Hello

Just replaced the alternator using the pull from top method (remove fan shroud, t stat housing and upper coolant hoses), put new alternator in and heard water pump squealing and saw drips from weep hole so new water pump--filled up with coolant and went for drive -- high temp light-- so must have screwed up t stat so got new one and same issue....will overheat and fans run until battery runs out (I pull ground off before that)
Strange thing is in June the coolant tank gave out and dumped the coolant--put a new one on and ran fine.. also last winter the lower rad hose popped off (o ring would not hold) when wife was driving and she came home empty on coolant--new hose and refill and no problems--only difference this time is I drained radiator so there must be air still? The top hoses are hot so I think the t stat is open....

David

 

David, if you let the car sit overnight (ie, block cold) and you start up the car. Does the temp gauge immediately jump to pegged high? If so, when you were doing the alternator, you accidentally unplugged the temp sensor and this is what is causing your issue. That or you damaged the wiring to the temp sensor and that is causing a high resistance.

I would like you to try something. Get in the car and depress the TRIP button on the end of the turn signal stalk. With the button still depressed, start the car. Keep the TRIP button depressed and be watching the message center. As soon as you see it say "Engineering Test" or "TEST" (or something to that effect), release the TRIP button. If you tap the TRIP button one more time, you should see all your gauges do a full sweep (this is normal for what you are doing). If this is the case, keep tapping the TRIP button till you see it say "XXXX C" (where XXXX is 4 digits, should be around 0230 if it is 23C outside at the time of starting). You will be depressing the TRIP button roughly 26 times and you will know you are getting close as the point just before where you want to be will say "FP XXX" (where XXX is a number between 0 and 254 where 0 is empty and 254 is a full tank and a half tank is 128) and then the next step will say "FG XXXX" (where the XXXX will be a number relating to the signal going to the instrument cluster, the value is not a useful number) and then you will hit the "XXXX C" value.

At this point, what does the number say? If you know the outside temp, this value should initially be very close to that (ie, 0230 relates to 23.0C or 1000 relates to 100.0C). If the value is up at 3695, then this is telling me that the computer is seeing a very high resistance and therefore thinks the engine is running at 369.5C (which is a very unlikely spot for the engine to be at). If you see "----", then this is another sign that it is seeing an open in the temperature sensor loop.

You can let the engine come up in temp and you should see the indication follow. You can let the car idle for up to around 5 minutes without the engine overheating. if in doubt, turn the engine off.

Lets see what you have at this point and we can hopefully get you taken care of.

 

Thermo
Thanks for the response--the car actually will sit idling for 10 min as the temp climbs to 1/2 mark and as soon as I drive it down the road it will peg hot--the fans cycle on but the overflow tank will start steaming -- I haven't looked at it since Tuesday as it threw multiple can codes for transmission and abs so I need to check that out too

David

 

Wahoo, if it will idle without overheating, but you are getting it to overheat once you start driving, then this tells me that you have either a bad thermostat or a problem with the water pump. Granted, it is possible that there may be significant blockage in the radiator. But, this would have resulted from something coming apart during your maintenance to have the situation that you are seeing.

My first instinct would be to have you pull the thermostat out of the car and put it in a pot of water on the stove. heat up the water and watch the thermostat. You should see it start to open up at around 180-190F (use a meat thermometer) and be pretty much fully open around 205F or so. That will then tell you if you have a thermostat problem or a water pump problem.

 

Thermo

I'm a dumb#$s--Sometimes when I do my initial assessment on this car that requires the upper hose to be removed I plug the hard pipe with a large vacuum plug to reduce coolant loss--when I did the alternator all that stuff was removed and I basically forgot 2 weeks later..removed it and popped out the plug--good as new.

So far I have 100 miles on the car after that p1799 and P1637 code -- installed a used TCM module and then got a reman (ebay) ABS module--good as new so far.....

David

 

OK, so I can set the test and page through all the various codes, but what do these mean? They are a jumble of letters and numbers that mean nothing without some kind of reference. And so many! I've tried unsucessfully to find anything relating to code meanings and no luck. Thanking y'all in advance, mechanic80.

 

They're irrelevant - many years old - so ignore them.

Get a proper tool if you want to read codes.

 

You didn't look very hard. This is just one of dozens of results in Google search (not even trying the search here).

Technical Service Bulletin
No.JTB00014

https://www.jaguarforum.com/showthread.php?t=14975

 

Mechanic80, if you are talking about what the various values mean when you are in Engineering Test Mode, they all have various meanings. that is where you need the TSB that Dell listed. that tells you how to take the value that the instrument cluster gives you and makes it meaningful. It can be helpful, but you also need to know where the values are coming from and that is where the TSB also helps with that tool, but it isn't real obvious.

 

But ignore the codes.

 

wrong thread. can't delete a post I guess.

 

Wtf?

 

Just a thought ,pop the thermostat out and put it in boiling water with a thermometer or just let it boil and watch it..its nice to see and see it open or not in your case I hazard a guess.. Least you can rule it out ..Si

 

they do self bleed a bit so i have been told

 

Looks like a dead thread so not worth adding anything.

 

still trying to get to grips with this ..pls excuse

 

Just joined. Hope someone can help. My Car is losing fluid in the reservoir daily. It's holds pressure in a pressure test but still loses fluid. Does anyone know if I have to burp the system since I did change the therm. Thanks in advance.

 

@chicagoborn38 you have an XJL? This is X Type forum (X400)