: Northstar 4.0L seems a little hot. Removed Thermostat. Bad Idea?



ERICMF
08-18-03, 11:25 PM
I have a 4.0L northstar in the olds aurora. I had the water pump replaced recently and the car still seems to be somewhat hot. The owners manual calls for 180 Thermostat. The car gets up to 200 in about 5-10 minutes of driving and then will stabilize if there is wind on the radiator. On the highway it gives me no problems. But in slow traffic it heats up to about 220-230. Once it got to about 235, which was too much for me. The redzone seems to start at 240 and goto 280. I know these gauges aren't always accurate but it seems to follow the following notches.

280
_Red
_Red
240
_
200
_
_
100

Anyway I've avoided idling for quite a bit and am now trying to find the problem. If there is one. The car has never overheated. I removed the thermostat last night and it seemed to help alot. The car gets to about 180 and stabilizes. If you drive it awhile then let it idle for about 5 minutes it will reach about 200-210. If you start driving again it will fall to just under 200 and then only gets hot again when you idle it. I pulled it into the garage tonight nad let it idle about another 10-15 minutes. It climbed to about 220-225 and wouldn't go much farther. However, the temp was bugging me and I couldn't let it get much closer. Is it a bad idea to run w/o a thermostat? I've always heard theyre only needed in the winter. I planned to put it back in when the outside temp isnt working against me. I've heard it can ruin fuel economy. I've been watching my avg mph on the vic and it hasn't changed. Car seems to be running well. It gets up to 180 in about 5-10 minutes of running. That seems average to me. Is there anything else dangerous about running w/o a thermostat? I've heard the coolant can be moving "too fast". If this is the case would re installing just the housing to the thermostat slow it down?? Do thermostats stick? I boiled this one and it opened...Not sure about what temp it opened at though.

Any help would be GREATLY appreciated.

elwesso
08-19-03, 12:10 AM
Hello, and welcome aboard :wave:

Personally, I wouldnt run without a Tstat...... Obviously there is something amiss...... The radiator could be getting a little old (and clogged up with all kinds of crap)..... I heard you can get it "cored", by taking it to a radiator shop, and they clean it out really good, so it performs to about new..... Maybe 200 to get that done, which is much less than a new radiator...... Also, are the fans working good..... When was the last time the AF was flushed good??

Tstats do get stuck from time to time, and even if it does open will probably not have the maximum amount of lift needed..... I just replaced the origional Tstat on my car from 1994, and needless to say it didnt look "bad", but I could tell a HUGE difference on how much cooler it runs.......

You CAN run without a Tstat if you have to.... Since you already took out the old one, might as well replace the it (maybe a 10-15 part)......

ERICMF
08-19-03, 12:30 AM
Hey thanks for your reply. Both fans work and I've checked the air dam for the radiator. Nothing blocking and no cracks. Other then that I'm confused. The thermostat out seems to be solving the problem but I've heard a variety of opinions on how the faster flow rate won't allow coolant to stay in the radiator long enough.

Also on how lower pressure coolant (w/o a thermostat) seems to have a lower boiling point. How it ruins gas milage.. And so on. Well so far my gas milage has stayed the same. The car has a VIC Display that takes averages. I've only driven maybe 30 miles since the removal. The car seems to be running good. Not rich or lean..At first the quick rise in temp on a idle bugged me. But it now stabalizes at 225 when idling 10-15 minutes. The system still seems to have a good amount of pressure in it. I'm stumped... Since the thermostat only costs $13.88. I thought about atleast giving it a shot. The only thing that sucks is whenever I open up the system the vacumm in it dumps about a gallon on the ground. No big deal though I guess. Once the car hits operating temp all the rumors/oppinions don't seem to bother me. Except for the one about lower pressure in the system caused by no thermostat. Honestly I think there are just too many opinions to digest!! However, yours is appreciated too.

By the way the system hasn't been flushed but it has been practically drained when the water pump was changed. This was about 500 miles ago.

ERICMF
08-19-03, 12:33 AM
Oh by the way. When I boiled the thermostat it seemed to open about 3/16th of an inch. or just shy of 1/4. Maybe 4 or 5CM. Any clue on how wide theyre supposed to open?

elwesso
08-19-03, 03:11 PM
If there is no pressure, the boiling point will be LOWER, meaing if it did overheat, it will boil over easier.....

If you go really fast, I suppose without a Tstat it could be possible to cavitate the water pump (not good)...... I guess you could start the engine, let it run for a minute, and then fill it back up......

And browsing through my FSM, I see that my Tstat (a 170*) opens 10mm/90*C (.39in/194*F).... That is something to go by, i would assume they would be similar.......

The only reason people might say it ruins gas mileage is because it causes the engine to run too cold, resulting in it staying in warm up mode (rich)......

Put in that new Tstat, and if thats not what was causing it, then you might be looking at getting (or core-ing the old one) a new radiator......

