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Vetus overheating. Or venting...


cheesegas

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Hi all. Asking for a boater moored next to me who has been stuck here for a while with engine issues, I've helped with his dodgy electrics and am more intrigued to learn about the engine, as it's different to mine, never seen a wet exhaust one up close. But also give him a hand of course... 

 

It's a Vetus P4.25 (Peugeot XD3P based), heat exchanger cooled with a water cooled exhaust manifold and wet exhaust. Starts very easily and runs with no smoke from the exhaust.

 

He bought it and hired a boat mover to get it from East London to Bristol, but the engine overheated a couple of days in so the mover scarpered with all his money and abandoned the boat. It's not known if it was run without water in the cooling system. He's since had an engineer look at it for lots of money, who replaced the muffler and all the exhaust tubing from manifold to skin fitting. I have doubts about the engineer though; he filled the system with plain water (didn't warn the owner to refill with antifreeze when it gets cold out) and left the new drive belt he fitted so loose the batteries weren't properly charging.

 

He also evidently didn't test the engine properly...and isn't returning calls now.

 

Anyway. Water intake screen is clear and has good flow, and a good amount of water is coming from the exhaust skin fitting. After about 5 minutes of idling the thermostat opens and water circulates around the heat exchanger's tank, with the cap off I can see the flow. After a further 5 minutes, the coolant cap's pressure relief valve lifts and it begins to vent coolant. We stopped the engine at this point.

 

However, the raw water outlet pipe from the heat exchanger into the exhaust injection point on the manifold remains cold - as in, canal water cold. Is this normal? I'd have expected a bit of heat here at least. The coolant  in the heat exchanger is hot and filled almost up the base of the filler cap. Pretty sure it's not head gasket as the system doesn't pressurise as soon as it starts, and there's no water contamination of the oil. No expansion tank or temperature sender is fitted, and I can't accurately measure coolant temp.

My thinking is that the raw water side of the heat exchanger isn't clogged, as there's flow coming in and out. Must be the coolant side of the heat exchanger being clogged, preventing heat exchange to the raw water? It does however have the wrong coolant cap fitted; it's got stamped on it Made in England so I have my doubts, and the venting pressure is 13 psi. Vetus part number STM1017 (image attached) says the venting pressure for this old style of metal cap is even lower though, at 0.5 bar / 7 psi!

 

The new part which replaces the metal filler cap and neck vents at 1 bar / 14 psi which is close to the cap it has now.

 

Any ideas? Thanks.

stm1017.jpg

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Just now, Ex Brummie said:

If there is flow through the heat exchanger raw water side, then the problem has to be with the primary engine side. Is the engine water pump working?

Yep, that's what makes me think the coolant side of the tube which the heat exchanger sits in may be blocked. Engine water pump appears to be working, there's visible flow when looking down the coolant filler cap, and all the engine side hoses get uniformly hot. 

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If it's indirect raw water cooled, the tubes inside the heat exchanger may be a bit clogged. Not sure of the precise arrangement on a P4, but removal of the tube stack and cleaning is a normal service item on an indirect water cooled engine. The discharge water from the exhaust should be warm once the engine warms up, so the injection point should be likewise. (warm, not hot)

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Apart from a small bypass port or a larger one if this engine uses a bypass thermostat that allows the ENGINE (not the Jabsco raw water pump) water pump to circulate water around the engine when the thermostat is closed all the coolant flow should be through the heat exchanger. Just like the radiator in a car, so I don't see how you can have lots of water movement in the header tank and none around the heat exchanger tube stack. It is possible the header tank is a two pipe job allowing water to flow through that as part of the bypass circuit. (I don't know the either the marine or automotive version of this engine).

 

The amount of water flowing from the exhaust gives some idea about how well the Jabsco/Johnson raw water pump is working, just make sure there is lots flowing with the engine revving because although the exhaust is new the mixing point where the raw water enters the exhaust is known to fur up and restrict the exhaust flow at high speeds. This causes back pressure that in turn can reduce or even stop the raw water pump delivery. However when the happens the exhaust often produces more steam than usual and be more noisy.

 

Can you fit a length of clear plastic pipe between the exhaust injection point and the heat exchanger so you can see the water flow because I find the cold pipe to the exhaust very puzzling. I wonder if the header tank  is a bypass type and the main thermostat has failed closed. that would explain the given symptoms. The raw water circuit should flow freely all the time.

