'Expansion' tank
Discussion
OK heres the story -
Saw that the coolant level on the expansion tank looked a little low (just over where the lower pipe outlet is - So I topped it up - 30 miles later it was right down the bottom again so I started to fret - then I did the sensible thing and searched the forums and found this thread:
www.pistonheads.com/gassing/topic.asp?t=27597&f=11&h=0&hw=expansion+tank
this helped a lot, as Dern's second reply:
implies that this is of little or no consequence. Is it normal to lose water on these old engines?
Should I worry if the coolant level in this tank is just below the lower outlet (Ive topped it up twice now and this is where it seems to want to be...)
Saw that the coolant level on the expansion tank looked a little low (just over where the lower pipe outlet is - So I topped it up - 30 miles later it was right down the bottom again so I started to fret - then I did the sensible thing and searched the forums and found this thread:
www.pistonheads.com/gassing/topic.asp?t=27597&f=11&h=0&hw=expansion+tank
this helped a lot, as Dern's second reply:
dern said:
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.
implies that this is of little or no consequence. Is it normal to lose water on these old engines?
Should I worry if the coolant level in this tank is just below the lower outlet (Ive topped it up twice now and this is where it seems to want to be...)
Well that was my opinion anyway 
The level you need to monitor is the level in the swirl tank which is the tall (probably red) tank next to the battery with the cap on. The tank will find its own level from full to something like 2 inches below full depending on car. I'd fill up the swirl tank and then let it find its own level (it'll eject what it doesn't want via the 'expansion' tank and then subsequently monitor the level in the swirl tank. It should stay constant when the engine is cold.
Be warned though, this is a subject subject to much debate
Mark
The level you need to monitor is the level in the swirl tank which is the tall (probably red) tank next to the battery with the cap on. The tank will find its own level from full to something like 2 inches below full depending on car. I'd fill up the swirl tank and then let it find its own level (it'll eject what it doesn't want via the 'expansion' tank and then subsequently monitor the level in the swirl tank. It should stay constant when the engine is cold.
Be warned though, this is a subject subject to much debate
Mark
If I understand you right and it drops to the lower pipe, then this must be at least a pint. These engines do tend to use water as they get hot and there are a lot of bastard pipes and hoses. If you are loosing this much water on a regular basis then obviously check all your hoses for leeks as it must be going somewhere!
As far as the overflow tank is concerned, this is a never ending story of arguments. It should be that the swirl tank should have a 15LB cap but most of the caps don't make that rate due poor seal contact. It is possible to put another ring of rubber from your old cap under the new one or put a 5mil rubber ring inside the top of the swirl tank to bolster it up a bit. I chose the former and was suprised what a difference this made to the temp of the engine. If the seal leaks out steam you will not hardly notice it until you let the engine cool down and look inside.
So, what temperature does your engine run at, does the fan not cut in early enough. Remember if the seal is not good the water will boil early and you will loose water here as well but you won't see it!
gadgit.
As far as the overflow tank is concerned, this is a never ending story of arguments. It should be that the swirl tank should have a 15LB cap but most of the caps don't make that rate due poor seal contact. It is possible to put another ring of rubber from your old cap under the new one or put a 5mil rubber ring inside the top of the swirl tank to bolster it up a bit. I chose the former and was suprised what a difference this made to the temp of the engine. If the seal leaks out steam you will not hardly notice it until you let the engine cool down and look inside.
So, what temperature does your engine run at, does the fan not cut in early enough. Remember if the seal is not good the water will boil early and you will loose water here as well but you won't see it!
gadgit.
Ahaaa someone beat me to it i have been having a problem since i had mine serviced ata garage i have used for a long time on other cars. Chap told me he had swapped the caps around i protested but went with him, then had ugly boiling noises as soon as the hot weather arrived. Swapped back filled up then no probs. He thinks i am mad i now can say with knowledge why it is that way. (Smug Mode on )
S1 wannabe said:
So whichway cause the ugly boiling noises? when the pressure cap was on the 'expansion tank' or on the swirl?
