Skin Tank / Overheating Advice, Please

[John Orentas]

Alan.

 

You should be able to do a bit of investigation, the two 90 deg. BSP fittings look as if they will screw out of the tank, you can then poke about with lengths of wire and confirm your ideas of how it should be, and I agree with all you say about that. But I still maintain that ideally the water must be encouraged/forced to flow close to the canal side of the tank as well as diagonally opposite.

 

To re-cap, your previous thread clearly implied that water is circulating (the tank would not get hot at all if it wasn't) the fact that the inlet and outlet pipe were at the same temperature means for one reason or another the cooling tank isn't working.

[alan_fincher]

Alan.

 

You should be able to do a bit of investigation, the two 90 deg. BSP fittings look as if they will screw out of the tank, you can then poke about with lengths of wire and confirm your ideas of how it should be, and I agree with all you say about that. But I still maintain that ideally the water must be encouraged/forced to flow close to the canal side of the tank as well as diagonally opposite.

 

To re-cap, your previous thread clearly implied that water is circulating (the tank would not get hot at all if it wasn't) the fact that the inlet and outlet pipe were at the same temperature means for one reason or another the cooling tank isn't working.

 

John,

 

I've done some furthur investigation today

 

(Or more accurately I have dismantled a whole heap of things, which I'm not sure I have the skills to put back together, and have left the poor old engine and engine room in a Goddam mess!.....)

 

As you suggest, the 90 degree elbows did twist off with a bit of brute force, although quite a struggle.

 

Returning to my picture....

 

Skin Tank Connections

 

Then the left hand connection, (Hot water from engine to tank), simply connects to the tank, with nothing extending inside, whereas the right hand connection, (water that should be cooled, back to engine), extends down inside the tank to within 2 or 3 inches of the bottom.

 

But here's the (major!) rub.....

 

There appears to be no internal baffles at all ! It's rather hard to poke anything sideways through the left hand hole, but certainly you can poke something downwards the whole depth of the tank !

 

To be honest, I'm amazed that the boat has been this way for the last 10 years, and apparently reasonably loved and looked after, (so presumably cruised ?).

 

I'm also kind of surprised that we have managed a day in the summer, soon after we got her, where we did some 22 miles and 36 locks more or less without pause, and with no issues.

 

I'm still struggling to believe that's possible, and yet the other day we couldn't get 3 miles - but anyway we clearly the decision we have already taken to get a new tank on the outside seems pretty essential.

 

But I now fear there must be something else wrong too.

 

So, whilst drained, I also have the stat and the water pump dismantled at the moment, as people keep coming back to these. These look OK to my untrained eye, and the stat seems to open at around it's marked temperture, (74 degrees) - although I may change it anyway (see a separate post).

 

Finally there does seem to be a lot of internal rusting in the engine behind where the pump is off. I'm not used to peering in holes like this, so how concerned should I be about this, please ?

Edited October 22, 2005 by alan_fincher

[John Orentas]

Alan.

 

I take your point entirely that why should the system suddely decide to misbehave when it has apparently worked satisfactorily for ten years, all we can do is look for a few clues and accept that minor physical changes can make a very big difference in performance. But is that presumption correct anyway, somebody didn't go to the trouble of making and fitting that extra cooling tank just for the fun of it. It may have had some effect whilst there was a reasonable thermal contact with the base-plate.

 

Some very minor change could have made the coolant decide to travel along the side of the tank inside the boat instead of the outside.

 

Did you say you have painted the hull recently, a nice insulating layer of bitumen!

 

Could those pipes have been changed around recently, though it could be argued that in the absence of baffles it work better as it is.

 

You can safely ignore the rust in the engine, as long as you use an anti-freeze it won't get any worse.

 

I admire your Sherlock Holmes spirit but you may have to accept at some stage that the design of your keel tank is not correct and a thousand others which perform reliably decade after decade are correct.

Edited October 22, 2005 by John Orentas

[alan_fincher]

Alan.

 

I take your point entirely that why should the system suddely decide to misbehave when it has apparently worked satisfactorily for ten years, all we can do is look for a few clues and accept that minor physical changes can make a very big difference in performance. But is that presumption correct anyway, somebody didn't go to the trouble of making and fitting that extra cooling tank just for the fun of it. It may have had some effect whilst there was a reasonable thermal contact with the base-plate.

 

I admire your Sherlock Holmes spirit but you may have to accept at some stage that the design of your keel tank is not correct and a thousand others which perform reliably decade after decade are correct.

 

John,

 

Many thanks for sticking with this one....

