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I've recently bought a '79 midget from a garage (sold as
having a recently reconditioned engine). It seemed to be
using rather a lot of oil (1L per 500ish miles - is this a
lot?, I'm new to this), however I assumed that all was well
and kept topping it up. However... whilst driving along the
other day, the engine started making a grinding noise (no oil
light came on). I pulled over, called the RAC and apparently
the big end has gone. The guy at the garage I got it from says
its my fault for letting it run out of oil (but as I said, the
warning light didn't come on). Nevertheless, he says he'll
do a bottom end rebuild for free.
My questions are:
1) What should the oil consumption be (bearing in mind the
engine was supposedly reconditioned). How would I know if
an oil cooler was fitted?
2) If the big end has gone, is a bottom end rebuild sufficient
to sort things out? Or will the whole engine now be knackered?
Answers:
Sounds like your not having much fun with MG ownership,
here goes my attempt to answer your questions!
1) What should the oil consumption be (bearing in mind the
engine was supposedly reconditioned). How would I know if
an oil cooler was fitted?
Firstly you say that the engine was recently reconditioned.
The pistons in the cylinders of the engine have seals on
them (piston rings). These rings are there to prevent oil
getting into the cylinder and being burnt (excessive oil
consumption). On a recently reconditioned engine these rings
do not seal properly straight away so what you tend to find
is that the oil consumption is quite high when the engine has
just been done, and with more miles the rings seal better and
the oil consumption actually improves.
Secondly oil consumption depends very much on the type of
driving you are doing, motorway driving produces a fairly
high oil consumption, I get around 500 miles per litre at
70 - 80 mph on 400 mile trips. Around town the engine will
use less as most of the time it is barely ticking over,
even if it is accelerating and decelerating a fair amount.
2) If the big end has gone, is a bottom end rebuild sufficient
to sort things out? Or will the whole engine now be knackered?
I assume that the car has not been run for very long
with low oil so I would take and guess and say that if the
bottom end rebuild is done properly, ie checking that the
crankshaft is not scored or oval, then you should be OK!!!
What does slightly concern me is this guys apparent generosity
in offering to rebuild it. Surely he would'nt do this for
free if he did'nt suspect there might have been something
wrong in the first place, or am I being a bit hard on him?
You say the oil warning light did not come on. I would have
the warning system checked out. Does it come on when you
switch the ignition on just before starting the engine? It
should do. Also the problem with the warning light is that
when it comes on, its usually too late anyway and the engine
is irreprably damaged, the lamp only operates when the oil
pressure is at 8lbs not nearly enough for normal running, it
should be at least 40 lbs. You could have been driving along
with the pressure at around 10 lbs pressure and therefore
not triggering the warning light.
Oh yeah, nearly forgot, the oil cooler.
If you open the bonnet, the oil cooler is usually positioned
in the tray that is in front of the radiator and behind
the bumper. It will be aluminium in colour, have two pipes
coming out of either side and be around 15-20cm tall. If you
have'nt got one, GET ONE! These engines do need them.
Interested to hear that an oil cooler is considered to be an
essential on a 1500. I haven't had mine long and am a bit
concerned about the oil pressure. I get about 60-70 lbs/ins
when cold but this drops to around 25 lbs/ins at 3000 revs
when hot. Any comments anyone.
Without an oil cooler the 1500 comprehensively cooks its oil,
especially at constant speeds of 40 mph and above. This
effectively turns the oil into the same consistency of water,
very thin. The thinner the oil the lower the oil pressure,
hence your good oil pressure when cold.
When the oil gets too thin it cannot do its job properly and
bottom end damage will result.
You did'nt mention what oil you had, 20W/50 is best at this
time of year (summer).
Get an oil cooler, for 70 pounds its well worth it, and I
assure you that you will see the difference with your oil
pressure.
Do you recommend a thermostaticaly controlled
system or not, rubber pipes or SS, 10 or 13 section cooler
and finally, where do you know of for £70?
I don't know what oil is in there at the moment, I haven't
had it long. I will change it for 20W/50 ASAP.
Definetly a thermostatically controlled system. Without one
on low speed journeys the oil will never get up to proper
temp preventing it from doing its job properly.
I opted for the rubber pipes on my system mainly because of
the cost. Wish I had'nt now though as I have noticed the
pipes were being cut into slightly by an edge. Would'nt
happen with the stainless pipes.
When I got my oil cooler I bought it in a kit, it came with
the 10 row oil cooler. I wanted the 13 row oil cooler and it
was exhanged free of charge. As far as I know there still is
no price differential between the two, so I'd definetly go
for the 13 row.
I got my kit from M+G international in Prestwich Manchester,
it was over a year ago so I suppose they may have increased
in price a bit since then.