For the second time in a year, the CEL came on and my code reader tells me its a P0128 (coolant thermostat) problem. This was fixed under warranty by Galpin here in the Valley. I wonder if they are using poor quality parts? I'm actually taking her into Steve's Jaguar tomorrow for an oil change so we'll see what they have to say. Car now has 35,500 miles.
News to follow!

 

My car had this same issue, the dealer replaced 3 thermostats under warranty and ignored the broken coolant housing until I took it apart and showed them. When the inner tube breaks apart, the coolant circuit does not function correctly. With mine, on cold days would never get up to temperature, and on warm days would start to overheat. New coolant crossover fixed it.

 

It's crap like this that causes folks to bad mouth dealership mechanics. They are not all bad but that is one reason I do my own work whenever possible.

 

Not to hijack the OP's thread, but yes, you're quite right. The only reason I didn't do the work myself was because the car is under warranty. Never relied on a mechanic before, only things I have a shop do are alignments and tires. From what I've heard others tell me, this Jag dealer I went to has become a glorified oil-change and tire rotation shop. Needless to say, I will not be returning.

 

And this is why regardless of miles, on older jags i no longer just replace the t stat. I replace the housing because i too have been burned on doing a t stat job only for the car to return later with the t stat retainer tangs inside coming apart down the road because theyre plastic and we all know plastic only last forever in the ocean and landfills not in cars..
why not just chalk it up to a tech not wanting to rip your head off on price by doing a big job when he thought because of youre mileage you only needed a t stat. Experiance is something you get from a mistake and someone out there is gonna be someones mistake no matter where or what youre dealing with. No one knows everything...cheers

 

Well Galpin fixed the car today. As expected, it was the plastic thermostat housing which had failed. They replaced that at a cost of $67 and put a new thermostat in. All is now back to normal.

 

Thanks Brutal for your comments well said.

 

After reading the posts above, I'm glad I went ahead and did a whole Tstat and housing replacement as I was sort of questioning the plastic after 70K. (code 0128 and not reaching operating temp) Actually found a Duralast by AutoZone for right at 60$ plus shipping (of course it's not in stock locally) so will find out how well that holds up. Doesn't include a gasket (advertised yes, but actuality no, they're changing the write up now, still didn't get me a gasket, tho). Fortunately the original sealed back up for now and the gas mileage has improved with a warmer engine.

 

Glad to hear it was a simple fix. You got off easy for $67, I think mid '06 the housing changed and is currently a dealer-only item, $200+ for the part.