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MG MGB Technical - Engine won't come up to Temp

Hello-

My GT has a 180 thermostat in it. In summer, it stays around 'N'. But now in 50 degree weather it stays at the 8:00 o'clock position, never goes up to "N". My roadster stays at "N" no matter what the outside temp is. Th GT thermostat is new so I don't suspect that. Any opinions on what's going on? Th GT engine is a 1976 18V, the roadster engine is a 1968 GA I believe.
The GT runs fine, but it bugs me that it is running below 'normal' temp.

Thanks,
Sam
Sam

It sure sounds like your new thermostat is stuck open. For the price of a gasket, you can verify that. You may also be able to tell if the radiator warms up too soon at idle. This is very subjective, but the radiator should stay pretty cold until the thermostat opens at 180° and then warm up fast. Try each car by touch (be careful) to see if the GT’s radiator warms up sooner and more gradually than the roadster.
George Champion

Wow, Sam;

I'm envious. A "B" that runs cold! No, really, that's unusual.

Some thoughts:

Did your fuel gauge stop working? Might be the voltage stabilizer affecting your gauge.

Check the connection to your temp. sensor?

Stuck-open thermostat may be a possibility.

Dave

Dave

I thought about stuck open thermostat also. Even though it is new it could be bad I guess.
Since he is getting some idication on the temp.gauge
I don't think it would be the wiring, but it could be that the sensor itself has gone bad. Feeling the engine and radiator by hand is a good suggetion. You might try sticking a thermometer in the thermostat housing opening, (after running the car for a while), you might do that when you open up the housing to check the Stat.
I too am jealous of your cool running B.
John-
John F

I have a '67 that does nearly the same thing; it runs 100 degrees F over ambient, no matter what. I've changed thermostats four times now, NEW temp gauge with integral sensor, and it still does it. The only way I get heat in the winter is to cover about 2/3 of the radiator with cardboard.
Ken Lessig

Hmm...
So if the stabilizer (fuel gauge works) is OK, the thermostat is OK, and the sensor is OK, could it be the timing?
I noticed during the warm months that when I got off the highway and drove stop & go that the temp needle would move to the left of 'N'. On the highway at speed the needle would be to the right of 'N'. My roadster, by comparison, stays dead on 'N' regardless of driving conditions.

Thanks again,
Sam
Sam

If the thermostat is reading correctly and the thermostat is working correctly you cannot get low readings (at temps of 50F anyway) for the simple reason that the thermostat should not open until the engine gets up to temp, by which time the gauge will be showing it. If the timing is off it causes the engine to run hotter regardless of whether it is retarded or advanced. The gauge should move towards normal while the stat is closed, then at some point (which should be around N) the stat should open and you may well see the gauge drop a little. The rush of cold water from the rad may cause the stat to close again and the gauge goes up again etc. On both my cars I can see the gauge oscillating slightly around N while the whole system reaches equilibrium. As others have said you should feel the rad get suddenly hot as the stat opens. If you have the mechanical fan leave it running at a fast idle with the rad blocked off. If it doesn't get up to temp (and beyond) then it is the gauge/sender, if it does it is the stat.

PaulH.
Paul Hunt

Sam,
I had similar problems getting both my B and TF to "normal" operating temps in the winter (35 to 50 degree F). In the summer I run a 180 degree thermostat in the B and a 160 degree thermostat in the TF. However, this week-end I will put 190 degree thermostats in both cars. I do not have a heater in the TF so I really need the engine heat coming thur the firewall holes to keep my feet warm. I also cover the oil cooler on the B with one of the Moss supplied covers. My personal experience, with the 190 degree thermostats, has been faster warm-ups and "normal" operating temps in 35 to 50 degree F weather.
In April I will switch back to the 180 and 160deg tremostats. If the other suggestions from the board don't give you the results you are looking for, you might try a 190 or 195 thermostat and see what happens.

Dave
David Kalp

You could also think about using a blanking sleeve along WITH your typical modern t-stat. Neil Cotty has a good article on this at his site http://www.apphosting.com/mgstuff/Athermostat.htm . I have done this with no bad consequences, summer or winter. The blanking sleeve replicates to some extent the action of the OEM Smiths T-stat design, blanking off the bypass passage and allowing for a quicker warm up and what seems to be a bit more stable temps. I run one of these in both my 68 GT and MGA, and the MGA is a somewhat harder car to keep at a happy temp than a B. Just a thought.
Bob Muenchausen

Thanks everyone for your comments. I'll experiment and see what happens. By the way, the thermostat is one of the new ones Moss is selling that 'locks open' if the system overheats. I wonder if that brand of thermostat is accurate/reliable.

Sam
Samuel Sullivan

The coolant take off for the heater runs out directly out of the cylinder head - before the thermostat. If the heater valve was even slightly open when your observations were made then it could be a contributory factor.
Out of interest, my '73 GT does exactly the same thing, and in the real depths of winter I use a radiator blind to keep the engine cosy. Ken's use of cardboard is just the same - and a lot less expensive.
Miles Banister

This thread was discussed between 21/11/2001 and 23/11/2001

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