 

I completely accept the tank is crap. We have already decided to go the route of a new one built on the outside, so what I've discovered today only goes to support that decision.

 

By the way, I'm not the one who ever had an added extra tank - that was another poster. Nor have I had any blacking done on her - yet. In fact we have changed nothing.

 

As the engineer can't tackle the boat for a week or two yet, we had hoped to keep using her - but it seems we are snookered on that, sadly.

 

So all I'm now trying to do at the moment is to investigate as many other things as possible to try and avoid finding it still boils even with a more sensibly designed tank.

 

I didn't think it was pump or stat, but it seemed sensible to look. Or so I thought, until I tried to get the stat housing off! There is a ridiculously short hose from the stat cover to the header tank, (just about visible in the picture, despite the forum logo trying to obscure it!), and its not obvious how to lift the stat cover off it's studs without wrecking the hose. (I think I probably have ). Perhaps someone knows the trick to this but I found it a real pain.

 

The one thing I really don't feel confident about proving or disproving is head gasket failure, without access to any test gear.

 

Any suggestions on trying to eliminate that would be gladly welcomed, (assuming I can reassemble all that which I have so far dis-assembled )

 

Alan

[alan_fincher]

In case it makes things any clearer, here's a photo of current arrangements now I have cut back the plywood that was obscuring the top of the tank.

 

Link to revised picture

[Speedwell]

The one thing I really don't feel confident about proving or disproving is head gasket failure, without access to any test gear.

Alan, Why so reticent about replacing the head gasket ? It's not a very difficult job if you have a decent set of spanners. The hardest part is usually getting the water out and you seem to have had some experience of that. Head gaskets are not very expensive (about £20) and you could check for cracking at the same time. If you do take the head off, don't expect to see anything spectacular or your problems wouldn't be intermittent. My experience with Skodas is that the leak path is scarcely discernible. For cracking, check for a very tiny crack between valve ports.

Arthur

[alan_fincher]

Alan, Why so reticent about replacing the head gasket ? It's not a very difficult job if you have a decent set of spanners.

 

Arthur

Arthur, thanks,

 

I suppose it's just that I don't feel confident about taking things apart to that degree - I certainly haven't done more than remove small external parts from engines in the last 30 years!

 

But you may have a point - and it's not exactly a hight tech engine, I guess

 

Although you say "if you have a decent set of spanners", I'm assuming as a minimum I'd need things like a torque wrench to retighten things sensibly afterwards... Correct ?

 

What else would I require, and how much else am I likely to disturb whilst removing the head, please ?

 

(Sorry if these are uneducated questions, but I really haven't studied the task too well up until now...)

Edited October 30, 2005 by alan_fincher

[John Orentas]

Arthur.

 

Where has this head gasket stuff come from, if Alan's boat had a blown gasket there would be ample symptoms but there are non. It certainly isn't a job you would undertake 'just in case'.

[alan_fincher]

Arthur.

 

Where has this head gasket stuff come from, if Alan's boat had a blown gasket there would be ample symptoms but there are non. It certainly isn't a job you would undertake 'just in case'.

John,

 

Perhaps others will correct me if they disagree, but I got the impression that some people feel this would account for the apparently intermittent, but progressively worsening of the situation.

 

Presumably, if failing, it may not behave identically each time, but will tend to get worse rather than better?

 

My understanding is that if exhaust gasses are getting into the coolant, (rather than being blown hot out of the exhaust pipe), this means an already inadequate cooling system is more likely to boil over, as extra heat is being introduced over what would be there without such a failure.

 

I have borrowed a chemical tester from Mike, who has also posted in this thread, in the hope that I can investigate this possibility rather more simply than stripping things down because it might be head gasket. I've yet to have an opportunity to try the test, though.

 

Additionally, I'd very much welcome a quick recap from you, on symptoms you'd expect to see if my problems were reated to gasket failure, (or to cracks in head or block).

 

What I can say is there appears to be nothing visibly unusual about the oil, (not drained, but that on the dipstick looks OK), nor any obvious signs of oil in the coolant, (although for a failure between exhaust port and cooling, I guess there might not be??)

 

What else might I expect to see, please ?

[John Orentas]

Hi Alan.

 

It is impossible to rule anything out but generally speaking a blown head gasket or cracked block or head would I think have rather different symptoms from the ones you are experiencing. Firstly most 'leakages' will be from the combustion chambers to, the water jacket, or via cracks into the exhaust or inlet tracts, all leaks on a diesel engine will cause misfiring and the engine will run generally 'rough'. As the pressures in the combustion chambers is so very much higher than in other areas leakage will be in only one direction (pressure in the cylinders at time of injection typ. 300 psi, immediately after combustion typ. in excess of 1,000 psi).

