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MG MGF Technical - Please explain this

Right here goes. Replaced coolant at the weekend don't ask why. Took the car for a " proper drive today " and when I got back the coolant had dropped about 6mm. Didn't really think too much about it as I assumed it was a little trapped air finally getting out after a good thrashing.

Upon unscrewing the cap and yes the coolant was at this stage only luke warm or there abouts, a bubble seemed to surface from the bottom of the tank and ofcourse the level rose. WHY ?
Steveo

Airlock by the sound of it. Did you bleed the system correctly at all 3 bleed points (or 4 according to some people)? Did you force fill the system or just tip it in the top? Did you have the heater on full when you filled it?
JohnP

pretty much as Mr P says, nothing too much to worry about, but do rebleed!
Will Munns

Oh yes it was bled. Rear of car higher than front,gentle flow continiously in the header tank, rad screw off and continious flow for 10 mins. Then the other two bleed points in the same way and then finally filled with coolant. Flipping heck how much bleeding do these things need ?
Stevo

I presume that you had the heat controller set to full heat when you bled the system? The heater is a classic place in which to entrap air.

I suspect that you haven't done anything wrong - just sometimes it take more than two bleed procedures to sucessfully rid of all the air.

Good luck!
Rob Bell

>>Flipping heck how much bleeding do these things need ? <<

Stevo, that is one of life's greatest and unexplainable mysteries.
JohnP

Rob the heater was indeed turned to full.

Oh well I have one more bottle of coolant so I suppose I will mix it up and bleed it thru the heater and return rail again.
stevo

And the radiator bleed screw?

Anyway, yup, looks as though you've done everything right. As John says, one of those great imponderables! LOL
Rob Bell

In every liquid there is some gas, which wants to come out at higher temperatures. This is probably the main reason the coolant level drops somewhat after replacing coolant, despite proper bleeding.

Johan
Johan Slagter

When I had to replace the radiator on my '95 1.8i, I was given the following advice by Bill at the MGF Centre

1) Flush through thoroughly with clean water, then take as much time as required in order to be sure ALL air is out of the system - bleed through the rad first, then the heater, finally the return rail.

2) Take the car for a run, ensuring that it gets properly up to temp.

3) Let the system cool, then add the correct amount of UNMIXED coolant. Starting at the rad, then the heater, finally the return rail. In each case, bleed until evidence of coolant can be seen at the relevant bleed point.


It worked for me !!


Jonty
M.J. Tait

This thread was discussed between 26/05/2004 and 27/05/2004

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