one for a while.

[bizzard]

Yes, its under the plate where the three nuts are. Go easy though looks like one is bodged, possible stripped thread or something. When off reface housing on a sheet off fine production paper on a mirror face. These housings tend to warp between stud holes and can leak if not nice and flat, Cork gasket takes up some warpage.

 Withdraw the last sentence, the plate and housing look all in one piece so probably not possible, Use cork gasket with sealant on it.

Edited November 12, 2019 by bizzard

[Vicki Kanninchen]

That's as I feared.... I'm a bit concerned about trying to remove the whole heat exchanger/ header tank due to my relatively basic mechanical skills and the fact that those bolts have been thoroughly bodged (it actually looks like someone's put metal putty around the join at some point).

 

Can anyone give any advice as to how I would go about safetly removing the heat exchanger without permanently bodging it? What's the best sealant to use, and how can I find out the specific gasket I'd need? 

[David Schweizer]

Here is a photo of the BMC engine we had in Helvetia . The thermostat is at the front of the engine, inside the casting with a hose pipe attached to it, located above the top pulley.

 

[Tony Brooks]

As far as I can see the whole thing is a bodge and have a horrible feeling its a very old heat exchanger indirect raw water cooled engine that has been converted to run on a skin tank.

 

The heat exchanger (the thing across the engine and held on with three nuts) should have one large diameter hose running from the main body to the automotive type engine water pump and the two thinner ones on the end plate. One comping from the raw water pump ad the other going to the manifold and from there into the exhaust.

 

I can't see the raw water pump sufficiently to determine the hose run or if it is large enough for the job and there is a hint it might be feeding water to the calorifier coil.

 

However the talk of steam from the exhaust suggests this is an indirect raw water cooled system and the overheating may well be caused by a blocked raw water inlet, failing raw water pump etc. A delaminating exhaust hose can also cause temporary overheating at higher speeds.

 

I would be very reluctant to suggest that you should even be thinking about a thermostat fault at this time, raw water failure is much more likely so make sure the raw water inlet/strainer id always clear with lots of water coming from the exhaust.

[David Mack]

Looks to me as if the normal thermostat housing (as in David S's picture) has been replaced with the heat exchanger/header tank unit. In which case there may not actually be a thermostat now unless it is in the bottom of the heat exchanger/header tank or somewhere completely different. The first will require you to take off the unit. If the thermostat is elsewhere it really needs someone who understands things to take a look to find it.

Can you confirm there is a heat exchanger in that unit. If you take off the 'radiator cap' you should see a number of small brass tubes running sideways beneath it. If there is just a large space, there is no heat exchanger core.

[Vicki Kanninchen]

I've checked all the filters and inlets several times and there's nothing obviously causing a blockage- plus there's still water coming out of the exhaust.

 

Someone suggested that I should have a look at the stack in the heat exchanger, so that might be my next port of call as I can do that without removing the whole heat exchanger... 

2 minutes ago, David Mack said:

 Can you confirm there is a heat exchanger in that unit. If you take off the 'radiator cap' you should see a number of small brass tubes running sideways beneath it. If there is just a large space, there is no heat exchanger core.

I'll need to drain off the coolant to have a look. Will get on that in the morning.. Thanks

[bizzard]

I reckon the thermostat fits ito the normal place beneath the heat exchangers 3 nuts, just an extention block to raise up the heat exchanger. The symtoms are thermostat failing to open. Of course there might not be one in there, if its been taken out, hence the dodgy nut, very ominous. There should be a bundle of tubes in the heat exchanger.

Edited November 12, 2019 by bizzard

[Tony Brooks]

20 minutes ago, bizzard said:

I reckon the thermostat fits ito the normal place beneath the heat exchangers 3 nuts, just an extention block to raise up the heat exchanger. The symtoms are thermostat failing to open. Of course there might not be one in there, if its been taken out, very ominous. There should be a bundle of tubes in the heat exchanger.

I agree about the location of the thermostat.

