Expansion Tank for BMC Engine

[David Schweizer]

38 minutes ago, Mikexx said:

 

I thought skin tanks generally came in pairs?

In which case it would also depend how they are coupled.

There is also the angle of the skin tank from the horizontal given most boats are lower at the stern.

One skin tank is the normal arrangement, although I suppose that if you have very short swims, one on each side may be needed.

[WotEver]

3 minutes ago, David Schweizer said:

One skin tank is the normal arrangement, although I suppose that if you have very short swims, one on each side may be needed.

Or, as Tony B points out, if the builder made the original too small and you had to add a 2nd one. 

[Peugeot 106]

On 26/05/2017 at 15:57, Tony Brooks said:

You have to be a bit careful with extrapolating your experience to other boats and engines. I always say fill the header tank to full just once, run the engine well up to temperature and then let it cool. Whatever level the coolant  is then at is the correct level. This is in effect what you have done but I have been told about more than one Beta where the level drops so much air is allowed into the cooling system  and then into the skin tank. In those cases a separate header tank cured the problem.

I do wonder if this happening with my arrangement. I have a 2 cylinder engine with water cooled manifold and integral header tank, The overflow runs into a 2 litre milk bottle which I have marked with two lines to represent hot and cold. They are around 1 1/2" apart and under normal canal operation the level cycles between the two. Sometimes if I stop the engine and start again a couple of hours later the coolant remains above the cold level and I just tip the correct amount back into the radiator cap. If I run the engine at full throttle for a while eg the Ribble Link, River Trent, Severn Estuary the level in the bottle goes way up and doesn't get sucked back into the engine. I can then bleed air out of the skin tank. Am I correct in thinking that as with Tony's Beta air is getting sucked in and blowing the coolant out?

I haven't used any extra coolant in 10 weeks cruising but I do have to redistribute it from milk bottle to header tank. The temperature gauge never goes much above 85 Deg C. There are no leaks, I have replaced the Polar end caps/ outlets with welded plates. The radiator cap is new and correct. I have no reason to be suspect of the head gasket as I replaced it  it last year when investigating an oil leak. The coolant and oil are perfectly clear and the engine starts on the button without preheat. It has done around 800 hours with me probably not more than 1000 total. The overflow is a new 8mm bore fuel pipe and jubilee with the outlet always submerged in coolant so it shouldn't be losing vacuum

The attached sheet shows Beta solution to fitting a calorifier sited higher than the engine. I think it is plumbed into the top of the thermostat housing. Would this work for giving me a bit more expansion space and would gravity feed negate any problems with vacuum.

 

Its OK now for me but I do worry that if my daughter borrows the boat they will forget to redistribute the coolant

 

Apologies I can't find a way to rotate the images

[Tony Brooks]

5 hours ago, Peugeot 106 said:

If I run the engine at full throttle for a while eg the Ribble Link, River Trent, Severn Estuary the level in the bottle goes way up and doesn't get sucked back into the engine. I can then bleed air out of the skin tank. Am I correct in thinking that as with Tony's Beta air is getting sucked in and blowing the coolant out?

 

When hot the header tank would normally be full so can't suck air. If the pressure cap does not have a decent rubber seal between the top of the filler neck and underside of the cap it could suck air in as the engine cooled. If the water is not being sucked back into the header tank it can only be because either it is sucking air into the engine, possibly via a loose hose, water pump seal or filler cap, or gas is getting in some other way and that tends to suggest a slight head gasket leak when hot and under high power for long periods.

 

I have a feeling that fitting the expansion bottle may not produce the result you hope for and if you do so it will mean either drilling and tapping the thermostat housing or the top of the manifold. Doing it high up will help to give entrapped air an exit point.  However, if doing runs that you describe means the system needs pressurizing to prevent localized boiling inside the engine, so the expansion bottle will need a pressure cap of at least  6 psi and the one on the manifold needs to be of a higher pressure. In this layout it will not need a rubber seal immediately under the cap top.

