Morris Minor Owners Club

Firstly - after 5 days of small A and B roads around Devon and Cornwall - can i just take my hat off to those of you driving round there regularly - 1 in 4 hills came as a culture shock!! We certainly struggled at times, which i still think is linked to some earlier performance issues - but we did compression tests (what are "right" levels btw?) and reset the gaps to 15 thou and she is running well apart from hills!!

Anyway, we were chatting about the rad cap being loose as we were losing water ( half an inch maybe every few hundred miles) and there are no other leaks. But now i wonder if i've got an overheating problem. Twice on the way back from cornwall we stopped and as i opened the rad cap hot water blew out from the cap (about 50cl each time). There is also a vaguely metallic smell from the rad. The cap is loose, and i was going to replace it, but the only autoparts place i could find only had 7psi caps and i guess that would be bad?

I've also realised as i have replaced water, no new coolant has gone in - so could it be that? My thinking is coolant, possible rad block and perhaps the thermostat is playing up? Anyone else have any ideas? How quick is just flushing the rad and refilling it?

Thanks

7 psi would be fine - as long as the cap is tight on the rad. Don't fill the rad right to the top! And don't worry about 'loss of coolant' - worry about when winter rolls round again.

I dont often have a lot to add to the forum Mark, but in this case...........
I replaced a water pump because 94000 miles finally did it in,a thermostat because it was only a couple of quid and seemed sensible,a new cap because the old one was tired out and not seating and finally the radiator because when I removed it and gently ran my finger down the fins with the lightest of touches, said fins literally crumbled away, see photo including decapitated wasps.
I flushed the system prior to fitting the new rad by pouring lots of water down the hoses.
How old is the radiator?, maybe worth taking it out for inspection if its long in the tooth.
Needless to say, she doesnt overheat now [frame][/frame]

Don't forget that the MInor radiator has a longer filler neck than what has become the standard. Makes finding higher rate caps more difficult - the highest I could find was 10lb. As part of a rad rebuild a couple of years ago I got the supplier to replace the neck with the later, shorter one, so that caps are more available.

I would get a cap that fits properly, 7lb will be fine, and then check to see if there is still a coolant loss. Antifreeze these days has all sorts of 'good' inhibitors, and slightly raises the boiling point as well, so once the loss is sorted, I would then make sure that the antifreeze % is right to get all the benefits from it.

'Old' antifreeze a number of years ago had some quite nasty corrosive properties and also reduced the boling point - times have definitely changed for the better!

Just seen the picture above, my old rad was a bit better than that, but not very much.

If you remove the rad cap when the rad is hot then you risk scalding yourself, even at 4lbs pressure.
Anti freeze acts as a corrosion inhibitor, particularly if you have alloy components such as thermostat housing. It will not affect the engine cooling during the summer, other than to seek out all the leaks, but should be kept to the correct mixture as much as possible.
You struggled on the A and B roads? What about all the single track roads which make driving interesting in that part of the country, especially in a Series MM, although I avoided the 1 in 7s and steeper with the trailer

BME - the rad cap isn't as tight as it might be - not wobbly, but you don't have to twist hard to get it off - indeed if you turn it too much as you put it on it comes loose again. My physics is vague but surely a loose cap would release pressure rather than build it up to make it geyser out? Though i'm probably wrong!!

What if a new cap is still loose? Then what's the next check?

My rad isn't as bad as the one in the photo, but is a bit green!

I suggest that your cap is actually fitting just fine - if it 'gushed; when you removed it..... If it wasn't sealing - it wouldn't have gushed............ The fact it can turn again and go loose - just means the rim lock is worn. I have a catch bottle on the overflow pipe from the rad - any water that escapes is returned to the rad when it cools. My rad is much worse than the on in the pic - but no overheating so far..... The Minor rad is very oversized for the job (cf a Mini rad). I do have a couple of spares for the day when it finally gives up.......