2002 Jaguar X-Type Heater

A radiator can't cause no heat. The only thing it could do, depending on how it fails, is cause overheating and too much heat.

Is there a temperature gauge on the dash? If there is, is it reading normal or low? If it's low, suspect the thermostat. If it's normal, the first suspect is a plugged heater core. That can be identified by feeling the heater hoses. They should be too hot to hold onto for very long.

Yup. If the gauge reads normal, feel the upper radiator hose and you'll find it's pretty hot. Now feel the heater hoses. They should be just as hot. If they are not, first look for a water valve inline with one of them and be sure that is switching open. They move from a cable or engine vacuum. Most likely a car this new won't use a cable.

If there is no water valve, that just leaves the heater core. I'm always nervous about pulling the hoses off the heater core because on some models the twisting can break the solder connections where the pipes attach, then you have a major leak and a lot of work. I pull the hoses off the engine, then use a garden hose to run water through it both ways. It doesn't take much pressure to dislodge the blockage.

The disadvantage to this is it is always possible a leak has developed due to corrosion from the acids that normally build up in coolant, and it's not uncommon for the mud to plug that leak. Once you flush the blockage out, you have to worry about having a leak. My guess is that only happens in about one out of fifty flush jobs, but you still want to keep it in mind.

I don't know what is involved in replacing the heater core. I've never had a blocked one that I had to fight to clear it. If it comes to that, get a copy of the manufacturer's service manual.

If the heater hoses are hot but you still get no heat, suspect a problem with the temperature door in the heater box. Ford has had a lot of trouble with their electric actuators in the mid to late '90s, and Chrysler had some trouble with moisture causing rust on the bottom of the hinge rod, and it would refuse to turn. On those, the cable was self-adjusting, and moving the temperature lever would make the cable slide through its adjuster and give the false impression that you were moving the temperature control. The fix was real simple, but you have to know how to do it. There was a service bulletin explaining that, and Ford is likely to have one too if that was a common cause of no heat.