Katshot
08-19-03, 03:48 PM
First of all, the temps you were running WITH the T'stat were fairly average. But, I can understand that you might want it to run cooler and apparently you've accomplished that via the T'stat removal. While it's true that coolant moving TOO fast because of removing the T'stat can actually CAUSE an overheat, in your case it seems to be OK. Don't worry about the pressure vs. T'stat presence, the T'stat just maintains a warm temp if it NEEDS to. in warm weather, it's open fully for most of the typical engine operational cycle. The pressure of the coolant is limited and will EVENTUALLY get to it's uppermost limit (approx 14psi) as the coolant temp increases. The increased pressure is actually what keeps the coolant from boiling that's why a sudden cooling system rupture can have such violent effects. The coolant is of course under pressure and trying to get out of the hole caused by the rupture but it's also INSTANTLY BOILING too and considering that water and steam have a 1:16 ratio, you can see why a boil-over looks so explosive.
Back to your car though. I would consider having the cooling system inspected (mainly the radiator), and make sure you're not getting any recirculating hot air around the radiator. There's supposed to be rubber insulators that connect between the radiator support and body panels to prevent this from happening and it's quite common to have some or all missing or damaged.
One more thing. The T'stat temp rating is when it starts to open, not when it's fully open. This why few cooling systems operate exactly at temp stamped on the T'stat. It's usually a good 15-20 degrees hotter.

2dfx
08-20-03, 02:08 AM
...on a side note the Aurora never came with the northstar. Thats a CADILLAC engine. He's referring to that 4L V8 that came as an option to the V6 on the auroras. Oh well, cosmetic note anyway

fristim
08-20-03, 07:08 AM
...on a side note the Aurora never came with the northstar. Thats a CADILLAC engine. He's referring to that 4L V8 that came as an option to the V6 on the auroras. Oh well, cosmetic note anyway


Same design different displacement!!!! If I'm not mistaken its actually called a shortstar!

Katshot
08-20-03, 08:32 AM
Same design different displacement!!!! If I'm not mistaken its actually called a shortstar!

Right you are!
The Northstar was ORIGINALLY an Oldsmobile design. There are two displacements, 4.0 and 4.6 liter. Cadillac got the larger one.

ERICMF
08-20-03, 12:49 PM
Right you are!
The Northstar was ORIGINALLY an Oldsmobile design. There are two displacements, 4.0 and 4.6 liter. Cadillac got the larger one.


Not entirely sure myself but my manual sales Northstar and its still 32-Valve. Infact we used the same OE thermostats. Same Transmissions as well.

Katshot
08-20-03, 02:39 PM
It's BASICALLY the same motor, just 4.0 instead of 4.6 liter. I could look in the book and tell you ALL the differences but who really cares?

elwesso
08-20-03, 11:34 PM
Its the MINIME to the cadillac northstar!

2dfx
08-21-03, 12:57 AM
Its the MINIME to the cadillac northstar!
Ya learn something new everyday!

I WANT A F*CKING AURORA!

elwesso
08-21-03, 05:55 PM
Why would you want the Aurora when you have 4.9l of Pimpin...... 4.6 just doesnt cut it........ :D

ERICMF
08-21-03, 07:42 PM
Alright guys here is the latest. I went to the autoparts store and got my new thermostat. This one seems alot more heavy duty then the last. It is a 180 Degree 54MM Stant. I tested my old thermostat and it didn't open till about 200 Degrees. It opened about 7MM. I am thinking that this old thermostat was sticking or not opening completely. Does 7MM seem normal? Actually that was the largest it opened. It took almost 20 minutes at 200 Degrees to get it that far. So what do you guys think? Is it a bad one? Either way I'm going to install the new one soon. I am debating if I am going to flush the system first. Am I correct in assuming that by flushing the system I will be able to idenity any clogs in the radiator?? Any advice on the flush? would you just cut the heater core or drop a hose of the radiator?

See the link to see what I'm talking about on the tstats. I am not sure if it means that it opens 54MM but the new one appears to be much more heavy duty and with almost twice the opening....

http://www.digiclipse.com/images/tstat.jpg

I appreciate your responses.

2dfx
08-21-03, 07:55 PM
Why would you want the Aurora when you have 4.9l of Pimpin...... 4.6 just doesnt cut it........ :D
Duh, you wouldn't think I'd drop in the ol pushrod? :D

elwesso
08-22-03, 12:24 AM
Flushing the system...... I assume you are planning on installing one of the backflush kits...... Thats fine (I guess, I wouldnt use one, the idea of cutting hoses makes me cringe)..... I highly doubt that there will be clogs, seeing that it would be WAY up in the temp guage if there was.......

ERICMF
08-22-03, 12:38 AM
Flushing the system...... I assume you are planning on installing one of the backflush kits...... Thats fine (I guess, I wouldnt use one, the idea of cutting hoses makes me cringe)..... I highly doubt that there will be clogs, seeing that it would be WAY up in the temp guage if there was.......

