Discussion
This works for me....
Pressure cap on swirl
Non Pressure on expansion tank
IMHO - Swirl should not lose any water, why would you want it too as eventually your engine will begin to boil (overheat) and potentially cause major damage, warping or cracked or maybe head gasket failure.
It should be a sealed system and should work.
When I bought my car it had done around 70k but only2000 miles in its previous 10 years so it was given a good recommissioning wthroughout which included several about (10 flushes of the cooling system) maybe over kill but the crud that came out was unreal, my system is now pretty clean but it will get flushed again this year. Again IMO the heater matrix corrodes inside so a lot of crud lives in there as well as the radiator and its hard to get it all out. Let face it most of our cars are knocking on and are around 20 years old and may not have been serviced correctly during this time.
Flush it flush it and flush it again its pretty easy to do this this should help the cooling system work better its not everything but knowing my system is just water and anti freeze gives me some piece of mind.
Good Luck !
Pressure cap on swirl
Non Pressure on expansion tank
IMHO - Swirl should not lose any water, why would you want it too as eventually your engine will begin to boil (overheat) and potentially cause major damage, warping or cracked or maybe head gasket failure.
It should be a sealed system and should work.
When I bought my car it had done around 70k but only2000 miles in its previous 10 years so it was given a good recommissioning wthroughout which included several about (10 flushes of the cooling system) maybe over kill but the crud that came out was unreal, my system is now pretty clean but it will get flushed again this year. Again IMO the heater matrix corrodes inside so a lot of crud lives in there as well as the radiator and its hard to get it all out. Let face it most of our cars are knocking on and are around 20 years old and may not have been serviced correctly during this time.
Flush it flush it and flush it again its pretty easy to do this this should help the cooling system work better its not everything but knowing my system is just water and anti freeze gives me some piece of mind.
Good Luck !
DJ8226 said:
Pressure cap on swirl
Non Pressure on expansion tank
This is fine as long as the pressure cap on the swirl pot allows the return flow from the expansion tank to the swirl pot NOT ALL OF THEM DO!!Non Pressure on expansion tank
If them dont then the swirl pot will loose 20 - 25 % of the coolant in it
i have the caps the other way around and it works fine, either way will work depending on the pressure cap
HTH
Norman
Barry S1 said:
yes i have changed the caps over non pressure cap on swirl pot i did this about
3 weeks ago and all is ok did n`t say anything just in case the world came to a stop
and i got the blame for it, still loses a bit of water from swirl pot, new pot and
new cap what more can i do
Barry
it took me a while to fix the seal on my swirl pot including removing a v poor ss replacement which had a rubbish filler neck that didn't pull the cap down enough to seal.3 weeks ago and all is ok did n`t say anything just in case the world came to a stop
and i got the blame for it, still loses a bit of water from swirl pot, new pot and
new cap what more can i do
Barry
also check you have a rubber ring in your blanking cap if its not sealing there you won't get the correct pressure in the system and it could boil at a lower temp than it should.
keep going you will sort it.
cheers D S3
Gerald-TVR said:
This is fine as long as the pressure cap on the swirl pot allows the return flow from the expansion tank to the swirl pot NOT ALL OF THEM DO!!
This is the important bit isn’t it? If the swirl tank is fitted with a pressure cap which doesn't allow expanded coolant in the expansion tank (there's a clue in the name) to flow back into the system as it cools then it won't be working as it was designed to. I’ve done about 4000 miles with the pressure cap on the expansion tank with no issues so far. sorry, I am going to bite 
Norm 
there are two key things here, what pressure cap you have and what expansion tank you have, if you have a pressure cap that allows bleed flow back and an expansion tank that does NOT have the sensor point in it then either way round will work with advantages and disadvantages to each. If you have a pressure cap that does not allow back bleed then it MUST go on the expansion tank. If you have an expansion tank with the sensor point blanked there is a chance it may not hold the pressure of the system if the pressure cap is fitted on it and as such the pressure cap should be on the swirl pot (hence the tech note that I'm sure someone will post soon).
Key thing here is it is a TVR and there are two types of pressure cap and two types of expansion tank both of which affect the way the system can work
Hope this is clear
Mark
Norm there are two key things here, what pressure cap you have and what expansion tank you have, if you have a pressure cap that allows bleed flow back and an expansion tank that does NOT have the sensor point in it then either way round will work with advantages and disadvantages to each. If you have a pressure cap that does not allow back bleed then it MUST go on the expansion tank. If you have an expansion tank with the sensor point blanked there is a chance it may not hold the pressure of the system if the pressure cap is fitted on it and as such the pressure cap should be on the swirl pot (hence the tech note that I'm sure someone will post soon).
Key thing here is it is a TVR and there are two types of pressure cap and two types of expansion tank both of which affect the way the system can work
Hope this is clear
Mark
pressure caps The other factor to consider is that both tanks have two sealing faces, and depending which way round you fit the caps different seals are under pressure. So if you have a knackered sealing face somewhere, you may you need to fit the caps one way round in order for it to hold pressure.
i have 2 sets of caps one for swirl pot and one for expansion tank
don't seem to make a lot of difference which way round it goes 1800
miles on the Scotland trip not a lot water loss some times i go
20 miles and will have to put a lot in it the roof is the same put it
on one day no leaks next day water comes in everywhere you don't get that
with a MX5 but where's the fun in that
don't seem to make a lot of difference which way round it goes 1800
miles on the Scotland trip not a lot water loss some times i go
20 miles and will have to put a lot in it the roof is the same put it
on one day no leaks next day water comes in everywhere you don't get that
with a MX5 but where's the fun in that
Barry S1 said:
yes i have changed the caps over non pressure cap on swirl pot i did this about
3 weeks ago and all is ok did n`t say anything just in case the world came to a stop
and i got the blame for it, still loses a bit of water from swirl pot, new pot and
new cap what more can i do
Barry
When i had my S I always made sure the level in the swirlpot was about 1cm below the top and that the expansion was empty (cold) that way when the engine warmed up and the coolant expanded then the levels were ok, I never ever lost any coolant and it never ever overheated even after a hot lap of the "ring" and queing for ages to rejoin the main carpark, that was what worked for me.3 weeks ago and all is ok did n`t say anything just in case the world came to a stop
and i got the blame for it, still loses a bit of water from swirl pot, new pot and
new cap what more can i do
Barry
Cheers.....Tony..
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