1991 300D OM602, 323,xxx miles. Recently repaired AC system. Removed radiator to install a working condenser. While radiator was out, I cleaned the coils, made sure no bent fins, and hosed it down. Refilled with 50/50 mix of MB coolant/distilled water. Put everything back together and have been driving with ice cold ac for a few weeks now.

I was prepared for temps to run a bit warmer with working ac on max and South Carolina heat, but temps seem to rise at odd times. I can sit in traffic all day with max ac, and temp stays between 80-85. Only under moderate to heavy acceleration temp rises quickly to 90-95, but then drops back to 85 range. On interstate temps stay at 80.

Updated 606 plastic fan and clutch, no debris between condenser and radiator, properly functioning auxiliary fans, all new temp switches done when overhauling ac system, expansion tank is old but no leaks and cap looks good (not hard or brittle).

My guess is radiator. The other day I noticed the upper hose had leaked/sprayed coolant on shroud. My assumption is that there is a blockage in radiator restricting coolant flow thereby causing coolant to spray out of upper hose. Radiator has not been replaced since my ownership (75,000+ miles). It never had these spikes in temp before (temp stayed at 80 religiously) but I had the aux fans jumpered to where they ran all the time (probably the reason why my old ones died). Could having the fans running at all times have masked my dying radiator?

Am i missing anything, is there something else I should be worried about or need to check? New Nissens radiator and upper hose will get here next week sometime.

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You might have air in the cooling system. They usually burp themselves over time. To speed the process, remove one of the temp sensors where the upper radiator hose attaches to the engine then top off the reservoir 'til coolant gets to the sensor hole.

Sixto
83 300SD

Treat your car with a new radiator and water pump may as well inspect and replace parts on the serpentine belt as well. You really don't want over heating problems with the 602 engine.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

If the problem only occurs under high engine rpm, when accelerating, check your LOWER radiator hose. If the hose is soft, the suction of the pump can make it collapse at high revs.