Without hearing the noise it would be hard to diagnose. Economists can't model
the
economy yet make 10 year predictions. So here goes.
It could be the coolant boiling. You could have a bad thermostat. To check it
put
it in a pan of water on the stove. Turn up the heat and see if it opens. Check
the
temp where it opens with a meat or candy thermometer. I had a new thermostat
fail
to open all the way. The coolant would boil inside the head making a violent
knocking noise. The noise would subside when I coasted.
YMMV http://srv1.pclnet.net/users/martin/abbreviations.html
Mike Quinn wrote:
> Last summer I went for a ride with my daughter. I was on the highway doing
> about 70 when I noticed the temp getting pretty close to H. This is not real
> unusual for the car and every time I checked the temp with a thermometer it
> would be about 190 when it got to H when the air temp is above 80 degrees.
> This time however when I got off the highway the temp came back down toward N
> but a strange rattle started. The oil pressure stayed around 50lbs, the car
> lost no power at all. From that point on when the car gets just above N the
> noise comes back. The noise only happens when you are giving it gas to
> maintain speed but goes away if I was to give it enough gas to go up a hill or
> quick acceleration. I've taken it to a mechanic that knows MG's in the area
> and he never seems to hear the problem (it could take 15minutes before the
> noise begins). To me it sounds like a bad valve rattle but I have no loss of
> power and the mechanic adjusted them. There must be some correlation with
> heat. I don't think the noise is lower engine because that would always be
> there and the oil pressure would drop. I just had an OD trans and new clutch
> put in so I can eliminate the noise coming from there. I also had the radiator
> cooked out and the temp gauge still pushes up to H. Could the problem with the
> heat and noise be something like a head gasket or water port problem that
> maybe doesn't cool the valve properly? I have no indication of water in the
> oil. The car really runs great other that. Any Clues? Should I be concerned?
> --Mike Quinn
> 74 MGB CB
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