 

But Vicki says "The boat runs fine for about half an hour (until the calorifier has heated the hot water tank?), then the temp gauge invariably starts to creep up accompanied by an increasing amount of steam from the exhaust. Running the hot water tap sometimes brings the temperature back down temporarily. "

 

That does not suggest a thermostat jammed shut to me but does suggest a loss of raw water. I think that we can ignore the running the hot water off part because that would provide additional cooling to the engine until the calorifier stops taking heat from the engine coolant.

 

The question is "why is sufficient raw water flow lost". To diagnose much further requires far more info than we have like what is the raw water intake. If this has only stared since leaf faThe boat runs fine for about half an hour (until the calorifier has heated the hot water tank?), then the temp gauge invariably starts to creep up accompanied by an increasing amount of steam from the exhaust. Running the hot water tap sometimes brings the temperature back down temporarily. ll then I suspect leaves (or bread wrappers etc.) being sucked over the intake hole/fitting.

 

Note she gives no indication about the quantity of water coming from the exhaust when the problem occurs. Because of he increase in steam I suspect the water flowing form the exhaust is reduced and if so that would be more indicative of a raw water failure than the thermostat.

 

We also have no info about the speed and power being produced when this happens. As I said de-laminating exhaust hose can cause the symptoms and at first it only tends to happen at higher speeds and powers.

 

As long as the two large O rings under the heat exchanger end caps will still seal it will not hurt to inspect the core for blockages but I would expect that not to cause an intermittent fault. The area that will collect debris is under the cover that has the two hoses in the photo attached to it. The two large hoses SHOULD only be carrying raw water so as long as the inlet tap is turned off no they will self drain when the end cap is removed. Unfortunately there is a long brass rod fixed in that end cap and its is secured by the nut on the other end cap. If care is taken to minimise the disturbance of the  O rings there is no need to drain the engine coolant. Some will leak out but the maximum will be the heat exchanger full because its above engine head level.

 

If it is speed and power related then maybe the Jabsco (brass raw water pump) impeller has broken or badly worn teeth so its pumping enough at low speeds to cool but not enough at high speed.

Edited November 12, 2019 by Tony Brooks

[David Mack]

49 minutes ago, Vicki Kanninchen said:

 

Someone suggested that I should have a look at the stack in the heat exchanger, so that might be my next port of call as I can do that without removing the whole heat exchanger... 

I'll need to drain off the coolant to have a look. Will get on that in the morning.. Thanks

You shouldn't need to drain the coolant. Just take off the cap (when the engine is cold) and look down inside. A torch might help.

[Tony Brooks]

1 minute ago, David Mack said:

You shouldn't need to drain the coolant. Just take off the cap (when the engine is cold) and look down inside. A torch might help.

That is not what the OP meant. Raw water passes through the tubes so debris collect at the inlet side of the tubes. This will be under half of the end cap with the big hoses on it. Looking at the outside of the tubes proves nothing. On salty water boats they sometimes have to "rod through" each tube but    I have not had to do it on inland craft.

[David Mack]

 

The other possibility is that the raw water pump is failing. This is probably a Jabsco or Johnson impeller pump, likely to be belt driven. If this has lost some of the impeller blades that could account for reduced raw water flow. What does the pulley in the first photo drive?

 

2 minutes ago, Tony Brooks said:

That is not what the OP meant. 

But its what I meant. Just to prove that there is indeed indirect cooling, and that the raw water doesn't go around the engine.

[Tony Brooks]

10 minutes ago, David Mack said:

 

The other possibility is that the raw water pump is failing. This is probably a Jabsco or Johnson impeller pump, likely to be belt driven. If this has lost some of the impeller blades that could account for reduced raw water flow. What does the pulley in the first photo drive?

 

But its what I meant. Just to prove that there is indeed indirect cooling, and that the raw water doesn't go around the engine.

That is different and I agree. An easy check to ensure the core is in the case but knowing those heat exchangers I  don't know how the O rings will seal without the core ends to keep them in place. The O rind is thin for its size and sits around the  core end in a slight taper machined into the end of the body and then  the end cap pushes up against it. Without a core the ring would just push away into the body. There is no sign of a gasket or sealer in the photos.