 

 

[Peugeot 106]

Thank you Tony. I was intrigued by your comment about the Beta engine’s water level falling low so that air was sucked into the skin tank? With my manifold the header part is not very big ( it is short as it is only 2 cyLinder) so I wondered if this was possibly happening. I take your point that the manifold will be full when running as the coolant expands but maybe not if the engine is stopped after running hard and the coolant is not all sucked back when it is started again or the coolant isn’t redistributed from the overflow milk bottle to the manifold header tank

I realise that though there are no coolant leaks or losses this does not preclude suction leaks in the same system under vacuum. Although I doubt head gasket leaks would it be worth using a gas detector fluid test kin in the radiator cap? I had considered localised boiling but am not sure how I would detect it. The cooling passages in the head all look clear. The engine runs steadily at around 80 deg C which never really varies. 

The engine is overpropped and maximum rpm is 2200 so I treat max as around 2000. Plenty of these engines run continuously at 1800 rpm so i’ve discounted the water pump not sending enough water round. My pipework is all 32mm bore short runs sloping upwards no kinks or high spots. I’ve seen other similar engines with 19mm cooling hose trailing everywhere that seem to work. 

I saw the Beta expansion bottle and was hoping that this could give more expansion capacity to the system. Also it would gravity or pressure feed back into the engine rather than relying on vacuum. Plumbing it into the thermostat top should not be too big a problem as I know where there is a cap already tapped with a banjo connection.

could you possibly explain why the bottle only has a connection in the bottom as most expansion tanks seem to have two pipes?

I realise I am being wordy giving you as many details as I can. Questions are

1) what was the story behind the Beta engines sucking air in?

2) would it be worth carrying out a gas detector test?

3) if I have a slight intermittent suction leak causing breakage of the vacuum would the Beta expansion tank provide gravity feed

4) why does this Beta expansion tank system only have one pipe rather than the more familiar two pipe system

 

As I have said to the forum previously a little knowledge in my case is probably dangerous but I am interested in other more experienced opinions. The engine seems to work perfectly but I enjoy tinkering to improve it and am always aware of the randomness with which it expels hot coolant even if there has never been evidence of any engine overheating 

 

 

 

 

[Tony Brooks]

10 minutes ago, Peugeot 106 said:

1) what was the story behind the Beta engines sucking air in?

 

A dammed great thick skin tank so the volume of expanding coolant that was blown out when running was so great the cold level was well below cylinder head level so topping up tended to trap air.

 

3) if I have a slight intermittent suction leak causing breakage of the vacuum would the Beta expansion tank provide gravity feed

10 minutes ago, Peugeot 106 said:

2) would it be worth carrying out a gas detector test?

 

If it is cheap enough to do why not.

 

10 minutes ago, Peugeot 106 said:

3) if I have a slight intermittent suction leak causing breakage of the vacuum would the Beta expansion tank provide gravity feed

 

Probably, but you have not yet confirmed that your pressure cap has a rubber seal right under the top. If you are relying on the brass diaphragm sealing on the filler neck no wonder it tend to leak vacuum - and probably coolant as well.

 

10 minutes ago, Peugeot 106 said:

4) why does this Beta expansion tank system only have one pipe rather than the more familiar two pipe system

 

It is very tempting to give a truthful, but not helpful answer of "how the hell should I know", but that is exactly how all the early car plastic or glass coolant expansion tanks were done. I think the two pipe system where coolant circulates through the tank assist in venting ant air bubbles in the system.

[Peugeot 106]

44 minutes ago, Tony Brooks said:

 

A dammed great thick skin tank so the volume of expanding coolant that was blown out when running was so great the cold level was well below cylinder head level so topping up tended to trap air.

 

3) if I have a slight intermittent suction leak causing breakage of the vacuum would the Beta expansion tank provide gravity feed

 

If it is cheap enough to do why not.

