Hi all-

Hoping someone has the solution here as everything I've searched regarding overheating suggests replacing water pump and t-stat (done that). Idles fine at dead middle temp mark. Drove down to have the car aligned and temp was fine. Wife drove the car back to our house and coming up a hill the car started to redline/overheat. No coolant on the road until she stopped to turn into our drive, then it purged prob 1/4gallon of coolant. Anyone else with this issue and if so what was your remedy?Maybe I'm searching the wrong wording in my searches...? Would like the car to be reliable and not overheat. All suggestions are welcome. I've worked on cars for years so I'm quite comfortable w/ MOST repairs if needed.

(99 XJ8L...V8/308 4.0L w 88kmi)

Thanks for any help offered!

Templar

 

Sounds like your car possibly has an air lock somewhere in the system.I had the coolant tank replaced on my S type and it required purging/flushing of the whole system to clear it of any possible air locks.Not too expensive to have done as really just involves the cost of new coolant and perhaps half an hours labour.

 

The system may not be holding pressure. Consider replacing the coolant fill tank cap which has a valve and seals which can fail.

BTW, the gauge will show 'dead middle' from 185 F all the way to about 235 F. It lies!

 

Also check the coolant tank for any hairline cracks,and any plastic junction points, the plastic over time becomes brittle due to engine heat.The system will slowly rid itself of coolant without you really knowing, eventually the car will overheat causing the warning light to come on,engine purges/burps coolant out causing you great worry and sometimes stranded on the side of the road.Tip, wait until engine cools down before adding coolant as much as you can,(hood up facing into cool breeze if possible) keep engine running while coolant is very gently added to avoid cylinder head/gasket damage and help prevent air locks.ALWAYS be extremely cautious when removing a coolant cap on a hot engine, keep face and body out of hot coolant firing line!!!

 

Thanks guys... I'll double check and keep burping the system. Really hoping against all hope that it's the head gasket.... Done plenty of them, just don't WANT to do another.. lol. I'll update if it's resolution is something other than what you've suggested. I like SOLVING car problems and if it helps others more the merrier.


Templar

 

Could be the new thermostat is stuck/not working.
When the work was done on the car, they may have put the pipes on the header tank the wrong way around. The correct way is to have them crossed( looks wrong)
Second the post re: temp gauge, it is a glorified idiot light.
If you have an OBD reader, you can use that to read the temperature.
These engines are very reliable, but overheating will kill them.

 

Yes, check the pipes going to the coolant reservoir, they should be crossed. There is a lot in the archives on this. Also, make sure the electric cooling fans are working. I believe they should be on whenever the A/C compressor is on. Mine blew a fuse and the radiator hoses started blowing off in traffic.