V8 S rad cap???

[wheels1]

Hi
do's any one know what cap fits on the expansion bottle on a V8S? And also the pressure it should be?
Thanks
Grant

[tubbystu]

wheels1 said:

Hi
do's any one know what cap fits on the expansion bottle on a V8S? And also the pressure it should be?
Thanks
Grant

Here we go

[GreenV8S]

It's a standard Ford cap (which any decent motor factor should be able to provide) at 15 psi.

[Barkychoc]

GreenV8S said:

It's a standard Ford cap (which any decent motor factor should be able to provide) at 15 psi.

Rearrange into a well known phrase

of can worms a opened



Where does the pressure cap go?

[Gerald-TVR]

Oh no it isnt!!!!!!!!!!!!!!!!

[Roy C]

Barkychoc said:

Where does the pressure cap go?

If I had a pound for everytime I've been asked that, I'd have 15psi.

[wheels1]

OK
went to the local ford garage and no luck with the expansion cap. They said they used to do a spring loaded cap but not now.
The cap in question is tucked behind the big black hose on the left of the engine bay near to the bulk head and you can just see it in the first pic.

The reason i was thinking of changing it was the car has suddenly decided to throw out coolant out of the expansion bottle over flow. The engine temp is as normal and the only thing i have done is move the heater control slider from inside the car, so it is most strange. i thought i could try this as if it works it would be an easy fix. Pic's below of engine bay and cap.
Could it be the wrong cap as it has no spring??

[Barkychoc]

Thats the same as mine on my V8S.
The spring loaded pressure cap goes on top of the swirl pot (Oh yes it does).
That cap is just a lid - it doesn't hold in any pressure and wouldn't really even matter if it wasn't there, so that isn't your problem.

There is a bleed valve on the top left of the rad - have you tried opening it to make sure there is no air trapped in there?

What is your temp gauge doing? Are you running any hotter?

Chris

[tubbystu]

Barkychoc said:

Thats the same as mine on my V8S. Te spring loaded pressure cap goes on top of the swirl pot (Oh yes it does).

Mine too.

It is a subject of much discussion (hence some of the frivolous posts). See here for most recent http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Somebody also posted a factory amendment notice a few weeks back that I cannot now find which didn't really help the clarity either.

It is best to leave the caps in whatever location works, my V8S will spit some fluid out if you fill the expansion tank right up, until it settles to its own level - which in itself isn't consistent.

It may also be air in the system that takes a while to work its way out. I would suggest carrying a 5 litre bottle of water to top up in hurry if your gauge starts to rise suddenly.

HTH

[wheels1]

Thanks for the info guy's.
It has only just started doing it and only seems to do it if i mess with the temp slider. the next time i go out i will leave it only and see what happens. [ there is a note in the history file about not adjusting it, maybe this is why?] Although why it should do this is baffling me.

The temp gauge is as normal, as soon as you get stuck in traffic it go's up to 3/4 and then the fan kicks in. There is some sort of adjuster screw on the hot start, kenlow thing on the swirl pot. would that do anything to make it run cooler in i adjusted that?

Edited by wheels1 on Friday 17th October 18:46

[mep12345]

tubbystu said:

Somebody also posted a factory amendment notice a few weeks back that I cannot now find which didn't really help the clarity either.

It is best to leave the caps in whatever location works, my V8S will spit some fluid out if you fill the expansion tank right up, until it settles to its own level - which in itself isn't consistent.

HTH

Agree with tubbystus comment here if it works leave it - see my explanation at this link which explains the situation from an engineer's (who works with high pressure fluid systems) perspective. Namely BOTH ways should work with advantages and disadvantages to each

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

Mark

[V8ish]

Just to add my 2-pennies worth, I agreed with Chris until Richad Thorpe at RT racing told me otherwise, many years of experience with these cars he tells me the pressure cap must go on the bottle, not the swirl pot, which I did. Didnt notice any diferent but I would say if you have a problem swap, if not leave it as they are.

Missing my V8s now!!! but my new 205 gti race car makes up for it!

[GreenV8S]

Since panto season is nearly here, I'll bite.

