Morris Minor Owners Club

I've found a 7 psi radiator cap and am wondering whether to use it.
From "Steam Tables" I see that the water boiling point with the standard 4 psi cap is raised to 106C, for the 7psi cap its raised to 111C and for 14 psi (which I think is Mini or Marina) its 119C. Do you think the pump seals, etc can stand a higher pressure? (I've got rid of the bypass hose, by the way.)
The reason for the speculation is that I'm using a 89C thermostat and am toying with the idea to go higher, and of course, with higher pressures you get more temperature "headroom" over the thermostat opening temp which seems a good thing.
Any thoughts? (And don't say "Why bother?" I'm a borne bodger and can't leave anything alone for long.) Regards, MikeN.

First move I suggest is to get a lower thermostat (72 ish) for summer use - that 89 will be fine for winter of course !! The water should not get near boiling - so really the cap is just there to seal the system - and to give slight reserve in moments of stress when the engine has to work extra hard! I would not specially go for a higher pressure cap - it's just more likey to burst hoses.
Run the engine too hot - the oil gets extra hot and thin - without an oil cooler there may be trouble ahead!

I run with a 88c stat & a 7lb cap all year. no probs the temp gauge sits steady at about this temp whether its a hot summer day or a cold winters night .
As long as they're not on there last legs the pump seals & hoses will be ok. after all Minis, Metros & Midgets etc seem to cope ok with higher pressures than this

That's exactly as it should be - but in summer the oil will be a LOT hotter due to reduced cooling effect over the sump. Everyone to their own choice of course - but I prefer lower stat in summer to give the engine a break!

Thanks Mogwai for the advice and encouragement. I'll give it a go and fit the 7 psi cap. The test comes if we boil (and only then will we have the full 7psi pressure) and I've only did that once, when I forgot all about a radiator blank I'd fitted.
Re Roy's point on oil temp, I see that Visard recommends a bulk sump temperature ".. somewhere near the 200[F] mark" ie around 93C (from "Tuning the A-Series Engine", page 424). Personally, on a standard engine I've only reached higher than this (210-212F, 98-100C ) on a long run at 65+ (true) with a low oil level on a hot August day. (That gave only 8 psi on tick over!) Normal running at 45-55 mph over journies of 20-30 miles gives no more than 180F (82C) which might be deemed the lowest temp one should really have. Short journies hardly get to 160F(71C), so I'm thinking of a oil heater using the heater water return.
Re water temp, surely Roy, the point of thermostat is to give a fast warm up to overcome condensation within the cylinders which with dissolved CO2 causes acidic corrosion of the bores. In essence, the higher you can get the bore surface temp the better - with due reference to lubrication, cylinder filling, etc. Regards, MikeN.
PS Thinking that picture at the bottom of old Roy's contributions was a steam engine I hought he knew all about steam tables, etc. But perhaps its really electric. (Just joking!)

" old Roy's " Well - thanks Mike !!
Yes - I do know about steam tables - point is - Minor should not be making steam - leave that to me and Morayshire! It's 'radcap' blows off at 180 psi!
Run your engine as hot as you like Mike - it's your engine - and yes - theoretically (Carnot cycle etc) it works most efficiently when hot - just unfortunate that the lubrication can then become a bit marginal and then it all gets into a bit of a mess. For me - cool in summer is more likely to give a lasting engine - my old rally Minor gave constant crank problems -until I fitted an oil cooler which solved everything!

I suppose really it does make the case for using a good quality oil if you're going to use a higher temp thermostat.
I find it difficult to understand why the concern about these engine temperatures when others say the Minor engine is overcooled

Most of the time it is overcooled - or at least , the rad is capable of overcooling it - but that's what the stat is for - to hold the temperature up to the desired level. However - on long hard slog up a hill - the lowish flow of air through the rad and the hard working engine - could raise the temperature beyond normal boiling point. One approach is to stop it boiling by raising the pressure - and hoping nothing lets go, the other is to have some reserve capacity in store by running the engine cooler to start with!

MikeNash wrote: ... so I'm thinking of a oil heater using the heater water return.

The MG Metro had that, though I thought it was intended as an oil cooler. Basically a sandwich block with water piped through it that fits between the oil filter and engine.

I've got one somewhere if you want to try it.

Aye - the MG Metro had the little water/oil heat exchanger - it was intended as a cooler - and was fitted exactly because of hot oil problems which are worse in FWD versions due to the churning effects of the gears in the sump! The Turbo Metro had a proper air/oil cooler - as did all but the first versions of the original Cooper S after early crankshaft disasters when that car was first introduced.

Millerman,
I'm using Adsa's and Wilkinson's oil at £6 a gallon, primarily 'cos its going out at the engine around 200-250 to the pint! Visard says that good quality conventional oils are OK to 220F (105C) If the engine was rebuilt or specially tuned for a lot more power then I'd spend more money on oil. But the engine keeps going on even tho' its done about 150K and it just won't die!
But I try to keep the oil clean as possible by using magnets, and before Old Roy wakes up and says you don't need them like Minis do (no gearbox chips and all that), magnets do collect down to very small sizes unlike ordinary filters. The latter full flow sort (unlike bypass filters) go only down to about 10-20 microns at best whereas magnets collect down to moleculear sizes - provided its close enough, of course. Years ago, I bought a "Filtermag" from Agriemach Ltd that clamps (magnetically) to the outside of the oil filter and attracts metal particles to the inside of the filter body. (They're available much cheaper on e-bay now.) And back in the past I'd fitted a short "Eclipse" magnet in the drain plug. Its always frightening to see what's on the magnet - but I'm always pleased to see its there and not travelling about in the engine! I've fitted them to the gearbox and back axle too. If you're interested, put "magnetic filters" in to google - its an interesting development.

Mike
Interesting points. I was using Asda 20/50 in a 1275 in my Trav and the engine was using oil, I use the car for towing and like to keep up with the traffic on A roads and motorways. Before going to france on MOT I changed to a branded 20/50 with the spec quoted on the tin. The result was 1100 miles and just over a pint used, again as far as possible keeping up with the traffic.

My point being if you are going to drive your Minor to keep up with the traffic/ as a working car, then a lot less oil is going to be consumed if a branded full spec oil is used.

I used to use Valvoline which is a very good oil but their 20/50 has got a bit expensive

Now that's interesting! I'll give it a try. Do you have an oil pressure gauge fitted, and if so, did you see any change there too? It drops to 42 psi max with hot oil - and it seems independent of oil temp above about 180F (82C) which seems odd to me. Its as though the viscocity doesn't change above that temp, which I wouldn't expect. MikeN.