I have a 2007 XK. It over heated 4 days ago. I opened the hood and the steam coming out of the coolant tank. like a pressure cooker it was fizzing from the side. then I put more coolant in it. Then car was driving ok. Drove from work home then parked for one hour then drove for 2 miles and then then the engine temp went high then warning for over heating came on. Again the coolant was bubbling and fizzing out of the side of coolant tank cap. Then added more coolant. Drove home no issues on the way back. what could it be? do i need a new thermostat or do I need to get the coolant system flushed? any ideas?

 

Might be a stuck thermostat. Does the hose after the thermostat get hot or is it cool to the touch after the car warms up?


Here is the xk service manual:http://www.google.com/url?sa=t&rct=j...bobYw5ZS-BDSdQ

 

How long have you had the car? How many miles?

Was it losing coolant? - if NO then probably the thermostat is stuck. If YES probably a worn water pump or possibly radiator or hoses if you know for sure that the car ran fine prior to this episode otherwise it could be air trapped in the system not allowing the water pump to pump so has anyone done a very recent coolant change?. Do NOT drive the car far at all, if the temp goes into the red you could easily and permanently damage the engine requiring ahead gasket amongst other things. If not losing coolant let it get to operating temp then feel the coolant hoses to see if they are warm to verify that the coolant is in fact being circulated. Don't let the temp get into the danger zone again

 

I replaced my thermostat unit including the housing ln december 15 roughly a 2.5h job , I recall removing the throttle body and throttle body neck to access the plastic housing

 

Seems this is a problem with the xk not so for the xkr, don't drive it at all till it's replaced

 

thanks for all your replies. The hoses were warm but no cool or extremely hot. no one recently changed the coolant. I have had the car long time and has gone 95k miles. no issues till now. Just started giving issues like this overheating. plus it has load knocking sound on dry start for like a second then doesn't do it again until starting up after the car has been off for 2-3 hours. It also hasn't over heated since I last wrote either.
I don't really want to take it in to the dealer they will charge me an arm a leg and then some. will watch it for now. if it happens will get a coolant system flush and check the thermostat then go from there

 

Not to sell the dealer short but you probably don't need to go to the dealer. I know we love our babies but any semi-skilled mechanic who is a trustworthy human at any shop should be able to change that thermostat and thermostat housing for you. My back was messed up earlier in the year and I would bring parts to the garage down the road from me and they would gladly do stuff like this. It might be cheap insurance.

 

95'000 miles, 9 years old, it's due for a new thermostat at least.

They don't last forever. Change the thermostat, it's cheaper than changing an engine!

 

just heated up again. took it in to mechanic. they did block test and said it was a blown head cover gasket. I am confused now.

 

Does the car sound rougher on idle or lack significant power ?

Depending on where the gasket has blown so check the oil what colour is it ? (has the water merged with the oil this is a tell tale sign of blown head gasket)

Buy yourself a compression tester and check all the cylinders / also you will notice when you pull the plugs out they will be wet from the coolant that is if you do in fact have blown a gasket

 

Your description does sound like a head gasket. The slight knock on cold start is most likely coolant in the cylinder. A simple hydrocarbon test in the coolant while running will verify it. The coolant will most likely also have a really bad smell to it also .

 

A cold start knock can also be due to a serpentine belt bad idler bearling causing the serpentine belt tensioner to jump back and forth until it warms up. Spilled coolant on the belt and pulleys can aggravate this. This would be a very minor issue.

I suggest a 2nd opinion before undertaking a major job like a head gasket. You may just need a thermostat and/or water pump and a new idler pulley and belt.

 

Like White says be sure to get a 2nd opinion as this whole thing doesn't make sense based upon what you've written thus far.

The head gasket would only blow as a result of the engine block getting excessively hot, that is a symptom not the cause meaning that this would only happen due to your coolant becoming very low for some reason or possibly a stuck thermostat. Even if the head gasket were blown the symptoms would likely include:

Coolant leaking externally from bellow the exhaust manifold.
White smoke from the exhaust pipe.
Overheating engine.
Bubbles in the radiator or coolant overflow tank.
White milky oil.
Significant loss of coolant with no visible leaks.


Your issue, unless you drove it after the warning lights came on and not let the engine cool does not sound like you've damaged it that much to cause the head gasket to defect. What you've been told to do is VERY costly and may well not be the problem. . At 90+K miles changing the thermostat, which costs very little is at the very least good preventative maintenance but it sounds like this mechanic is padding his pocket.

 

Have someone do a simple pressure test of cooling system; if no leaks, then I also vote for thermostat replacement...................do NOT drive when overheating; very expensive.

Good luck, Adrian

 

In the case of a cylinder head gasket leak, a pressurized test may not result in a visible external leak if the coolant is pushed into the cylinder. It would however, most likely show up in the crankcase oil as has been noted above.