Engine Temperature spikes to full scale

[Win]

This has been a chronic condition for our V8 2001 LS. The engine temperature gauge will swing up to full scale. But, turn off the ignition for a few seconds at a traffic light and as likely as not the gauge will drop to normal for the rest of the trip.

I've sort of ruled out a wiring problem because the temperature creeps up over perhaps 20 seconds. If the wiring was intermittently shorting the gauge would most likely jump rather than creep.

The computer seems to be "fooled" along with the analog gauge because it doesn't take long for the computer to feather the engine in an attempt to reduce further overheating. Odds are the computer does not control the analog gauge so the abrupt return to a normal reading is unlikely to be an artifact of rebooting the computer when the ignition is cycled.

These observations lead to the tentative conclusion that the temperature sensor has problems.

Over the years the car has gone to the dealer twice over this issue. Each time the costly bill has detailed thermostat replacement and other ministrations to the cooling system. Each time the problem was "cured" for a year or two. But on only one occasion was the temperature sensor replaced.

Yet every time the problem has occurred the symptoms were identical, and in every case "curable" for minutes, hours, days or months by simply turning the ignition off and back on.

Have any of you run into this spiking temperature reading problem? What's the best way to test the coolant temperature sensor?

 

[joegr]

Sorry, but your LS really is overheating. The gauge is actually "computer" controlled and is very non-linear. This fools people into thinking that the problem is not real. You can plug in a scan tool and read the real (non-buffered) temperatures from both the coolant/oil temperature sensor and the head temperature sensor. You will see that the temperatures really are going too high. You will also see that they only have to drop a few degrees (still over 230) for the gauge to fall back to the half way mark.

I haven't heard of anyone having to do it every year of two, but every six or seven years all of the cooling system plastic parts have to be replaced. Perhaps you have never replaced all of it, and are just letting parts fail every so often? Alternately, the commonly available aftermarket cooling system parts only last from a few months to maybe a year or two.
Also, your year has a hydraulic cooling fan. Those also have some common failures. You should verify that it is working correctly as well.

 

[Win]

Interesting and useful observations, thanks.

Indeed the failures are roughly 6 years apart. All were repaired by Lincoln dealers. Presumably both the quality and number of parts replaced were appropriate. At this point, however, the sole remaining dealers in this area are the ones with seriously tattered reputations so I'm hoping to transfer a few skills as an aircraft mechanic and veteran engine builder to the Lincoln [those early LSs are the only sedans they have that fit navigate easily into a 10' alley with sharp turns.]

Both non-contact and NIST traceable contact thermometers show the same temperatures at mid-scale during warm up and at full scale during an "overheating" event.

If a sensor is off, wouldn't it stand to reason that the raw logged temperature would also be off? I suppose, however, that reconciling the readings from multiple sensors has merit if we're talking about only a few degrees between "normal" and "overheating".

Mentioning the plastic parts brought flipping the heater on to mind. Sure enough it's pretty wimpy. Next check is to pressure test and make sure the coolant's bled properly.

 

[grizzlyls]

What your describing is exactly the same issues I had on my Gen 1 when I had small minute leaks somewhere. Each time it spike hard after driving for a bit, and after pull over it settled a bit. You can confirm this by trying to fill the system at the tstat housing. If it takes a good bit, then you have a leak somewhere. If it takes some and the degas level goes up (bounce the front end some after putting in) then you might not have a leak. You can also get an OBD II connector from amazon and monitor the coolant temp on your cell phone. If if isnt sitting below 210 most the time something isn't quite right I have found.

Having said that, if your due another refresh on the system, make sure you get the aluminum housing, replace the upper radiator tube at least, and the degas bottle is likely ok if its replaced at dealer once already, but needs a good inspection which probably means pulling it up out of its well to see its bottom.

 

[Win]

Your comments, grisslyls, build nicely on joegr's. Thanks for extending the diagnostic road map (and I'd welcome any iPod compatible WiFi OBD2 adapters & software -- there's an awful lot of generic ELM-327 adapters floating around.)

One question though. To what does the suggestion to "...make sure you get the aluminum housing..." apply?

 

[Gary Vogeler]

Win,
How often does this occur? Does it only go away after cooling system parts are replaced?

Reason I ask is my 02 has done something like this twice in the 14 years I've had her. First time was at about 3 years old. Last time was around 5 years ago. Each time, the temp gauge pegged along with the audible warning chime within 3-4 miles of my departure location and both times I was traveling at highway speed on the interstate. I pull over, shut off the engine for a few seconds, restart the engine and the gauge is back to normal and the pegged temp gauge does not come back. To date, aside from cooling system flushes, I've only had to replace the degass bottle in 2014 or 15. Can't recall the year, I've misplaced the receipt.

I've suspected my issues were due to the notorious LS electrical gremlins since I do experience the random, one off warning chime while driving every 6 months or so. Do you experience the random warning chimes?

I work with a former Ford electrical engineer who has confirmed the ground points on the LS chassis have had reliability issues and the temp gauge pegging and not returning would not be a surprise.

 

[Win]

Yeah Gary, that's what's happening -- down to the one-off, kinda random, chimes.

With the advent of composite skins & structures, electronic ground planes are a design challenge for aircraft control systems. I imagine with the increased use of plastics the Ford engineers wrestled with the same thing. [One sidebar is that the mashup of materials in a common copper wire /steel lug terminal tempts corrosion -- particularly around moisture.]

In the end though, taking a real close look at the OBD data should shed a bit of light on the problem.

 

[joegr]

...One question though. To what does the suggestion to "...make sure you get the aluminum housing..." apply?

The thermostat housing.
"Jaguar" Aluminum Thermostat Housing

 

[Gary Vogeler]

Thanks Win.
I've had my OBDlink MX connected with my phone many times over the past year but with the random chime occurring so infrequently, it has not occurred while I've been monitoring. Still trying though.