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As engine water can be seen to be flowing through primary side of the heat exchanger, and exhaust water can be seen to be flowing through the secondary side, yet heat is not being transferred from the engine water to the (cold) exhaust water, the only conclusion than can be drawn is the heat exchanger is contaminated with something insulating one side from the other.

 

The most likely candidate is water scale. My bet is the tubes in the heat exchanger are liberally coated with calcium and either a new heat exchanger is needed, or descale the existing. I suspect there might have originally been a coolant leak and constant topping up of the engine circuit with fresh water has lead to the primary side of the HE getting scaled. 

 

 

 

 

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These people are the 'experts' on marinising the Peugeot XD3 engines and can supply all the parts you need.

 

I have found them to be easy to talk to and give freely of their time to help out with problems. A 'proper customer orientated buisness'.

 

Price Book - Page 21 (lancingmarine.com)

 

Phone number on the top of the page in the link.

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5 minutes ago, MtB said:

As engine water can be seen to be flowing through primary side of the heat exchanger, and exhaust water can be seen to be flowing through the secondary side, yet heat is not being transferred from the engine water to the (cold) exhaust water, the only conclusion than can be drawn is the heat exchanger is contaminated with something insulating one side from the other.

 

The most likely candidate is water scale. My bet is the tubes in the heat exchanger are liberally coated with calcium and either a new heat exchanger is needed, or descale the existing. I suspect there might have originally been a coolant leak and constant topping up of the engine circuit with fresh water has lead to the primary side of the HE getting scaled. 

 

 

 

 

 

Certainly perfectly possible so worth pulling the core and having a look. If it s badly scaled then I would be tempted to immerse it in a domestic descaler like Limelight but don't know how it would affect the brass/copper/solder.

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5 hours ago, Iain_S said:

If it's indirect raw water cooled, the tubes inside the heat exchanger may be a bit clogged. Not sure of the precise arrangement on a P4, but removal of the tube stack and cleaning is a normal service item on an indirect water cooled engine. The discharge water from the exhaust should be warm once the engine warms up, so the injection point should be likewise. (warm, not hot)

Thanks, now I know to expect some kind of warmth on the raw water output. Canal water is pretty cold at the moment so I wasn't sure if the flow rate typically results in cold water. The raw water side of the heat exchanger is flowing fine, so it must be the coolant side which is outside of the tube. Apparently the tube stack was cleaned by the last engineer, but given the standard of his work this may not have been done. Removal is simple, two (hopefully not corroded!) Allen bolts on the end caps, and the tube stack pulls out. 

 

2 hours ago, Tony Brooks said:

Apart from a small bypass port or a larger one if this engine uses a bypass thermostat that allows the ENGINE (not the Jabsco raw water pump) water pump to circulate water around the engine when the thermostat is closed all the coolant flow should be through the heat exchanger. Just like the radiator in a car, so I don't see how you can have lots of water movement in the header tank and none around the heat exchanger tube stack. It is possible the header tank is a two pipe job allowing water to flow through that as part of the bypass circuit. (I don't know the either the marine or automotive version of this engine).

 

The amount of water flowing from the exhaust gives some idea about how well the Jabsco/Johnson raw water pump is working, just make sure there is lots flowing with the engine revving because although the exhaust is new the mixing point where the raw water enters the exhaust is known to fur up and restrict the exhaust flow at high speeds. This causes back pressure that in turn can reduce or even stop the raw water pump delivery. However when the happens the exhaust often produces more steam than usual and be more noisy.

 

Can you fit a length of clear plastic pipe between the exhaust injection point and the heat exchanger so you can see the water flow because I find the cold pipe to the exhaust very puzzling. I wonder if the header tank  is a bypass type and the main thermostat has failed closed. that would explain the given symptoms. The raw water circuit should flow freely all the time.

Thanks for the detailed reply. I pulled the raw water output hose off from the exhaust injection point and ran it for about 30 seconds, plenty of water coming out which increased with revs. I haven't run it much above idle. There's only four hoses going into the heat exchanger (raw water in/out, coolant in/out) so I don't think it's a bypass type. I haven't verified that the engine coolant pump is working - pulley is spinning and some movement can be seen through the coolant cap in the heat exchanger, but the impeller may have all but totally cavitated away so there's little water flow... However, the water in the header tank is hot but the raw water output is cold so something's not right in there. It has connections for a calorifier which is looped back into itself, I'll pull off the hose and see if there's water flow.