Mine is currently on the expansion - which I am starting to think is wrong...
By the way - why is it called a swirl tank?
Just been working on the cooling system today, the pressure cap on mine is on the swirl tank.
I have owned the car for five years and never had any problems which suggests that the pressure cap should be on the swirl tank.
Bible page 140 second colum 3rd paragrarh
Quote " The radiator pressure cap is not found on the radiator,as its name suggests,but on top of the SWIRL tank in front of the radiator"
Bible page 146 second colum 3rd paragraph
Quote " It is important but not quite catastrophic that the two caps are not swapped over ( the pressure cap is placed on the SWIRL tankand the sealing cap without spring on the expansion tank......"
please read your bible's and if you ain't got one.....GET ONE
edited for smiles
>> Edited by pies on Sunday 31st August 22:56
Quote " The radiator pressure cap is not found on the radiator,as its name suggests,but on top of the SWIRL tank in front of the radiator"
Bible page 146 second colum 3rd paragraph
Quote " It is important but not quite catastrophic that the two caps are not swapped over ( the pressure cap is placed on the SWIRL tankand the sealing cap without spring on the expansion tank......"
please read your bible's and if you ain't got one.....GET ONE edited for smiles
>> Edited by pies on Sunday 31st August 22:56
No. The preassure cap goes on the swirl tank, end of story!
Why the "Swirl" tank. Well TVR have come up with this little device to remove all the air out of the system so to reduce the problem of overheating I believe.
Now back to the subject matter the pressure cap. The owners manual says that it goes on the overflow tank, but, TVR Blackpool say on the swirl tank. The parts manual says on the swirl tank. I think in general if all the caps and tanks, and rad are all new you might get away with it but it is vital to keep the pressure on the swirl tank to keep the boiling point high so the car is less likely to overheat. Just imagine all the pipework with just a small leak the thing will boil in no time. Even a lack of spring pressure will cause it to quickly over heat.
The only confusing point here is that the pressure cap has no return valve fitted which would contradict putting it on the swirl tank, as the water would not be able to return to the rad as a normal modern car. I think the expansion tank is the wrong name, it should be the overflow tank and is only there for that purpose, to catch excess water.
What do you think?
gadgit.
Why the "Swirl" tank. Well TVR have come up with this little device to remove all the air out of the system so to reduce the problem of overheating I believe.
Now back to the subject matter the pressure cap. The owners manual says that it goes on the overflow tank, but, TVR Blackpool say on the swirl tank. The parts manual says on the swirl tank. I think in general if all the caps and tanks, and rad are all new you might get away with it but it is vital to keep the pressure on the swirl tank to keep the boiling point high so the car is less likely to overheat. Just imagine all the pipework with just a small leak the thing will boil in no time. Even a lack of spring pressure will cause it to quickly over heat.
The only confusing point here is that the pressure cap has no return valve fitted which would contradict putting it on the swirl tank, as the water would not be able to return to the rad as a normal modern car. I think the expansion tank is the wrong name, it should be the overflow tank and is only there for that purpose, to catch excess water.
What do you think?
gadgit.
yellabelly said:
the pressure cap goes on the expansion tank not the swirl tank
Sorry spivvy that is incorrect, the pressure cap fits the swirl pot only, the white plastic tank is an overflow tank with no return flow to the swirl pot.
From Steve Heath On Previous Thread ( so everyone is correct depends on the car also page 18 of the TVR manual states the reservoir tanks has the pressure cap on )
shpub said:
All pressure caps have this return usually except for the ones that don't.
I looked into this really big time for the S bibles and found that pressure cap on the swirl tank is the way the vast majority of cars will work correctly. There are a few out there that either were built differently or were replumbed that will work either way. If you car is happy one way then fine leave it. If it is losing water try swapping them over.
Like many things TVR, nothing is black or white.
Steve
www.tvrbooks.co.uk
( so everyone is correct depends on the car also page 18 of the TVR manual states the reservoir tanks has the pressure cap on )
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