It's more of an aggravation than anything else.

 

[Win]

Thanks joegr for the tip about the aluminum Thermostat housing.

Thanks Gary for recounting that the OBDlink MX ELM-327 compliant link works with his phone.

More once I've had a chance to gather information.

 

[RigsLS]

Transmission E chime

 

[joegr]

Transmission E chime

Actually, the "mystery beeps" have many different sources. I've seen (with scan tool after event) fuel data errors probably the most (maybe once a year). I think this has to do with noise from one or both of the fuel float potentiometers. I also have seen some phantom bulb out triggers for the mystery beep as well. Basically, the mystery beep is any monitored error condition that is detected but self resolves before any actual message can be displayed or read.
To me this is a software bug. Either such short duration events shouldn't be reacted to, or they should always hold the message long enough to be displayed and read.

 

[joegr]

...I've suspected my issues were due to the notorious LS electrical gremlins since I do experience the random...

I suspect that you are deluding yourself. All the reported quick overheat events that I can recall where the poster believed it was an electrical error were resolved by fixing the cooling system (meaning that the overheating was real).

 

[WhoBeDaPlaya]

I suspect that you are deluding yourself. All the reported quick overheat events that I can recall where the poster believed it was an electrical error were resolved by fixing the cooling system (meaning that the overheating was real).

+1 It is painful financially, but you have to bite the bullet, or risk drawing it out for months on end, replacing one part after another, constantly refilling coolant, and never having real peace of mind whether your ride is reliable.

 

[Gary Vogeler]

If I am deluding myself, why did these 2 events occur and not recur again? If I had a crack in the system at age 3 allowing air in, I have a hard time believing I would only have 1 more overheat until age 12 or 13 when the degass bottle finally failed.

After the degass was replaced, I did have air in the system that led to a few legit overheat warnings before I finally got all the air purged. At that time, I had temps rising above normal when climbing a long hill out of the Ohio river valley which allowed the sensor to be uncovered in the air pocket. No issues since the air was purged.

I do expect to experience another cooling system failure, just a matter of time.

It's just difficult to believe that the one off gauge peggings with a warning chime were not electrical. Everyone else on the forum who has experienced plastic failures has an overheat trend. I only had a trend after the degass bottle was replaced and the system was not completely purged of air.

Ironically, I had another random warning chime on the drive to work this morning. Again, no message, no gauge outside of normal, no misfire, no lighting issue, no fuel economy or odometer resets, no CEL, no code, nothing but the chime. Had been on the interstate at speed for 7 miles. Probably won't occur again until fall if history repeats itself.

Does anyone else have this occur?

 

[Gary Vogeler]

Sorry, missed Joegr and rigLS comments.

Transmission does not fit this morning's event. Had been in 5th for 7 miles. No obvious trigger.

Fuel float potentiometer is interesting. I was coasting down the same hill toward the river and about 1/2 way down after coming out of a slight turn, the chime activated.

Thanks for the feedback gents.

 

[cammerfe]

I believe Joe's comment at #12 is your best answer.

KS

 

[grizzlyls]

Yup. Random chime out of the blue whenever. Scares the crap out of me then pisses me off when I cant find the code or nothing.

Anyhow, you musta cursed me. hit an overheat on the way to work, pulled over, it settled once I went full on heater at 90 degrees. Popped the obd on and monitored it pulsing the fan a bit and spiking at stop lights to 215 ish.

Made it to work and checked underneath after about half hour. Not a drop! dammit! Easier IMO if there was a mass leak to solve. Anyhow topped it off like I suggested on my post it did seem full so now its a little fuller. Hope it was a fluke, we will see in about 40 minutes on the way home.

 

[Gary Vogeler]

Sorry to hear you had an overheat. Didn't mean to bring bad luck. Let us know how your situation works out.

As for my mystery temp gauge peggings being real overheats, I can't accept that I had a degass bottle leak that started in '05, then didn't have any coolant reach the ground until '14 or '15 and during that time only had 2 gauge readings above normal. When the degass let go, I came outside after being in a meeting for about an hour and had a puddle behind the drivers front wheel about 6" across with a strong anti freeze smell. Fortunately it was spring and I limped it the 30 miles to home. First and only time I had a noticeable anti freeze smell. I've had no issues since completing the air purge after degass bottle replacement.

If it was the degass in '05, was I extremely lucky that it did not let go until '14 or '15? Or is the '05 failure still lurking 12 years on? Or did my dealer identify the problem without me reporting anything and they repaired it for free and left it off of my repair bill so I would not know about it? (Yeah right)

Leaks don't cure themselves. I believe most on this forum agree with that statement. Has to be another explanation for the temp gauge pegging and not recurring events.

Hopefully it will not occur again. If it does, maybe. Ill be lucky and have my OBDmx connected. However I expect to have another real failure before that.

 

[grizzlyls]

You could be due a bottle. It is all relative to the over all heat whre you live and time used/cycle. If there is a small leak it may be depressurizing the system. After a drive, twist the degas bottle cap just a little. BUT BE CAREFUL to not undue it and have explosive boil. It should his air vacuum pretty quick on the turn, quickly shut it because then you know you are pressurized and that's not it. That's one of the tests I did on mine

 

[02LincLS]

The temp readings are real. You are overheating. Most likely the degas tank where you can't see it, but possibly at any other point in the plastic tubing. Or as joegr has said in the past, you may be the first exception on these forums. You typically only need a new temp sensor if you removed or loosened the old one.

And my mystery beep is always the Gear Select Data Error. Software glitch that happens likely from communication issues between different modules. If you had ground issues, you would have a slew of random issues popping up.