Expansion tank question
Discussion
Hi people,
A quick question for you S owners out there. I'm trying to source a coolant expansion tank for my 1600M and am having major problems as all the usual stockists for M-bits are completely out. I've just spoken to Adrian Venn, however, who reckons that it's the same tank that is fitted to the S-series cars, in which case I can get it from the factory. Does this look familiar to any of you??
Any help gratefully appreciated,
Kris..
'75 1600M
>>> Edited by krispy on Monday 27th January 15:00
A quick question for you S owners out there. I'm trying to source a coolant expansion tank for my 1600M and am having major problems as all the usual stockists for M-bits are completely out. I've just spoken to Adrian Venn, however, who reckons that it's the same tank that is fitted to the S-series cars, in which case I can get it from the factory. Does this look familiar to any of you??
Any help gratefully appreciated,
Kris..
'75 1600M
>>> Edited by krispy on Monday 27th January 15:00
Krispy: You're welcome.
Psychobert: Don't worry about the brown sludge. The tank isn't acting as an expansion tank on the S. The hose into the tank comes from the very top outlet from the swirl tank. The only way for water to get along this hose and into the tank is for there to be enough pressure in the cooling system to open the pressure cap on the top of the swirl tank. The reason I say that the tank doesn't act as an expansion tank is that normally the water in the expansion tank would be pulled back into the system when the pressure in the system drops. This can't happen in the S because when the pressure drops in the system the pressure cap seals and the path from the cooling system to the tank is closed. Therefore the only time the path from the swirl port to the tank is open is when the pressure in the system is much greater than in the tank and therefore water can only flow one way. When this happens the water is invariably hot and under pressure and almost always shoots straight out of the little nozzle of the neck of the tank (which should not have a pressure cap fitted) and down the little hose onto the floor (if you have one fitted (not a floor, obviously, a little hose)). That's why all the S's I've seen have cruddy deposits in the plastic tank which I suspect is the rusty remains of the tank cap innards which are occasionally subjected to this hot steamy shower. If you have cruddy deposits floating about in the water in the top of your swirl tank then you need to investigate further.
This will doubtless lead to another thorough discussion of where you should have the pressure cap but all of the other threads have concluded that the swirl pot is where it should be and that the plastic tank should have a non-pressure cap on it regardless of how stupid this may seem of how redundant this appears to render the plastic tank as it doesn't appear to do the job of an expansion tank and is spectacularly bad at doing the job of a catch tank in my experience.
Regards,
Mark
Edited to add: all in my opinion, obviously
Edited to add: in fact, thinking about it, the swirl tank *is* the expansion tank isn't it? So why do we need the plastic tank? Given that it appears to serve no useful purpose, makes the engine bay scruffy and makes potential buyers wonder why there's so much sh*t in the cooling system I may well bin mine. Krispy, how much are these things worth
>> Edited by dern on Monday 27th January 15:48
Psychobert: Don't worry about the brown sludge. The tank isn't acting as an expansion tank on the S. The hose into the tank comes from the very top outlet from the swirl tank. The only way for water to get along this hose and into the tank is for there to be enough pressure in the cooling system to open the pressure cap on the top of the swirl tank. The reason I say that the tank doesn't act as an expansion tank is that normally the water in the expansion tank would be pulled back into the system when the pressure in the system drops. This can't happen in the S because when the pressure drops in the system the pressure cap seals and the path from the cooling system to the tank is closed. Therefore the only time the path from the swirl port to the tank is open is when the pressure in the system is much greater than in the tank and therefore water can only flow one way. When this happens the water is invariably hot and under pressure and almost always shoots straight out of the little nozzle of the neck of the tank (which should not have a pressure cap fitted) and down the little hose onto the floor (if you have one fitted (not a floor, obviously, a little hose)). That's why all the S's I've seen have cruddy deposits in the plastic tank which I suspect is the rusty remains of the tank cap innards which are occasionally subjected to this hot steamy shower. If you have cruddy deposits floating about in the water in the top of your swirl tank then you need to investigate further.
This will doubtless lead to another thorough discussion of where you should have the pressure cap but all of the other threads have concluded that the swirl pot is where it should be and that the plastic tank should have a non-pressure cap on it regardless of how stupid this may seem of how redundant this appears to render the plastic tank as it doesn't appear to do the job of an expansion tank and is spectacularly bad at doing the job of a catch tank in my experience.
Regards,
Mark
Edited to add: all in my opinion, obviously
Edited to add: in fact, thinking about it, the swirl tank *is* the expansion tank isn't it? So why do we need the plastic tank? Given that it appears to serve no useful purpose, makes the engine bay scruffy and makes potential buyers wonder why there's so much sh*t in the cooling system I may well bin mine. Krispy, how much are these things worth
>> Edited by dern on Monday 27th January 15:48
bigtone said:
Does this look familiar to any of you??
Erm, yep!
Still having problems getting hold of them Kris?