 

The pulley in the first photo drives the raw water pump but there are three pump sizes - heat exchanger engines us the largest one - and one pipe usually comes from the raw water intake or gearbox oil cooler while the other goes to one of the connections on the neat exchanger end cap. The hoses on that cap look far larger than normal to me.

Edited November 12, 2019 by Tony Brooks

[Mad Harold]

Had overheating on my BMC 1.5 on my last boat.In my case the cover on the Jabsco water pump had quite deep grooves worn on the inside of the cover worn by the impellor.

The fix was simply to reverse the cover.The outside unworn face becoming the inner face.

[Tony Brooks]

8 hours ago, Mad Harold said:

Had overheating on my BMC 1.5 on my last boat.In my case the cover on the Jabsco water pump had quite deep grooves worn on the inside of the cover worn by the impellor.

The fix was simply to reverse the cover.The outside unworn face becoming the inner face.

A very common fault on older pumps but not usually intermittent but possibly power/speed dependant. Often the early signs is a refusal to self prime without a few more revs. However because of the number of pump types fitted this particular pump back plate may be one that uses a rear shaft bearing and on those the back plate is not reversible because it has a "nose" sticking backwards with a grease cap on it.

 

Any raw water pumps fitted with grease caps (can't see enough of this one) run the shaft in the pump body itself (plain bearing) and these are subject to wear in the body that gain prevents the pump priming but again not usually intermittent. All these pumps I have seen have a mini-stern gland where the shaft exits the pump and when the body is worn fitting new packing can hide the problem for a short while.

[Vicki Kanninchen]

Hi, in response to some of the points raised- the bottom of the coolant tank appears to just be flat inside. 

 

The water pump does have 2 little grease pots that lubricate the shaft- one of the grease pots was recently replaced, but there's still a pretty consistent drip from the shaft. 

 

I had an engineer come and look at the issue in July- at which point there was no water at all coming from the exhaust. He said the impeller blades were fine and diagnosed the issue as being caused by a blockage in my oil cooler which he cleared. After this the exhaust started spurting water again and everything seemed fine initially. But after a few hours cruising the overheating issue came back although water still came from the exhaust. 

 

I'm guessing the next step is going to be to check under the end cap of the heat exchanger as suggested.... 

Edited November 13, 2019 by Vicki Kanninchen
Grammar

[David Mack]

What filter(s) do you have on the raw water inlet?

[Eeyore]

2 hours ago, Vicki Kanninchen said:

Hi, in response to some of the points raised- the bottom of the coolant tank appears to just be flat inside. 

 

 

 

I'm guessing the next step is going to be to check under the end cap of the heat exchanger as suggested.... 

If the first statement is correct there is no tube stack, making the suggested action in the second statement pointless.

Use something soft such as a coffee stirrer or drinking straw to probe beneath the filler. If it goes to the bottom and can be moved side to side (as per the orientation of the photos) there is no tube stack. If it only goes in a short way there is probably a tube stack; moving the probe side to side will be a bit like the the cardboard that kids sometimes put into the spokes of their bikes.   

[Tony Brooks]

1 hour ago, David Mack said:

What filter(s) do you have on the raw water inlet?

Yes, I fear a high lever "Vetus" style one that are prone to leaking air into the system and stopping or reducing the raw water flow.

[Tony Brooks]

1 minute ago, Eeyore said:

If the first statement is correct there is no tube stack, making the suggested action in the second statement pointless.

Use something soft such as a coffee stirrer or drinking straw to probe beneath the filler. If it goes to the bottom and can be moved side to side (as per the orientation of the photos) there is no tube stack. If it only goes in a short way there is probably a tube stack; moving the probe side to side will be a bit like the the cardboard that kids sometimes put into the spokes of their bikes.   

 

Since David Mack's post I have been trying to remember exactly how those heat exchangers are constructed and think there core may be in a sort of cast in tube so the base of it, through the filler cap, may well not show the tubes and probing as you suggest will not do any good either as the probe will just scrape the outside of the "tube". As I said I don't see how the end caps can seal without a tube stack. I think there should be a large engine coolant inlet on the bottom of the unit towards one end that leads into the stack space and then and an inlet from the main volume of the header tank at the other ends so coolant is forced to travel the full length of the stack.

