Good Morning! Or not really!

My '04 XJ8 gave me a "Low Coolant " light the other day, just after a long period of storage, and I added a cup or two to the recovery tank, but it did it again a few days later, and again 2 days after that. There is no sign of anything leaking out of the underside of the car, there is no white smoke of any kind from the exhausts, even with spirited driving; the engire purrs smoothly in all modes, and my local garage pressure tested the system over night, and the system holds pressure all night no problem! The only thing I have noticed (otherwise) is that there is no heat to speak of in the interior, even with the temp control set to Max. With the car up to operating temperature at idle, should there be a lot of activity\flow in the recovery tank? I'm kind of baffled.

 

You are unlikely to see much activity in the recovery tank. Lack of heat could be-- auxiliary coolant pump stopped working, ---- air lock in heater circuit ----or flow restriction(sludge) in heater core.

 

Any one, or all three is possible.

 

A coolant drain with a good backflush will get you back to square one....when i replaced my radiator i did it just because and was amazed at the crud that came out even with the radiator removed already.... different vehicle but same principle

 

Well, that infamous, chintzy, plastic thermostat housing strikes again! Jeeze Louise: how many of them are left out there? I know I replaced the one on my XK8 4 Litre while I was doing the secondary cam-chain tensioners (just in the nick of time!) but I thought they had got their act together by the 4.2s !!?? My mistake. Add to the list a water-pump that's on its way out, and a lower rad hose that looks like it's in its 3rd trimester.......nothing 2 grand won't fix. I guess if that resolves the heater issue (with a rad flush and coolant change) I won't bitch too much more. Really the first problem in a 16 yearold car.

 

Wow ...sounds like you diffused a bomb there....are you diy or take to the shop ....either way, pretty good repair to years ratio ...best of luck

 

Yes Scott, I think I averted a catastrophic failure. I was headed for Florida for a few months with my 2 Greyhounds in the car with me; A blown rad hose on the side of the Interstate somewhere in Pennsyltucky would have been a disaster, even if the engine wasn't toasted in the proces

There was a time when I would have tackled this myself- I did the secondary cam chain tensioners on the XK8 myself years back, but I'm retired now and without access to my old shop space, and not as flexible as I used to be. I let the Pros handle this stuff now. I can still putter around with my "B" in the garage by myself, but the Jag and the V8V are beyond my skills now. The shop I use (Birkshire Motors in Thornhill) is very competent and cooperative.

 

1. Pressure test again. Any Auto part would have a loaner kit for you to borrow. I do not trust shop no matter what. I only take five minutes to identified leak, You do not need to wait over right.
2. Turn on heater, refill coolant, open reservoir cap, and see if any circulation motion. If there is nor circulation, you have a dead auxiliary pump, which resulted in no heat.

 

I hear you, annamiata, but the system DID pass a pressure test. It seems that either cold, or fully up to temperature, the cracked housing didn't leak. I'm guessing that the housing changes shape or warps slightly just before the thermostat opens for the first time, and loses some coolant into the valley of the engine (hence the hot coolant smell sometimes) but never in sufficient quantities to run down the side of the block and be apparent from under the car. It was this seemingly random, intermittent nature of the leak that was driving us nuts. Nonetheless, I will have it pressure-tested after the repairs are complete.

 

nice you have a shop that takes good care of you ....hope the Florida trip happens sooner than later.....are the Greyhounds racers

 

Yes. 2 retired Racers, both females, 5 and 9. Sweet, sweet dogs with wonderful personalities. They require surprisingly little exercize; (they're called "30 mph couch potatoes") Highly recommended as pets.

Car should be ready to head south by Monday late. I'm just hoping the snow holds off for a few more days; I like lots of things about the XJ8, but I miss the sure-footedness of the X-Type in winter driving.

 

Excellent.....dogs make great conversation starters too, along with being your buddies

 

Read that many are killed after their racing career is finished, what a crime.
Yet we pay to keep worthless people in prison for decades, that is, also a crime.

 

My 06 vdp cheapo thermostat housing broke with a loud "clunk" upon starting (was first start of the day,average outside temp). I stopped the engine not knowing what happened, it ran fine, no overtemp on the road , BUT as soon as I stopped the temp began to rise to the limit.
IF YOU HEAR A BANG OR CRACK ON FIRST STARTING, IT MIGHT BE THE PLASTIC THERMOSTAT HOUSING BREAKING - IF AN INTERNAL BREAK IT WILL SHOW NO SIGNS OF MALFUNCTION FROM THE OUTSIDE.

 

Fortunately I didn't hear a bang or crack and I may not have an issue but I am curious about a seemingly very long time to for the temp gauge to register any reading after refilling the system. Does the temp sensor for the gauge and a diagnostic reader measure the temp within the block or on the radiator side of the thermostat? After I replaced a seeping water pump and put the whole system back together, started the engine and turned the heater to full blast after filling the reservoir driving around the block it still registers in the 80's on the reader.

 

Outside temperature has a factor in how fast things warm up to temperature in the cooling system.

 

Temp sensor is located on the plastic thermostat 'tree'.

 

Before housing replacement my live data showed up too 106 and fan went to super drive. Afterwards, never over 95. My thermostat seat was broken in pieces impeding flow, inside gauge was acting weird, sometimes very high or low not acting gradually. Inside gauge at middle, live data should read 90-95 when normal operation.

 

The plastic housing is a piece of junk, my 07 acted as you said, & was broken inside.

The 04's was not broken inside, but had started leaking slightly.

A small hose connection, on the P O S thermostat housing.

 

Thanks for the update. This is exactly how my car acted on my first 10 mile drive. My live data went to 116 and the gauge would settle at normal while idling. Time to replace housing tonight...