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In July of 06, my 1993 960 with 185K B6304 sprung a coolant leak (head/block gasket failure) at the read of the engine, just below the ECT. Though it never officially overheated, it did run low on coolant on several occasions (low coolant sensor failed) before I finally found the leak. Couldn’t understand why the fan was running with the ignition off.
I took old Blue in to a very reputable Volvo mechanic and two week later it was finished. During that time I stopped in time to time to check the progress. All was good. (Verified they cleaned the old gasket material from surfaces, saw cams on floor with gears still attached, viewed new parts, gasket set, etc.) The head was sent to another reputable shop which cleaned it, checked for cracks, resurfaced it and lapped the valves. Other work performed was replacing the plugs, oil trap, hoses, timing belt, tensioner, pulley, engine temp sensor at thermostat housing, seals and oil change. (Old head bolts were used.)
I picked the car up as was one happy camper until I went to check the oil after the first road trip. I got out of the car and notice a heat wave pour past my feet from under the car. I lifted the hood and another intense heat wave rolled off the engine. I went to remove the oil fill cap and it was HOT AND I MEAN REALLY HOT, I needed a rag just to remove the cap. When I did remove it, there was billowing oil mist/smoke flowing out of the filler neck. Engine temp gage, oil and coolant levels were normal.
Beside the obvious heat up, I have more tappet noise, it has set a variety of repeating MIL codes and the radiator fan now runs very frequently, even in the winter. Never did that before. Seems to be sensing that the head is hot but the coolant temp is normal per the gage.
Codes are:
2-3-1-Long term fuel trim, part load
5-1-1 Long term fuel trim, idling
5-1-2 Short term fuel trim.
Over the past six months, I’ve tried everything short of removing the head for inspection. I changed the O2 sensor with a Bosch generic, the ECT with Volvo brand, thermostat change, flush & filled with Volvo coolant, oil change, connector cleaning and etc, and still no good.
I returned Blue to the shop and suggested that maybe the timing was off or some of the coolant or oil galleries were plugged. They said nope, if the timing was off it wouldn’t start and the engine was too clean to think sludge plugged up any of the passages. They changed the thermostat to a colder range and offered the following diagnosis. Apparently the head was machined before and with the additional machining has reduced it enough to cause an increase in compression and thus the higher operating temp. There is nothing more we can do, have a nice day.
The water pump is 1 year old and radiator is 4 years. Always used Mobile 1 and Volvo.
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