Thorney Old Problem where to put the Pressure Cap

[Ragtop]

I can't resist joining in this one!

Norman, I have a QH FC53 on my swirlypot and it performs impeccablibly.

mep12345 said:

If Adrian's comment is correct it does mak sense, but then this is really down to TVR's poor workmanship in sealing the unused sensor hole in the expansion tank. This is because as I understand it the Triumph Herald that uses this expansion chamber as OE equipment also fits a 15psi cap to it, so the TVR bodge to seal the unused sensor is the only bit that could not be up to spec.

Mark

Mark, my expandytank hasn't been bodgered by TVR - it still has the senderysensorythingy in it (blue arrow). The one on my previous S3 was the same.



And yes, I know the expandytank's not in the usual place - it's there so I can see the level (red arrow) - which never changes from this position when cold, no topping up ever needy, and swirlypot always lovely-full.

[Adrian@]

Poor workmanship by TVR.....ooh err..I have in the past replaced the plastic tanks in the past because they have split, when the pressure caps have been on the wrong way and as Norman knows it was I who fitted a FC60 (I too sometimes read things on the bloody internet and I stupidly think that..can I pass on that reply) and corrected it! HEY, I used to supply 20lb caps to the MOD until I could not back trace supply..... when production jumped to Turkey or was Greece/China!
Adrian@

[Gerald-TVR]

Adrian - no problems and the difference between the FC53 and FC60 is ?????

Edited by Gerald-TVR on Thursday 26th November 23:06

[Adrian@]

OH Norman....I just cannot resist any more....FC7 ....I thought someone might of replied by now with the QH info.
Adrian@

Edited by Adrian@ on Friday 27th November 08:39

[ketvrin]

Adrian@ said:

OH Norman....I just cannot resist any more....FC7 ....I thought someone might of replied by now with the QH info.
Adrian@

FC7

maybe I should add a column to the owners list so you could post which way round you have your caps to see if we have concensus

my pressure cap is on the swirl tank...

K :nailed colours to mast smiley:

[zombeh]

mep12345 said:

If Adrian's comment is correct it does mak sense, but then this is really down to TVR's poor workmanship in sealing the unused sensor hole in the expansion tank. This is because as I understand it the Triumph Herald that uses this expansion chamber as OE equipment also fits a 15psi cap to it, so the TVR bodge to seal the unused sensor is the only bit that could not be up to spec.

The bottle without that sensor is from the Dolomite (and a quick look through parts catalogues shows totaly different ones on other triumphs), so the one with the sensor is something else BL later than that, not sure what though. It's fitted with a 15psi cap and has a nasty tendancy to not seal properly.

fwiw I have the pressure cap (robbed from my dolly, which now has a golf bottle fitted) on the bottle and the blank one on the swirl pot.

[ketvrin]

Allegro ?

[Gerald-TVR]

Adrian@ said:

OH Norman....I just cannot resist any more....FC7 ....I thought someone might of replied by now with the QH info.
Adrian@

Edited by Adrian@ on Friday 27th November 08:39

Should have known better

[tozerman]

mep12345 said:

Tony that is actually potentially unsafe and you should change one or other as soon as possible. The reasons for this are that to lift on over pressurising the swirl pot would have to reach 28psi i.e. the back pressure on the second cap would act on the reverse seide of the swirl pot relief valve meaning you would need 13psi to overcome this and then another 15psi to overcome the spring pressure. You will therefore be more likely to blow a jubilee clipped joint.

Mark, the reason I do that is when it is running hot ie sitting in traffic the level in the header tank rises and rises and I fear that if I didn't have a pressure cap on there then it would just all shoot down the overflow ! As it is the car never overheats what so ever no matter how hot the weather is and how long I am stationary, if I put a blanking cap on the header tank how can I be sure that the tank won't boil over ?
Cheers.....Tony..

[mep12345]

OP is correct, my memory was wrong I bid on one on ebay the other week that was cleaner than mine, but lost. However it is the dolomite not the Herald. However my statement about the pressure cap was correct and if you check at Rimmer brothers here and quiller here you will see the cap for the Dolomite is a 13psi one, therefore the tank will be pressurised in its original design use.

tozerman said:

I fear that if I didn't have a pressure cap on there then it would just all shoot down the overflow !

Tony,

If it is doing this then there is something else wrong with the system, probably air in it somewhere. When hot the expansion tank will be almost full, mine is even with the pressure cap on it and the blanking cap on the swirl pot as this is the way round I prefer to run it but both should work as I've said before. With your arrangement you will not see an issue until the exansion bottle pressurises when it will increase the running pressure in the engine/coolant system above that for which it was designed (and possibly to almost double the design value) This will still be ok unless you have a weak point or you exceed the pressure that the design can take in a weaker part of the system - most likely failure areas are jubilee clipped joints and head gasket. The moral here is that pressure relief systems are designed to lift at a pressure for a reason and to increase this arbitrarily is not advised. The best analagy is to think of it in the same way as putting a nail in the place of a fuse because your house ringmain keeps tripping. If you wouldn't do it with electrics why do it with fluid systems.

