did the same here wheelmang when you have a nice sunny day to work on get the aluminum replacement for the stat assembly can crack the old one off which makes getting to the old bolts easier then replace the rear bolts with either hex bolts or ones cut with a screw slot on top also.... (make it your self with a hacksaw or dremel tool ) makes getting those rear bolts alot easier to get out if necessary in the future .

 

So, I finally replaced the thermostat and hose, but the car's heater still has the same problem. It worked fine for the first 10 minutes after the car warmed up and blew hot air for about 10 minutes, and then the hot air stopped, and would only blow cold air. Any ideas what to check next?
And Yes, my first thought is that there's an air bubble stuck somewhere in the system. I've been squeezing and pumping the hoses trying to get any possible air bubbles out, but anyone got any better ideas, if that is what my problem is?

 

Keep in mind that it usually takes several days to work all of the ingested air out of the system. Just keep checking the coolant level in the expansion tank and top up as necessary. When I replaced the plastic coolant outlet duct assembly in my wife's 2006 XK8 in late November, I had to add a bit of coolant on three successive mornings. By the fourth morning the coolant level finally stabilized where it belongs and has not changed since....

 

I overestimated the ability of these cars in the snow...My new thermostat test drive turned into a family event with everyone pushing it back into the garage!

 

Yep, when the snow flies both of our Jaguars stay safely at home. That's what my 1999 Dodge Ram pickup is for....

 

Now I think its gotten more serious. I think I've got a leaking head gasket or something like that?

My latest symptoms;

1.) On my last test drive, the engine appeared to overheat right as I got home, and there was lots of either smoke or steam coming from under the hood. The engine temp gauge read normal, but from what you all have told me in this very thread earlier, that the gauge doesn't function like a normal temp gauge. It didn't smell purely like the sweet radiator cooking on the engine smell, just smelt like a wicked hot engine. There was possibly with some coolant smell, along with whatever else, because it wasn't a white colored steam, it was kind of a darker shade of steam/smoke, if that makes any sense. I shut the engine off when I first saw it, and it stopped shortly after. It cooled down, I added coolant, and drove it into the garage without any further issues.

2.) The air bubbles in the coolant don't seem to stop coming, its a constant flow of bubbles now matter how long the engine runs.

3.) When I have the cap on and the system is closed up like normal, the pressure in the hoses seems to be unreasonably high. Like, they're under such high pressure, I'm surprised they all don't pop off and explode.

4.) The heater still only works for the first 10 minutes, then it only blows cold air.

5.) After I replaced the thermostat, both the upper and lower coolant hoses are now hot, where as before, only the upper hose was hot, so thats my only good news.

Whats the verdict, Blown head gasket?

 

Forgot to mention, The oil is still normal looking(at the moment), meaning I can't see any coolant on the dip stick, and the coolant color looks normal also.

 

Yup!

There is a test kit to detect combustion gasses in the coolant as a final conformation.

 

How big of an ordeal is fixing a blown head gasket on these cars for a real mechanic? I'm pretty sure I don't want to try doing it myself.

 

Bump this old thread.

Just put in the alum water pump, alum thermostat housing, and new thermostat.

Not sure if the thermostat is working however. Running at idle for about 10 minutes now and the top heater hose is pretty tight - starting to bulge. The temp according to Torque App is 188.6 degrees F. The bottom hose is tight but not bulging. Both the top and bottom hoses are hot. They relax after cooling down.

Does this indicate my thermostat is stuck?

 

Your TORQUE temperature reading is just where it is supposed to be. You rebuilt most of the coolant system on a 15 year old car without replacing the hoses?

 

Waiting on the hoses to arrive. Transmission and all tensioners and chains were done too. So, I wanted to test the engine now rather than wait for the hoses to come. Thanks for the reply.

 

Check the radiator by removing the radiator hoses at both entry points: top and bottom. See if you can get a clear stream of water to run in and out if these hoses with a garden hose. If yes, then your radiator is most likely not the cause. Obviously while you are doing this, change the top hose [er balloon]. I'd change both.