Board logo

Coolant overflow - where to?
ShaunB - 21/2/10 at 08:35 AM

Does the coolant overflow from header tank have to run into a catch tank or is it allowed to drain onto the ground?

Cheers,
Shaun.

speedyxjs - 21/2/10 at 08:56 AM

On mine it goes to the thermostat. It should be connected to something otherwise you would loose all your coolant when cornering.

vinny1275 - 21/2/10 at 09:08 AM

It's not really an overflow - it's a breather to allow air to get to the top of the coolant system - you shouldn't completely fill the header tank, to give the air room to expand once it heats up - like Speedy said, leaving any of the coolant system connections open will mean you'll just lose it all once it's up to temperature....

HTH


Vince

ShaunB - 21/2/10 at 09:43 AM

Sorry, think I've confused you here. I meant the small outlet/breather that sits above the pressure cap seal in the neck of the header tank. Used to release any excess coolant due to expansion, and allow air back in air as the system cools.

The actual cooling system is sealed, not open, the 2 lower outlets on the header tank connect to 1) the stat housing (blanking cap fitted) 2) the small connection on the top of the water pump.

Cheers,
Shaun.

r1_pete - 21/2/10 at 10:06 AM

Yes the one above the pressure cap seal just vents to atmosphere, it may drip a little at first until the coolant finds its level.

Simon - 21/2/10 at 10:52 AM

Run a small tube from the outlet, down to the bottom of the engine bay. That way you engine bay stays cleanish if engine overheats.

ATB

Simon

02GF74 - 21/2/10 at 12:23 PM

quote:
Originally posted by ShaunB
Sorry, think I've confused you here. I meant the small outlet/breather that sits above the pressure cap seal in the neck of the header tank.


what exactly are you talking about here?

thre are two types of systems that I am aware of.

old type, e.g.ford drossflow.
small outlet in neck of radiator filler cap. this goes to a collector tank that is open to air.

the radiator cap is a 2 way valve. when water expands, it opens to allow water into the tank. when the water in radiator cools, a second valve opens and sucks water from the collector tank back in to the radiator. you can leave out the collector tank but then the water will be spat onto the road and the radiator will not fill up full.

second system on modern cars e.g. ford zetec.
no radiator cap but sealed radiator. an expansion tank with pressure cap takes the water when it expands, also connected to it is a breather to get air out of the coooling system. the water level rises and falls in the expansion tank as the water exapnds and cools. it is a closed system, the pressure cap will release air, or in exrteme cases water should the coolant get overly hot [ problems.

radiator caps in both system types keep the water under pressure so its boiling point is raised to about 110 C.

ShaunB - 21/2/10 at 07:00 PM

This is a 750MC race car (hence the posting in Race Issues) and has the modern system you mention with the seperate header tank with a pressure cap mounted high up on the bulkhead. The rad is a sealed type, the stat housing is from Mk1 XR2 (or Burtons), has a fan switch in the side and blanking cap in place of a pressure rad cap.

My actual question was: From a scrutineering point of view does the header tank vent pipe have to be plumbed into a catch tank or can it vent onto the track? With a healthy cooling system and as long as the header tank has not been overfilled, I would not expect any coolant loss via the vent pipe. The Blue book and Locost Regs do not give a specific answer.

ironside - 22/2/10 at 10:48 AM

Hi Shaun,

I have exactly the system you describe on my race car. My vent from the pressure cap goes nowhere. I didn't even run a hose to the bottom of the engine bay and was fine at scrutineering all last season.

Cheers,
Simon.

modee - 22/2/10 at 11:17 AM

You will get away without a catch tank until you are sitting on the grid after a red flag on a hot day. You will spray coolant onto the track and the marshalls will hook you. Your choice.

ironside - 22/2/10 at 11:25 AM

Perhaps an idea to vent mine into the oil catch tank then. Just means I won't be able to pour the contents of that back into the engine anymore