17 replies to this topic

[AndrewUK1990]

Hello again everyone, ive just returned from a massive trip from Fort William to Leeds from the mtb downhill world cup in my mini and ive noticed its spewed oil out of a few seals on the journey back. Admitadly i was doing about 3.5k - 4k RPM most of the way home :0 so im not too surprised but i was wondering if people had any opinions and or experience with oil coolers for minis? It still had good oil pressure 65 psi all the way back but its obviously just getting too hot and running thin then leaking. It doesnt leak under normal running, just at prelonged high RPM like on a motorway. I always make sure the oil is at correct levels etc and i use Mineral Classic HPR 30 (20wt60). I am aware that i should fit a thermostat to the oil cooler also to avoid running cold oil.

Basically what im asking is for peoples thoughts and opinions on weather an oil cooler might be a good idea as i do a fair amount of motorway driving unfortunatly and i have a mental 3.9 FD! Also i would be greatful if anyone could point out possible problems i may run into trying to fit one under a standard round nose - for that matter do they even fit under the bonnet?

Also i should add it has a 4 core water rad and overall engine temps are spot on at 88c.

Thankyou all in advance as always!

Edited by AndrewUK1990, 06 June 2011 - 12:40 PM.

[Cooperman]

For road use with sustained high revs an oil cooler is a good idea. Unless you are running a sump guard, a 10-row cooler would be fine and if you wish an oil thermostat would be a good idea. If you have a sump guard then a 13-row is better as the guard does really take away a lot of oil cooling potential. I run a 3.9 FD with a full-length sump guard and find a 13-row is the right one and I don't run a 'stat with mine as I know the oil will get very hot. I use Valvoline Racing 20w50 mineral oil.
I hope this helps you.

[jaydee]

Oil cooler fits behind the grill using two brackets.
I dont know about the oil you're using, personally my choice is miller or castrol, either 20W50 mineral, and never had a leak with them.
Have you got an oil temp gauge so you can check if thats really an overheating problem?
If its a problem of overheating on motorway journeys, you can fit a small oil cooler -10 or 13 rows- with a thermostat, which opens at about 74 deg (it is a bit low imoh).
It is also very important to not overcool oil, this causes excessive wear and performance loss, but if your engine is tuned (you didnt state you engine spec) and you do a lot of motorway miles, then an oil cooler should help to keep your temperatures OK.

[reallybig]

i use 10/40. If it doesn't leak it's not a real mini

[jaydee]

Minis ALWAYS leaks yes..but
When you're pusing and oil starts to go past the oil clutch seal, well, you'll steer clear of the cheapo 10w40 stuff..LOL

[Cooperman]

Minis ALWAYS leaks yes..but
When you're pusing and oil starts to go past the oil clutch seal, well, you'll steer clear of the cheapo 10w40 stuff..LOL

In fact, steer clear of all 10w40 stuff. The gearbox needs a thicker oil - actually that design of box was intended to use EP80 gear oil, so the oil grade issue is more concerned with the 'box. That's why a 20w50 mineral is generally accepted as the one to use, and a good quality one at that. It has been said that some of the current synthetics and semi-synthetics are OK, but it may well be best to stick with the better 20w50 minerals and have the confidence that it's the right oil.

[jaydee]

Well, there are two shools about the gearbox, some says 10w40 is OK, others say NO NO.. I'm stuck with the good old stuff.
From my experience, most of the problems i've had with 10w40 and with synthetic stuff, is that they go past the seals very easily.
About the gerbox, from what i've found, it seems that 20w50 oil preserves it a bit better and makes it work smooth when driving hard.

[Cooperman]

My thought process says that ideally the gearbox/diff needs EP80 but can't have that as it has to share the oil with the engine. Thus a 50 grade is better than a 40 grade as 50 is nearer to 80 than 40. And change it very, very often, like every 3000 miles maximum.

[Ivor Badger]

My thought process says that ideally the gearbox/diff needs EP80 but can't have that as it has to share the oil with the engine. Thus a 50 grade is better than a 40 grade as 50 is nearer to 80 than 40. And change it very, very often, like every 3000 miles maximum.

The oil requirement surely depends on the design of the transmission. For example, a Rover 2000 P6 uses engine oil in the box, but people fill them with gear oil when not checking. This results in a notchy box until the oil heats up. Or in the case of the 3500, an extra howl from the gearbox oil pump until the oil is thin enough to get through it. Since the mini box is designed to run engine oil and the C&P is no different to any other gear, why would the box need EP gear oil?

[Cooperman]

My thought process says that ideally the gearbox/diff needs EP80 but can't have that as it has to share the oil with the engine. Thus a 50 grade is better than a 40 grade as 50 is nearer to 80 than 40. And change it very, very often, like every 3000 miles maximum.

The oil requirement surely depends on the design of the transmission. For example, a Rover 2000 P6 uses engine oil in the box, but people fill them with gear oil when not checking. This results in a notchy box until the oil heats up. Or in the case of the 3500, an extra howl from the gearbox oil pump until the oil is thin enough to get through it. Since the mini box is designed to run engine oil and the C&P is no different to any other gear, why would the box need EP gear oil?