 

 

[Tony Brooks]

2 hours ago, Vicki Kanninchen said:

Hi, in response to some of the points raised- the bottom of the coolant tank appears to just be flat inside. 

 

The water pump does have 2 little grease pots that lubricate the shaft- one of the grease pots was recently replaced, but there's still a pretty consistent drip from the shaft. 

 

I had an engineer come and look at the issue in July- at which point there was no water at all coming from the exhaust. He said the impeller blades were fine and diagnosed the issue as being caused by a blockage in my oil cooler which he cleared. After this the exhaust started spurting water again and everything seemed fine initially. But after a few hours cruising the overheating issue came back although water still came from the exhaust. 

 

I'm guessing the next step is going to be to check under the end cap of the heat exchanger as suggested.... 

It is almost certain that the leak indicates a worn pump body and shaft. Using the front greaser often seals it enough to get the pump priming but then during use the grease is dispensed so the pump sucks air. BUT most if not all narrow boats will have the pump well below the water level so I don't think this is the problem in this case.

 

It is a question of how much water comes from the exhaust when this happens compared with when the engine is hot and working but not overheating. You mentioned steam and on that sort of cooling system usually (but not always) indicates a loss or reduction in raw water flow.

 

Try not to disturb the rubber O rings when you take the exchanger end cap off, leave them stuck between the core and the main body if you can.

 

With this sort of thing it is often more satisfactory if a knowledgable member can have a look at the boat and tell us exactly what is going on and what you have/how its plumbed. I can well understand you may not want to broadcast you exact location on the internet but giving us some idea of the area may get you help. If you are within 20 miles or so of Reading I would be happy to have a look FOC and suspect MtB would as well.

[Vicki Kanninchen]

Hi- I'm currently moored in Victoria Park in Hackney. I appreciate this is probably a nightmare to get to for most, but if anyone local is happy to have a look then that would be amazing! 

[Tony Brooks]

Sorry, that's me out. I won't go anywhere near the Smoke.

 

After another night's pondering.

 

I still think it is most likely a raw water issue and in view of the intermittent nature and the symptoms but could well be leaves and/or wrappings being sucked over the raw water intake that then float away when you stop the engine and thus stop the suction. To a degree thsi depends upon where the raw water intake is located.

 

Giving further thought to the drip from the raw water pump.

 

If the raw water strainer is above the waterline so you can clean it without water flowing into the boat it is likely to look something like this:

 

It may or may not have the wing nut to secure the cap. This type are notorious for developing a poor seal  between cap and body and on the wing nut one around the thread and nut. Ignore this if your strainer is different. If the rubber cap seal or the O ring/soft washer around the thread are old they may well allow air to be drawn into the raw water system and thus reduce the cooling. Checking its clear could well allow a temporary seal that then fails after a while. It may also be why the engineer appeared to cure it for the problem only to come back again.

 

With a high level strainer a leaking pump gland might also allow the raw water system to drain down when the engine is stopped and not pump properly when running so despite what I said earlier about a pump being below the water line this needs keeping in the back of your mind until all other causes have been ruled out.

 

The above is conjecture based on the information available so can not be taken as n authoritative diagnosis.

 

MAKE SURE THE ENGINEER HAS NOT LEFT A HOSE CLIP LOOSE ON THE OIL COOLER because that will usually allow the  pump to suck air instead of water.

 

Its a good idea to check the heat exchanger for blockages. If there are any they will be at the end where the two hoses are fitted.

 

After that I need to know about the speed and power being demanded when the overheat happens and the comparative amount of water coming from the exhaust when it happens. Also does the exhaust develop a louder hissing sound and if the normal exhaust noise gets louder. This is because any partial blockage in the exhaust can prevent the pump delivering sufficient raw water. It usually shows at higher engine speeds, not tickover. The two most common causes for a partially blocked exhaust are a de-laminating hose (as I said) or a scaled up/furred up exhaust mixing elbow where the raw water is injected into the exhaust.

 

I hope someone offers help bit I fear the member in that location ma well be a professional engineer so it would be unreasonable to expect a freeby.

 

Only after we have ruled out a raw water problem should you start thinking about the thermostat.