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MG Midget and Sprite Technical - Over heating/cut out 1500?

Hi all,
I went to Wilton House supercars the other day, so decided to take the midget (1500). After driving 16 miles I got stuck in traffic and after about 10 minutes the temp guage rose slightly, it got halfway between N & where the solid white starts. Then the engine began to splutter and would not tick over without the ocassional blip on the throttle and there was also no power (car would die when trying to pull off). Eventually it cut out completely about 100yds from the entrance gates. I waited with the bonnet up for about 15 min and then managed to get it started and limped into the carpark. After being parked up for about 7 hours the return journey home was faultless. Any ideas what could have caused this? Fuel evaporation? Day temp was 24-26 degrees.
Car has oil cooler fitted.
Thanks
Kevin
K Grice

I have read of similar problems being caused by a lack of a heat shield between the carbs and manifold, causing, as you suggest, fuel evaporation.

If you do have a proper shield fitted correctly then I can't help you!.....(but someone will be along who can, I am sure)
JB Anderson

Have been having similar problems with my 1275 but cured it by changing to electronic distributor & coil
p kiely

Car has a new lucas coil, new points & condensor and a new heat shield in place.
I do have an electronic replacement for the points & condensor which I might try.
K Grice

Hi Kevin,

it could be combination of fuel evaperation, pesermistic gauge and low idle

or many other things like timing or tuning

or other stuff :)

or - how's your coolant system, it is often overlooked as a whole

I'm sure you'll think this is over the top but it's just things to consider on the coolant system

debris blocking the radiator fins or obstructions in the air path to the rad

fanbelt and fan are in good condition, fitted well and working correctly

pressure cap is fully funtioning (and correct pressure)

good condition oil and filter (regular changes and clean oil passenges)

coolant in good condition (changes are required even if anti-freeze part still works)

clean pathways for coolant in engine, radiator (and heater matrix) - flush cleaning sometimes required

hoses can disintergrate from inside

thermostat can seize or sludge up (and heater valve)

the water pump especially if you find the rest of the system is sludged up
Nigel At

Heatshield ok, but where does the fuel line run? close to the exhaust? Could heat up enough there maybe.
Alex G Matla

Hi Kevin,

Sounds very like what I was seeing on my 1500 before I replaced the radiator. Sitting in traffic temp gauge rises, engine bay gets hotter either fuel evaporates or waxstats (if you have them) means engine runs lean, pinks, lacks power, though mine never died completely.

After toying with the idea of elecetric fans etc. I took the advice I got from many people here and changed:
Radiator, Pressure cap, all hoses. While this lot was off I flushed the engine running a hose pipe in anywhere I could, I also removed the heater to check the matix in there and flush it. (that also makes changing the hoses easier!) My radiator was old & very tired and not worth trying to fix. A new one from MGB Hive was cheaper than I was quoted for repairs. I also had issues with the header tank not holding pressure.

Since doing this the engine runs cooler, I can turn the heater off, and generally things all seem much better. The temperatures have stayed low on the few warm days we've had since. I did also change the carb heatsheild to a Stainless Ashley Hinton one while I was at it.

I'd definately recommend checking the radiator, its probably like mine and full of crud. Although most of my hoses looked OK(ish) I'm glad I changed them all as I found one completely blocked with crud.

Again on BBS members info I refilled with pink type Antifreeze.

I'm pretty sure the rad was the main issue but as always one thing seems to lead to another, besides hoses are cheap to replace.

Richard
r parker

flushing through with water is ok if that was also done say 2,3,4 5 years ago but if you don't know then a full clean is required

imagine a flush as rinsing, it's not cleaning

the rad may be beyond saving but then again it might just need thoroughly cleaning (see below) as for rubber hoses I hope they are better now than the ones I put on 4 years ago, if you're keeping the car more than say 4 years you might be better to go to silicone

I thoroughly cleaned my car's coolant system soon after getting it and it runs cool and the heater gets very hot

it's amazing how many jobs boil down to cleaning and lubeing, the lube in this case is in the coolant (apart from the odd drops of light oil on vavles, a flap and cables)

this is is the way I suggest to clean the whole coolant system -

before starting consider if the water pump and heater fan motor need replacing and (if not already fitted) whether to install an electric fan as this would fit in with the work below, also you may also want to check and change if required the thermostat, heater valve/tap, fan belt and filler pressure cap

first clean the whole system with something like Bars Flush Cooling System Cleaner

then drain the whole system - engine block, heater matrix and radiator

get the radiator and heater matrix out of the car to give them a good shake at the same time as flushing and back flushing

flush clean water through each of the three until water runs out thoroughly clean

reverse flush each of the three until water runs out thoroughly clean

final flush through each of the three until water runs out thoroughly clean

gently brush clean both sides of the radiator

gently brush clean heater matrix and renew the seals and foam around the heater matrix and heater box case

refill with the correct coolant mixture but bear in mind in tap water isn’t always the best water to use, distilled would be better

follow the refill instructions from the owners Handbook to avoid getting air locks or ‘hotspots’ that could cause overheating of the engine

as recent new rubber cooling hoses have tended to be poor quality you may also want to change your existing rubber hoses set to silicone with rounded-edge clips - http://www.classicsiliconehoses.com/
Nigel At

Cautionary tale about flushing the cooling system..when I bought my current Midget about 15 years ago I bought some Rad-Flush as I would normally clean everything out, oil and coolant wise on a car new to me and start afresh.

Unfortunately the Rad-Flush managed to destroy the internal seals in the water pump and I ended up having to change it, as well as the coolant.

The PO had changed it previously only about a year earlier but it may have been a shoddy pattern part, as the one I put in has done about 50,000 miles since then without problems, touch wood.

It was probably just bad luck on my part but these things can happen when you least want them to!
JB Anderson

yeap cleaning stuff that only has muck/gunge/deposits hold them together or stopping leaks will find the leaks

radiators can leak after cleaning but they can be repaired or replaced and if in doubt the water pumps are very cheap and well made at the moment

I was told in the old days that Cosworth suggested adding the liquid Bar's Leaks as a conditioner to their engines
Nigel At

I seem to remember somebody saying that BMC used to add Bar's Leak to all new spridgets!
As a matter of interest, if you can't get rad flush you can use dishwasher detergent(not the 4in1 tabs), it is evil stuff and will shift all sorts of debris, just remember to flush it out fully after use as it doesn't do aluminium a lot of good if left in long term.
Graham.
Graham P 1330 Frogeye

dare I say BMC probably didn't put Bar's Leaks in as a coolant conditioner like Cosworth but probably as something to plug holes :)

coolants have conditioners in that's what goes off over time/use (?)
Nigel At

This thread was discussed between 27/08/2011 and 29/08/2011

MG Midget and Sprite Technical index

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