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MG Midget and Sprite Technical - Head Gasket Failiure?

Hi All just as I was finally going to clear my garage for respraying my car I think the head gasket is gone. I have a 1500 midget, I Have changed the coolant and water in my radiator and now water seems to flow out of the expansion tank is this normal? Have I overfilled it or is the head gasket failure causing this? The water doesn't bubble out the level just rises up and flows out? Is there a block in the coolant system?

No milky white in expansion tank, engine is running fine, no white smoke out of exhaust and no water in exhaust? I am going to pressure test it tonight hopefully but any advice will be appreciated?

C Carter

This may be no problem at all.
After filling the system up to the "Max" mark on the tank, put the pressure cap on and run the engine. As the coolant heats up it will expand and any air in the system and excess coolant will flow out of the overflow pipe. Stop the engine and leave to cool. As it cools the coolant will contract again and the level should return to the Max mark on the tank. If there was air in it the level may drop below the mark and need topping up again a bit. After a couple of cycles of this it should pretty well stabilise.

If you run the car with the expansion cap off the fluid level will rise and overflow, and this may be what you are experiencing.

Make sure the filler cap is in good condition and is the right one for your car.
Guy

I think there maybe just too much water in the system and trapped air? I took the cap off when the engine wasn't running and it still overflowed?
C Carter

I agree with guy

It sounds like a classic case of air,,,,these engines are notorious for trapping air when you change out coolant

My method is to add the coolant run the engine 20 minutes with cap off let cool 1/2 hour put cap on then drive
Prop

When you say cap off do you mean the expansion tank cap or the filler cap on the thermostat housing?
C Carter

Yes, if there was too much coolant in the system then it would overflow whether the engine is running or not once the coolant has heated up and expanded.

If you did over fill it, following Guy's procedure will alow the excess coolant to be purged - after which the sytem should stabilise. If it continues to push out coolant then you have a problem.

There are two other ways of determining the likelihood of a problem:
Is there any sign of small bubbles/frothing?
Is there any residual pressure in the system if you let the everything cool roperly (eg overnight) and then remove the expansion tank cap?

Yes of either of these indicates probabley either head gasket leaking or (even worse but at least as common) a crack in the head.
Paul Walbran

This thread was discussed between 10/06/2011 and 13/06/2011

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