 

 

20 minutes ago, MtB said:

As engine water can be seen to be flowing through primary side of the heat exchanger, and exhaust water can be seen to be flowing through the secondary side, yet heat is not being transferred from the engine water to the (cold) exhaust water, the only conclusion than can be drawn is the heat exchanger is contaminated with something insulating one side from the other.

 

The most likely candidate is water scale. My bet is the tubes in the heat exchanger are liberally coated with calcium and either a new heat exchanger is needed, or descale the existing. I suspect there might have originally been a coolant leak and constant topping up of the engine circuit with fresh water has lead to the primary side of the HE getting scaled. 

Great, thanks - good to know that someone's arrived at the same conclusion as me! Heat's not being transferred across the heat exchanger from raw water to coolant. I'll suggest pulling the tube stack and seeing how the outside of the tubes look, it's not visible down the coolant cap. Good point on the scaling from using water, the history of this engine is unknown and it may have always had plain water in it. I certainly can't see any staining from antifreeze from the first time it boiled over.

 

 

16 minutes ago, Alan de Enfield said:

These people are the 'experts' on marinising the Peugeot XD3 engines and can supply all the parts you need.

I have found them to be easy to talk to and give freely of their time to help out with problems. A 'proper customer orientated buisness'.

Price Book - Page 21 (lancingmarine.com)

Phone number on the top of the page in the link.

Thanks, will pass on this info. I don't know how the last engineer made such a mess of it...his wiring was awful too, used a mix of speaker wire and 2 core mains.

Edited by cheesegas
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If the engine is not steaming from the filler cap but just pushing water out, are you overfilling the engine and its just expansion?  If the neck is new, is it the correct cap? Does it actually reach?

 

The XUD engines have a tiny bleed hole in the ally under the thermostat that had a habit of healing up and preventing air from bleeding out. There may be similar in this engine.  When this happened the engines rapidly overheated and eventually blew the head gaskets. I used to stick a 3mm drill through, solved it.

Edited by Tracy D'arth
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3 minutes ago, Tracy D'arth said:

If the engine is not steaming from the filler cap but just pushing water out, are you overfilling the engine and its just expansion?  If the neck is new, is it the correct cap? Does it actually reach?

I've got doubts over this too, the last bit of my original post mentions the tracing and research I've been through with the cap. It suggests that the original bayonet style cap is 4 or 7 psi, the new part number with the new screw style filler neck is 14 psi and the non-original current cap is 13 psi as it's stamped on the top. The filler neck looks original but the cap is not. And yep, the seal reaches and holds pressure - if I release it slowly with a warm engine, it vents. Its mating surface is clean and dent-free, and the rubber is in good condition.

 

As it's rated at close to the same pressure as the new cap, I don't think it should be venting. It's filled to just under an inch below the neck but it still may be expansion... The cold raw water output is concerning so we haven't run the engine for long after the cap vents. 

 

Thanks for the help!

16 minutes ago, Tony Brooks said:

The engineer may have just rodded through or just cleaned the raw water part of the tubes rather than having it out and descaling it as Alan suggests.

Yep that makes sense, owner says the cleaning was very quick so there's no chance he took the tube stack out for descaling. May have just done only a coolant flush...

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12 minutes ago, cheesegas said:

I've got doubts over this too, the last bit of my original post mentions the tracing and research I've been through with the cap. It suggests that the original bayonet style cap is 4 or 7 psi, the new part number with the new screw style filler neck is 14 psi and the non-original current cap is 13 psi as it's stamped on the top. The filler neck looks original but the cap is not. And yep, the seal reaches and holds pressure - if I release it slowly with a warm engine, it vents. Its mating surface is clean and dent-free, and the rubber is in good condition.

 

As it's rated at close to the same pressure as the new cap, I don't think it should be venting. It's filled to just under an inch below the neck but it still may be expansion... The cold raw water output is concerning so we haven't run the engine for long after the cap vents. 

 

Thanks for the help!

Yep that makes sense, owner says the cleaning was very quick so there's no chance he took the tube stack out for descaling. May have just done only a coolant flush...

