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Discussion Starter · #1 ·
I ran over something on the interstate. It damaged my radiator. I probably drove about 25 miles (going about 75 mph) after striking the object in the road before I got home. Once home, I noticed a slight amount of steam coming out of the driver's side, front fender well. I gave the engine an hour to cool down. Then I went out to check the car. I could see NO COOLANT in the overfill reservoir. When I added coolant, it quickly ran out. It was obvious that I had damaged the radiator.

I took it to the shop for repairs. They replaced the radiator. They drove it a bit. The mechanic said his test drive did not cause the car to overheat. He told me that he next, did a 'block' test. He described it as putting a device over the overfill container. He said when he looks down into the device, it should appear blue (the color of the antifreeze he installed in the car). Unfortunately, he told me that he saw YELLOW, instead of BLUE. He said it 'failed the block test, but it still did not overheat when he drove it'. Then he shrugged his shoulders and had a kind of 'sucks to be you' face on - (grin).

I putted around town after picking the car up. I drove it in the city around 30 mph, for about 15 minutes. Normally, that type of driving would register 'two bars' on the temperature gauge/display which is behind the steering wheel, on the dashboard. However, to my disappointment, that little bit of driving had the temp gauge exactly at the halfway point (which I think put it at FIVE bars) on the temp display. I'll drive it around tomorrow and monitor the temp gauge and coolant level to see what happens. I will fill the radiator first thing in the morning.

My guess is that it is probably time to be looking for a car to replace this one. My guess is that it is only a matter of a very few drives, and because of the engine block . . . now most likely being ruined due to its overheating, that I have turned my perfectly good DeVille -- into a piece of junk.

Isn't this the most likely scenario -- that the overheating will get worse . . . and make it so that it will no longer run safely (or, at all)? Today, it was already 'missing' (idling a bit rough) a bit when the engine was running. I assume . . . this problem will not magically start to get better over time. It will get worse. Correct? And this will most likely get worse SOONER, than LATER. Correct?

And, that being the case, I was thinking I need to look for a replacement for this Caddy. I killed my Caddy. And it will not get better. And in no more than possibly just 2 or 3 weeks, it will 'give up the ghost' and go to that 'DeVille Heaven in the Sky'. That being the case, I need to find a replacement car ASAP - correct? I'd rather much go 'used car shopping' in the summer, then the winter.

Is my thinking correct on this issue?

Thank you for your time and assistance. I really appreciate it.

Dean
 

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2000 Deville Base, 2019 Corvette GS
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I can offer you some encouragement. The Northstar motor was designed to run on NO COOLANT for 50 miles and up to 65 mph.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Welcome Aboard !!! ALL 2004 Devilles are 4 door Northstar V8 cars. I changed your thread title to be a bit more descriptive of your problem.

If you have the digital dash display with a series of horizontal bars for temperature steps then the engine is supposed to run 24/7/265 at the middle (longer) bar. That's highly damped at the 190 - 210 temp range - normal temp.

YOU rent an exhaust gas tester from a parts store, follow the instructions and do it yourself. You sample the airspace over the coolant in the surge tank. Correct level is half full, ambient cold - look at the FULL COLD legend and flat arrow molded into the top and side of the surge tank. (It's NOT an overflow tank) You may need to correct the fill level two or three times - the system is self-purging and there may still be one or more air pockets in the smaller flow passages. Check for good heater air temp output - the heater core is full flow at all times.

Your bars correspond to the ticks on my STS analog gauge - these cars all use the same coolant temp sender. The correct thermostat is set to begin opening at 188 and fully open at 206. Most Northstars run at that 190 - 200 line all the time.

Temp gauge - my numbers.jpg
 

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I'd bet you still have air in the system after the radiator replacement. Top it off and you'll most likely be just fine. Then find a new mechanic.
 

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Discussion Starter · #6 · (Edited by Moderator)
I can offer you some encouragement. The Northstar motor was designed to run on NO COOLANT for 50 miles and up to 65 mph.
Amazing! I put similar numbers on it today. It runs a little warmer now. IE The temp gauge used to always stay at 2. Today after idling for just four minutes it was at 4 (the halfway point). But, it never went over 4. It is telling me to 'change the oil'. I wonder if that is because it might have some coolant in it? Still idles a tad rough. Misses just a little. Still has power. I hit 85 mph for about 15 seconds before slowing back down.

I imagine a tune-up will help its performance. But, I was figuring on waiting a bit. Its last two repair bills have put me in the poor house. And, I didn't want to get it tuned up . . .just to have it fail the 'next' day due to my overheating issue.

Finally, while in town, at one stoplight, i dropped it into neutral cause it sounded like it was going to die. I was wondering, for in-town driving (stop and go - 30 mph) would it be better to put the tranny in like gear 2 or 3 OR just leave it in D all the time?

Thanks so much!

Dean

I can offer you some encouragement. The Northstar motor was designed to run on NO COOLANT for 50 miles and up to 65 mph.
For some reason, my first reply to this shows up a few posts below.

Welcome Aboard !!! ALL 2004 Devilles are 4 door Northstar V8 cars. I changed your thread title to be a bit more descriptive of your problem.

