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Topic: Hot coolant and dead battery? (Read 514 times) |
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Bennekov
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Hot coolant and dead battery?
« on: May 31st, 2007, 1:36pm » |
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Hi all,
I have this very strange problem with my car. At slow speeds (not on the Motorway) the coolant get's burning hot and I see no battery problems. Then if I go on a longer trip with high speed driving the coolant stays cool but instead I can't start the car after a stop as for fuelling (drive approximately 400 miles) due to a completely flat battery.
New battery did not change anything.
There are absolutely no battery problems after jumpstarting if short trips at lower speeds are done.
Any suggestions why battery charging works properly at low speeds but not at high? And any suggestions to explain the hot coolant at low speeds only! No instrument warning lights go off.
2.9, 12V, 1996
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1996, V6, 12V
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TiberiuS
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Ex. 1996 2.3 Ultima - RIP P789 KHJ
 
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Re: Hot coolant and dead battery?
« Reply #1 on: May 31st, 2007, 3:56pm » |
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Flat battery? In the time it takes to stop for petrol? 
Would have to be a pretty severe current drain to do that, are you sure it's a flat battery and not a sticking inhibitor relay of something?
Burning hot coolant? Whereabouts on the temp gauge? Near the red? Is the thermostat ok?
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Snoopy
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Re: Hot coolant and dead battery?
« Reply #2 on: May 31st, 2007, 4:19pm » |
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Sounds like the thermostat is stuck in the open position, really easy to do on the 12v get the proper FMD one it comes with the proper silicone gasket sealing ring otheres only come with a paper one.
As regards the battery, you need to check out the output from the battery when running at speed, you can do this on the Instrument check as shown HERE
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Bennekov
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Re: Hot coolant and dead battery?
« Reply #3 on: May 31st, 2007, 4:26pm » |
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Well,
I'm not suggesting the battery goes flat DURING the petrol stop, rather that it may be discharged for whatever reason during a long drive.
Quite sure the battery is flat! No cranking at all, interior lights dim to nothing when trying. Jump starting cures problem as well as external recharging.
Coolant temp gauge shows all is normal, far from red (increases slowly to normal in about 5 min drive and changes only little from this position despite the reservoir is too hot to keep the hand on for longer time).
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Snoopy
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Re: Hot coolant and dead battery?
« Reply #4 on: May 31st, 2007, 4:29pm » |
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The temperature sounds about right the thermostat is designed to open at 88 C and the coolant temp most likely rises closer to 100 when running in HOT weather . You must remember that it contains Antifreeze and is under presure which BOTH combine to raise the Boiling point.
As regards the battery still suggest you check the charge rate !
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Bennekov
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Re: Hot coolant and dead battery?
« Reply #5 on: May 31st, 2007, 4:58pm » |
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Snoopy if the thermostat is stuck in the open position would the engine then be very hot as well?
Engine correspondingly seems to be unusually hot when driving at lower speeds compared to Motorway speeds.
Thanks for the tip on Instrument check - I'll try it this evening!
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Jonnycab
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Former owner of 2.3 Ultima Facelift saloon
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Re: Hot coolant and dead battery?
« Reply #6 on: Jun 1st, 2007, 2:27am » |
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If the temp guage shows all is fine then I wouldn't worry. The coolant will be hotter at low speeds as you haven't got the air rush to cool the radiator, so the fans have to cool it & they will kick in when the temp is getting too hot & stop when they have cooled it to an acceptable temp 
Regarding the battery, I would say that the battery either isn't holding charge or the alternator output is getting low.
If you have a multimeter, then with the engine ticking over, test the battery terminals. A good reading should be around 14volts, but any lower than 12.5volts probably means the alternator needs replacing 
If the reading is a healthy 14volts, but the battery keeps going flat, then the battery isn't holding the charge & will need replacing
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Bennekov
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Re: Hot coolant and dead battery?
« Reply #7 on: Jun 1st, 2007, 10:47am » |
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Thanks Jonnycab,
The only reason I worry about the temperature is that the reservoir or something else get's so hot it smells like burnt plastic. I'm unable to localise the smell further but it's been going on for more than a year now (worse doing mountain driving than slow speeds). Fans seem to kick in properly.
I used the instrument check to measure the battery output which as expected was low (7V). This was too little to start the car so I could not get a value on the alternator. I'll try again after a jumpstart this weekend.
I'm quite confident the battery is ok (the current one is two weeks old and verified from the shop. This was the second change during the last two months because I was unsure of the quality of the first one).
An alternator replacement therefore seems likely.
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