What happens if you run the engine with the cap off and keep topping it up as the water goes down?  Have you got all the air out of the engine circuit bearing in mind that it includes the calorifier? Warming air up causes a bigger expansion than warming water up.

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Just now, Tracy D'arth said:

What happens if you run the engine with the cap off and keep topping it up as the water goes down?  Have you got all the air out of the engine circuit bearing in mind that it includes the calorifier? Warming air up causes a bigger expansion than warming water up.

Ran it with a warm engine, thermostat open and cap off and the water rose up until it came out the filler neck. Good point, didn't think of an airlock in the system! The air heating up might be expanding and pushing the water out the cap. I haven't drained the coolant since the engineer visited so he may not have bled the system properly. I'll advise bypassing the calorifier with a bit of hose, draining the coolant and refilling. Thanks.

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46 minutes ago, cheesegas said:

Yep that makes sense, owner says the cleaning was very quick so there's no chance he took the tube stack out for descaling. May have just done only a coolant flush...

 

May have just taken the inlet rubber boot off where debris usually build up and left it at that.

 

Re Tracy's input. There are long and short neck pressure caps and both can  be set to the same pressure so pressure is not the deciding factor. If you can just drop the cap into place and turn it then it is a short neck cap in a long neck. If you then have to push down so you can twist it into place it is the correct cap. It is correct about trapped air.

 

1" below the filler neck should be fine for a heat exchanger cooled engine, it should not "boil over". The coolant capacity is known and the expansion tank should be sized to allow for the expansion but not if there is trapped air.

 

The pressurisation only has an effect on engines working hard long so for canal use a 1 psi difference in cap pressure is absolutely nothing. I doubt this has anything to do with the cap pressure.

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38 minutes ago, Tony Brooks said:

May have just taken the inlet rubber boot off where debris usually build up and left it at that.

 

Re Tracy's input. There are long and short neck pressure caps and both can  be set to the same pressure so pressure is not the deciding factor. If you can just drop the cap into place and turn it then it is a short neck cap in a long neck. If you then have to push down so you can twist it into place it is the correct cap. It is correct about trapped air.

 

1" below the filler neck should be fine for a heat exchanger cooled engine, it should not "boil over". The coolant capacity is known and the expansion tank should be sized to allow for the expansion but not if there is trapped air.

 

The pressurisation only has an effect on engines working hard long so for canal use a 1 psi difference in cap pressure is absolutely nothing. I doubt this has anything to do with the cap pressure.

This heat exchanger doesn't have rubber boots - they're alloy caps to reduce the 3" dia to 1" of the hose, manual says there's an allen bolt inside in direct contact with water which clamps it on. Bet it's seized solid as well, hence it not being removed...

 

Sorry, think you missed what I put above, it's been a fast thread! (thanks for all the replies). The cap is sealing properly, rubber against the seat and it holds pressure, it's got to be pushed down against the spring. If I release the cap with a warm engine, once the rubber seal unseats, it vents so pressure's being held fine. And yep, agreed that 1 psi is nothing, I was just comparing the current cap to the original cap. Although the new part number for this same engine states a venting pressure of double...wonder why it was changed.

 

There's no expansion tank fitted to the system, although the Vetus manual says it should have one. Looks like two styles of OEM cap available, one without a pressure relief valve and one with (the type fitted to this engine), so I'm guessing the valveless ones are for the installations with an expansion tank.

 

Will check for air locks and report back... If that doesn't work, I hope he finds a good engineer, I don't want to go pulling his heat exchanger apart only to strip bolts etc when it's not my engine. 

Edited by cheesegas
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1 minute ago, cheesegas said:

This heat exchanger doesn't have rubber boots - they're alloy caps to reduce the 3" to 1" of the hose, manual says there's an allen bolt inside which clamps it on. Bet it's seized solid as well.

 

Sorry, think you missed what I put above, it's been a fast thread! (thanks for all the replies). The cap is sealing properly, rubber against the seat and it holds pressure, it's got to be pushed down against the spring. If I release the cap with a warm engine, once the rubber seal unseats, it vents so pressure's being held fine. And yep, agreed that 1 psi is nothing, I was just comparing the current cap to the original cap. Although the new part number for this same engine states a venting pressure of double...wonder why it was changed.

