need just a little help

i own a 1979 300td 150,000 miles after taking a drive down the road at 75mph for a any amount of time and come to a stop the temp. goes up about 25, then after moving down the road it drops
right down to 175 normal ????? next it idles fine but once its in drive i can feel a vibration, not in the shifter, but the steering wheel. i've uped the idle speed but that does not feel right is it the motor mounts or the little shocks, next i've ordered the rebuild kit for the rear height adjuster are they hard to rebuild, or like a wheel cylinder, i will say thanks now for your help in case i forget
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1. When underway the temp is OK but rises when the car is brought to a stop. Not unusual, when was the cooling system last flushed? If the engine gets hot in slow heavy traffic on a warm day I'd suggest you check the fans - the engine driven one plus the electric fan behind the grill which should run when the engine > 100 degrees C (212 F.) If not, there's no problem.
When were the engine's valves last adjusted? If > than 15K miles ago, or if unknown suggest you adjust valves before undertaking motor mounts etc.. If you do move on to motor mounts know that they have sides, R & L; don't mix them.
Others will have to tell you about the rear suspension.
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Water pump. Mine did this once.
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It could be a weak pump, but I would have expected the original to have leaked a long time before this. A pressure test would be in order. I'd suspect a blocked radiator and/or failed fan.
wrote:

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When driving at 75 mph the engine generates a certain amount of heat, but at the same time the speed forces air through the radiator, providing sufficient cooling capacity.
When suddenly stopping, the air flow stops, thereby decreasing decreasin cooling capacity drastically before the engine gets rid of all the generated heat , which leads to the rise in temperature.
The rise in temperature is high, it should switch on the fans to provide more cooling capacity. When moving down the road, airflow starts in any case to provide more cooling.
So, the situation is not necessarily unusual.
But it could indicate a cooling capacity problem, which could be caused either by reduced water flow in the cooling system or by corroded cooling fins of the radiator (not unusual.. I have tried it with two cars).
I don't know the steering system of your specific car. But if the problem is connected whith the above situation at all, the only thing I can think of is the cooling (or lack of it) of the servo oil. I do however not have particular experience with it.
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