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Author: Subject: expansion tank dilema
Dave J

posted on 10/5/05 at 01:42 PM Reply With Quote
expansion tank dilema

Hi all,

I have an aluminium expansion tank which has I believe a pressure cap. It has two pipes welded on, 16mm bore at the bottom and 6mm bore at the top below the pressure cap (any excess pressure blows thru the cap and not down the pipe....not ideal).
As my radiator is lower than the top of the coolant run, I want to use this tank as the highest part of the system so enabling me to completely fill the system as well as looking after the expansion business.

At the moment I have the bottom hose from the exp' tank tee'd into the bottom rad hose. Does anyone know where the top exp tank hose should go? Top rad hose or onto the rad neck pressure relief tube? or (gasp) neither? or am I doing it all completely wrongly?
I just cannot get my head round this DOH!!

Please prevent me from frying my engine.

Any help would be sooo welcome.

Rover V8, no heater.

Many thanks.

Dave.

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Fifer

posted on 10/5/05 at 02:21 PM Reply With Quote
does the 6 mm pipe not vent when the pressure cap lifts ?
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NS Dev

posted on 10/5/05 at 03:14 PM Reply With Quote
Ahhh, another local!

Whereabouts in Leicester are you? I am down the road in Barwell and have a reasonable wealth of car knowledge so can probably help.

Basically, the 6mm feed to the header tank needs to be connected to the highest part of the system in order to bleed the air from it, on a crossflow I think this usually ends up being the thermostat housing top.

There should be a connection on the pressure cap neck which vents the steam when the cap blows. A small pipe connected to this then feeds said steam down to ground level should the worst happen.

If you mean that your tank only has the big connection and the one on the neck then you could really do with adding another connection, not difficult using techno-weld if you don't have access to aluminium welding facilities (I have done it this way a few times now)

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britishtrident

posted on 10/5/05 at 03:15 PM Reply With Quote
If you tee into the bottom hose you need a small dia bleed from the head into the top of the expansion tank, this arangement works I used in my first racing Imp.
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Dave J

posted on 10/5/05 at 03:23 PM Reply With Quote
Hi Fifer, thanks for the reply,

The pipe is below the pressure cap, therefore it cannot do the same job as the radiator pressure cap.
If you imagine a bottle, the pipe is placed just below the shoulder on the main body of the bottle and not on the neck.

The cap has what looks like a sprung loaded plastic disc inside that I assume lifts and releases any excess pressure to atmosphere. The small tube is approximately 30mm below the cap, positioned as decribed above.

I was considering plumbing this upper pipe to the rad neck outlet, so at least any vented coolant would find its way into the expansion tank.
Hopefully the lower pipe plumbed to the bottom rad hose would 'suck' the coolant back when the system cooled.
Any idea if this would work?

Thanks.

Dave

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NS Dev

posted on 10/5/05 at 03:27 PM Reply With Quote
aHHH so you mean you have two pressure caps????

You only want one! Use a "normal" cap on the header tank and a solid or very high pressure one on the radiator. One from the radiator (rather than the header tank) on a Capri 2.8i should do the trick. Then plumb the 6mm outlet(or inlet actually!) into somewhere high up on your engine (inlet manifold water connection on the rover v8??)

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Fifer

posted on 10/5/05 at 03:37 PM Reply With Quote
Ok, ive got you now
My X Flow is as follows.....
My rad has solid cap
a 6 mm pipe goes from ther to a Burton type thermo housing which i fitted a solid cap to, it then goes to my exp tank 6 mm connection (like yours).
the expansion tank has the pressure cap and does not require a pipe. The cap vents to atmosphere and sucks in air as the water expands and contracts.
Air is vented to the exp tank when filling through the 6mm pipe.
Dont know if thats clear but it's how I did mine is and the level in the exp tank sitts at 50% all the time wit small variations when cold or hot.


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Dave J

posted on 10/5/05 at 04:07 PM Reply With Quote
Thanks for the replies all. Certainly a few ideas to mull over.

