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1999 Seville STS Northstar 32 Valve V8
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78 Posts
Discussion Starter #1
Still having problems with the 99 Caddy Seville STS N* 4.6 V8...

Changed all the coil packs, spark plugs and wires. ALL NEW PARTS!!!

ENGINE LIGHT STAYS LIT, AND THEN BLINKS FOR A LITTLE BUT, THEN STOPS AGAIN (REPEATS SEVERAL TIMES WHEN DRIVING)

Had a faulty Oxygen Sensor changed that too like 3 months ago.

Only when at idle it shakes like crazy, when pressing gas seems to stutter then its smooth.
Again once reaching idle shaking like crazy.

Codes I pulled earlier today:

B1341 Air Mix Door Two Movement Fault CURRENT
B1343 Air Inlet Door Movement Fault CURRENT
P0300 Engine Misfire Detected CURRENT
P0155 HO2S Heater Performance Bank 2 Sensor 1 CURRENT


Now onto the next issue coolant loss.. Every week or so I have to refill with coolant, don't know where its going. (burning it maybe, causing the rough idle, perhaps??)

No leaks on ground had waterpump, waterpump belt, and the cross-over fixed like 6 months ago.

Always get the "check coolant level" every week or so. I look and its empty.

The gauge moves past the 12 o'clock mark to the 1 o'clock position, then slowly moves back to 12 o'clock.

ANY SUGGESTIONS

Thank you.

:worship:
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,261 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Still having problems with the 99 Caddy Seville STS N* 4.6 V8...

Changed all the coil packs, spark plugs and wires. ALL NEW PARTS!!!

ENGINE LIGHT STAYS LIT, AND THEN BLINKS FOR A LITTLE BUT, THEN STOPS AGAIN (REPEATS SEVERAL TIMES WHEN DRIVING)

Had a faulty Oxygen Sensor changed that too like 3 months ago.

Only when at idle it shakes like crazy, when pressing gas seems to stutter then its smooth.
Again once reaching idle shaking like crazy.

Codes I pulled earlier today:

B1341 Air Mix Door Two Movement Fault CURRENT
B1343 Air Inlet Door Movement Fault CURRENT
P0300 Engine Misfire Detected CURRENT
P0155 HO2S Heater Performance Bank 2 Sensor 1 CURRENT


Now onto the next issue coolant loss.. Every week or so I have to refill with coolant, don't know where its going. (burning it maybe, causing the rough idle, perhaps??)

No leaks on ground had waterpump, waterpump belt, and the cross-over fixed like 6 months ago.

Always get the "check coolant level" every week or so. I look and its empty.

The gauge moves past the 12 o'clock mark to the 1 o'clock position, then slowly moves back to 12 o'clock.

ANY SUGGESTIONS

Thank you.

:worship:
============================
P0300 is a generic misfire code -
our on-board code readers will not display WHICH cylinder/cylinders is/are misfiring -
only that there IS a misfire -

take the car to any large auto parts store - they will check your codes for free -

P0301 is a misfire in cylinder #1 - P0302 is cylinder #2 - P0303 is #3 - etc -

once you discover WHICH cylinder is misfiring - diagnosis becomes much easier -

-----------------------------------------

looks like you need a new Bank 2 Sensor 1 - O2 sensor -

------------------------

Now onto the next issue coolant loss
cross your fingers -

with the engine COLD -
connect a pressure tester - and pump it up to 20-PSI -

it should hold that pressure forever -

if the pressure leaks down -
start searching for a leak -
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Before you replace any parts or attempt to fix the idle, figure out where that coolant is going. Considering it is a '99, the HG is highly suspect. Are you overheating at all?
 

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1999 Seville STS Northstar 32 Valve V8
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78 Posts
Discussion Starter #5
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Unless you're talking about the needle moving past the 12 o'clock mark, then no overheating issues.

The gauge moves past the 12 o'clock mark to the 1 o'clock position, then slowly moves back to 12 o'clock.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,440 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Under different driving conditions with different A/C compressor settings it is perfectly normal for the temp gauge needle to move. What condition causes the needle to move toward the next (12:45) position ?

If the car is sitting still, idling with no A/C compressor function set, fans go to SLOW at 224 degrees, the engine cools to 213 degrees, the cycle repeats. With some A/c function set, fans run in SLOW all the time, so the temp gauge should stay pretty much near 12 o'clock except in August traffic jams in Death Valley.

The older gauges with less sweep - the temp tick marks represent the same temperatures ...............

Honest question: Have you studied the sticky posts in Engines; Northstar concerning cooling systems, fan operation, gauge operation ???
 

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White Diamond '03 DHS (with DTS floor shift)
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Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

The gauge moves past the 12 o'clock mark to the 1 o'clock position, then slowly moves back to 12 o'clock.
Don't like the sound of that. Normally the gauge never moves off of 12:00. 1:00 is getting well above normal operating temperatures.
This sounds a bit like air (exhaust gases) in the system. The air bubble reaches the WP and the gauge starts to rise. Coolant finally drains into the WP, starts to flow again and the temp comes down. If that's the case, it WILL get worse.
 
C

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Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

AS FAR as the coolant, mine was leaking out from the water pump, changed the pump. then changed the coolant reservoir itself; plastic, they get old and crack. then changed the clamp from the bottom hose of the coolant reservoir. this fixed the problem. I changed all of the clamps that I could easily reach. the original clamps loosen over time.
 

