I have put this listing up before but the problem still remains. My radiator wont neutralise pressure, I have replaced my overflow tank, and both caps, the new ones have both been tested and work as new. Where does the problem lie? Blown head gasket... doubt it.

Jay

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Jay: 0431404607

Huh ?? Both caps are new ?????

Is this the typical overflow system fitted by BMC/Leyland on Morris 1100's and Mokes with a radiator and the overflow hose goes up to a second small tank on the mounted on the fire wall.

On that system (which is the standard fitting) the cap on the radiator is NOT a pressure cap. It is just a cap to allow the free passge of coolant to and from the resevoir tank on the fire wall. The cap on the resevoir tank is a pressure cap.

If you have two pressure caps on the system then it is not going to neutralise.

There are two type of pressures caps in any case. Those designed for an overflow tank and those designed for systems without an overflow tank.

If you system is the standard BMC type then the single pressure cap you require is a non overflow type.

AFAIK if you have the BMC style pressurised overflow tank then, as Mike says, you need a blanking cap on the radiator (CPC 2001), as the overflow tank basically acts as an extension of the radiator capacity. The cap on the overflow tank should be a standard type radiator cap (usually short neck, CPC520-13).

If you have an aftermarket style overflow tank that is not pressurised (a la modern cars) then you need a special pressure cap on the radiator (CPC543-13, I think?) which allows the water to be drawn back in to the radiator once it cools down.

If you have standard caps on both the radiator and overflow tank I don't know that it would cause pressure problems, but it certainly wouldn't work properly.

thanks for your help.
Yes the overflow tank is the origional one as used on the moke and i do have the blanking cap for the radiator and the right cap for the overflow and Yes they are both new.
Any new ideas.
The cooling system is unmodified, besides a few extra holes drilled in the thermostat.

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Jay: 0431404607

Okay now we start the methodical backtracking.

The engine - how old is it ???????? Has it ever been rebuilt and or hot dipped.

The radiator - has it it ever had the tanks of it and then the cores cleaned by pushing a rod through (by a radiator specialist) as the radiator may be partially or reasonably blocked.

The water pump - are the vanes on it fairly well corroded and unable to pump the coolant around. If you need a new water pump the best one to get is the high-capacity version with extended vanes that are cast metal. They are about $70 from any of the mini retail specialists.

My money is on a partially blocked radiator.

Mike

Keep note, they are will never exceed 80, which is a very reasonable temp considering, a blocked radiator, But yes the engine is old and the radiator may be blocked... But surly i would get hot temps if this was the case.

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Jay: 0431404607

yes you are right - I was mentally thinking of overheating problems.

Mike

My guess is you have an air pocket in the system, which is being held in place by a blocked gallery or core. Can't think of any other reason as to why your holding pressure. You have obviously flushed your system, but maybe you need to give it a good chemcal flush. Just think out loud. Will be interested myself as to what it is.

Cheers
Aaron

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On this note i had to buy a new radiator cap as my disappeared....not sure where.

I went to repco and they just fitted one to my spare radiator. However im loosing coolant out the overflow tube.

I've probably got the wrong cap? or is something else wrong?

The radiator was completely recored 3 weeks ago. Runs at around 65-75 degrees.

Cheer,


Michael.

I went to repco and they just fitted one to my spare radiator. However im loosing coolant out the overflow tube.

I've probably got the wrong cap? or is something else wrong?


lossing 1/2ltr once off is normal mate. When opening the cap when cold you should always be able to see the water, just above the fins... or do you lose water everytime the car is run?

Anyway back to be Q's air pocket?? sounds possible i guess, best way to get it out without pulling the Rad out.. CBF doing that

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Jay: 0431404607

Yes it's not unusual to loose a bit of coolant out the overflow if you have just topped it up as Minis tend to find their natural level and stay there. If it is continually loosing coolant though you have a problem - a dodgy or wrong cap can cause this so check that first.

yeah i thought it was trying to find its levels as well but i changed the coolant on sunday and now its thursday and still trying to find levels, something isn't right.

atm i can see the water level marker on the radiator it appears to be just on that.

i've got another cap on the way, hopefully that will fix it.

A new cap should hopefully sort you out. If the guys at Repco just found a cap that fits rather than looking at the catalogue to find the correct cap, then it could easily be wrong and you wouldn't know. I take it you don't have the part number from the packaging?

no i dont think i do, i threw it out.

thanks everyone.