If I went along the lines Trident suggests, would teeing the small dia upper hose into the top rad hose do the same job as the 'bleed' for the top of the head? I already have a Tee on that hose so as to bleed the air when filling the system. That would provide a convenient location for the 6mm hose (albeit the wrong side of the stat).

Are all rad caps the same in terms of their size?. In other words are they all interchangable (apart from pressure rating)

I'm off home now, so I'll get my brain cell around your suggestions in the morning.

I need a beer!

Thanks again for your help guys.

Dave.

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ReMan

posted on 10/5/05 at 09:16 PM Reply With Quote
So where are you Dave J?
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tks

posted on 10/5/05 at 09:35 PM Reply With Quote
uhhh???

Basicly

what you want is this.

One pressure relieve valve (some later bottle have an complex one like polo and golfs etc.)

Then you have an rad with maybe a built in T piece (i mean with this a small entrance what gives you the possibilty not to use an Tpiece)

Well a Thermostat housing has 3 Pipes
An entrance and 2 outlets an small one and a big one.

The 2 big ones you hooke up to the radiator.

(the one that that is an input (to the pump) to the lower hole)

then the other to the upper rad conections.

The small outlet of the theromstaat is for when the engine is cold, to use a small quick warmup system.

that one you connect to the upper one of your bottle.

the lowerone of your bottle then automaticly goes to the Pump entrance (T piece) or to the radiator (its there to compensate temperatures and to be able to fill the system if small circuti is used.

If you have an rad with a 2 tops then you don't need T piece (builtin)

If you don't have the small outlet on the thermostat then you don't need an bottle with 2 conections...

but just hook it the bottle up to highest point and connect it to rad or to Tpiece

The engine is then always using high circuit... (or nothing when heating up)

TKS





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NS Dev

posted on 11/5/05 at 08:59 AM Reply With Quote
UHHHHHHHHHHH!!

It all depends on the relative heights of the components!!!!!!!!!

On my grasser none of that would do any good as the top of the rad (which is side entry/exit and has no top cap) is the highest point apart from the header tank and gets an airlock in it, so I have fitted a bleed from here to the tank.

Basically, there are no rules other than make sure no air can get trapped anywhere. I would assume that the point on a Rover V8 where air would end up would be the inlet manifold as this is the highest point??

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NS Dev

posted on 11/5/05 at 09:00 AM Reply With Quote
So, where in Leics are you, ReMan and I are dying to know, like to know about fellow yocals you know!
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Dave J

posted on 11/5/05 at 10:49 AM Reply With Quote
Reman, NS Dev,

Have a look in your U2U

Dave

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Dave J

posted on 11/5/05 at 11:27 AM Reply With Quote
Thanks again for the replies all.

Can I describe what I had originally planned, as I am just starting to get a little confused with the various permutations and perhaps somebody could say if this would work or not.

At present, I have a tee in the top hose-radiator side of the thermostat housing. This I intended to go into the top connection of my exp tank (6mm dia).

On the bottom hose from the rad to the pump is another tee (15mm), this I intend to go onto the bottom connection of the exp tank (15mm).

If I can locate a solid rad cap, this would replace the existing rad cap, leaving the pressure cap on the exp bottle to handle excess pressure.

Concern: If the engine 'boils' for any reason then water will vent via the exp tank cap probably all over my battery etc (remember, the top tube is below the pressure side of the cap).

With this in mind, should I keep the standard rad cap and 'convert' the exp tank cap to solid and have the 6mm upper connection go to the rad neck rather than the top hose tee?

Sorry if I'm coming across as a bit of a tedious thicko. The ol brain ain't what it used to be. Come to think of it, it wasn't much cop to start with!

Cheers all

Dave

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NS Dev

posted on 11/5/05 at 12:29 PM Reply With Quote
Right, that all sounds good given one proviso, that the point on the top hose at which you plan to tee off the 6mm hose is the highest point in the system (apart from the tank itself) and therefore is where the air will collect.



What you are trying to achieve is to make the system so that when you fill it via the tank cap, it fills and self-bleeds all the air that the water is displacing back up the 6mm pipe. If the position of the tee piece for this pipe will permit this then this should be fine.

