Header Tank Success

[kevin the chicken]

Having had problems with air locks in my S7 Redtop I decided to install a header tank. Sounds simple but space is limited under the bonnet so in the end I had to move the windscreen washer bottle and put that in the side of the passenger footwell out of the way.

The problem had been that every time the cooling system was disturbed air was getting trapped somewhere and causing either the water to blow out through the overflow bottle, leaving the radiator half empty or if running with the cap off to fill it would overflow in a great big gout of water all over the garage floor again leaving the radiator half empty and it would take several cycles of running up to temp, cooling down and then refilling before it eventually settled.

Even when it had settled and found its own level to me the level was too low leaving the top tank portion of the radiator mostly empty and the engine temp always seemed to be around the 100 mark or just below although it never actually overheated even on the rolling road where I was expecting trouble.

So in went a header tank, after a lot of head scratching as height was an issue too. In the end I installed it on the side of the pedal box as high up as I could reasoning that as long as the water in the tank was higher than the top of the radiator then it ought to work. I plumbed the bottom hose from the header into the pipe from the bottom of the rad using a T piece from ebay and the top hose went to the rad overflow with a blank cap replacing the one now on the header (following a post on here by Bob Tucker I think). I also drilled a hole in the thermostat.

I was dreading filling up and running it in case it didnt work but I can claim total success with no overflowing or overheating, took it out for a careful 20 mile run the other day and a not very careful at all 40 mile run today and the level is stable with the temp steady between 90 and 95.

I also blanked off the gaps around the rad so that the air has to go through it rather than around it. The corrugated plastic that estate agents use for their for sale signs is good for this being very rigid in one plane, flexible to a degreee in the other and very light. And its free after stormy weather.

[tractor]

_{sounds like you've had a bit of a saga glad to see you've sorted it I still don't have a thermostat in mine cos runs to hot still got to sort it}

[kevin the chicken]

You are not kidding! one thing that does niggle me though is how accurate are the temperature gauges? As I said earlier my car never boiled over even though the gauge said that it was really hot.

[agent_zed]

a pressurised system will not boil until about 110 degrees C, which is partly the point of a pressurised system. This depends on the pressure setting of your rad cap. I think i run a 13psi but you can get higher pressure ones.

 

In contrast water boils at the top of everest at 90degrees c due to the lower pressure (although its hard getting the 2b up there )

 

don't know how accurate the gauges are to be honest but it sounds like you are sitting at a better temp now.

[tractor]

_{I need to get digital stat instead of a gauge that just has hot and cold indicators}