Anywaymust go and do my lines now:

I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again

Only another 991 to go

Oh and apologies for the TVR poor workmanship I really shouldn't have slandered their quality assurance processes should I

Mark

Edited by mep12345 on Friday 27th November 18:56

[Gerald-TVR]

mep12345 said:

I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again

You'll be back

[mep12345]

Gerald-TVR said:

mep12345 said:

I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again
I will not respond to the pressure cap threads again

You'll be back

Bugger just have been, but by editing - Oh no and this post

[Adrian@]

Mark/all,
It is fair to say that it is poor workmanship ...and the using of the BL parts bin esp. in applications where they they should not be used. But, the blank caps by design have minor tangs on them and TVR could/should/would of defined the swirl pot into only allowing the use of a blank cap at that point....IMHO PROOF that the cap is a pressure cap at this point AND that this is BY DESIGN, because someone CHOSE the pressured cap version the fitting to be soldered onto the top of the swirl pot rather than the blank cap version. Again IMHO the expansion tank is not used as an expansion tank here just a reservoir to over flow into ...Because it just looks bad dumping excess down to earth.
All this said the poor design (again using BL radiator) with that high spot lead up to the top pipe inlet gives a on going issue of an air lock in the pipe that painful to eek out...
I did my lines ..never believe anything you see/read on the interweb
Adrian@

Edited by Adrian@ on Friday 27th November 23:00

[johnnywgk]

Ouch! i've got a headache now.


I've recently polished my caps, and can't remember what one went where

The descriptions of the two caps confuses me, ie pressure/non pressure cap, i have one with a spring valve thingy, and one without. What's what.

Without shouting at me (hehe) can someone tell me what one goes where, as in, the one with the spring valvey thingy goes ------. Then i know where to put the other one.

Many thanks guys.

Ps, stop arguing you lot, this is getting like the lounge

[page3]

johnnywgk said:

Without shouting at me (hehe) can someone tell me what one goes where, as in, the one with the spring valvey thingy goes ------. Then i know where to put the other one.

Spring one = pressured.
Non-spring = non-pressured.

Pressured one on swirl tank. Non-pressured on overflow tank. If your car overheats in a plume of steam swap them around.

[johnnywgk]

Cheers Adam, I'll do that .

Not sure about swapping them around if all fails. Can't i just put them somewhere
and forget about them, rather than worry about over heating, blowing up expansion tanks, and other stuff.

I can't believe (whoops, yes i can it's a TVR) that there is no FULLSTOP answer to this.

What setup have you got on your car??????? What's the proper way???

Does it overheat?
Blow holes in expansion tanks?
Make the tea?

HELP!!!!

C'mon Mr Mep, please be gentle with me.

[Gerald-TVR]

Had they both ways round. Worked fine except when i had a new pressure cap on swirl pot and lost coolant - put the old cap back and it was fine

[page3]

johnnywgk said:

Not sure about swapping them around if all fails. Can't i just put them somewhere
and forget about them, rather than worry about over heating, blowing up expansion tanks, and other stuff.

I never worried about overheating during the first 5 years of ownership. Not in Spain, not on the track, not in London traffic.

It then overheated in Germany (while doing 110-120mph ), due to the water pump failing - one big overheat took out quite a few "weak points" - a few hoses and the pressure cap. I spent the next year worrying about overheating all the time, where as I should have just replaced all the weak points (all cheap) right from the start.

My opinion is that if the cooling system is working properly, it takes quite a lot to overheat an S - they really are quite robust.

Drive more, worry less, is what I'm always told

[mep12345]

Still couldn't resist. In theory either way round should work, but my knowledge is based on general fluid systems theory while Adrian@'s knowledge of this specific car is significantly above most peoples, especially mine, and he says he has replaced several bottles that have split - therefore take your pick.

For my car the bottle is from the Dolomite as OP states above and that bottle is rated to be pressurised (see links I posted above) plus the pressurised cap will not seal on my swirl pot as the tangs just click over the tapered part of the neck so you can't get the cap to "pull down" onto the top and seal. I tried this in the summer just to see what was better for my car and when it wouldn't fit swapped them back to how I've always had it - the cap of course may be a different (possibly even the wrong) cap but it fits the expansion bottle, is the bleed back variety and is rated correctly so why it doesn't fit I don't know - it doesn't appear to be damaged at the tangs either.

My expansion tank doesn't have that sensor bit in it - and IIRC the one I tried to buy on ebay didn't either, so the splitting bottles/sensor point may be because TVR sourced a different bottle from another vehicle not designed to hold pressure and fitted it to some cars (mine is a 1992 S3). This could well explain why some are one way round, some are the other and TVR couldn't make their minds up (the tech note posted above clearly shows with them reversing an earlier tech note). Who knows? but in theory as I said both should work with advantages and disadvantages to each. I gave a full explanation in a thread called "stirring a hornets nest" but the search facility doesn't seem to locate it. I think Barkchoc started the thread, may have been KeTVRin though.

Norm you were right - Yet more lines to do

Mark

[tvrgit]

Mark and Adrian

I have posted before that I suspect that at some point, they changed how the expansion bottle was pressurised (possibly because they changed the bottle from the non-sensor one you have). Some cars seem to work better one way, some the other.

Mine has a sensor, and it pulls out pretty easily, so I can't imagine how it could have been meant to have been pressurised.

Although, when I got the car, the pressure cap was on the bottle and the plain cap on the swirl pot, and the car was prone to overheating. I changed the caps around and it was much better.

It was a lot better, mind, when I fixed the hole in the radiator...