pressure caps

[vjay48]

I have recently bought a s3,on checking water levels and topping up ,I am a little bit confused,which way found should caps be,spring cap is on plastic overflow tank,non sprung cap on swirl tank.

[mk1fan]

The metal swirl pot needs to 'vent' into the expansion tank so the cap with the spring needs to go on that - it acts a bit like a thermostat.

The plastic expansion tank needs to remain sealed so the non-spring cap goes there.

[vjay48]

OK seems funny that the car has been run with caps the wrong way round?

[mk1fan]

Is there any writing on the top of the caps?

[AutoAndy]

...just wait for the responses...they're coming....Lets just say that this has been the subject of some debate


My answer is the way round that they came on my car when I got it, as it works in all temps...not sure I should admit which way that is though....

[mk1fan]

In fairness, I can see how they would work either way round.

If there were no issues before then run them as they were.

[mep12345]

Look up "stir a hornets nest". Basically it depends whether you have an expansion tank with or without the sealed up sensor hole. If you have one with then spring on swirl pot if not then either way round will work. Or remove expansion tank and fit an aluminium one like I have. Avoids the arguments

[v8s4me]

If you put the pressure cap on the expansion tank the worst that can happen is that it splits because it's old and can't take the pressure - like me

Get Shaun to make you a stainless expansion tank and you can put the cap where you like.



Look! No cap on swirl tank - problem solved

[vjay48]

Ididnt realise I would open a can of worms,sorry guys,since car runs cool,i will leave the bonnet closed!

[steve j]

Not again, aaaaarrrrrrrggggghhh.

[DamianS3]

v8s4me said:

If you put the pressure cap on the expansion tank the worst that can happen is that it splits because it's old and can't take the pressure - like me

Get Shaun to make you a stainless expansion tank and you can put the cap where you like.



Look! No cap on swirl tank - problem solved

That's what I did but in a less impressive fashion.. Nice work.

Cheers Damian S3

[Roy C]

steve j said:

Not again, aaaaarrrrrrrggggghhh.

That old chestnut!

[v8s4me]

Can this finally be the end of the debate? Or will someone find a subsequent bulletin claiming the earlier one was written by an apprentice who got his tanks muddled up?

[glenrobbo]

I don't care Joe, I'm leaving Austin's caps exactly the same as they always have been for all the time I've been looking after him. It may be wrong, but it works, so if it ain't broke........

[greymrj]

Interesting, was the bulletin the tenth one on S types or the tenth one on fitting the rad cap on S types!!!! It seems all too likely that it was the latter!

I was going to return to my thermodynamics lecture notes but I believe that bulletin has saved my ageing brain from going through all that stress again. Like Glen I am going to stick with what works on my S, which is exactly the opposite of Glen!!

[Spanish S2]

I'll just put my twopenneth in to this long running debate. When I purchased the car the blank cap was on the swirl pot and the pressure cap on the expansion tank. I have left them in these positions and never had any problems with the cooling system in the Spanish climate. The debate will no doubt roll on.

[v8s4me]

Spanish S2 said:

.....I have left them in these positions and never had any problems with the cooling system in the Spanish climate. .....

You won't, so long as....

v8s4me said:

..If you put the pressure cap on the expansion tank the worst that can happen is that it splits because it's old and can't take the pressure - like me

On a sensible note, if anyone has been running with the pressure cap on the expansion tank without problems but can't resist the temptation to swap it to the swirl tank MAKE SURE it is the right type of cap ie with the bleed-back valve as described in the TVR technical update.

Spanish S2 said:

.....The debate will no doubt roll on.

No no please no

[Alan461]

Quote v8s4me
"On a sensible note, if anyone has been running with the pressure cap on the expansion tank without problems but can't resist the temptation to swap it to the swirl tank MAKE SURE it is the right type of cap ie with the bleed-back valve as described in the TVR technical update."

Maybe:

Pressure cap on the expansion tank if it's a quality metal one; making use of the air space for expansion.

Pressure cap on the swirl pot with plastic expansion tank; avoiding pressurising and risk of failure.

Caps need to be of the correct type and good condition.

This gives credence to either position. ?

Edited by Alan461 on Sunday 5th October 10:44

[steve j]

Roy C said:

That old chestnut!

Yup, that old chestnut

[Top Gear TVR]

Roy C has it.

There is only one way: pressure release and return on the swirl pot. Plain cap on the expansion tank.