Radiator expansion tanks Explanation and Q,s!

[ROD]

Allied to my bleedin'radiator thread,thought this deserved a thread on its own!
 So Ive discovered that there are at least 2 pipe connections to an exp tank. One is at the bottom of the tank,larger than the other pipe(s)(sometimes much larger diam) The other is a smaller diam pipe outlet,which is at the top of the tank,ie above the waterline, is connected to a high point in the system,where it can bleed air from the highest point. This pipe can be seen running into the exp tank,the faster the water flows round the system,the more coolant is pumped through this pipe.In my case I have T'd this pipe into a take off I fitted to the top of the thermostat housing,which is the highest point in the system.
 The larger outlet on the tank feeds,as far as I can tell ,into the suction side of the water pump,which to me is the bottom hose(tried it in the top hose,but it ran a little cooler in the bottom hose.)All the diagrams Ive seen seem to have this connected into the bottom hose.
 Question.....
 Now,to T this into the bottom hose makes an awful spaghetti of ugly pipework and jubilee clips! So Im wondering if it can actually be T'd into one of the smaller diam hoses on the water pump ie the the hose from the rear of the head?This is still the suction side of the pump,and would make a much neater joint,to be able to fit a T into the pipe immediately above the water pump pipe stub,so that the water flows direct into the pump more or less by gravity ,which will give the pump less work to do.This will also aid topping up the system for its initial run,as the collant will be going more or less straight into the pipe to the rear of the head.
 Question... how can I work out how much the coolant in the system will expand? I think theres a formula for this.Then I could work out a tank size for when I remake the tank with altered outlet positions.
   Thanks all
 

[terry t]

if its set up right then yes it will work. look at a lot of modern motors low rad in relation to engine and heater. ii think as long as there is provision to vent the air out of the system like the renaults air screw vent in the heater hose then yes put a high pressure cap on the rad and a 10lb on bottle for the over flow

[fifer]

The standard system on the Reliants is as follows ;

The small diameter hose runs from the breather pipe at the side of the radiator cap funnel to the bottom of the overflow / expansion / extra coolant bottle and is securely clipped at both ends .
Another small diameter hose is connected to breather pipe at the top side of the overflow / expansion / extra coolant bottle on the bottle neck where another radiator cap is fitted .
This hose has to be open to atmosphere at all times .
The bottle is higher than the rad top .

System { 1 }
The following system  gives you more coolant in the system .

{ 1a } The radiator is filled to just level with the overflow pipe hole
{ 1b } A zero rated rad cap is then fitted to the radiator
{ 1c } The overflow / expansion / extra coolant bottle is then filled up to the marked fill line { about 1/3 to half full ? }
{ 1d } The 13lb radiator cap is fitted to the bottle
{ 1e } The engine is then run and any air will work its way into the bottle
{ 1f } Once fully cooled , remove the rad cap from the bottle , top up as required and replace the 13 lb cap on the bottle  



System { 2 }
The following system works as an overflow/expansion system and the bottle is not pressurised due to the fact that it is connected direct to atmoshere via the top overflow hose on the bottle .

{ 1a } The radiator is filled to just level with the overflow pipe hole
{ 1b } A 7lb or 13lb rated rad cap is then fitted to the radiator
{ 1c } The overflow / expansion bottle is then filled up to the marked fill line { about 1/3 to half full ? }
{ 1d } The blank radiator cap is fitted to the bottle
{ 1e } The engine is then run and any air will work its way into the bottle
{ 1f } Once fully cooled the engine will suck any expanded coolant back into the rad  


.
.

[spanners]

system 2 is what i made and fitted to ,EMILY, and it works a treat .

[Olds]

The coolant hardly changes in volume as water has a coefficient of thermal expansion of only 0.000214 per deg. C.
Even a Rover V8 as fitted to Land Rovers or Andy's pop have a small expansion tank. Guessing the capacity of the tank is about 1/2 litre

[ROD]

ON...I thought it expanded more than that,so I'll try to work out a size from your figure.
 
