Hey Lads,

My temp gauge is acting funky. Thought it might have been the sensor so I replaced it with a new one with no good result.

The gauge shows warmup to slightly below N which is how it has always run. BTW - I have read some of the history on these gauges.

So it sits at N and then all of a sudden it rises between N and H randomly and drops back. This continuously changes and sometimes it drops right back to the N position. First time I thought for sure it had overheated but then I looked again and it had dropped back down. Got the car home and my pyrometer showed constant temps on the thermostat housing in the 180ish range. By no means cause for alarm.

It takes a while for it to happen. It sits there at N until it wants to do its thing. Anyone else encountered this issue? Also does the RealGauge work on the XJ6?

TIA

Bernie

 

Can't help you on the "why" your gauge is acting funny, other than I'd check wiring of course, but on the question of using a "RealGauge" see the thread below:

https://www.jaguarforums.com/forum/x...analog-141058/


.

 

Random temp gauge can be a symptom of poor engine grounding.

I seem to remember you had a problem with engine earth way back when you got the car, so check that first.

 

Yes, that was a big issue in the beginning.
I took your advice and went to doublecheck the connection.
It is tight and I am showing no resistance between the engine and the chassis. I suspect it is something in the dash maybe?

I may grab an aftermarket water temp gauge to hook up to the sensor and see if the readings are consistent.

Bernie

 

Hey Bernie!

Hope the wife is enjoying the Birthday Jag! Minor problems notwithstanding.

Are your cooling fans running all the time (low speed) like they are supposed to? Any coolant getting away? I can't remember but did you do a coolant and hoses changeover? You can read the real-time coolant temperature if you have a scan tool, maybe get one of those instead?

If you answer yes-no-yes-maybe, then it might only be a funky gauge.

 

Yes, the fans have always run constantly since I joined the forum and discovered how to bridge the connector. I can't see any major loss of coolant either.

No, I have not changed over all the hoses, I did change the upper and lower radiator hoses and put in a new thermostat but nothing beyond that. The rest of the hoses look ok, not perfect but ok.

I guess a scan tool might be in order to check out the overall health of the cooling system. As I said, my laser pyrometer was measuring in the 180's right at the housing that holds the temp sensor even though the temp gauge in the car was pegged.

Is it common, even when the car really does have cooling issues, for the temp needle to randomly jump from N to H and then back again? Reading about how these gauges basically go from you're good to OMG! you're overheated makes me wonder.

BTW - Even with the temp needle pegged, the car has never actually overheated

 

Hey Guys,

What tool do you recommend for me to pick up so I can check actual engine temps?

Bernie

 

So in doing a little research on my temp gauge problem, I have discovered one piece of information and want to confirm it here. Its possible that my gauge is actually correct due to another symptom that we experienced.

When the car started pegging its temp needle, it started to stall out. This happened numerous times during this brief period but would immediately refire and then the gauge would be in N for a minute or two before shooting straight back to H. The car would then run poorly and stall again.

I have read a post from a XJ12 owner that said that the temp sensors are plugged into the ECU and that high temps would cause the ECU to shut the car off. Is this true? If so, maybe I do have a temp problem.

Haven't driven the car since as I have been travelling so my wife has been using my X5. The thermostat was new as well as the upper rad hose but everything else is as I got it. I am going to accurately test the temperature today and then I guess its time to dig into the cooling system and find out exactly what is going on.

Bernie

 

Hey Lads,

Turns out the car was heating up after all?!

This is weird and I haven't completely concluded it yet but here is what happened.

When I originally got the car a year or so ago, I replaced the upper rad hose as it looked swelled and past it. At the same time I put a thermostat in the car as there wasn't one which was strange?

So a few weeks ago the temp needle pegged but it would randomly jump between pegged and normal. The car was stalling out too when the needle pegged but I didn't think the two were related at the time. The car never showed signs of overheating and I was able to easily open the cap on the surge tank regardless of temperature. I was even able to stick my finger into the coolant of the surge tank without burning myself. This was all confusing and I thought for sure it must be the temp gauge acting up.

After checking a number of things, I decided to go buy an aftermarket temp gauge and hooked it to the car. It didn't take but 10 minutes from cold for the temp to rise above 210F with the car idling and fans running. Yup, I have an overheating car. I put the thermostat last on the list of possible causes as It was new compared to everything else in the system but it was also the easiest thing to check. When I popped it out of the car, it was completely closed. I left it out and ran the car again and the temps stayed totally cool. So it was the thermostat afterall.

I put a new one in the car and wouldn't you know it, the car started overheating again. Popped it out and it was closed too? Maybe I got a bad stat because with the stat removed, the car runs totally cool. At idle it barely gets over 170F. So I am not sure if I have a restriction somewhere in the system where the extra flow minus the T-stat helps or if I was simply unlucky with a second bad T-stat?

Currently working on another issue posted on another thread but I plan to revisit this again after I get a few other things done. For now, the car runs cool and that's good since Vegas is going to get stupid hot here soon.

Bernie

 

You can test the Thermostat off the car to eliminate it or otherwise.

Put it in a saucepan of water and heat it up on the hob/stove/cooker. You should be able to observe the stat opening fully. If you have a thermometer then even better as you can note the temp it starts to open and then fully open.

 

I bet it was. If so, it probably wouldnt be able to open all the way, causing build up of heat as flow to the radiator would be restricted.

If I recall correctly, the spring side should face towards the back of the car. How was yours installed?