So a couple weeks ago while on a 100 mile trip at a steady 70mph, about 50 miles in i notice the Dash Temp gauge has pegged out with the light on. i pulled over and shut it down, popped the hood and everything appeared to be ok. no steam or boiling noises. as soon as i start back up the gauge shows half below midway. back on the rd for 15 min it happens again. it slowly rises to half then quickly runs to Max.
it doesnt do this around town in stop and go traffic. ive bled the system of air. i can smell hot coolant as if it is leaking but i cant find the leak or see any droppings. i got the codes scanned at autozone and they came back as
0171 too lean bank one
0116 coolant temp sensor
0128 coolant below thermostat
...The coolant is at max fill. i went ahead and baught a thermostat and coolant sensor, i havent installed them yet. im thinking the waterpump may also be a problem. ive heard the impeller is plastic and my conspiracy theory is that maybe it has crack and could be 'freewheeling' at low highway rpm and not pushing the coolant. idk.
ive also read that this could trigger the Too Lean problem somehow.
(this might be a seperate issue) but yesterday the car began idling rough like its missing or running on 7 cylinders. seems to be comming from the US driver's side of the engine. i had used STP injector cleaner in the most recent tank of gas (thinking i was doing something good at 108k mi) only to read now that they dont reccomend using the stuff on jags.
any ideas about what might be going on? im thinking of ordering a waterpump since theyre only $38 and just doing everything at once. im also considering leaving it parked on the street with the keys in it with the windows down lol

 

Usually when the water pumps go bad, you can either hear it or see coolant leaking on the front side of the block. Seems like your issue is either the tstat not actuating as it should or the coolant temp sensor (probably the sensor). If you have the means, replace the tstat and pump and sensor together. Also check the wiring harness on the coolant temp sensor is not damaged or has wires exposed. Btw newer replacement water pumps come with metal impellers, i recommend switching since it's something that you will have to do eventually.

 

If it is any help to you, I had a problem last winter where the temp gauge would quickly rise to max and give the restricted performance message. Shut the engine down, and restart it 10 seconds later, and the gauge would show normal or just a tad below normal. In my case it turned out to be the t-stat housing. Having said that, I wouldn't rule out pump, t-stat, or head gasket, among other possibilities.

 

My guess is thermostat since this has happened twice to me on my 160,000 XJ8L. I am on my third thermostat, the past two episodes are exactly as you described to me. I replaced the sensor last time, but it wasn't the issue. Change the thermostat.

 

Well i took everything apart and dove in. Decided to put in a new h2o pump, and coolant temp sensor, and thermostat. I went ahead and pulled the belts off and put new ones on. At 109k miles they were pretty much cooked. For whatever reason, the main belt tensioner is 1/2inch socket and the Supercharger belt is 1/4. Since i had everything out of the way i swapped out the swaybar bushings which wasnt nearly as hard as i had imagined.just need a rachet extension and a swivel connector at the end. The orig water pump was still intact, but it feels alot better knowing the new impeller isnt made out of plastic. Changing that out was a piece of cake. The thermostat was stuck open i beleive as it warms up much faster now. It was fairly easy to do. The bottom of the 3 bolts holding the housing on was impossible to get a ratchet on since there isnt enough room to fit it in there. I just held the end of the torx bit in place with a finger and turned it with a tiny wrench.
this solved the High Temp light false alarm problem. It also runs alot quieter with the new belts.
the rough running issue turned out to be a bad coil pack which took less than 5 minutes to change and about $40. The Jaguar dealership wanted 171 each just for the part and told me i should do that entire side of the engine lol (if that sides bad why not the entire otherside too)i gess she sensed i wouldnt fall for doing All 8. ive seen them trick an unsuspecting elderly customer with this before. Sure the other packs may go out soon, but they either work or they dont so ill just replace each as they go. Then they tried to charge me $280 for a diagnosis when they had told me it would be only $150 when i scheduled it. I just told them No. She got all huffy and changed the invoice to 150 and said she would have to find a way to pay the poor shop guys, (like she was gunna have to dig through her purse to makeup for my cheapness) whatever.. theyll make it up on the next $120 oil change customer that comes in .
now, i just have to sell this thing before something else breaks again. Lol

 

Well done!
And thank you for the feedback.
Did you need a specific Torx driver (T60) for the housing?

 

Ha! good story-those dealers are shameless and they are even useless at lying!

 

Catsgame,

Thanks for the entertaining account and resolution to your problem!

Contrary to popular myth, Jaguar did not use plastic impellers simply to save money. They did so because Extended Life OAT (Organic Acid Technology) coolant does not protect steel impellers from cavitation erosion or the aluminum cooling system from electrolysis erosion due to the presence of two dissimilar metals in contact with electrolytes.

Early X100s and X308s had black Nylon 66 impellers that were known to deteriorate, but Jaguar did not replace them with steel impellers. Instead, they used another plastic, black polyphenyl sulfide (PPS). Jaguar specified that pumps with black Nylon 66 impellers should be replaced but that those with black PPS impellers did not need to be replaced. Early S-Types had the black PPS impellers, but those were subsequently changed to white poly phenyl sulfide. As far as I know, all or most of the X350s have had white PPS impellers. Orange OAT Extended Life Coolant (XLC) was specified for all S-Types and all X350s. Here are a couple of relevant TSBs (I think there were others):

TSB 303-60 Coolant Pumps - Identifying Impeller Materials - Pump Replacement Guidelines

TSB S100-06 Extended Life Coolant (XLC) - Identification - Precautions


Here's a photo of a genuine OE Jaguar water pump posted by Box in another thread:




And here's a photo of the pump made by Airtex, a Ford OEM who I suspect made the Jaguar pumps:




Cheers,

Don