My old grey matter is now coming to life and thinking about it, on the Rover the top hose is right at the top of the engine isn't it? In fact the thermostat housing is about the highest point other than the carbs isn't it? If so then a tee from the top hose near to the stat end should be fine.

Certainly the "bottom of header tank to bottom hose" is quite correct.

To make another obvious point, you need to make sure that your header tank is located so that the water level in it is at or above the highest water level within the "engine" (i.e. the thermostat housing)

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tks

posted on 11/5/05 at 12:32 PM Reply With Quote
..

Shoot some pics of your bottle

and of his Cap...

I havemy rad also converted to a non press cap i simply took the grinder and gone was the first rubber...

then i took the "autogeen" with a bit of iron i welded the small pipe rigid/solid..

and done was the jobb... (my rad is made from copper its an oldiy)

i only use the cap to be able to take out all the air from the rad...

i just fill up my bottle then it starts coming out the rad and i then put the cap on......

It works fine....

BACK TO YOUR SITU.

I think you don't need the upper hose T - one..

becaus ein your situ the pump could be using the bottle as circuit and thats not what you want....

the water coming out of the thermostat need to go through the radiator..

so if i was you i took of that Tpiece and hook it up directly..

Here are 2 examples:
I mention bike type its simply 2 outlets on the thermostat....

the dotted line (optionally) is not always there..or maybe its hard wired to the pump....

one thing is for sure if thermo opens water needs!!! to pass radiator....else engine overheats...

the pressure cap should also always??? be mounted where the air is..soow many times in the bottle...



TKS Rescued attachment WaterSystem.JPG
Rescued attachment WaterSystem.JPG






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NS Dev

posted on 11/5/05 at 12:38 PM Reply With Quote
quote:
Originally posted by tks

BACK TO YOUR SITU.

I think you don't need the upper hose T - one..

becaus ein your situ the pump could be using the bottle as circuit and thats not what you want...

TKS


It is plumbed in exactly this way by numerous car mnaufacturers!!!!!

The donors of all my vauxhall 16v engines have had a connection from the "top of the engine" (be it top hose or cyl head) direct to the header tank, and a larger pipe from the bottom of the tank to the bottom hose.

please don't confuse any more on this very simple issue!!!!

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Dave J

posted on 11/5/05 at 01:55 PM Reply With Quote
Many thanks TKS for your time and considerable effort on posting your suggestions, it's much appreciated the diagrams are especially helpful. I think my set up is maybe somewhat different to how you see it.

NS Dev, you are spot on re the Rover V8.

Because of the awkward route for the top hose to the thermostat housing (it has to go over the distributor), my T in the top hose is lower than the themostat housing but higher than the inlet manifold. I may get a little air trapped in the top bend (the stat housing casting outlet pipe goes up for about 50mm and then downwards by the same amount onto which my T adaptor is fitted via a 90 deg hose) but hopefully it will not become 'locked'.

Incidentally being a leicester lad, do you know of a good motor factor in the area where such things as solid rad caps can be bought?
I keep trying Parkers, but they never have what I want!.

Anyway thanks all, here and overseas for your help

Dave.

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rusty nuts

posted on 11/5/05 at 05:38 PM Reply With Quote
Early Rover V8 engines had a "bleeder " built in to the inlet manifold between the carbs . This was a small stub about 6-8 mm IIRC. and was connected to top of rad to automatically bleed the system . Engines would overheat if this was clogged, clearing out used to solve problem if done early enough. It may be possible to fit one on your engine if not already there?
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tks

posted on 12/5/05 at 11:34 AM Reply With Quote
quote:

It is plumbed in exactly this way by numerous car mnaufacturers!!!!!



What do you mean with that? Do i have it good or Wrong???

anyway the Header tank goes exctly to the pumpinlet..thats what every ones do.. ant want..

but when your engine is hot you want your system using the rad and not the small circuit...and thats where the thermostaat is for.....

it also has a keen valve system wich with more tempereture opens more...

in that way the temperature keeps stable..

TKS





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