If you have the digital dash display with a series of horizontal bars for temperature steps then the engine is supposed to run 24/7/265 at the middle (longer) bar. That's highly damped at the 190 - 210 temp range - normal temp.

YOU rent an exhaust gas tester from a parts store, follow the instructions and do it yourself. You sample the airspace over the coolant in the surge tank. Correct level is half full, ambient cold - look at the FULL COLD legend and flat arrow molded into the top and side of the surge tank. (It's NOT an overflow tank) You may need to correct the fill level two or three times - the system is self-purging and there may still be one or more air pockets in the smaller flow passages. Check for good heater air temp output - the heater core is full flow at all times.

Your bars correspond to the ticks on my STS analog gauge - these cars all use the same coolant temp sender. The correct thermostat is set to begin opening at 188 and fully open at 206. Most Northstars run at that 190 - 200 line all the time.

View attachment 598875
WOW! Tons of good stuff! Thank you so much! Can you reply to a question in this thread that I recently typed about what gear to have the tranny in when putting around town. Thanks so much!

Some "mechanics" will always say a Northstar always has failed HG. I went to a shop to get brakes done after rebuilding my 99 and I was told I had blown HG.
Yeah, I heard from a GOOD FRIEND who has a used car lot the same story about Northstar's HG. So, just to be clear, you are saying that the Northstar has no higher of % fails than the average car? Thanks!

I'd bet you still have air in the system after the radiator replacement.

^^^ Good point. I did hear it make some gurgling type of noise after about 7 minutes of city driving, while I was stopped at a traffic light.

^^^ Thank you for the advice. Why find a new mechanic? I appreciated his transparency in telling me it "MIGHT have an HG problem." He didn't 'hardsell' me on the 'fact' that I 'needed a HG." The car was NOT missing at ALL and was idling smooth as can be . . . UNTIL I messed it up by busting the radiator. What would cause it to NOW have the performance issues it is having?

What would be a fair price to RR the radiator and the serpentine (?) or is it called a 'serpent' belt? After a few of ya share prices, I will tell you how much I paid. My buddy with the used car lot said, "OUCH! That is a little high ($$)". I would have had my friend fix it, but he could not get it into his shop for at least 10 days. He reccd this mechanic before. He did a good job for me then. A sensor issue of some sort. I'll try to find the receipt tomorrow.

Thanks!

Top it off and you'll most likely be just fine. Then find a new mechanic.
I just now noticed your thumbnail! My Caddy looks alot like yours! Metallic Red. Chrome wheels. Yours is cleaner and your paint looks much more healthy than mine . . . AND . . . I only got ONE window that works -- the rear side passenger. UGH. But, too much money for me to fix them. Is the window assembly designed poorly OR do I just have BAD window luck?

Welcome Aboard !!! ALL 2004 Devilles are 4 door Northstar V8 cars. I changed your thread title to be a bit more descriptive of your problem.

If you have the digital dash display with a series of horizontal bars for temperature steps then the engine is supposed to run 24/7/265 at the middle (longer) bar. That's highly damped at the 190 - 210 temp range - normal temp.

YOU rent an exhaust gas tester from a parts store, follow the instructions and do it yourself. You sample the airspace over the coolant in the surge tank. Correct level is half full, ambient cold - look at the FULL COLD legend and flat arrow molded into the top and side of the surge tank. (It's NOT an overflow tank) You may need to correct the fill level two or three times - the system is self-purging and there may still be one or more air pockets in the smaller flow passages. Check for good heater air temp output - the heater core is full flow at all times.

Your bars correspond to the ticks on my STS analog gauge - these cars all use the same coolant temp sender. The correct thermostat is set to begin opening at 188 and fully open at 206. Most Northstars run at that 190 - 200 line all the time.

View attachment 598875
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Your poor idle and driving performance - you need to pull any trouble codes from the car's built-in diagnostic system. You need diagnosis and maybe a tune-up. Use the sticky thread "How to pull codes" correct model/year section. Use the embedded link to decipher any found codes and post it all here.




Your transmission gear question. Your powertrain uses the 4T80E 4-speed automatic transmission with TCC (Torque Converter Clutch) to remove the last 300 or so rpm of slip when in 4th gear at low load highway cruise speeds over 42 mph. 3rd gear is the direct drive at 1.00:1, 4th gear is OD at 0.68:1.

Use D in town - and all the time. If your car is a base model or DHS it is speed limited to 112 mph. The speed rating of the original tires on the driver's door sticker.

You can put the shift stick in 1, punch it, and go all the way to speed limiter without touching the stick. The transmission will upshift and downshift at the correct speed/load and WILL NOT damage anything.

The engine is rpm limited to 4,000 in P or N and will upshift at about 6400 rpm under WOT acceleration loads. It will downshift at the correct speed/rpm/load points.

Here's a table of engine/car speeds with TCC engaged. The base and DHS use the VIN Y table. That table is cut off at 115 due to the 112 speed limiter. No, you cannot remove the limiter. No one has hacked the 2000 - 2004 PCM yet.

