The radiator cap on my Micra radiator has started blowing (overflowing) and I wondered if anyone else had come across this problem?

It started happening immediatly after I weakened the mixtures on my Fireblade engine to get my MK Indy through a CAT test in prep for my SVA on Oct 4th. It appears the engine is now running hotter (90 deg instead of 80 deg).

I asked my local motor factors for a higher presure cap that fits a Micra rad but they say there isn't one.

Has any one had this problem and more importrantly solved it?

Can't you just richen the mixtures back up to normal, thereby reducing the temperature? Sounds like you may be getting predetonation in which case it will eventually bu88er your engine/valves up anyway.

Sounds like the engine is now running too weak causing the increase in temperature, as already advised this may cause engine damage. As a stop gap remedy try a bottle of Red Line Water Wetter, this will reduce temperature by maybe 20 deg. Will probably get you through S.V.A. . Advise you rectify problem before damaging engine. Rusty

What do you mean by 'blowing'?

Is the engine pushing some water out of the breather pipe-or is the radiator doing a fine impression of a kettle at 'brew-up' time?

If the answer is a), that is likely to be mormal. Some water loss in a totally filled system is fine, as the engine warms up. An expanding liquid has to go somewhere! If this is all it is, you ideally need to fit an expansion tank, so the water that it pushes out as it gets warm, is sucked back in again as it cools. To be double sure, treat it to a new standard radiator cap-the seal and the pressure spring will deteriorate with age, and leak, causing the water to leave the system far earlier than it should.
Your guage says 90c, which if it can be believed, is not indicating that the engine is boiling or owt. I say that, because temp guages-especially electric ones, can be notoriously inaccurate. But if the leccy fan is cutting in/out (but some dont come in to nearly boiling point, if it is reading 90c it may not ...) and isnt doing impersonations of a little steam train in your garage, it doesnt sound to be too much of a problem...

I can't adjust the mixtures until after SVA in early Oct so I'm looking for a short term solution so that I can drive to the testing station in Norwich (50 mls) without spraying anti-freeze all over the car.

When I say blow I guess I mean leak. I have an expansion bottle fitted with its own pressure cap (http://www.dodgyroger.com/locost/headertank.jpg )but the rad cap must have a lower pressure so it blows first (no I can't swap them as they are different caps).

I may fit a second fluid capture tank adjacent to the radiator.

Thanks,
Roger

you should only have 1 pressure car,normally any excess water(dont overfill rad first)will go into the expansion bottle and suck back when it cools down,try exp bottle without pressure cap

Indeed. As Conrod says, junk the pressure cap on the Exp.tank if there is one fitted.

But I would still advise getting a new Micra cap, just to be sure...