V-12 XJS Overheating

[Michael J.]

A warning to all!

After several weeks of gradually getting a higher and higher engine operating temperature, temp guage suddenly maxed out. It took a few minutes to get off the road. That was too long.

Both thermostats passed the boiling water test.

DO NOT FOLLOW THE OWNERS MANUAL RECOMMENDATION TO ADD STOP LEAK WITH EACH COOLANT CHANGE!

Radiator was 75% plugged. Clogging had been taking place for a very long time as a slow process.

Right cylander head "paid the price" by having one valve seat come loose. Luckily I had a spare head. I'm not back together yet. Having the replacement head redone first. That however is turning out to be another story.

With my hands full, I have not finished troubleshooting my earlier string on the battery drain. I will post an update after I get the head changed out.

 

[John S Farrington]

Your message is very correct and important. The Jag V12 is a great engine but with the alloy heads, etc., does not like to be overheated. If you notice that your V12 begins to have higher than normal operating temperatures, immediately investigate it. Do not drive down the road to the next gas station if your temperature gage is going out of sight. Radiators and hoses are cheap. Fan belts and coolant hoses should be changed out at shorter than normal intervals. Preventative maintenance cannot be stressed too much. I love my V12 convertible but it must be over maintained because it is special. The cost of a total engine rebuild usually starts at about $10,000. Dont get into that fix.