Temperature needle all the way to hot

[dkbjain]

I have a 2001 3.0 liter x5 that had a problem this morning.

The car hadn't been driven for about 2.5 weeks, and the temperature was cold (about 35 F).

The car started right up, but while I was letting it warm up the engine died. So I started it again. It looked like it wanted to die, so I started driving. The temperature gauge read all the way to the left (cold).

About 30 seconds later I noticed that the temperature gauge was all the way to the right (hot). So I immediately turned around and went back home and parked the car.

Since the temperature gauge was on hot, I expected that a coolant hose or something had failed and all the coolant had leaked out. But I didn't see any evidence of coolant leaking out.

I checked on my scanner, and it showed the following codes:
F0 Misfire, cylinder 3
F3 Misfire, cylinder 6
DE Oxygen sensor control not active after specified time

Any guesses as to what happened and how I should proceed?

Thanks.
-Danny

[andrewwynn]

There is a known bug with the computer on E53 and temp gauge. If the coolant is full and the temp seems normal (when my car did this it was about 5°F out and I only had the car running for 10 minutes so I knew it was impossible). I stopped the car, opened the hood and grabbed the upper radiator hose. I could hold it firmly so I knew the temp was below about 150 and the gauge was in error. I turned the car off then back on and bingo gauge fixed. I only found out about a year later that is a know bug.


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[andrewwynn]

The misfire can be a lot of things. Reset codes and see if they come back. Sometimes a misfire will put the car into safe mode and the engine will run like shit. Very likely why it stalled. Did the engine feel like it was running on three cylinders?



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[upallnight]

Originally Posted by andrewwynn

There is a known bug with the computer on E53 and temp gauge. If the coolant is full and the temp seems normal (when my car did this it was about 5°F out and I only had the car running for 10 minutes so I knew it was impossible). I stopped the car, opened the hood and grabbed the upper radiator hose. I could hold it firmly so I knew the temp was below about 150 and the gauge was in error. I turned the car off then back on and bingo gauge fixed. I only found out about a year later that is a know bug.


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A thermostat that is stuck closed will not allow coolant to enter the radiator, so the engine could be overheating but the radiator will still be cool enough to the touch. If the temp gauge shows an overheat condition set the interior heat to as high as possible and see if you have heat. The interior heater core will allow coolant to flow into it and cool the coolant before returning it to the engine. Get it fix before you ruin the engine.

[dkbjain]

Originally Posted by andrewwynn

The misfire can be a lot of things. Reset codes and see if they come back. Sometimes a misfire will put the car into safe mode and the engine will run like shit. Very likely why it stalled. Did the engine feel like it was running on three cylinders?



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Thanks for the tip on the temperature gauge bug. I have had the car for 17.5 years and never noticed this. But it would be nice if this was the problem. I'll try starting the car again when I'm back home and see what happens.

Yes, the car was running rough due to the misfires. I have fairly new spark plugs and ignition coils, because I have had misfires in the past. But none recently until now.

-Danny

[dkbjain]

Here's an update. I got to look at the X5 further at lunchtime.

I checked the coolant and noticed that it was low. I had to add about 20 ounces to fill it up. (I read the entire system is 8.5 liters).

I cleared all the faults. Temperature was now 50F.

I started the car and everything was back to normal. Car was not running rough, no new fault codes, and the temperature gauge gradually moved from the left (cold) to the middle (normal). I left the car on for 20 minutes and drove it too.

I'm hoping that what happened this morning is a fluke, but we'll see.

Maybe the engine wasn't really hot this morning and it was the temperature gauge bug. I found that service bulletin on another thread and have attached it. But in my case I didn't really meet their conditions. Temperature was 0c instead of -10C. And I wasn't running full heat.

Maybe the engine really did get hot due to the coolant being low. Doesn't make sense to me that it would get all the way to hot that fast for coolant low.

Maybe the coolant thermostat was stuck closed this morning and the engine really was heating up. But I would think this would cause a fault code, and I didn't get one.

Anyone have any opinions?

Thanks.
-Danny

[andrewwynn]

You are correct about the needle jumping to hot. I guarantee it was the bug. You could have just turned off and on and it would have fixed. I left it running to use my IR thermometer and my hand to confirm the temp wasn't high then (being a computer troubleshooting expert since 1989) I predicted it was just a computer bug and restarting would fix it. It did and a year later I actually found a TSB about the problem. I'm not aware of a fix.

The misfire codes can be from a lot of causes. I get a random no fuel cylinder misfire about every six months. Car will run like shit until I clear the code. Once I do, while driving with my iPhone car kicks out of failsafe and runs perfectly. Fun that I don't even have to pull over or slow down.


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[andrewwynn]

That was the TSB I found.


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[1BADM6]

Generally if your temp gauge gets that high and you continue to drive then engine failure is almost a guarantee but you'll see other signs like steam and coolant leaks. That pressure has to go somewhere unless your coolant is really low then it's possible the empty capacity will retain all of that steam. 20 oz really isn't that much. Glad it's working.

[andrewwynn]

That is if the temp gauge climbs to that temp not this failure mode where it would literally need atomic power to achieve the rate of increase.

The gauge went from 120° to 230° instantly not five seconds. Zero seconds. It was pretty clearly an error. I first figured my temp sensor just failed open/closes whichever would give high output but I cautiously checked the actual temp of my engine knowing that at 10° ambient it was physically impossible to achieve 230° in ten minutes. When IR thermometer confirmed, I crossed my fingers it was software not hardware and restarted the computer. Bingo it worked I wasn't even surorised I just figured it's probably normal for a 16 yo car to have some computer coding errors and moved on with my day.


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