Hi All,

Question: Can (poorly) jumpstarting your car damage the ECU or other electronics in such a was as to cause severe overheating?

1)
Please excuse the foolishness that lead to this situation.
I have a 2004 X-Type. Recently I left the headlights on - and was away for a week. Oops.

I tried to jump start it with a 2000A booster pack, that indicator said was at 25% capacity (was all I had at the time). There was not enough juice to start, so, lacking any other option in that location, left the booster connected for an hour, hoping battery would charge some.
Result: Car still wouldn't turn over, booster pack had dropped to 0%.

Clearly a lower-than-acceptable voltage would have been delivered to the car, and it's electronics.

2)
Found someone to come and jump start me vehicle-to-vehicle, started immediately.

3)
Drove about 30 minutes. Heard a ticking sound, a small amount of steam came from hood/bonnet, temp gauge in red, car had overheated, immediately pulled over. Significant amount of water on road, with a trail going back at least 50m. Radiator cooling fan running after car turned off.

Inspected car, no leaks found, could not find any evidence of e.g broken water pipe. Allowed car to cool, filled water reservoir, allowed car to idle for some time, no water leaking, temp gauge dead centre.

4)
After some time, decided to try drive carefully home - 15 minutes - had broken down in a bad spot. Drive was uneventful, temp gauge remained center, water resovoir level did not change. Only difference was that radiator fan remained running for some time after I switched off engine. Think was perhaps just beginning to heat up...


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The two incidents could be unrelated - but generally I'm not a believer in coincidence - seems strange that immediately after jump starting the car (for the first time ever) it is immediately overheating and dumping water on the road. No leaks found.

So far I have removed fuses F32 & F36 for 30 min to reset the ECU. Have started the car, idles fine.

Is there anything else I should check or test before taking it for a careful test drive, to see if it still has the problem?

Thankyou :-)

 

Jump starting your car should not have caused any overheating. You need to get the system pressure tested to identify any leaks. It is possible that the thermostat is no longer opening and creating the overheating conditions. I had a coolant loss with no indication where it was going and found that the plastic pipe section of the upper hose assembly had a crack that opened under full system pressure.

 

DrVertigo, from the sounds of things, if you were doing a lot of stop and go driving, this would possibly result in the overheating that you saw, making the assumption that because of the low voltage, the ECU saw a temperature that wasn't right and did not turn on the fan in time.

As for the water, I would venture to guess that the expansion tank (overflow bottle) got to high in pressure and it relieved, allowing a mix of steam and water to escape (hence your water trail).

I would keep an eye on things. From the sounds of it, everything went haywire due to your car seeing too low of a voltage due to the discharged battery. Granted, I would also get your battery checked for capacity (any local auto parts store can do this for free) and if you have 75% capacity or less, probably good to get a new battery. Standard starting batteries in cars do not like to be discharged like you did and that can cause permanent damage to the battery. when the capacity of the battery drops, it doesn't filter the output of the alternator as well and this causes the voltage to change in the car too much, leading to random problems.

 

Thank you both for the excellent answers, I learnt a fair few things from you, cheers.

Including the rest of my experience for completeness:
I took it for a few more careful test drives, around town, 50km/hr.

Temp would remain stable for about 30-40 minutes - then rapidly start overheating.
Letting the car idle with the heaters on full would bring the temp back down.

No leaks.

Took out the thermostat, it was stuck closed. Seemed in very new condition, but put a new one in regardless. Problem fixed - it was the thermostat in this case.

Not usually a big believer in coincidences, but I guess in this case the timing of the two events, was just that.

Thanks for your help!

P.S does anyone know where to get a copy of "Jim's little black book"?

 

My bet would be someone leaned on one of the small 1/4" nipples on the coolant tank during the multiple jump process's and cracked one.
Check the two small nipples on each side of the coolant tank, press down lightly on each and see if it feels wrong. You typically will not see this leak until the engine is at temp and has pressure on it. Very common issues, I know about it and have still broke a 2nd one somehow. If you find an issue there is a decent easy cheap fix.