 Fifer...I see your point,but this isnt a standard Reliant set up.Not trying to teach anyone to suck eggs,but.......
 
   This rad cap is lower than the stat ,and as I have said in other threads,a catch tank type system from the rad overflow isnt any good ,cos as the rad vents at the cap,it not only vents the expanded water into the catch bottle,but also the pipe from the rear of head,and probably the head coolant as well ie the coolant from the highest points,or should I say the coolant from all the areas higher than the rad cap,drains down and escapes. Even if the catch bottle had capacity to take all this water,it wouldnt draw back in as it cools.cos you end up with an air lock in the head or pipe to the head. Also if it loses all that coolant from the high points whilst running,you are then running with no coolant in the high areas,which you would be merrily blatting along ,unaware of.I tried it and it just overflows the bottle .
 Originally it was venting out the rad overflow tube a small amount now and then,and I was losing coolant,but I was told,dont worry about it just ride it !
 
  
 Hence why I need a sealed system with a 'head' of water,and why I was asking if the exp tank connections sounded ok.

[fifer]

Rod , I believe that it does not matter the height of the radiator when using system 1 .
System 1 to my mind is a sealed system with a head of coolant because the bottle is mounted higher than the thermostat and the hoses .

Using that setup with the blank on the radiator , the coolant in the system is in the entire system as the radiator is completely full and is topped up from the extra permanent coolant in the bottle which is connected and can flow freely in and out the rad .
The bottle is mounted higher than any hose on the engine , therefore , once initial burping takes place and airlocks are dispersed upwards into the bottle and the bottle is topped up the system should only need minor top ups .
You are effectively raising the level in the rad to the fill level in the bottle .
.
.

[dr big750]

If the top hose from the thermostat runs down hill to the radiator an air lock will be trapped here and a bleed screw will be needed irrespective of the header height, other wise there is no reason either system won't work.
Alan

[ROD]

DRB750....I think the air in top hose will rise to the stat cap area,which is where I have fitted a bleed in the stat cap.
 
 Fifer........Ive re-read and see your point Pete. That system is more or less what Im doing ,but Im adding a connection to the suction side of the pump.
 
 Can someone pls tell me if my idea of 't'ing into the w/pump stub at the point where the rear pipe joins will be as effective as 't' ing into the bottom hose? (the stub is actually nearer the pump than the bott hose 't' would be,and also the coolant has a more direct path to the pump.)
 
 I believe this way will allow continuous use of the 'extra' 'spare' coolant .
 
 Going to look at an engine today,if I buy it I will be trying out the water system by next week hopefully!

[fifer]

Originally posted by ROD ;
Can someone pls tell me if my idea of 't'ing into the w/pump stub at the point where the rear pipe joins will be as effective as 't' ing into the bottom hose? (the stub is actually nearer the pump than the bott hose 't' would be,and also the coolant has a more direct path to the pump.)

I might be wrong but I see no reason to put any other connections in the system .
The connection from the rad overflow stub to the bottom of the reservoir bottle supplies the extra coolant .
The bottle is now , in effect , the top of the radiator .
The hot water enters into the rad top and falls/is drawn down through the cooling fins and cooler water is drawn into the engine .

Originally posted by ROD ; ;
I believe this way will allow continuous use of the 'extra' 'spare' coolant .

I know that your system is not standard due to the rad being lower than the thermostat but the standard system 1 setup works well in the enclosed much hotter under bonnet environment in the Reliant 3 wheeler cars .
.

[hunter]

If it was me,i wouldn't fit a tank there is no need,
Just fit a filler above the rad and stat housing.

[digger06]

im with the above, keep it simple, try and get the filler high, and if you think theres air in the hoses, run it and give em a squeeze half a dozen times to shift the bubbles,
simpler the better

[ROD]

So,zero rated cap on the rad,and 7lb cap on a filler neck in the top hose?

[fifer]

I am with Hunter and Digger06 on this 

[ROD]

Ok I will try that,but Im struggling to find another engine at the moment..One I looked at today wasnt very good!