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MG Midget and Sprite Technical - Over heating solutions

Hi all, I am looking for some help with some over heating issues I am having with a 78 midget I purchased last weekend. When I bought it the temp dash dial didn't work! Which didn't fill me with confidence on its ability to run cool. Low and behold it overheated. On inspection I found that the thermostat was stuck closed and the water pump was not working. I have now replaced water pump , radiator, thermostat and temp sender. Dash dial now works and shows car running hot 1 bar below the H on the temp dial. What am I missing ??? What else would make it read so hot so quickly? Water pump is definitely working as I am getting hot air in the cabin when I switch the heaters on. Could the head gasket have gone ? Can't see bubbles forming in the header tank though. No losing water through split hosed either :-/ And no mayo in the oil. Your thoughts please :)) oh and car is a 1500 . Thanks in advance
Ben.
B G Rhodes

Timing... head gasket... radiator... just have patience, look at a manual and go through things one at a time.
Good luck, and let us know how you make out.
don g

Lean mixture will run hot, retarded timing will run hot. Head gasket issues should give you "white smoke" at the tailpipe if the failure is minor. Not sure what a split hosed or header tank is..Don't know if you chaps over there have the catalytic converter fitted to the 1500 but if you're running rich it has a tendency to get really hot. You might want to do a oil change to see if anything other than oil drains from the block. Try adjusting your valves to spec, might make a difference. Good luck.

Richard
Richard Reeves

I take it you have an electric temperature gauge - if so it needs a voltage stabiliser to feed it 10V or it will over read. You can get the original bi metallic type from Holden or solid state from Maplins.
F Pollock

did you say its 1 bar below the H on the gauge? does that mean 3/4 (as there are 4 divisions) - that is normal operating temp... I wouldn't worry... if you haven't got an oil cooler fitted then its going to run hottish in the summer anyway.

Also if you've replaced the radiator then its very possible you have an airlock in the system... you need to burp it out... very easy to get air in the 1500 I've found.

C L Carter

How do you know the gauge is reading correctly? These are not high tech instruments and could be considerably out of kilter. If the car doesn't boil over, then it isn't actually overheating.
Mike Howlett

Less critical than where the needle points is the ability to maintain constant temp whatever the driving conditions. Which of course it will also do if the needle is stuck ! ;-)
Guy W

I'd put the temperature sender in the kettle, along with a known good thermometer, and check that the gauge reads properly. It should be up near the H mark when the kettle is boiling.

I suspect the voltage regulator too, if it's an electrical gauge. The usual test for that is to turn the key on while the engine's hot, but don't start the car. Note the gauge reading, then turn on the headlights and heater fan. If the gauge reading changes noticeably then your voltage stabiliser is probably shot.

Growler

Thanks everyone for all the great feedback, c. L. Carter was right it was an airlock :)) I sorted it today it now sits at halfway in the temp gauge when idling. I am going to take it for a run out this weekend and see if it holds its ability to stay cool. Thoroughly enjoyed my test run out in it today, boy oh boy those 1500 lumps can pull:-0 I usually drive a hillman imp sport so felt a big difference:))
B G Rhodes

Hi Ben,
A very warm welcome. I knew that you'd find the answer here.
Gary
frogeye Gary

This thread was discussed on 01/10/2012

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