Tony
Indeed I am. It appears that you probably had the last one off the shelf at Moss! They don't have any left in stock and their ETA for more is, and I quote, '2005'. O joy. Nobody else claims to have anything like it in stock but I spoke to Adrian and he suggested that it was also an S part......which it appears to be. He contacted the factory and they've got some in, so fingers crossed I'll have one by the weekend
. What are you doing reading the S list anyway??
Kris..
Edited to add: in fact, thinking about it, the swirl tank *is* the expansion tank isn't it? So why do we need the plastic tank? Given that it appears to serve no useful purpose, makes the engine bay scruffy and makes potential buyers wonder why there's so much sh*t in the cooling system I may well bin mine.
I took my plastic 'expansion' tank of and binned it for precisely this reason! It has the added benefit of making access to the oil filter much easier as well!
I just routed the small bore tube from the swan neck filler down under the car like they did with cars in the old days where there was a radiator overflow.
There is a theory though that you can use the 'expansion' tank as a guide to see how much water the cooling system requires for a top up and this is a reason to leave it in place. However I prefer to just check the level in the swan neck rather than take a chance on a sight reading from the dodgy 'expansion' tank.
Jas.
dern said:
Given that it appears to serve no useful purpose, makes the engine bay scruffy and makes potential buyers wonder why there's so much sh*t in the cooling system I may well bin mine. Krispy, how much are these things worth
A very good point. In fact, getting rid of the thing would, in my case, free up a substantial amount of space on the bulkhead and allow me to relocate my oil catch tank somewhere nice and accessible (and high-up like it's supposed to be). Why did they fit them in the first place though? Easy reading of the coolant level sounds logical, but then the majority of M-series and earlier cars had brass tanks...not reknowned for their transparency.
Kris..
Have you got the pressure cap on the plastic tank and the non-pressure cap on the swirl pot? As far as I can see that's the only way fluid can move from the swirl pot to the plastic tank. Despite this all the regular sources of authority tell us that this is not the right way around.
roy c said: The expansion tank in my S2 works. Coolant level increases when hot and cold water syphons back into the swirl tank when cold (as described in the "Bible").
Anyway, whatever works for your car, I suspect this issue will never cease to be a source of debate.
All the best,
Mark
dern said:Have you got the pressure cap on the plastic tank and the non-pressure cap on the swirl pot? As far as I can see that's the only way fluid can move from the swirl pot to the plastic tank. Despite this all the regular sources of authority tell us that this is not the right way around.
Swirl Tank = pressure cap
Overflow Tank = plain cap
It works just as Steve Heath describes, but some cars have been "modified" (caps & tubes swopped around) since they left the factory.
Hmm, don't know why yours works as described and mine doesn't then. The very top tube on the swirl tank goes to the plastic tank on my car and I can't see how water can get from the plastic tank back into the swirl tank past the pressure cap which must, by definition, be closed when the pressure in the system is low enough to allow water to flow into the system unless the pressure cap has a one way valve in it (in addition to the pressure operated bit) that allows water back into the system. If that isn't the case then the only way I can see how water could get back to the system from the plastic tank is if the next pipe down was connected to it, however, that would mean that the system was never pressurised as the plastic tank is open to the atmosphere.
Swirl Tank = pressure cap
Overflow Tank = plain cap
It works just as Steve Heath describes, but some cars have been "modified" (caps & tubes swopped around) since they left the factory.
Confused.
Mark
OK, I don't pick up the S until Sunday, so ignore me if you wish, but from what I've seen whilst looking round and partly jogged by Mark's photo, there are reasons why the expansion tank is there and why it should be the one with the pressure cap on.
An expansion tank serves as a reservoir to the main system, it is easy to see the water level in it and easy to top it up. It is mounted high in the engine bay. To be effective it must be above the water level in the engine and heater matrix. I'm not sure that the swirl pot is sufficiently high enough to allow all trapped air to bleed into it, and act as a reservoir to replace the bled air with water.
Although the general concensus is for the swirl pot to double up as the expansion tank, I have a feeling that the expansion tank itself would be better at the job, and may have been fitted for one or two of the above reasons.
Could be wrong.
Andy
An expansion tank serves as a reservoir to the main system, it is easy to see the water level in it and easy to top it up. It is mounted high in the engine bay. To be effective it must be above the water level in the engine and heater matrix. I'm not sure that the swirl pot is sufficiently high enough to allow all trapped air to bleed into it, and act as a reservoir to replace the bled air with water.
Although the general concensus is for the swirl pot to double up as the expansion tank, I have a feeling that the expansion tank itself would be better at the job, and may have been fitted for one or two of the above reasons.
Could be wrong.
Andy
I agree that that would make sense but in past discussions it has been established that tvr themselves put the pressure cap on the swirl pot and not on the plastic tank. Hence the confusion.
Although the general concensus is for the swirl pot to double up as the expansion tank, I have a feeling that the expansion tank itself would be better at the job, and may have been fitted for one or two of the above reasons.
Have fun with your car.
Regards,
Mark
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