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Thornycroft 1.8 BMC engine over heating after 15/20 mins with white smoke


BILLYBONGO

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Hi guys I’m no mechanic and a rookie took my old narrowboat out for a cruise today and after 15/20 mins the engine cap on the coolant part and white smoke started to get thicker. CAN ANYBODY HELP! It’s a raw water cooled, starts lovely runs lovely in idle and symptoms are happening whilst cruising. I bout it as a project boat and have totally started from scratch but work now is to get her running ready to move her  to Ashby Canal from the River Soar. Apparently it had a service November last year before a purchased her and has had a new mud filter! Water pump and alternator. Hope that helps! Sorry for long description ???

2734E664-48D2-4384-96A1-278F67FBED8D.jpeg

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Thanks

 

It is heat exchanger, some times called indirect raw water cooled with no sign of a sin tank so an airlock in the cooling system is not so likely.

 

How much water is coming out f the exhaust and how quickly after starting does the exhaust note change from a bark to more of a burble? This info will help us rule out a raw water system full or partial failure.

 

You have ensured the weed trap or mud box is clear of debris I assume.

 

Are you sure it is diesel smelling smoke and not a lot of steam. If it is steam then it points to a raw water failure, possibly a failed impeller in the brass raw water pump. I would like a photo of the front of the engine so I can identify the raw water pump.

 

With your system you can get the gearbox oil cooler or the heat exchanger core bocked with debris from the canal/river bt before investigating that sort f thing we need to establish if it is steam or smoke

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Do you mean the cap on the coolant part started to leak or blow water out? and was the white smoke from the exhaust? If so then the diagnosis is going to be cylinder head gasket or something very much like it. Pressure in the cylinder getting into the water system and pressurising the water so that it blows water out of the pressure cap and water entering the cylinder and coming out of the exhaust as steam. As a rookie mechanic its not impossible to fix but a reasonably savvy car mechanic would be useful to give advice and some things need to be correct. Its a fairly modern engine so if, for example, the head is cracked it is not the end of the world to replace. Good luck.    Edit, Tony knows more about these things than me so follow his advice above.

Edited by Bee
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2 minutes ago, Tony Brooks said:

If it is steam then it points to a raw water failure, possibly a failed impeller in the brass raw water pump. I would like a photo of the front of the engine so I can identify the raw water pump.

That would be my first guess too. 

 

I'd guess at a Jabsco on that style of Bowman cooler, but a photo would indeed help!

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4 minutes ago, TheBiscuits said:

That would be my first guess too. 

 

I'd guess at a Jabsco on that style of Bowman cooler, but a photo would indeed help!

Quiet likely if its steam but things like missing O rings from the weed trap, worn Jabsco pump body/seals or lose hose joints on the suction side would do it.

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Thanks guys Bees description is bang on, it start to blow water out ? and smoke comes out back!  I can get some more photos tomorrow but I think it’s a job for a mechanic! I was hoping to head off on my voyage next weekend! Doesn’t look like it ☹️ Thanks guys

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3 minutes ago, Tony Brooks said:

worn Jabsco pump body/seals

The thing I like about the jabsco pumps is that you can just flip the plate round and reseal it if you need to.  It was deliberate design as a "get you home from sea" feature.

 

It does help to have a spare impeller onboard though!

4 minutes ago, BILLYBONGO said:

Thanks guys Bees description is bang on, it start to blow water out ? and smoke comes out back!

Erm, you did open the stopcock for the raw water cooling before setting off didn't you?  If you don't open that tap the cooling water can't come through.

 

If that's what happened, you will definitely need a new impeller, and you want to buy 2 so you have a spare.

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8 minutes ago, BILLYBONGO said:

Thanks guys Bees description is bang on, it start to blow water out ? and smoke comes out back!  I can get some more photos tomorrow but I think it’s a job for a mechanic! I was hoping to head off on my voyage next weekend! Doesn’t look like it ☹️ Thanks guys

 

on the present information I can not agree with you.

 

is it smoke or seam from the exhaust?

 

How much water exits the exhaust with the engine running?

 

How quickly does the exhaust bark drop to a burble upon starting?

 

At present the symptoms may indicate a head gasket OR a raw water failure so the engine boils. We can not narrow it down until you try to answer questions asked.

 

I wlll check back in a while to see if you give the information requested ans then shut down for the night.

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Ok guys many thanks I will check mud box and weed impeller. I will also get you a photo Tony. Stock tap is on fully but I noticed a little little leak dripping from mud box. I will take all of your advice and check. Many thanks 

Ok will check tomorrow ?? Thank you all again 

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A raw water cooled engine does give out 'white smoke' as normal. It just depends on how much. Some posh boats have a separator - mine doesn't and has bee rinning for nearly 20 yeas now....

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40 minutes ago, OldGoat said:

A raw water cooled engine does give out 'white smoke' as normal. It just depends on how much. Some posh boats have a separator - mine doesn't and has bee rinning for nearly 20 yeas now....

Its the water being blown out of the coolant filler that is the main problem and wee are still trying to find out if it is boiling because of something like a head gasket or low coolant or boiling because there is a raw water fault. Actually very few if any of our heat exchanger boats on the fleet gave out much steam (white smoke) unless something was wrong.

 

This could even be a de-laminating exhaust hose creating sufficient back pressure to force the Jabsco wings back. and thus reducing raw water flow but without answers to the questions I have now asked twice there is no way of knowing.