 

 

Probably, but you have not yet confirmed that your pressure cap has a rubber seal right under the top. If you are relying on the brass diaphragm sealing on the filler neck no wonder it tend to leak vacuum - and probably coolant as well.

 

 

It is very tempting to give a truthful, but not helpful answer of "how the hell should I know", but that is exactly how all the early car plastic or glass coolant expansion tanks were done. I think the two pipe system where coolant circulates through the tank assist in venting ant air bubbles in the system.

My tank is around 1” thick so probably doesn’t qualify as a damned great thick skin tank though it could be thinner and could do with baffles. I used to work without the spill pipe being submerged in the milk bottle and it was fine most of the time though I do suspect that there is not enough expansion room in the header under some conditions

 

a combustion gas test is around £20 for a cheap test and I can afford it so will give it a go. The difficulty is finding somewhere to run the engine on full throttle without making myself very unpopular!

 

Apologies for not replying to this. I attach a picture of a spare pressure cap. It doesn’t seem to leak though there is no seal for the top of the neck only at the bottom. If that is the problem where would I get a large rubber washer from or if I have to make one what material and thickness do you suggest?

 

i’m glad You don’t completely understand the differences in coolant tanks and pipework arrangements. I spent quite a lot of time looking at explanations on the web and confess I could never really get my head round it! The Beta arrangement seems specifically to give a calorifier head but I was hoping it would operate as an expansion vessel too. If it used to be used on early cars that’s good enough for me. 

 

i hope you can bear with me. The washer under the pressure cap may be all that is required along with my milk bottle though a gravity fed expansion tank may give more assurance

 

[Tracy D'arth]

If there is a side spout in the filler neck you connect the expansion to that. Or blank it off.

Top seal on a pressure cap needs to be thin or you won't fasten the cap.

[Peugeot 106]

6 minutes ago, Tracy D'arth said:

If there is a side spout in the filler neck you connect the expansion to that. Or blank it off.

Top seal on a pressure cap needs to be thin or you won't fasten the cap.

I did think of that. I have already blanked off the inlets/outlet to the coolant connections to get rid of the Polar caps. I think it would need pretty major surgery to free the filler neck from the manifold and it could result in damage to the threads so that if I wanted to backtrack it would be impossible. It would also be difficult to fill the system with coolant unless I put the header tank on the deck which I don’t like. I’ve never seen a Lister manifold/header like mine so a replacement is probably impossible. I considered a used cast iron manifold without header but the only one I have seen is expensive and I suspect has suffered from heat damage and could be warped. At 2/3rd the price of a new one I may as well buy new.  A new one would be around£300 + bronze fittings. 

 

Maybe a header tank and washer on the cap is the way to go or even just a washer on the cap might demonstrate that it is an air leak causing the problem

 

 

I 

[Peugeot 106]

I have found some caps for vintage cars and tractors with the same rating and size. The ones with washers seem a few mm deeper. The washer looks fairly hefty nitrile I will apply with a spot of grease. I’ve got one on order. 

Thank you Tony and Tracy I had no idea that some have washers, some don’t but most importantly I need washers

[Peugeot 106]

6 hours ago, Tracy D'arth said:

If there is a side spout in the filler neck you connect the expansion to that. Or blank it off.

Top seal on a pressure cap needs to be thin or you won't fasten the cap.

I’ve been for a stagger in the heat and some thinking. If I port the side spout into the 

expansion tank, when the pressure is relieved in the manifold header tank will it not just build pressure in the expansion tank where it could build to an unacceptable level? Do I need a 7lbs cap on the expansion tank too to protect the engine rather than the Beta 21psi one. Or could I use a cap that vents permanently to atmosphere on the expansion tank as hopefully it will only be air being displaced. What did the old cars do when they gad a similar system?

