[Mgs] Running hot

[Robert's New iPad]

Hi Rick,
   Those of us shivering at 9 degrees this morning, with a wind blowing, almost wish we had your problem.
   Same temp at radiator neck and ‘stat housing suggests that the thermostat is working, though if you have any doubt about it and do not know its age, you might consider replacing it anyway. 
   Were you able to measure top/bottom, left/right the radiator core temperature? If temp does not reduce from top to bottom, or there are different temps at the same distance down from top, you could suspect the radiator.    I have not had stellar success with radiator cleaning products. My recommendation is to take it to a radiator shop and have it cleaned and serviced.
   If you wanted to try a cleaning product, you know there is a mess about to happen, so first take a garden hose and flush the heater, shielding the distributor first.  A surprising amount of sediment is often found in the heater, usually more than is in the radiator. Re-connect the hoses and use whatever your nearby auto parts shop suggests.  
   What do you know about this water pump? Chances are that original has been replaced at least once, and there are different qualities of replacements.  If, when your bring up engine temp from cold, with the rad cap off, you do not see some swirling in top of the radiator, the water pump is suspect. 
   Last week, before the weather turned bitter, some of us were invited to check out a 1978 MGB with two HIFs installed. Engine was smooth at idle, baulky at acceleration with no load, stalled at acceleration when in gear.  HIFs were balanced, piston-lift test was OK, spark plugs showed good mixture, timing was what the label said it should be. Hmmm. Distributor advance was OK too.  Double hmmm.   Answer: Car was gift to new owner by wife, who had not driven it.  DPO had ‘tuned’ engine, but set the distributor to the marks —- with vac hose connected.  We disconnected the hose, plugged the manifold connection, rotated distributor about 25 degrees to test, and it fired right up. Set per specs, the engine purred.  
Bob


> On Jan 29, 2021, at 9:12 PM, rolindsay at 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
> -----------+‐--------------------+--‐----------
> 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
> -----------+‐--------------------+--‐----------
> 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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