Hi All

I am stumped in trying to figure this one out. Its my brothers 91 124 with 102 Euro engine. Recently the car is running high temps when in traffic. Conditions include:
1) High cooling system pressure, hoses feel rock hard. System also has residual pressure when engine is cold in the mornings. Is this an indication of a head gasket leak or crack? Water is very clean with no oil.
2) Electromagnetic fan turns on, high speed electric fan turns on. There is a low speed but that comes on with the A/C. Low speed does not come on without A/C. Is there a low speed fan that is suppose to kick in from an engine temps sensor?
3) Overheat problem is unpredictable - one happens once in a while.

Any advice is greatly appreciated. Thank you.

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1992 124 E200 (Euro)