 

Leakage into the water jacket will take with it fuel and oil which will be evident in the water and gasses blown into the coolant will pressurise it and will give the impression of boiling. Leakage into other areas perhaps through cracks between valve seats will have less evident symptoms but will result in rough running or may even cease firing on one cylinder, probably getting worse as the engine reaches a higher temperature.

 

Going back to one of your earlier comments, I am certain that all types of thermostat when fully open will allow coolant circulation through all the engine unobstructed to the keel tank.

[rayman]

these heads are WELL known to go down,have a go at the job,buy a haynes manual but, don't refer to it too much. only when you really need it.just get your timing right,it does look frightening, if you do it your self youll really buzz of it, it's a simple job, believe me, if i was your neighbour, it would be done ages ago , by the way,i'm with arther

[alan_fincher]

Hi Alan.

 

It is impossible to rule anything out but generally speaking a blown head gasket or cracked block or head would I think have rather different symptoms from the ones you are experiencing. Firstly most 'leakages' will be from the combustion chambers to, the water jacket, or via cracks into the exhaust or inlet tracts, all leaks on a diesel engine will cause misfiring and the engine will run generally 'rough'. .................

 

 

................but will result in rough running or may even cease firing on one cylinder, probably getting worse as the engine reaches a higher temperature.

 

John,

 

Thanks for staying with this - I really value the experience of yourselves and others....

 

All I can say, is that I don't think this engine is running in any way rough - just hot.

 

If there's roughness, or misfiring there, then I'm not experienced enough to notice.... (but an expert ear might disagree, of course!..)

 

Going back to one of your earlier comments, I am certain that all types of thermostat when fully open will allow coolant circulation through all the engine unobstructed to the keel tank.

 

I don't for one moment challenge the fact that when the thermostat is fully open there is an unobstructed path round the keel tank circuit. I totally agree EITHER of the stats will provide this.

 

What bothers me, if I fit a conventional stat, is that the ADDITIONAL bypass path within the engine is not being closed off when the stat opens.

 

This then presents two possible paths for any pumped water. Firstly, the long route through the fully open stat, and ther skin tank. But additionally a very short path (6 inches maximum) through the uncapped internal bypass in the engine block, (albeit much smaller diameter). I can't predict what percentage of the hot water from the engine will chose to go the skin tank route, but my guess is that it will be substantially less than 100%, with a significant amount going instead down the bypass, simply because it is so short, (and hence not being cooled in any way at all before it's re-pumped around the engine).

 

At the moment the original stat, (with the bit that closes the bypass) is back in, because I couldn't fault it when testing it whilst out, and I saw no reason to risk any heated water bypassing the skin tank, once operating temp is reached.

 

I now firmly believe that current water pump and stat are not in any way contributing to overheating - they were only taken out because it's a job I felt comfortable with, and a relatively easy way to remove two suggestions people had made from the list.

 

Now I've read some feedback from others, it's even possible that autumn leaves are the reason it's got hotter quicker on the last two trips. To me, they didn't seem significant - but I accept others may know better.

Edited October 30, 2005 by alan_fincher

[Speedwell]

Arthur.

 

Where has this head gasket stuff come from, if Alan's boat had a blown gasket there would be ample symptoms but there are non. It certainly isn't a job you would undertake 'just in case'.

 

John

It came from my original post on 26th Sept. I would have done it by now on a "just in case" basis as nothing else has been found and it's a lot cheaper than all that welding. Perhaps a different matter if I had to pay a mechanic to do it.

What I am thinking of would scarcely be considered a "blown" gasket, where the symptoms would be as you describe, but a minute leak path from the cylinder into the coolant. This would be the first stage in the gasket blowing and I suspect that gas only escapes in the high pressure of the firing stroke. The symptom of this, at least in a Skoda Estelle engine, is intermittent boiling, which is more likely to occur if one is a bit heavy footed with the throttle.

I've no experience of cracking, but I imagine the early stages of a crack could well behave similarly. In my working days, I have known cracks that were so tight even crack detecting ink couldn't get into them.

Arthur

[Speedwell]

Arthur, thanks,

I suppose it's just that I don't feel confident about taking things apart to that degree - I certainly haven't done more than remove small external parts from engines in the last 30 years!

But you may have a point - and it's not exactly a hight tech engine, I guess

Although you say "if you have a decent set of spanners", I'm assuming as a minimum I'd need things like a torque wrench to retighten things sensibly afterwards... Correct ?

What else would I require, and how much else am I likely to disturb whilst removing the head, please ?