1 hour ago, BILLYBONGO said:

Ok guys many thanks I will check mud box and weed impeller. I will also get you a photo Tony. Stock tap is on fully but I noticed a little little leak dripping from mud box. I will take all of your advice and check. Many thanks 

Ok will check tomorrow ?? Thank you all again 

Don't bother with the photos unless you answer the questions I asked. Only once it looks as if it might be a Jabsco pump problem will a photo be much use.

 

The raw water pump (Jabsco) may be driven by a separate belt, if so is the belt in place?

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8 minutes ago, Tony Brooks said:

without answers to the questions I have now asked twice there is no way of knowing.

He did say he would post pictures tomorrow Tony.

 

He probably does not know the answers as it's a new-to-him boat, but we can help him find them over the next few days.

 

1 hour ago, BILLYBONGO said:

I noticed a little little leak dripping from mud box

That's enough of a leak to drain the pump housing that holds the impeller (the rubber fan that pumps the water).  If it gets dry, it rips itself apart with heat and friction (the raw water cools the blades), and you can get blades off it stuck in hoses that stop water coming through.  Been there, done that, got the T-shirt!

 

That sounds like what is happening to me - the 15 minutes or so is just long enough for the engine to heat up, and you are getting steam off the coolant.  Note that keeping doing this without fixing it will damage your engine if you keep running it without fixing it. 

Edited by TheBiscuits
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My boat is direct raw water cooled  and I have a few suggestions as to where to look to solve your problem.

Inlet strainer. Blocked or partially blocked.

Water filter ditto.

Weed can block the pipes leading to the water filter and from the water filter to the water pump especially if there are 90 degree joints in the pipework anywhere.

Pump impeller worn out.

Heat exchanger full of silt.

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11 hours ago, TheBiscuits said:

He did say he would post pictures tomorrow Tony.

 

But he made no reference to the questions apart from saying the drip from the mud box and confirming the two symptoms he originally gave us. How much effort would it have been to say from the start "I don't know the answers to those questions but will answer them tomorrow after I have checked on the boat".

 

Instead he talked about getting a mechanic out to take the head off. As a few of us had indicated it could simply be a raw water issue that action may be a waste of money.

 

We were all beginners at one time so know there is a lack of knowledge and questions can't be answered immediately sometimes but if only the OP and so many others would tell us. Pictures will only identify how the  raw water pump is driven and if it is of the type that has the reversible back plate. Not all heat exchanger pumps on BMC 1.x engines use that style of pump. Some have an extension on a cast rear plate to form a rear shaft bearing. To attempt any further diagnosis needs much more in the way of symptoms.

 

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28 minutes ago, Tony Brooks said:

But he made no reference to the questions apart from saying the drip from the mud box and confirming the two symptoms he originally gave us. How much effort would it have been to say from the start "I don't know the answers to those questions but will answer them tomorrow after I have checked on the boat".

 

he talked about getting a mechanic out to take the head off. As a few of us had indicated it could simply be a raw water issue that action may Instead be a waste of money.

 

We were all beginners at one time so know there is a lack of knowledge and questions can't be answered immediately sometimes but if only the OP and so many others would tell us. Pictures will only identify how the  raw water pump is driven and if it is of the type that has the reversible back plate. Not all heat exchanger pumps on BMC 1.x engines use that style of pump. Some have an extension on a cast rear plate to form a rear shaft bearing. To attempt any further diagnosis needs much more in the way of symptoms.

 

With respect Tony he didn't.   Bee introduced that red herring.

 

I reckon its a simple raw water not circulating problem, if the OP would answer the question as to whether the exhaust is dumping water out we would be half way there.

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54 minutes ago, BILLYBONGO said:

All fixed checked what most people advices no water coming out back so I screwed water tap in instead of out! And all working again ha ha ha ha ha sorry to waste your time guys and thank you for your support 

Well done, We ave all done that sort of thing and most continue to do it occasionally.

4 hours ago, Boater Sam said:

With respect Tony he didn't.   Bee introduced that red herring.

 

I reckon its a simple raw water not circulating problem, if the OP would answer the question as to whether the exhaust is dumping water out we would be half way there.

Post 6 - "but I think it’s a job for a mechanic"

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23 minutes ago, Tony Brooks said:

Always keep an ear on the exhaust noise because when it gets louder and starts to bark a bit it means the raw water circuit has failed an dthe engine will soon overeat.

That's why raw water engines get too fat Tony. They over........

 

Never had one myself, was moored next to one in a marina, it was a pain in the butt every time he ran his engine it washed my stern with dirty water.

My present boat had a wet exhaust when I bought it, could never see the point so I dumped the pump and sealed the exhaust elbow up. It drew water from the weed hatch.

Now with the hospital silencer fitted I can't do it anyway, its not stainless.

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3 hours ago, BILLYBONGO said:

All fixed checked what most people advices no water coming out back so I screwed water tap in instead of out! And all working again ha ha ha ha ha sorry to waste your time guys and thank you for your support 

Glad you found the problem, but you will have probably damaged your impeller by doing that.  Get a new one and a spare before you need them.

 

I would check the one that's in the pump before running your engine anymore.

 

That's also why I changed the screwtap for a lever valve on my old boat.  You could see at a glance if it was open or closed.

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