Radiator cap

**Kiwivan** · 26-09-2015, 03:40 PM

Is there a difference in radiator caps for the 8 and 6 in the HX non recovery systems?
It is just one of the caps I got from repco used water? forced it out, So I went and got another(about 6 months latter and it was different and this one is ok
Ours is the 8

Cheers Kiwivan

**gregbark** · 26-09-2015, 04:37 PM

There is a difference between 6 & 8, 6=13lb & 8=15lb. You are better off with a recovery system than just venting to the ground.

**Kiwivan** · 27-09-2015, 10:35 AM

Why change it?
Worked well in the past.

Cheers Kiwivan

**wbute** · 27-09-2015, 10:37 AM

It's a better system. Radiator stays full. Only difference is the cap and overflow bottle.

**sandasharpe** · 27-09-2015, 02:45 PM

Recovery systems came in mostly to stop venting glycol. When radiators were full of water it was not such a problem. Glycol is not the nastiest stuff around but its still a chemical that shouldn't find its way into water ways and soil. There is also some small benefit by not having the air gap in the top header tank that results iwith a non recovery system.

Also I think there was another cap for slightly higher pressure when running airconditioning. Greg Barker or one of the other Gurus should be able to confirm.

Just cause it worked well doesn't mean it can't work better hey?

**wbute** · 27-09-2015, 05:57 PM

That's not right. Running a radiator at higher pressure causes the coolant to have a higher boiling point. There is more advantage than not losing coolant.

**gregbark** · 27-09-2015, 08:03 PM

If you look up the "Autocaps" website or CPC as they are known you can get nearly all the information you require. IF you still have a concern then ring them to discuss your issues. They are in Melbourne.

**sandasharpe** · 27-09-2015, 10:02 PM

Originally Posted by wbute

That's not right. Running a radiator at higher pressure causes the coolant to have a higher boiling point. There is more advantage than not losing coolant.

The pressure the cap vents at is independent of whether or not you have a recovery system. The pressure the cooling system runs at is set by the engine designers and affects the type of seals and gaskets used in the engine. Thats why different pressures for 6, 8, Ford GM etc. You can have a low pressure cap on one engine and still have a recovery system so you don't vent to ground.

When you don't have recovery, the radiator vents an inch or so of fluid out of the header tank and then finds an equilibrium so that when you keep checking there is always about an inch or so missing. This is under normal running. This can change if you tow or otherwise load up the cooling system. That's why I'm pretty sure A/C cars used to run slightly more pressure.