Alan

You're right about a torque wrench, but you'll only really need it for tightening the cylinder head nuts. You could probably borrow one but, if not, they're only about £15. You'll need sockets to go with the torque wrench and perhaps ring spanners. You'll certainly need a set of good open ended spanners as some nuts and bolts are not accessible to rings or sockets. I believe you said it was a BMC 1800 (same as mine) so all the nuts and bolts are AF sizes. You'll need a set of feeler gauges to reset your tappets and a large socket to fit the crankshaft nut to turn the engine over as you set the tappets.

As for disturbing things, you'll need to remove the exhaust pipe, the injector pipes, fuel supply and the alternator and probably a few more things that I have forgotten. Try not to remove the heat exchanger/exhaust manifold as this will give you some leverage when trying to move the head. Then it's just remove the rocker box, remove the rocker shaft complete, remove the pushrods, undo the head nuts, working from ends to centre, then a big heave and pull off the head. Try to have somebody standing by to put a bit of wood into the gap - mine fell back on to my finger which was very painful

You can get all the gaskets and parts (if any) from AMC diesel ( Same as Thornycroft) at Longton. They also sell the workshop manual. I have a workshop manual so I could photocopy relevant pages and post them to you if you email your address. Unfortunately, I have no scanner so I can't email pages.

Arthur

[alan_fincher]

As for disturbing things, you'll need to remove the exhaust pipe, the injector pipes, fuel supply and the alternator and probably a few more things that I have forgotten. Try not to remove the heat exchanger/exhaust manifold as this will give you some leverage when trying to move the head. Then it's just remove the rocker box, remove the rocker shaft complete, remove the pushrods, undo the head nuts, working from ends to centre, then a big heave and pull off the head..................

 

Arthur,

 

Thanks for all the advice, and offer of manual pages.

 

Whilst I'm sure this is an easy amateur job for many people, it sounds to go a bit beyond my current "comfort zone" for dismantling large lumps of iron and steel, I'm afraid. I'll turn my hand to quite a number of jobs, but although I have tackled worse mechanical engineering tasks many years ago, I'm really not feeling confident on this one, (yet at least!....)

 

By way of an update, another poster, Mike, has lent me his "Automotive Cylinder Head Combustion Tester" kit. This is basically a large bulb driven hand pump that sucks gasses out of radiator, (or header tank when used on a boat), and is supposed to turn a special blue fluid either green or yellow if exhaust gasses are present.

 

I got the engine fully hot, then tried this test for (at least) 10 minutes whilst it was being run pretty hard against it's moorings.

 

I'm not sure how conclusive such a test is, but it came up fully negative - no visible change of colour of the magic fluid...

 

From this I "conclude"....

 

Either

a) I don't have head gasket problems

or

If I do have head gasket problems, they are either intermittent, or relatively mild

or

c) I did the test wrong in some way, or not for long enough

or

d) Such a test can't be relied on anyway.......

 

Seriously though, if such a test is reliable, it hasn't turned up anything on my engine......

 

I'm also getting close to when the boat is supposed to be being slipped for a number of jobs.

 

One of these is still planned to be a new bigger, (but much flatter) skin tank built externally on the swim. I'm doing this because, whatever else may be wrong, it is pretty obvious that a 60 cm x 60 cm x 10 cm tank, with no baffles, would not be adequate for an engine of over 30BHP, if it were to be used in anger, (against a river, for example).

 

I'm not likely to try anything else major with the engine, until the skin tank work is done, (assuming engineer sticks to his dates...)

[Paul Evans]

From this I "conclude"....

Either

a) I don't have head gasket problems

or

If I do have head gasket problems, they are either intermittent, or relatively mild

or

c) I did the test wrong in some way, or not for long enough

or

d) Such a test can't be relied on anyway.......

Don't be pessimistic Alan! You've done the test and shown that there is no problem with the head gasket. My guess is that the new swim tank will solve your problem. The current one is definitely undersized and, by the sound of things, poorly designed. Good luck and keep smiling - you have to!

[alan_fincher]

Don't be pessimistic Alan! You've done the test and shown that there is no problem with the head gasket. My guess is that the new swim tank will solve your problem. The current one is definitely undersized and, by the sound of things, poorly designed. Good luck and keep smiling - you have to!

Paul,

 

I hope you are right !

 

I bargained for a certain amount of unexpected expense when I started, but I'd very much like to think there might be some bits I can leave untouched for a while.

 

Having said that, my wife and I managed a few superb hours on the boat yesterday, and I doubt I've ever seen better November weather. The trees along our local summit stretch looked spectacular, so if they are putting leaves around my prop occasionally, I think I'll forgive them

 

I only wish we could have carried on down the locks, and off into the sunset. One day, one day........