Final drive speed graph.jpg
 

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Yeah, I heard from a GOOD FRIEND who has a used car lot the same story about Northstar's HG. So, just to be clear, you are saying that the Northstar has no higher of % fails than the average car?
Depends on the year. From '03 on up, yes. Late '90's, not so much.




The temp gauge used to always stay at 2. Today after idling for just four minutes it was at 4 (the halfway point). But, it never went over 4. It is telling me to 'change the oil'. I wonder if that is because it might have some coolant in it?
No. Conventional oil (what your engine was spec'd with) deteriorates at high temperatures. When the ECT sensor senses a high temp, it triggers that message.
 

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Northstars with failing head gaskets due to cylinder block head bolt hole thread damage very seldom mix oil and coolant or vice versa. The various sensors have no way of knowing what's in the cooling system or crankcase.

If the temp gauge never went over bar 4 then the "Change Oil Soon" message is being tripped by the OLM. If he or the shop didn't reset the OLM then it has no way to keep track of actual oil life.

Dean, do you speak "OLM"?

Owner's manual - when all else fails, read the instructions.
 

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Discussion Starter · #10 · (Edited by Moderator)
Northstars with failing head gaskets due to cylinder block head bolt hole thread damage very seldom mix oil and coolant or vice versa. The various sensors have no way of knowing what's in the cooling system or crankcase.

%%%%%%%%%%%% Thank you for sharing your knowledge.


If the temp gauge never went over bar 4 then the "Change Oil Soon" message is being tripped by the OLM.


%%%%%%%%%%%% After the repair, it has never been above bar 4. However, I have only driven it about 50 miles since the repair (if that matters any). BTW, that surge tank is next to impossible to see through. That makes checking the level difficult. Other than shining a powerful flashlight (with the beam narrowed), are there other effective ways to check the coolant level? IE - I remove the cap from the surge tank (only when the engine is cool - 'cool' defined as, 'before I even start the car for the first time that day) and stick my index finger into the surge tank. If my finger can touch the coolant, then the level is fine? And, 'yes', I know - check it while it is parked on level ground.

If he or the shop didn't reset the OLM then it has no way to keep track of actual oil life.

Dean, do you speak "OLM"?


**** I do not know what OLM means. O'Reilly's will 'check the stop engine light for free'. Something to that effect. If his device does not print out the codes -- then I will ask him to slowly speak the codes into my recorder. I was there yesterday afternoon. But, they were understaffed (Covid) and too busy to test it then. I'll try again today.


Owner's manual - when all else fails, read the instructions.


&&&&&&&&&&&& Agreed. I learned some interesting stuff in that book. One being that I wished they would have bound the paper to the spine with a better quality of glue. Pages falling out all over the place. ;-) Thanks again.
 

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Please read the first paragraph and link in Post #7 again. You don't need anyone to pull diagnostic codes for you. DIY in the driveway.

OLM = Oil Life Monitor. You call it up using the DIC control buttons. It is a deadly accurate monitoring system for the engine oil condition and tells you when to change it and the filter. Google "automobile engine oil life monitor" for plenty of homework.

Driver Information Center (instrument panel) controls - Owner's manual again -

DIC controls.jpg



Some owners make a wooden dipstick for the surge tank level checks. Yes, check it only when ambient cold - coolant expands and contracts quite a bit with engine temp changes and is one reason why expanding coolant increases system pressure to about 18 psi - for several reasons: 1. To raise coolant boil point; 2. To increase heat transfer between engine metal and coolant and: 3. To assure "solid" coolant to the water pump. The water pump is a centrifugal - not solid displacement - pump and will not pump bubbles or air. You do NOT need any sort of aftermarket coolant supplements, magic potions, or water wetter agents. Coolant removes heat from the engine metal. The thermostat controls coolant temperature.

2000 - 2005 Deville surge tank, cap removed -

Deville 2000 reservoir tankside.jpg


Yes, if you stick your index finger into the filler neck as far as you can, you should be just able to get a drop of coolant on your fingertip, cold.
 

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Yeah, I heard from a GOOD FRIEND who has a used car lot the same story about Northstar's HG. So, just to be clear, you are saying that the Northstar has no higher of % fails than the average car? Thanks!
No, I meant that incompetent mechanics will always flag a Northstar for blown HG regardless of the actual condition "because they all do that eventually". They don't all do that eventually. It is one of the infamous quirks of the Northstar, but it's not as bad as some of the oil jockeys think.

I can tell the HG diagnosis was bogus with a high probability because

he saw YELLOW, instead of BLUE
The newly replaced and refilled radiator and surge tank with fresh coolant in it will most likely not show any exhaust gas present and it will not produce reliable block test results. Unless it has gotten to the point that the pressure leak is so bad you cannot drive the car because it is constantly overpressurizing and overheating. The rest of your post confirms that it does not have drivability problems.
 

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The best time to perform a cylinder block exhaust gas test is immediately after an unexplained overheat - BUT that usually occurs out in the boonies at O-dark-hundred.

If you want to see a truly positive exhaust gas test example, sample the tailpipe exhaust gas.
 
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