 

[Tony Brooks]

41 minutes ago, Peugeot 106 said:

I’ve been for a stagger in the heat and some thinking. If I port the side spout into the 

expansion tank, when the pressure is relieved in the manifold header tank will it not just build pressure in the expansion tank where it could build to an unacceptable level? Do I need a 7lbs cap on the expansion tank too to protect the engine rather than the Beta 21psi one. Or could I use a cap that vents permanently to atmosphere on the expansion tank as hopefully it will only be air being displaced. What did the old cars do when they gad a similar system?

 

 

I think this topic may be going to confuse people looking for BMC information in the BMC section. Peugeot 106 seems to be discussing a twin pot Lister.

 

In view of what you say about running at high speeds then you would be foolish to run your engine unpressurised.

 

With an expansion tank you can pressurize in two ways:

1. With a plain cap with rubber seal on the manifold filler and pressure cap on the expansion tank (if it will accept one or is already fitted)

2. With a pressure cap on the manifold and an open vented cap on the new expansion tank but in this case you need a pressure cap with the seal under the top.

 

If you intend to feed the new expansion tank from the pipe on the filler neck then the manifold cap must have the seal under its top but it may ALSO need the full pressure cap mechanism in case of 2, above.

 

However, you pressurize the system the working pressure should be dictated by the engine manufacturer, so presumably Lister. If Lister specify a 7 psi cap then that is the pressure that you should run at. I doubt running a 10 psi would cause any problems but running a system designed for 7 psi at three times that pressure might cause the seal on the water pump, a core plug, hose or gasket to leak.

 

I think that I have been through all this before, I will not tell you what you should do because I don't have the data and as you have not fully identified the engine can not look it up (if Lister have online manuals).

 

 

 

 

 

 

[Peugeot 106]

LPWS2 Alpha 400 series Lister Petter

 

Thanks Tony i’m sorry but i’m still confused. I’ve been running with a 10lbs cap which I got to replace the 7lbs one originally fitted. I’ve bought 7 lbs ones as these are as

originally fitted but the marinisation manual says 15 lbs. The maintenance manual and parts list says 10 or 15lb depending on radiator. 

Am I right in thinking that the determining factor would be 7lbs for Polar rubbish rubber end caps, 10lbs for some radiators otherwise 15lbs will be fine?

 

What i’m thinking is that if I use the pipe on the filler neck the bottle will be the same as my milk bottle now where coolant siphons back in only it will be above the engine so that gravity will help as per your 2)

 

or I could leave the milk bottle as it is. A seal under the pressure cap should stop air  leaks when fluid is being pulled back into the engine which is almost certainly what has been happening.

 

BUT as you say I will source a cap with a rubber seal at the TOP of the rubber pressure cap

 

i will contact Sleeman Hawken tomorrow to see if there are any pressure restrictions on the engine

 

Very Many Thanks

 

[Tony Brooks]

9 hours ago, Peugeot 106 said:

Am I right in thinking that the determining factor would be 7lbs for Polar rubbish rubber end caps, 10lbs for some radiators otherwise 15lbs will be fine?

 

With the known weakness of the Polar end caps you may well be correct about the 7psi cap.

 

If you fit an expansion tank above the engine and do not ensure the pressure cap top is sealed to the neck there is every possibility that the tank will empty itself into the drip tray via the unsealed pressure cap.

 

If this were mine I would leave as t is and try a pressure cap with a seal under the top. I am sure that will be far cheaper than buying a Beta expansion vessel, and it may well work. I am also sure that you could find an automotive expansion tank for less cost that the Beta one.

 

9 hours ago, Peugeot 106 said:

Am I right in thinking that the determining factor would be 7lbs for Polar rubbish rubber end caps, 10lbs for some radiators otherwise 15lbs will be fine?

 

We are back to you asking someone to override a manufacturer's advice. I can not do that, but can say the 21 psi is right at the top of what one would find on vehicles with around 10 to 15 being more typical.

