Radiator Blow Off

[Guest boggie]

Hi All,

I have a 2.0L Exmo and am using the RHE supplied radiator. Occasionally water is blown off through the overflow pipe even though the water level started out at the correct amount. Has anyone a fix for this? I spoke to a few people at a recent show and they suggest using a catch tank / top-up tank, any idea which one?

Cheers, Boggie

[Longboarder]

You need to arrange a simple container which can be as basic as a coke bottle. Take the radiator overflow hose into it and nearly to the bottom. Add a little water so the end of the overflow hose is submerged. You may have to change the rad cap to one with a rubber seal for the top of the rad filler neck as well as the pressure spring/seal/valve in it. Then as your engine gets hot, water is pushed into the tank. As it cools it is sucked back keeping the rad filled at all times. If this doesnt work its almost certainly failure to seal round the rim of the rad filler neck.

 

Nigel

[Guest nick coram]

I am currently revising the cooling system on my S7 and I've seen this method suggested else where. A capri tank was recomended.

 

What I dont understand is how the presure cap on the top of the rad can allow water to be drawen back in. The cap on my rad has a sprung seal and will only open with an amount of positive presure from inside the radiator pushes it of the seat like a safty valve. When the presure is below this level the cap seals again. It apears to act like a one way valve. I cant see how water can be drawn back in to the top of the rad as this would require negitive presure and make the cap seal even more tightly.

 

Couldent this be rooted to the top of the header tank ?

[Guest chris]

I am told that a nissan micra header tank is a good bet,I used an early primera tank and it works a treat.I understand that the valve on the top of the rad opens due to temperature which is how it can suck the water back in.Also look at dave andrews site

regards chris

[Guest Ant]

The radiator cap is a one way valve, becoming two way once the pressure builds up on the radiator side.

 

Re tanks - I got one off a capri with a 2.0 pinto in it. It's fairly small, has a non-pressurised cap, and a single small hose connection in the bottom. I copied my installation exactly from this capri and it works just fine (so far!). If you get a different bottle from another car and it has a pressurised cap then you simply need to remove the seals from it to form a non-pressurised cap. A petrol 205 has a nice cylinderical bottle ideal for this, again with a single outlet in the bottom. Failing that then lots of people seem to use cyclists drinking bottles, with a hose pushed in the top but extending in to the bottom, effectively making it the same as having a single outlet at the bottom.

 

Ant

[Guest TerryBarry]

The Nissan Micra tank could be useful on 89/90 models ( and maybe others) it has a small triangular cross section is about 30cm deep with a bottom entry, a simple plastic cap and a moulded vent at the top.

On radiator caps - it's that little metal disc on the underside of the cap that is the valve that allows re-entry of air / water when the radiator cools.

 

If anyone has any ideas of what other goodies a Nissan Micra could provide PLEASE let me know - we've got one shortly to be despatched to that great yard in the sky.

 

Terry

[Longboarder]

This shows a basic arrangement.

 

Nigel

[Longboarder]

And the cap when water is flowing back into the rad.

 

Nigel

[Guest boggie]

Ahh, I seeeee.

Which cap should I buy to make this rather splendid diagramme work in practice on my car.

Cheers,

Boggie

[Guest 2BBoulton]

I guess that expansion tank has to be near the top of the rad as shown in the above diagram for it to work properly and not at the bottom where there is more room to fit one.

 

Bruce

[Longboarder]

No. It can be low down. As long as the tube is underwater and there are no air leaks it sucks back water fine. Just need to get a big rubber seal for the sierra rad cap.

 

Nigel

[Guest 2BBoulton]

Thats Ok then, Another job for the list

[Guest nick coram]

AH! I See said the blind man! Thanks Bruce.

 

My S7 rad vent is currently blanked off and a header tank with a presure cap is fitted to the top hose. this is also (I asume) a two way cap. This gives a presureised system.

 

Three further questions spring to mind.

If I connect the rad top as indicated, will this lift at a lower presure?

How can I be sure that when the system cools it will draw from the rad bottle and not through the header tank?

Is there any way of geting rid of the header tank and only using the rad bottle? This would be most similar to the original cortina system.

 

Nick

[Longboarder]

If you want to get rid of your pressurised header you can remove it and blank off the top hose junction. Discard the rad blanking cap but pinch its big rubber seal. Cut out the centre and use it with the header tanks pressure cap on the rad to ensure a good seal. Then open up the rad overflow pipe and connect up an overflow bottle. Should be translucent so you can check the water level. Fill from the rad cap. (You can't run both systems together. Not sure why you would want to.)

 

Nigel

Edited April 15, 2003 by Longboarder

[Guest nick coram]

I've moved my rad in to the nose cone and so accesability to the top cap is poor if not impossible so I need to keep the header tank. I've had a problem with air building up in the rad (before I moved it) which for some reason diden't escape back to the header tank. This eventually lead to a head gasket problem. I thought that alowing the top of the rad to vent under presure would purge any air build up.

 

Nick/.