 

There's no expansion tank fitted to the system, although the Vetus manual says it should have one. There's two styles of OEM cap available, one without a pressure relief valve and one with (the type fitted to this engine), so I'm guessing the valveless ones are for the installations with an expansion tank.

 

There must be some kind of hearer or expansion tank, even if it is just headroom in a water cooled manifold. I think your guess is correct.

 

That venting over makes me think you have air or gas in the system and if it is gas I fear for the head gasket.

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9 minutes ago, Tony Brooks said:

There must be some kind of hearer or expansion tank, even if it is just headroom in a water cooled manifold. I think your guess is correct.

 

That venting over makes me think you have air or gas in the system and if it is gas I fear for the head gasket.

Thanks. Definitely no expansion tank at all in the system so it must rely on headroom in the manifold, using it as a header tank.

 

Image of the engine below, it's the same model in a different boat. Just the one cap on the combined header tank/manifold. Just realised I may be using the wrong terminology for this sort of thing, I'm from a car background!

50631-25.jpg

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Thanks all, think this is solved.

 

Drained the system, bypassed the calorifier and refilled carefully to avoid airlocks. Still cold raw water from the heat exchanger, but at least the water level wasn't increasing with heat now. It still vented from the cap after 20 min of idling though.

 

Removed the tube stack - the two allen bolts sheared as soon as any pressure was put on them as predicted. Luckily, they thread into the tube stack assembly and not the block. Got it out after a lot of whacking with a mallet and bit of wood, and the coolant side is completely blocked with crud and scale. Given the sheared bolts and state of it, he's ordered a new heat exchanger. As it's Vetus it's £££ but it should solve the overheating.

  • Greenie 3
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24 minutes ago, cheesegas said:

Thanks all, think this is solved.

 

Drained the system, bypassed the calorifier and refilled carefully to avoid airlocks. Still cold raw water from the heat exchanger, but at least the water level wasn't increasing with heat now. It still vented from the cap after 20 min of idling though.

 

Removed the tube stack - the two allen bolts sheared as soon as any pressure was put on them as predicted. Luckily, they thread into the tube stack assembly and not the block. Got it out after a lot of whacking with a mallet and bit of wood, and the coolant side is completely blocked with crud and scale. Given the sheared bolts and state of it, he's ordered a new heat exchanger. As it's Vetus it's £££ but it should solve the overheating.

 

Thanks for the feedback. So much for the mechanic claiming he had cleaned the stack.

 

It may be worth seeing if he can get a 60C to 75C thermostat so the engine runs cooler, which lessens the chnace of scale formation. That is why direct raw water cooled automotive engines tend to run with low temperate thermostats. It also sounds as if previous owners have been over filling the engine long term so have kept on introducing more lime in to the coolant.

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Yep, it sounds like this was an ongoing issue, maybe caused by a poor coolant loop design which was impossible to bleed. Turns out the calorifier is at the front of the boat with garden hosepipe going to/from it, probably an 80ft round trip. I reckon air in the system continually caused it to boil over out the cap, they kept on adding plain water and it eventually scaled up the tube stack. There's no paint around the cap either, a clue it's been happening for a while. The boatmover then wasn't aware of it and didn't refill properly, so it overheated.

 

The mechanic must have only flushed the raw water side of the tube stack, there's no way to rod through it with the alloy end caps bolted in place. Or he plain lied and didn't do it at all!

 

Thanks for the tip on the thermostat, I'll recommend it!

Edited by cheesegas
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It may well be possible to descale the tube stack rather than buy a new one. 

 

Scalebreaker or FX2 from Kamco Ltd is very effective at dissolving scale if you can devise a way of pumping it though/over the scale for an hour or two. Immersion simply doesn't work, it needs to be pumped around or through. A plumber's power flushing pump is the ting to borrow or hire. 

 

https://kamco.co.uk/kamco-descaling-chemicals.html

 

Beware of the Scalebreaker HD, it's vicious and evil. I think it is sulphuric acid but I don't know for sure. The vapour from it is painful to breathe and just the vapour will corrode through stainless steel. DAMHIK. 

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A the stack is out of the engine I would put it in a bowl or bucket (one end at time if necessary) and soak it  in a domestic descaler for a first try because I am unsure how a stronger acid would affect the  brass. copper and solder in the stack. it might just take longer than a more powerful product. If I could be sure i think Brick  Cleaner would do the job. I think that is somewhat dilute hydrochloric acid.

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