[Peugeot 106]

Thanks Tony that is exactly what I plan to do. I have asked Hawker Sleeman for the coolant pressure that my engine should see. 

 

The key key to all this is you telling me that there are two types of pressure caps and I realise that I have almost certainly been using the wrong one. (Saying that I am not absolutely certain that the cap I am using doesn’t have a seal under it but the spares I have at home don’t) My milk bottle with felt pen marks has worked fine but I will find a stronger bottle

 

I do wonder how much heart ache and money you have saved us all over the years

 

[Tony Brooks]

6 hours ago, Peugeot 106 said:

Thanks Tony that is exactly what I plan to do. I have asked Hawker Sleeman for the coolant pressure that my engine should see. 

 

The key key to all this is you telling me that there are two types of pressure caps and I realise that I have almost certainly been using the wrong one. (Saying that I am not absolutely certain that the cap I am using doesn’t have a seal under it but the spares I have at home don’t) My milk bottle with felt pen marks has worked fine but I will find a stronger bottle

 

I do wonder how much heart ache and money you have saved us all over the years

 

 

There are far more than two types of pressure caps. For a start long filler neck and short filler neck, then there are the screw on types.

 

Most standard ones use  a brass diaphragm bearing on the top of the filler neck to make some kind of very poor seal. Especially as the filler neck ages and seems to distorted. It was on;y when the single pipe expansion bottles but with the rubber seal.n bottles wee fitted on cars that the caps with a rubber seal under the top appeared. Probably the easiest way to get one is to take the old cap to an old school motor factors and  ask for one like this but with the seal

 

 

[Peugeot 106]

Thanks Tony I am aware of the different types. It was you telling me about the seal under the neck that suddenly made sense as it is obvious that the vacuum will be lost if it doesn’t seal there. I will be at the boat this week and will bring the cap back to make sure it fits. I note from the net that some caps with seals at the neck are a few mm longer presumably to account for the rubber seal. I am pretty practised at finding odd bits and bobs off the net and from agricultural and classic car merchants so am quietly confident. 

Hawker Sleeman have come back to me advising 11 psi with the Polar caps. I’ve told them i’ve ditched those can they confirm that all core engines are good for 15 psi. I’m pretty sure they are but an taking your advice to get it confirmed

Thank you again

PS I didn’t start a new thread as I thought that the cooling systems were similar and that my queries could equally apply to a BMC. I didn’t intend to hijack the old thread. Apologies if you think this has made it a bit confusing. I won’t mind at all if you want to move my bit to a new thread. I have read other people talking about an arrangement like mine but I don’t remember mention of a sealing washer so this may be useful to someone else

[Psychalist]

On 14/08/2022 at 13:57, Peugeot 106 said:

a combustion gas test is around £20 for a cheap test and I can afford it so will give it a go. The difficulty is finding somewhere to run the engine on full throttle without making myself very unpopular!

I commented in this thread that these test kits don't necessarily produce a conclusive result. I may have had a duff kit, but that was my experience when I did have a cylinder head gasket leak. I also mentioned my experience with loss of coolant. Apologies for the crossed threads.

[Peugeot 106]

5 minutes ago, Psychalist said:

I commented in this thread that these test kits don't necessarily produce a conclusive result. I may have had a duff kit, but that was my experience when I did have a cylinder head gasket leak. I also mentioned my experience with loss of coolant. Apologies for the crossed threads.

Thanks that is good to know. I don’t think I have a duff head gasket and hope that it’s just a case of air getting in under the coolant when the coolant is cooling. I will try the cap with a seal first

[alan_fincher]

On 15/08/2022 at 10:50, Peugeot 106 said:

 I have asked Hawker Sleeman for the coolant pressure that my engine should see.

 

For the benefit of others I assume you mean Sleeman & Hawken?

[Peugeot 106]

16 minutes ago, alan_fincher said:

 

For the benefit of others I assume you mean Sleeman & Hawken?

Correct Apologies