How old is the water pump? Maybe the blades have corroded away.
Does the car have a mechanical fan as well?
Is the radiator temp even across the face, or does it have cold spots?
Sent from my iPad
> On Jan 29, 2021, at 6:14 PM, rolindsay@yahoo.com wrote:
>
> 
> Hello friends. I haven't written to bother you for a long time, but now I do
> so because I need advice. My recently resurrected '72 MGB's engine runs hot.
> It doesn't boil over but it 'overheats'. Here are the details from two tests.
>
> 1972 MGB, idling from cold start, bonnet open, 50:50 antifreeze mix, heater
> valve open, new water pump, flushed radiator, 10# radiator cap, timing set
> correctly, air:fuel ratio set correctly, carbs balanced.
>
> First day tests, w/o electric fan on:
>
> Time
> Since Coolant Gauge
> Start Temperature Reading
> -----------+â??--------------------+--â??----------
> 0 min 71°F minimum
> 1 min 72°F minimum
> 5 min 160°F 1/4 scale
> 10 min 195°F 5/8 scale
> 15 min 220°F 7/8 scale
>
>
> Second day tests, with electric fan on:
>
> Time
> Since Coolant Gauge
> Start Temperature Reading
> -----------+â??--------------------+--â??----------
> 0 min 63°F minimum
> 1 min 64°F minimum
> 5 min 159°F 1/4 scale
> 10 min 195°F 5/8 scale
> 15 min 228°F edge of 'H'
>
> Conclusions:
> 1. Engine starts easily, idles smoothly, and runs great.
> 2. No boil over in either test case.
> 3. Electric fan 'on' cannot overcome whatever is causing the car to run hot.
> 4. Temperatures measured at top of thermostat housing, but verified to be the
> same at the radiator top neck.
> 5. Charge is neither lean nor rich.
> 6. Timing is set correctly.
>
> What product might I use to flush debris from the block and head, if that is
> indeed the problem? Thoughts? And thanks.
>
> -Rick, in Houston, TX
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