Simply because the Mini gearbox was designed in 1958/9 and used an A35/AH Sprite type gear cluster design. The A35 and Sprite had EP80 gear oil specified as the correct gear oil and, ideally, that is what the Mini needs but, of course, can't have.
It is not a later Rover gearbox with or without a gearbox oil pump, it is just an immersed gearbox with splash-feed as fitted to all BMC cars of the late 50's but with the diff built in as well and sharing its oil with the engine. That is why the transmission has always been the weak point on the Mini and to use a really thin oil just makes the gearbox repairers rich.

[Ivor Badger]

My thought process says that ideally the gearbox/diff needs EP80 but can't have that as it has to share the oil with the engine. Thus a 50 grade is better than a 40 grade as 50 is nearer to 80 than 40. And change it very, very often, like every 3000 miles maximum.

The oil requirement surely depends on the design of the transmission. For example, a Rover 2000 P6 uses engine oil in the box, but people fill them with gear oil when not checking. This results in a notchy box until the oil heats up. Or in the case of the 3500, an extra howl from the gearbox oil pump until the oil is thin enough to get through it. Since the mini box is designed to run engine oil and the C&P is no different to any other gear, why would the box need EP gear oil?

Simply because the Mini gearbox was designed in 1958/9 and used an A35/AH Sprite type gear cluster design. The A35 and Sprite had EP80 gear oil specified as the correct gear oil and, ideally, that is what the Mini needs but, of course, can't have.
It is not a later Rover gearbox with or without a gearbox oil pump, it is just an immersed gearbox with splash-feed as fitted to all BMC cars of the late 50's but with the diff built in as well and sharing its oil with the engine. That is why the transmission has always been the weak point on the Mini and to use a really thin oil just makes the gearbox repairers rich.

And the box was re engineered slightly in the early 60s to cover up the only problem thrown up by the design, ie the original cone tye synchro to b type gears. The box was the re engineered for the 4 sychro box and if any changes were required for the oil, they ould surely have been icorporated then. Out of all the mini boxes i have seen broken, not one has been caused by the oil used. In fact I have only seen one broken gear and that was not caused by use, but by myself.

[Cooperman]

In my years with Minis and other BMC cars I've seen many badly worn gearboxes. I don't think that the thin oil causes failure of the actual gears, more that the wear on the gearbox shafts, syncros and bearings, and the diff-pin, is greater than on the corresponding 'in-line' boxes of the same basic design but which use the specified EP80 gear oil.
The box was never 're-designed' in the true sense of the word, it was just modified to the minimum amout possible to reduce warranty claims, as was the way with BMC and its successors. The limitations of the Mini box have always been dimensional and fitting a box with the gear sizes the same as for a 30 bhp car to one giving over 70 bhp, but with only minor alterations, was always going to be a poor compromise, but there was no viable, in costing terms, alternative. Engine and gearbox oil should never be shared and later transverse engine designs have just confirmed this.
The oil grade issue has never gone away and was always known to be a reliability and life-cycle issue right back in the 60's and 70's. Why those loonies at Rover, or Austin-Rover, or whatever they were calling themselves that week, ever down-graded the oil recommendation from 20/50 to 10/40 whilst at the same time having even poorer quality control at the point of manufacture is beyond anyones comprenhension.

[reallybig]

20w50 is far too thick for colder temperaturees in the uk 10w40 is much better. plus it runs well in tractors.

[AndrewUK1990]

wow cheers for the replies! I had a feeling the old oil debate may spark up from this haha! Anyway im sticking with 20wt60 as its a little thicker at higher temps and it is for classic cars and it contains plenty of zinc etc for the gearbox. I am almost sure it leaks because of high oil temps because it only does it for prelonged high RPM. Just spots a little otherwise if left stood for a while but nothing unusual. After coming back from Fort William tho and chasing nutters from the MTB world cup (which drive rediculously fast) it had spewed oil out of just about every seal by the time i got back to Leeds. Still though it had only gone from max to min on the dipstick, so not too worrying. Normally i only need to top it up once every 800 miles or so if i drive carefully and not at prelonged high RPM. Anyway i think ill get a 13 row cooler with a thermostat so it will shut off when just town driving and only get used when im blasting down the motorways!

by the way I did forget to state my engine spec, its an MG Metro engine with unleaded head, runs very well, all standard and has 10.5:1 comp pistons and mild road cam, stage 1 etc, got 75BHP (ATFW) with 70 ft*lbs torque on RR about a month ago with ignition advance set for 97 RON fuel.

Thanks for replies everyone, very helpful indeed!

Edited by AndrewUK1990, 06 June 2011 - 07:16 PM.

[Cooperman]

20w50 is far too thick for colder temperaturees in the uk 10w40 is much better. plus it runs well in tractors.

Where on earth did you get that from. The mineral-based 20w50 is the very best oil to use in a Mini and the only time I would consider using anything else would be in a country where the ambient temp in Winter was well below zero. What have tractors to do with Mini oil?