Why not remove expansion tank?
Discussion
Old topic, new question? It seems quite possible to put the pressure cap on the swirl chamber, and some do, some don't. If you do, why not remove the expansion tank?? It has no function in that case, the over flow pipe can go straight to the floor.
I would like to do this, it would tidy up the underbonnet a bit. Any theories?
Nic
I would like to do this, it would tidy up the underbonnet a bit. Any theories?
Nic
kentishS2 said:
Only if the pressure cap is on the expansion tank, otherwise there is no water movement from the swirl tank.
And with nowhere for it to go, what is likely to happen?
I use to be a hydraulics engineers and personally I'd leave it as TVR designed it.
On a positive note, you'll soon find any weak components and hoses!
mmm. Actually I am pretty sure TVR wanted the expansion tank to have the pressure cap, and a fixed cap on the swirl tank, so this idea may be a bit contentious (spelling?). But, 3000m's don't have the expansion tank (to my recollection), and I wonder if the expansion tank just makes it easier to see the water level?
From earlier discussions, many TVR S owners seem to put the pressure cap on the swirl and fixed on the exapansion - in which case the expansion tank does nothing other than catch the water, it cannot go back into the cooling system once it gets past the pressure cap?
Nic
From earlier discussions, many TVR S owners seem to put the pressure cap on the swirl and fixed on the exapansion - in which case the expansion tank does nothing other than catch the water, it cannot go back into the cooling system once it gets past the pressure cap?
Nic
Here we go again....
MY UNDERSTANDING - Version 1
1. Engine gets hot...
2. Water gets hot and pressurises the system...
3. The Swirl pot fills up...
4. The Pressure cap on the swirl pot takes the pressure...
5. If the pressure gets high enough or expansion gets high enough...
6. Pressure cap expels hot water into the expansion tank...
7. Water level in expansion tank rises...
8. If the system is over full...
9. Expansion tank over flows without any resistance as the is no pressure cap...
STOP...Engine cools
10. Water contracts...
11. System De-pressurises...
12. Water level in Expansion tank goes down...
13. When cold level is a few inches down in the Swirl pot...
MY UNDERSTANDING - Version 2
1. Engine gets hot...
2. Water gets hot and pressurises the system...
3. The Swirl pot fills up...
4. The Cap on the swirl pot lets water straight through the tubes to the expansion tank...
5. Water level in expansion tank rises...
6. Pressure cap on the Expansion tank resists expansion...
7. If the system is over full...
8. Pressure cap releases and overflows...
STOP...Engine cools
10. Water contracts...
11. System De-pressurises...
12. Water level in Expansion tank goes down...
13. When cold, level is a few inches down in the Swirl pot...
Come on then....Shoot me down, (if I'm wrong....)
AFAIK
There is no right or wrong way. Both versions have worked for me...
They just pressurise different areas of the system at different times.
Dave
BERGS2 said:
Mine came to me with version 2 - tried version 1 for a bit but kept losing water 
therefore for my car (&probably roughly 50% of S's) this is the right way round....
horses for courses though....
By the way - nice diagrams
I keep finding a small puddle under my car, perhaps I'll swap my caps around?
Oh my god ........they're baking cookies downstairs ..........I can smell them.
Where's my card ....must have cookies, I need a cookie .....now!
kentishS2 said:
Mine came to me with version 2 - tried version 1 for a bit but kept losing water
therefore for my car (&probably roughly 50% of S's) this is the right way round....
horses for courses though....
By the way - nice diagrams
I keep finding a small puddle under my car, perhaps I'll swap my caps around?
Oh my god ........they're baking cookies downstairs ..........I can smell them.
Where's my card ....must have cookies, I need a cookie .....now!
Ahh, that's better, having my cookie fix now.
There are also a few of other things to bear in mind....
The Release value of the Pressure Cap...!
Making sure if the cap is on the swirl pot that it is a long reach type...! Similarly on the Expansion. So that it seals on the inner rim.
If Version 2 is used...The tube runs are secure between Expansion tank and Swirl pot...!
Dave
The Release value of the Pressure Cap...!
Making sure if the cap is on the swirl pot that it is a long reach type...! Similarly on the Expansion. So that it seals on the inner rim.
If Version 2 is used...The tube runs are secure between Expansion tank and Swirl pot...!
Dave
Both ways work, as long as the caps both seal properly. Neither way works if the caps leak under pressure. Sometimes, the caps will seal on one tank and not on the other so swapping the caps back will cure the problem. Also, since the sealing face on the swirl tank is lower than the one on the header tank, the standard pressure cap doesn't seal properly on the swirl tank. This means it blows off at a lower pressure. Reducing the pressure may be enough to prevent a weak cap from leaking, although it also means the system boild over at lower temperatures. Having said all that ...
The system works best if you put the blank cap on the swirl tank and the pressure cap on the header tank. What these tanks do is separate gas out of the water system. The swirl tank is very good at separating large air bubbles out, but because it is a full flow tank the water is not in there long enough for the fine bubbles to separate out. With the blank cap on the swirl tank, it actually works as a two stage separator: large bubbles and froth settle at the top of the swirl tank. As the engine revs vary the pressure in the swirl tank varies and this pumps a small volume between the top of the swirl tank and the bottom of the header tank. This is quite elegant because it pumps the worst, gassiest water from the top of the swirl tank to the header tank, and the best degassed water from the bottom of the header tank back to the swirl pot. End result is the system degasses the water very well, which is good for the cooling system.
Edited to add, if you put the pressure cap on the swirl tank water will be drawn back from the header tank (now just used as an overflow tank) because the pressure cap has a one-way poppet valve in it. But this only works if the pressure cap is absolutely air tight, otherwise it just sucks in air instead of water.
>> Edited by GreenV8S on Tuesday 21st September 20:21
The system works best if you put the blank cap on the swirl tank and the pressure cap on the header tank. What these tanks do is separate gas out of the water system. The swirl tank is very good at separating large air bubbles out, but because it is a full flow tank the water is not in there long enough for the fine bubbles to separate out. With the blank cap on the swirl tank, it actually works as a two stage separator: large bubbles and froth settle at the top of the swirl tank. As the engine revs vary the pressure in the swirl tank varies and this pumps a small volume between the top of the swirl tank and the bottom of the header tank. This is quite elegant because it pumps the worst, gassiest water from the top of the swirl tank to the header tank, and the best degassed water from the bottom of the header tank back to the swirl pot. End result is the system degasses the water very well, which is good for the cooling system.
Edited to add, if you put the pressure cap on the swirl tank water will be drawn back from the header tank (now just used as an overflow tank) because the pressure cap has a one-way poppet valve in it. But this only works if the pressure cap is absolutely air tight, otherwise it just sucks in air instead of water.
>> Edited by GreenV8S on Tuesday 21st September 20:21
GreenV8S said:
Both ways work, as long as the caps both seal properly.
Which is the normally the problem. If you have the right pressure cap for the header, its not right for the swirl tank.
What the overall effect is depends on the coolant level you have. Mine is happiest when totally full (and pressure cap on swirl tank).
Some people seem to have coolant levels that would never overflow and probably never need an expansion tank??
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