FirstAde

Many thanks, Joe. That's really helpful. I will pass on to the garage and let you know. Yes cooling fans are ok, they go like a train once up to temperature, and continue to run after engine stop. The expansion tank cap was replaced and does eject coolant, but only once the 140 kpa limit is reached due to overheat. Thats where the coolant has been going, say the garage. They whole system was pressure tested and declared sound with no leaks, so I'm happy that the seams have held together on the expansion tank. The aux coolant pump in the rad is a new one for me, I'll get the garage to check it out. Thanks again. I'll post an update once the specialist has had a look, or if they get a solution using the above. Cheers, Adrian

Hi Guys and Girls in the Owners club. This is my first Jaguar. I went with a low cost S-type with a full history and plenty of signs of good ownership. The first 1500 miles were fine, then the coolant system problems started. All so far covered under warranty- Phew! The question is "what an earth is still causing the overheating given all the work below?" 1) Thermostat EML - Not warming up quickly enough. Replaced thermostat 2) 1000 miles later Coolant loss - a few small leaks from the water pump leading to "coolant low" message. Replaced coolant pump, checked all hoses and connections for leaks, replaced expansion tank cap, due to small leak around the cap. Sniffer test for leaking head gasket. OK. Oil check for coolant, OK. 3) 200 miles later. Coolant low after sitting in traffic jam. Temp got high. Kept it under control by opening all the windows and blasting the heater on full fan with HI temp on the climate control. Diagnosis by garage: likely blocked radiator. Replaced. Repeat Sniffer test for leaking head gasket. OK. Oil check for coolant, OK. Double check temp of engine, it was high, gauges are all correctly reading and the radiator cooling fans are running properly. 4) Drove to Cambridge and back 240 miles. Joy! no problems. Then.,... 100 miles later. Coolant low and temp high at tick over (near red sector, but not in it) Lifting the revs to 1200 rpm, gives a return of the temp gauge to normal position, so there is insufficient coolant flow to control the temperature at tick over. All this despite new Radiator, coolant flushed out and renewed, new thermostat, new coolant pump, head gasket tests ok, 5) Garage and warranty company given up and referred to local Jaguar specialist who will be able to look at it in about 10 days time as he's very busy :-) Any suggestions gratefully received. Thanks, Adrian