Hm., its the only way i know how. I dont want to really though. Do you know a better way? I always heard you can drop the outlet hose on the radiator and flush it there.. Never learned how... Good point, I guess I meant more of a detecting "congestion".

Anyways thanks for the advice, very appreciated.

elwesso
08-22-03, 11:51 PM
I dont know if the radiator has a drain cock on it or not, but mine does.... heres how I did mine (along with a Tstat change)

First, I went out and got all the stuff...... AF, DISTILLED WATER (very important, its only like 50c gallon, get about 5 gallons), and cleaner stuff...... I got a radiator cleaner that you put in and then drive the car for like 3 hours..... I got Zerex cleaner, and I think it worked good.......

Anyway, I drained the radiator twice (by draining, and filling with distilled water) and then added the stuff, and topped it off with water...... A few days later (after driving it in the city), I took a 2hr road trip with the heater core wide open half the way (its hot, but youll be glad in the winter)..... When i got there, I kept repeating the drain/refill procedure (Drain, and refill with water) until clear water came out.... Then i drained once more, and then filled with appropriate mix of AF.......

After I refilled, I ran the car (with the Tstat OUT) for 2 mins with the heater core OPEN.... Then I repeated..... You should be able to pour the AF from the car down the drain, as long as your hooked up to a sewer system.....

Note- If you dont have a drain cock easily accessible, you can undo the lower radiator hose, but be prepared for the flood gates to open...... AF is VERY toxic, so if you spill any (you will, trust me), make sure you spray it down good...... Even a few licks of the stuff could kill a pet......

Also, I know with the northstar you are supposed to get the coolant supplement nuggets..... Available at any cadillac dealer.... When your done (before the final fill), put the nuggets in the lower radiator hose (crumble them up a little).... make sure you put the Tstat in before the final fill.......

When you get the Tstat in, run the car for a few minutes, and top it off (you'll be low)..... Drive it, and check every time for the next few times you drive it, and you should be golden!!!

This is for an undermaintained cooling system, and after this, a once a year radiator flush (Drain and refill with AF) is adequate.... it will renew with fresh water and corrosion inhibitors......

ERICMF
08-24-03, 02:18 AM
Well guys here are the intial results. I finally got around to reinstalling a Thermostat approximately 1 week later. I installed the STANT in question above very easily, buttoned everything back up and started the car. The car came to spec temp in about half the time it did with no thermostat (4-5 minutes of idling). Once it reached 200 degrees I checked around the thermostat housing for leaks. Still bone dry. I then began a bit of an edurance test. Idling the car to 3500 RPM approximately 5 times then watching its result. The temp very slowly rose to 210 in approximately 15 minutes. I let it sit there till about 20 minutes when it finally hit 220. The fans kicked on and put it right where it needed to be 215ish where I let it sit till about 25 minutes. The fans were holding the temp rather well so I decided to endurance test it again. This rose the temp back up to 225 but once the fans reengaged it brought it right back to 215(fans are on at 220 btw). This time I was reaching 30 minutes so I took it all the way and flipped the air on and ran it for about 5 minutes while doing yet another 4-5 3500 RPM gradual climbs. The car reached a reccord 225-230 and then held itsself firmly. I shut off the air and let it run for about another 5 minutes. In this time it dropped back down to slightly below 220 for a total of 40 minutes of idling with intermittant RPM and air conditioning running w/o any forced air into the radiator.

I think the new thermo might have done the trick however I wont count my chickens yet. It is only about 70 degrees out tonight and I did start testing the car from a remotely cool state. I am sure that repeated driving, running the air and temps in the 80-90s tommorow will make their own impact. However, the car also wont be running for 40 minutes stationary. So hopefully these two situations will trade off.

Anyway what do you think? 40 minutes at idle and 225ish was the max temp?? Sound like a northstar or a hot northstar??

Any comments appeciated.

PS: didn't get to flush it this week. not enough time. next weekends project.

fristim
08-24-03, 07:16 AM
Ya learn something new everyday!

I WANT A F*CKING AURORA!




Uh Ohh, that would mean you'd own a NORTH*

elwesso
08-24-03, 10:23 AM
Sounds good!!

03CADDY
08-25-03, 12:27 AM
I had this problem on my 93 STS after I hit about 180K miles. I didn't bother fixing it myseld - but I did spend over a grand on a new radiator etc. After a few months the radiator blew. After it was replaced again - could not keep the car from over heating (ie the mechanics could not do it). I finally just traded the old girl in.

On a completely unrelated topic- The car was raced often... It could turn a 1/4 mile in about 15.5 secs with 175K miles on it!! I think maybe it was trying to tell me something...

kcnewell
08-27-03, 01:24 AM
225 is not unusual for these engines...Don't worry about it.

dpower
08-30-03, 06:29 PM
This is a little late because you have already changed your thermostat. Next time ask for a failsafe thermostat, they usually have to order them but if the thermostat dies it fails open rather than closed. Overheating seems to kill just about any motor and the northstars seem to be very sensitive to it, itís worth the extra ten dollars for the insurance.

David