[Paul Evans]

You'll forgive lots for the sheer pleasure of boating! Lie back and enjoy.

[alan_fincher]

You'll forgive lots for the sheer pleasure of boating! Lie back and enjoy.

The boat seems to still be on target to get slipped at my marina next week.

 

By the end, the old internal skin tank should be history, and a new one should have appeared on the outside of the swim, at least doubling the current cooling area.

 

I'm still hoping that will be all I have to throw at this particular problem, but remain philosophical...

 

It should also have had other "out of water" jobs done, such as reducing the prop shaft length to give a more normal separation from stern tube, (and greater from rudder).

 

Alan

[alan_fincher]

The boat seems to still be on target to get slipped at my marina next week.

 

By the end, the old internal skin tank should be history, and a new one should have appeared on the outside of the swim, at least doubling the current cooling area.

 

Update:

 

The boat was finally handed back to us on Monday, following completion of various work by local engineer.

 

The one relevant to this post is a new external skin stank, on the outside of the swim, to replace the previous undersized and poorly designed one, (which has been cut out).

 

I had hoped to measure and photograph the replacement, but unfortunately the engineer put the boat back in the water sooner than he said he would, and I missed the chance.

 

But broadly new tank is about twice the surface area of the old, and a quarter of the thickness, (so only holds about half as much coolant). It is horizontally baffled with 2 baffles, making 3 compartments, with the water following an elongated 'S' shape. It is also plumbed so that air locks are far less likely, (I hope!).

 

And the result....

 

We took a trip out today, involving about 3 miles of summit, and then a flight of 7 locks. The temperature gauge at no point rose above the 70 degree mark, (although I suspect it's a tad inaccurate, as it's a 74 degree stat is fitted, and seemed to open at that temp when I tested it). We went to pub to celebrate , then did return trip, pushing it quite a bit harder than the kid-glove handling we have been giving it. The tempertature stayed rock steady at 70 degrees, again.

 

Moreover, the return pipe from the tank is now no more than luke-warm at the end of a trip, whereas with the old tank the inlet and outlet hoses seemed nearly equally hot.

 

Of course the fact that the ice had literally only just melted off the water means we were probably operating with more cooling effect than ever before anyway, but this still looks very encouraging.

 

At this time of year, I'm not sure when we will get to run it longer, (unless we miss the pub stop ), so it may be a while before we know definitively that we have no other problems.

 

Once we have a clear bill of health, I think I might consider changing the 74 degree stat to an 82 degree one, which seems to be the more common. Collective wisdom seems to say these engines probably run cleaner if run a bit warmer.

 

My extereme thanks to all who have contributed, and especially to Mike, who's "coolant gas tester" I now need to return to him....

 

Alan

[John Orentas]

Looks like good news Alan. I think the higher the temperature within reason the better.

Edited November 23, 2005 by John Orentas

[Paul Evans]

That's great news Alan. Now just enjoy your boating or - given the latest weather forecasts - look forward to enjoying it. But don't forget B-O-A-T stands for Bung Out Another Thousand.

[alan_fincher]

But don't forget B-O-A-T stands for Bung Out Another Thousand.

Paul - That's pretty damned accurate for that particular part of the work I had done, unfortunately

 

And overall, a great deal more than that , but has included sorting out a number of known areas on which I expected spend when I bought the boat. (Remaking weld between bottom plates, replacing a wooden hatch cover in steel, water tank refurb, adding drain holes to grab rails where low point of roof filled with water, shortening an overly long prop shaft, etc, etc).

 

Hopefully getting down now to jobs where you don't need to be a welder or a heavy engineer to tackle them - i.e. things I expect to do, and feel confident to do, myself.

[alan_fincher]

Re-opening this very old topic, just for completeness, and (hopefully !), final sign off.....

 

The boat has just had it's first really intensive use since the old skin tank was replaced by a completely new one of much more sensible design.

 

Prevevious tests with the new set-up have looked promising, but until now vno run has been long enough to be completely convinced the overheating problem has gone away.

 

But in a week long return trip from Hertfordshire to Braunston, the temperature has stayed rock steady, never rising above the operating temperature of the thermostat.

 

This bash has included some pretty long pounds where we didn't stop, as well as fairly high speed pushes north through both Blisworth and Braunston tunnels, (nothing encountered coming south in either on the outward trip, so we didn't exactly hang about!....).

 

Looks like we may have cracked it, although the mystery of how the previous owner endured 10 years with the old skin tank remains....