Either way around can work fine. Theory says that when everything is in good condition, it is better for the cooling system to have the pressure cap on the plastic header tank and the blanking cap on the metal swirl tank. This works better for several reasons:

• The volume of water in the pressurised system is increased, and more water is *always* better.
• In this configuration there is a steady tidal flow between the swirl tank and the header tank, which enables the header tank to work as a very effective degas settling tank.
• The gas volume in the header tank acts as a gas spring which increases the flexibility in the system, meaning that it maintains a more consistent pressure. Since the system will vent whenever a pressure spike exceeds the cap blow-off pressure, this means in practice the system tends to run at a slightly higher pressure too. As a knock-on effect, because the system isn't venting so often it's likely to have fewer problems maintaining a seal on the pressure cap.

The most important thing whichever way round you fit the caps is that the pressure cap maintains a good seal, and everything on the pressurised side is water tight. Depending which way round you fit the caps different seals and components are under pressure. For example, if the pressure cap seat on the expansion tank is damaged the cap won't seat properly - you can avoid this problem by putting the caps the other way round. Similarly if the pressure cap seat on the swirl tank is damaged then you'll get the opposite problem. If the hose between the swirl tank and the expansion tank is damaged then putting it under pressure would cause a leak so putting the pressure cap on the expansion tank would cure that. So depending what problems you have, your system might work better one way round or the other. But if everything is in good working order then it is better for the cooling system to have the pressure cap on the expansion tank.

[Barkychoc]

I think you're probably right Pete / Grant - most other cars have the pressure cap on the expansion tank - only TVR could invent a solution where you need to make your own rubber washer out of a bike inner tube.

It's behind you

Edited by Barkychoc on Friday 17th October 21:02

[TonupS2]

Just to change the topic slightly. Can anybody tell me whether its the swirl pot or the header tank that has the pressure release cap?

[mep12345]

TonupS2 said:

Just to change the topic slightly. Can anybody tell me whether its the swirl pot or the header tank that has the pressure release cap?

As you'll see from my earlier post (look at the link) and V8S's post either way will (in theory) work choose the one that suits you best. My preference is pressure cap on expansion bottle blanking cap on swirl pot for the advantages I and V8S list - but there is argument over this. You pays your money and takes your choice. I am a chartered engineer working on high pressure fluid systems fitted to nuclear power plants and I can't answer the question definitvely as in theory BOTH should work but you must make sure the seals seal properly. A system that doesn't seal well or is in poor condition will stop BOTH configurations from working (or at least reduce their effectiveness).

Oh I'll try not to rise to this one again!!!!

Mark

Edited by mep12345 on Saturday 18th October 09:43

[Barkychoc]

For me it would work better if the expansion tank was bigger (with more air available) so it stands no chance of spitting coolant out behind the pressure cap on the expansion tank.
I know Ray S used an expansion tank from a Renault of some description and it looked a very good solution to me.

[GreenV8S]

When I had my new swirl tank made I also had an expansion tank made in the same style that mounts onto the side of it.

[wheels1]

I have had some time to think about this now. So heres my newbe thoughts:-
All other cars, i have had with expansion tanks, have had a spring loaded cap. This is because the overflow outlet is in the neck of the tank, so no water can escape until the pressure builds above 15-16lbs, thus pushing the spring up and letting the water escape out. The way my S was set up, the expansion tank was not under pressure?? so as soon as the pressue built up the water should come out of the overflow [ so how come it has been fine all summer ]??
I think the swirl pot should have a spring loaded cap as other wise it would constantly send water to the expansion tank via the connected hose. So my next question is has anyone tried 2 spring loaded caps?? This way the system should be kept under pressure.

[GreenV8S]

wheels1 said:

I think the swirl pot should have a spring loaded cap as other wise it would constantly send water to the expansion tank via the connected hose. So my next question is has anyone tried 2 spring loaded caps?? This way the system should be kept under pressure.

There have been two reasonably detailed explanations in this thread about the two alternatives and relative pros and cons. "constantly sending water to the expansion tank" is not an issue.

If you fitted two pressure caps then your system would run at 30 psi - or at least it would get part way there before it started blowing gaskets and hoses.