Expansion tank

[Lemp1953]

Hi, I am thinking of fitting a expansion tank from a mk3 ford Mondeo and wondered if any one else has done the same (i think that i have seen one in a back issue of the Stag mag) The pressure cap for the Stag is i believe is 20 psi where as the Mondeo is 21 psi .
Will the fact that 1 psi extra will make any difference.
Cheers
Mike

[mjheathcote]

No not really, manufacturing tolerance will be greater!
However I wouldn't personally want a 20psi cap, I have run a 13psi cap for decades.
Why? Well if the boiling point of water at 13psi is reached, I'm in big trouble anyway, and why expose the cooling system to a higher 20psi which could blow out weak hoses/gaskets?

[SHL565S]

my stag has an expansion tank from a Mercedes. looks quite hood and seems very suitable for a stag I think the pressure caps around 15 psi but not sure

[Donkey]

Hi, I am thinking of fitting a expansion tank from a mk3 ford Mondeo and wondered if any one else has done the same (i think that i have seen one in a back issue of the Stag mag) The pressure cap for the Stag is i believe is 20 psi where as the Mondeo is 21 psi .
Will the fact that 1 psi extra will make any difference.
Cheers
Mike

Hi Mike,
What's wrong with your present one?

[Lingen]

Are we talking header tanks or expansion tanks here? They are different animals.
Mike.

[Lemp1953]

Its the header tank (or over flow) i'm thinking of as they are of a slightly larger capacity . the original one works fine at the moment. The temp gauge rests just under left of centre ( is that normal running temp ?) Would it be any better than the standard one already fitted and would i be wasting my time and effort fitting one in ?
Mike.

[Lingen]

Mike.
Fitting a slightly larger expansion tank will make no difference, as it is only there to receive and return the small amount of excess coolant created by expansion as it warms up, and this amount is pre-determined..
Only by fitting a header tank can the capacity be increased.
Mike.

[Lemp1953]

Thanks, that's been of great help. As to the temp gauge needle position, what is the ideal position?

[KOY 23]

I also have the Merc tank which is see through, easy to check level without removing cap, baffled and adequate capacity so no surges and false alarms. I run with a 13psi cap for the same reasons as Mike H. Merc hose ideal as it is the correct shape to run to rad without looking like a plumbing shop.
Temp gauge position sounds about right but depends on sender fitted. LD parts sell one that makes the needle vertical at 90degrees.

[Lemp1953]

Hi, Koy 23. Would have got back sooner but forum was playing up. Have you got a picture of the tank and pipework please.
Mike

[Mark S]

I have a similar Merc 124 (I think) header tank.
Standard rad cap fitting.
Bottom tank connection connected to the Mk2 rad expansion pipe on the top of the rad. (connected to the "cool" side of the rad).
Top tank connection connected to an additional pipe soldered into the side of the rad filler neck.
Tank mounted on a plate clamped under the wiper motor for easy removal but I can still get to the plugs and fusebox with it fitted.
Low level float switch connected in parallel to the brake bias light. (Most modern tanks just have electrodes connected to an ECU)

The system has been fitted for over 10 years and works well. Any air that may get in under vacuum is bled into the tank.
With the engine up to temp and the stat open you can see a good squirt of water into the top of the tank when the engine is rev'd which shows it works and bleeds any trapped air out of the system.
The tank is clear and higher than the rad so you can see how much water is in there,

Engine is in bits but I'll take some pics tomorrow.

I would not use the original Mk2 low round bottle with pressure cap as I believe the design is fundamentally flawed and doomed to fill the cooling system with air.

[Danny]

Have a look at the Grampian Stags website, we have a couple of different header tank setups on the Technical page. http://www.grampianstags.net/restorations.htm

[jbuckl]

I have a similar Merc 124 (I think) header tank.
Standard rad cap fitting.
Bottom tank connection connected to the Mk2 rad expansion pipe on the top of the rad. (connected to the "cool" side of the rad).
Top tank connection connected to an additional pipe soldered into the side of the rad filler neck.
Tank mounted on a plate clamped under the wiper motor for easy removal but I can still get to the plugs and fusebox with it fitted.
Low level float switch connected in parallel to the brake bias light. (Most modern tanks just have electrodes connected to an ECU)

The system has been fitted for over 10 years and works well. Any air that may get in under vacuum is bled into the tank.
With the engine up to temp and the stat open you can see a good squirt of water into the top of the tank when the engine is rev'd which shows it works and bleeds any trapped air out of the system.
The tank is clear and higher than the rad so you can see how much water is in there,

Engine is in bits but I'll take some pics tomorrow.

I would not use the original Mk2 low round bottle with pressure cap as I believe the design is fundamentally flawed and doomed to fill the cooling system with air.

Mk2 bottle working well on mine. However some of the new replacement mk2 bottles do not allow the pressure cap to seal correctly.

[jbuckl]

One benefit of a header tank is that it can provide self bleeding of air. However quite a few that have been shown have the return plumbed into the top hose / hi pressure side, which cannot allow self bleeding & also reduces the tanks function to ‘extra coolant capacity’. Metered or restricted feed into the tank should be from the top hose/hi-pressure side & return / outlet should be to the low pressure side / bottom hose. Should I get my coat now?

[tvrgeek]

Thanks, that's been of great help. As to the temp gauge needle position, what is the ideal position?

I just tested a new sender from RImmer. Without the external resistor that was on my gauge, I am 185F at the center. So normal ( 195) is just above center. With the resistor, center of gauge was almost 210. THis is with a stable 10V supply.