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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
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34 Posts
Discussion Starter #1
1999 Deville 85,000 miles. Today experience overheating, idle engine stop engine signals. Sound of bubbling from expansion tank. Topped up with dexcool and same thing. No smoke etc from exhaust but engine life 0 comes on as well. Fearing the worst!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,854 Posts
Before hanging your hat on failed head bolt hole threads leading to head gasket failure, please perform the several other tests and checks recommended throughout Seville, Deville, and Northstar for many years. You're a long-time member and so should know what to check.

Water pump drive system; purge line flow; heater core flow; leaking heater supply/return piping.

The OLM will indicate 0 Oil Life after an overheat event. Not to worry. If the oil/filter had low time/miles on it then simply reset the OLM. The engine was designed, built, and tested to run 50 miles with NO coolant in it.
 

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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
Joined
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34 Posts
Discussion Starter #3
Thanks will do. Just had it idling on driveway. Temperature 230 to 255 F. Fans working at about 230. No smoke or water from exhaust, coolant looks ok no oil. Will check spark plugs tomorrow for anything nasty. I changed coolant a while but not used the car for a while until today when it went for its yearly test which would have included a smog test. She passed ok but overheated on way back. No leaks anywhere but I have topped up expansion tank twice, about three quarts!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,854 Posts
The tick marks on your 1999 gauge correspond to these on my 2002 Seville gauge. All these Northstars use the same temp sender.

Temp gauge - my numbers.jpg
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,854 Posts
BEFORE DOING ANYTHING DRASTIC - labor intensive or time consuming -

1) check the PURGE LINE for a constant - gentle - flow of coolant ANYTIME the engine is running -

assuming the purge line is open and flowing coolant -

2) do a BLOCK TEST -
the blue fluid reacts to hydrocarbons - the stronger the concentration -
the more dramatic the color change - lighter blue - clear - green - yellow -
BUT -
ANY color change is a POSITIVE result -
 

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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
Joined
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34 Posts
Discussion Starter #7
Yeah that ^^^^^^^^^^^
BEFORE DOING ANYTHING DRASTIC - labor intensive or time consuming -

1) check the PURGE LINE for a constant - gentle - flow of coolant ANYTIME the engine is running -

assuming the purge line is open and flowing coolant -

2) do a BLOCK TEST -
the blue fluid reacts to hydrocarbons - the stronger the concentration -
the more dramatic the color change - lighter blue - clear - green - yellow -
BUT -
ANY color change is a POSITIVE result -
Checked along the purge line, all clear until the hollow bolt. Removed from block and pushed solder wire thru from wider end. Seems to be rubber type PTFE or something like Permatex. So hopefully that is the cause but will fit new thermostat whilst I am there. Ordered from Rock Auto so should be here an end of next week. Ordered a few other bits as well. And have block test to do when all back together.
Many thanks will update later
585432
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
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69,854 Posts
If you have drained the cooling system it might take a dozen or so start-run-drive cycles to bleed all the air out of the system until the surge tank remains at about half full, cold.

That plug of snot in the purge line nipple would be enough to cause overheats due to air bubbles in the main coolant flow = water pump cavitation and loss of pumping ability.

Check the small reinforcement tube in the surge tank purge line nipple - they clog, too.

Install the 'stat correctly oriented -

Thermostat and cover diagram.gif
 

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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
Joined
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34 Posts
Discussion Starter #9
If you have drained the cooling system it might take a dozen or so start-run-drive cycles to bleed all the air out of the system until the surge tank remains at about half full, cold.

That plug of snot in the purge line nipple would be enough to cause overheats due to air bubbles in the main coolant flow = water pump cavitation and loss of pumping ability.

Check the small reinforcement tube in the surge tank purge line nipple - they clog, too.

Install the 'stat correctly oriented -

View attachment 585434
Many thanks really appreciated
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,854 Posts
If DEX-COOL is too expensive or unavailable you can use any modern green coolant mixed 50/50 with (preferably) distilled water. New green coolant is low- or no- silicate formula, so the old water pump seal wear drawback no longer exists with green coolants. Whatever you use, exchange it every 3 or 4 years, time recommendations notwithstanding.

Note that the 50/50 line is out of sequence. Install a new pressure cap, too.

Coolant Boiling point.jpg
 

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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
Joined
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34 Posts
Discussion Starter #11
If DEX-COOL is too expensive or unavailable you can use any modern green coolant mixed 50/50 with (preferably) distilled water. New green coolant is low- or no- silicate formula, so the old water pump seal wear drawback no longer exists with green coolants. Whatever you use, exchange it every 3 or 4 years, time recommendations notwithstanding.

Note that the 50/50 line is out of sequence. Install a new pressure cap, too.

View attachment 585438
I have Dexcool, delivered yesterday and have the OEM cap ordered from Rock Auto
 

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Premium Member
1999 Sedan Deville 50th Anniversary Edition.
Joined
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34 Posts
Discussion Starter #13
Update. Hollow bolt cleaned out, radiator flushed, purge line clear including purge tank nipple. New thermostat. All now delivered from Rock Auto, fitted and all seems ok. Thanks guys. Will check with block test and change oil.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,854 Posts
Check the cold (ambient) coolant level each day for a week. Half full, cold is correct so you may add a cup or two as the air pockets purge out.
 
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