I have great heat at all speeds all the time; until the temp guage fluctuates and then things go crazy. Mine is usually opposite from yours, I'll have heat when accellerating, and cold when at a stop. I'm thinking a sticy thermostat in the closed position.. Possibly.. Was hoping for a few more ideas before I start throwing parts at it. The T-Stat is $60 from AutoZone. Thanks!

 

Since bleeding it again I've driven her over 200 miles with no issue.. But last time it took almost 1000 miles before she acted up.

 

Thermostat is $20 at rock auto.

 

Yah steve, I was pretty confident a hard reset would do the same thing, but i've recently learned (through motorcarman and others) that it does not, must have the IDS/SDD to clear the adaptations, and/or update the programming. It seems sometimes that it works, but the hard reset clears the fuel trims and other ECM behaviours, that often messes with shifting...but only for a short time, and long-term adaptations return eventually.

Not just a jag dealer, but anyone with SDD and a real (or cloned mongoose cable) can do the same procedure at home. Cleared my xk8 a few weeks ago when it was in the tranny shop getting some new guts. More and more of us are investing the $200-$500 for the very same tools the dealer has.

 

Another day, another myth out of the window, well worth knowing.
I'll add it to the 'disconnecting the battery sticky'.

 

Request this step be expained in a bit more detail:




Are the cable ends touched together or a cable end to battery post?
Do both cables need to be disconnected or just the ground?

Don't want to damage any components.

 

I really love this forum I'm learning all kinds of great stuff (like how to save $40 on a T-Stat).

 

Take the ground (-ve) lead off the battery.
The battery is now only connected via its +ve lead.
Touch the -ve lead to the battery +ve post - you are not shorting anything out.

 

Anyone else have any input?

 

Randy, I've merged your two threads to keep things together.

 

Thank you.

 

Anyone else???

 

UPDATE:

After flushing the cooling system several times, I haven't had any more issues with the heat going cold on me. I took the XJ8 to a local "garage" and had them do a transmission flush using Castrol Multi Import fluid. At first I had erratic shifts, and harsh shifts.. I was very upset, but I'm happy to say that more than 1,000 miles in 2 days on her she is so much better. The "lurge" from 2-1 is almost completely gone, but still there on occasion. I am at Scholfield Auto Plaza in Wichita, KS and they are reflashing the TCM, and adding any fluids if needed. I'll update more after the car is returned to me. FWIW Scholfield is VERY reasonable on prices ($75 to flash the TCM), loaner cars if needed, huge customer waiting area with free Wi-Fi, free "courtesy work stations", free coffee, soda, etc. Very friendly!!

 

UPDATE 2:

Ok, so they are finished. They gave me a free 140 point inspection, most everything is ok. Needs some minor suspension work (mainly just ripped tie rod end boots, and ripped ball joint boots), tranny pan and connector seal are leaking a little bit. Tranny was 2 1/2 qts low.. (just had it flushed and filled a few days ago, so it appears the shop didn't fill it properly. The tranny leak is small, never any drips on the garage. Just kinda "damp" pan. He had 1 1/2 qts in his cabinet and gave it to me free, only charged me for 1qt. (THANK YOU MASTER TECH!!) TCM reflashed, ECM reflashed, free car wash. This place is absolutely amazing! I'll update after the car relearns everything. The master tech said it'll take about a week to get the ECM and TCM adjusted again. He advised it might be a little querky for a bit lol.

 

This sounds like the thermostat to me. It is probably sticking. Thermostats should be changred at 60K so you are due anyway. There is also an electric pump in the heat system that could be bad. Just check to see if its working.

 

Old mots,
Can you tell me where this pump is located?
How to check its function?
I am already looking for a fuse.
Thanks.
Gary

 

^^^^ I 2nd that question lol. Where is the pump at? Thanks.

 

It is underneath the coolant header tank where all the coolant hoses come together.

 

Perfectly hidden.
Thank you!

 

Sounds fun to check... At 104K could be going bad.