Mi16 radiator cap.

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GRAHAM WALLIS

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I have been having a lot of trouble keeping coolant in 309 GTi16 under competition conditions. No leakage found under pressure testing, everything from head gasket to coolant reservoir has been replaced. Today I was told that the cap should be 20 lbs, and this checks out after an on line search I have a 13 lb one at present. This could be the problem? Any comments?
 
Years ago I tried to get a new cap for my 405 from Autobarn. I asked for a 13 psi cap and they told me I needed a 20 psi one. I held out for a lower one without issue. Possibly that’s the spec for another model?
 
Seen 20lb listed in 3 different places on line. I will definitely try it.
 
Ive got a special radiator but using standard 205/309 remote reservoir.
 
Found a 20 lb cap and fitted it. Just waiting for an event to give it a try now, hopefully the Valley Stages at the end of November will go ahead. If Covid numbers stay as they are, 0 increase today, we should be good to go. Fingers crossed. They sold me a recovery cap, removed the rubber ring to make it a non recovery one.
 
Are your fans cooling properly? The thermo fan switch can also cause similar problems if its not working at the correct range. I had a faulty switch fail to bring fans on which then pushed water out of header tank. Once i replaced the switch everything went back to normal.
 
Yes, the car doesn't overheat. It has a Davies Craig fan and I left it on in the last event. I need to try it out in anger with the 20lb cap. Unfortunately motorsport by the end of the year is not certain after Andrews announcements today. And usually not much on over the Christmas period.
 
I was looking at my 205 cap on the weekend. The 205 has always used a small amount of water. It has had a 306 plastic cap on it. I compared the 306 cap to the (spare) steel 205 cap I carry and it would appear that the 306 cap is about 3mm shorter than the steel 205 cap (Seal face to clamping lugs)? The 205 reservoir neck and the 306 radiator neck appear the same though.
A neat trick that Owen had was to extend the reservoir overflow tube up onto the bottom of the windscreen, that way he could see if the cap was blowing off.
 
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