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'01 Cadillac Seville STS 146k Miles / '15 Hyundai I20
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151 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

AS FAR as the coolant, mine was leaking out from the water pump, changed the pump. then changed the coolant reservoir itself; plastic, they get old and crack. then changed the clamp from the bottom hose of the coolant reservoir. this fixed the problem. I changed all of the clamps that I could easily reach. the original clamps loosen over time.
Yes exactly that, when I was starting to have overheating issues I first replaced the resevoir only to find out it was leaking cause the clamp wasn't clamping the hose tight enough... Had no more exessive needle movement since...
 

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1999 Seville STS Northstar 32 Valve V8
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78 Posts
Discussion Starter #10
Sub, in answer to your question. I always have the A/C on set to 60-65 degrees.

After driving for about 20-30 minutes I see the gauge moving off the 12 o'clock position. Slowly moving to the 1 o'clock.
(when idle) it stays there and then when accelerating goes back to 12. o'clock.

I haven't tried with the A/C off to see what it would do. Should I try that, and see what happens??
 

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1999 Seville STS Northstar 32 Valve V8
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78 Posts
Discussion Starter #12
So I think it's official... Head gaskets are bad!! Yesterday while driving the temperature gauge went to the 2 o'clock position (245 degrees) stayed for a little bit then came back up to the half mark 12 o'clock position.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,440 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

If you have not done the cylinder block exhaust gas test it's nowhere near "official".

http://www.sjdiscounttools.com/lis75500.html

Or rent the tester and buy the fluid from any large parts store.

............ and check the purge line - do you have a coolant heated throttlebody ??? If so, that's a prime suspect. Bypass the whole mess with one piece of proper sized reinforced rubber fuel line from any parts store - straight shot from the hollow bolt to the surge tank nipple. As suggested, check the hollow bolt/nipple for free flow. Rod it out.
 

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1999 Seville STS Northstar 32 Valve V8
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78 Posts
Discussion Starter #14
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Sorry it took so long, finally figured out my problem.. Hopefully :want:

Update on my car:

The leaking "mystery puddle" underneath the car..was the plastic coolant reservoir. Had a crack under the bottom hose connection. Replaced a week ago

So far no overheating issues, but the head-gaskets are blown, had mechanic do an oil change, and he found it (antifreeze in oil). White smoke pouring out of both tailpipes.

Stops smoking after a few mins of driving. Car is now sitting at home covered. Don't want to drive it, might cease the motor.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

White "smoke" is not good, but coolant in the oil is rare on a Northstar.
 

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1999 Seville STS Northstar 32 Valve V8
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Discussion Starter #16
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Ranger,

Mechanic did a pressure test to find the leak, and then replaced the coolant reservoir. No more leak

Then he did another test with some blue liquid, started pumping it with a little rubber black ball type thing, into the coolant tank; and the liquid changed color
(yellow I think or maybe it was green).

Then he came with the result that the head-gaskets were bad.
Mechanic said its not worth the fix, since the engine is sealed and you'll never get it back together correctly.(sealed engine?? what??)

His honest opinion was either drive it till it burns out... or trade it for something else. I might just get rid of it, wont get much but oh well. Time for a newer car.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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That was a block test that he performed. It a detects the presence of hydrocarbons in the cooling system (a sign of HG failure).

As for a "sealed engine", he's either an idiot or just doesn't want to work on it.. The head bolt hole threads in the block have failed. The permanent fix is to insert or stud the block and replace the head gaskets. $2,000+ depending on where you go. Weather or not its worth it is up to you, but the issue is 100% repairable.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,261 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

Ranger,

Mechanic did a pressure test to find the leak, and then replaced the coolant reservoir. No more leak

Then he did another test with some blue liquid, started pumping it with a little rubber black ball type thing, into the coolant tank; and the liquid changed color
(yellow I think or maybe it was green).

Then he came with the result that the head-gaskets were bad.
Mechanic said its not worth the fix, since the engine is sealed and you'll never get it back together correctly.(sealed engine?? what??)

His honest opinion was either drive it till it burns out... or trade it for something else. I might just get rid of it, wont get much but oh well. Time for a newer car.
==========================
Mechanic said its not worth the fix, since the engine is sealed
and you'll never get it back together correctly.
(sealed engine?? what??)

you spelled MECHANIC wrong -
in this case the correct spelling is IDIOT -

----------

That was a block test that he performed. It a detects the presence of hydro second in the cooking system (a sign of HG failure).

As for a "sealed engine", he's either an idiot or just doesn't want to work on it.. The head bolt hole threads in the block have failed. The permanent fix is to insert or stud the block and replace the head gaskets. $2,000+ depending on where you go. Weather or not its worth it is up to you, but the issue is 100% repairable.
=======================
It a detects the presence of hydro second in the cooking system
WHAT? :bonkers:
really? :hmm:
:alchi:
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Re: Did a complete tune-up and still rough idle/ losing coolant... :-(

As for a "sealed engine", he's either an idiot or just doesn't want to work on it.
:yeah:

----------

Mechanic said its not worth the fix,
If he had stopped right there, he'd be technically correct considering it's age and the cost of the repair, but continuing on to say "the engine is sealed and you'll never get it back together correctly", does great damage to his credibility.
 
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