: Northstar indicates overheat



Crouter
06-27-04, 02:23 PM
I have a '96 SLS with 74K. New radiator, temp. sensor, surge tank cap, thermostat, proper coolant mix, etc. It still goes into overheat protect mode, sometimes. It appears to happen at 90 degrees F. or above outside air temp after a moderate uphill run. Latest incident the a/c shut down, all warnings came up including "change oil," it went to protect mode (4 cylinders only). Shut it down and checked cooling system. No overflow or boiling from the surge tank, used a temp guage on all the hoses and nothing over 208 degrees. Mechanic now thinks it may be a problem in the computer that is giving a false reading and causing the overheat and initiation of the protection mode. The heat guage in the dash does go to full hot.

Ranger
06-27-04, 09:42 PM
Have you checked the waterpump drive belt tensioner to be sure it is not rusted and hung up and not providing the proper belt tension, thus a slipping belt and a pump that is not moving coolant as it should? If you are absolutely sure it is not overheating I would have a look at the coolant tempurature sensor.

CAJUN-Z
06-27-04, 11:01 PM
I just purchased a '96 Deville that did exactly the same thing (display-wise) and when I stopped, the coolant was extremely low. I just checked it yesterday and took about a 50 mile trip in the vehicle, and the display had the same overheating message and change oil, A/C shut down and went into "limp" mode. Do these engines protect themselves via PCM from a "melt-down"?...

Anthony Cipriano
06-27-04, 11:49 PM
I just purchased a '96 Deville that did exactly the same thing (display-wise) and when I stopped, the coolant was extremely low. I just checked it yesterday and took about a 50 mile trip in the vehicle, and the display had the same overheating message and change oil, A/C shut down and went into "limp" mode. Do these engines protect themselves via PCM from a "melt-down"?...

Yes.

Anthony Cipriano
06-27-04, 11:52 PM
I have a '96 SLS with 74K. New radiator, temp. sensor, surge tank cap, thermostat, proper coolant mix, etc. It still goes into overheat protect mode, sometimes. It appears to happen at 90 degrees F. or above outside air temp after a moderate uphill run. Latest incident the a/c shut down, all warnings came up including "change oil," it went to protect mode (4 cylinders only). Shut it down and checked cooling system. No overflow or boiling from the surge tank, used a temp guage on all the hoses and nothing over 208 degrees. Mechanic now thinks it may be a problem in the computer that is giving a false reading and causing the overheat and initiation of the protection mode. The heat guage in the dash does go to full hot.
Either the coolant isn't circulating or the temperature sensor is bottoming into the hole and the center of the sensor is touching the exhaust port wall casting inside the head. I'd carefully check the water pump drive belt and tensioner to make positively sure the belt is good and that the tensioner isn't frozen. Exercise the tensioner and lube the pivot point to make sure that the tensioner is tensioning the water pump drive adequately. Replace the water pump drive belt, too.

The water pump is driven off the left bank intake cam at the rear of the engine - not at the front off the main accessory drive. There's a small, separate belt just for the water pump at the rear of the engine.

If the water pump drive is okay, then remove the coolant temperature sensor from the cylinder head and double check that it's not being screwed in so far that the tip is touching the exhaust port wall beyond it. Not common but it has happens when a mechanic gets gruesome tightening the coolant temperature sensor into the head.

CAJUN-Z
06-28-04, 09:39 PM
Bad news...the mechanic just finished the diagnosis...blown head gasket(s)...
The book says 12.6 hours for both to be replaced. Then there's the gaskets, new water pump and all the trimmings...total is around $1500 smackers! Ouch!...What a day....

zonie77
06-29-04, 12:34 AM
If the headgaskets are leaking the threads in the block may be stripped. make sure the block is timeserted before reassembly. The kit (new) is a little over $300. You may be able to find a used kit and buy more inserts.

http://www.timesert.com/

Anthony Cipriano
06-29-04, 11:01 AM
What test did the mechanic run to confirm blown head gaskets? If they didn't pressurize each cylinder with compressed air to confirm the leakage then I wouldn't necessarily say it's head gaskets.

Did you also check the vapor vent line from the engine to the surge tank for proper flow? If the vapor vent line gets restricted due a small piece of debris then it can also cause the water pump to lock up on vapor and stop pumping. With the engine cold, remove the 3/8 hose from the pressurized surge tank and start the engine. You should see a solid stream of coolant peeing from the 3/8 hose. If not, the vent line isn't venting and the restriction needs to be found and repaired.

If the hoses measure cold like you indicate when the overheat occurs it doesn't necessarily sound like head gaskets. It might be - but something is stopping the flow of coolant, too, because if the engine is getting hot enough to engage limp home mode and turn on the hot lights then the whole system should be hot and the surge tank should be boiling and empty. It's hard to understand how head gaskets cause it to overheat so severely with no coolant loss and no evidence of boiling coolant in the surge tank and the rest of the system.

Crouter
06-29-04, 12:54 PM
It now appears that coolant is being lost, down two gallons in last incident which probably explains the hoses not hot, no coolant. We cannot determine where it is going. No steam from the exhaust, no external fuids showing on the block and no mis-fire.

If it is a head gasket, what should I expect to pay for repair?

RLLOVETT
06-30-04, 01:07 AM
I've been quoted "1400"...lol...one of the resources I've looked at puts the labor at 19 hours, so do the math for your area...I'm prayerfully budgeting 1500 to 2500, but I dropped the car off on Fri and it was still where I parked it late on Mon...there are a couple of engines on Ebay which brings me to my question: will the 93 N* fit my 94? Thanks!

Anthony Cipriano
06-30-04, 11:38 AM
I've been quoted "1400"...lol...one of the resources I've looked at puts the labor at 19 hours, so do the math for your area...I'm prayerfully budgeting 1500 to 2500, but I dropped the car off on Fri and it was still where I parked it late on Mon...there are a couple of engines on Ebay which brings me to my question: will the 93 N* fit my 94? Thanks!


A 93 into a 94? Yes.

Rhuiefn
06-30-04, 11:43 AM
I am still yet to get the cylindar pressure test done on mine but the Cadillac dealer here said ballpark figure of $3000 for the headgasket. I could probably get a new engine for that much... Its just insane. When I told them what it was doing (see thread 1996 Eldorado ETC Overheating for the details) they said "yeah... you are looking at a head gasket replacement." I know this has been discussed a lot on this board and I am still new but it seems like this is fairly common. I do understand that people usually come to this board to discuss problems but there just seems that too many people have this. A engine that has been well maintained and has 100k miles on it should not be blowing a head gasket. I would like to get another Cadillac in the future, I just don't know if I want to spend $3000 every 100k to replace the headgaskets. Do the dealers just like to say "headgasket" so they can make money?

RLLOVETT
06-30-04, 04:14 PM
I called my 2 local dealers to price the head gasket repair and they BOTH told me there were "too many miles" on the car (125k) and they basically weren't interested...good luck finding somebody willing to do the work! I finally found a place big enough to take it on and had done a couple and now they're in staff shortage mode due to an injury and I'm without my car at least another week (and the $200 replecement rental) but I' sticking with my mantra: it's cheaper than a new one, cheaper than a new one...

CAJUN-Z
07-02-04, 05:28 AM
Here's a site (http://www.arrowheadradiator.com/overheating_causes_and_cures.htm) that has a bit of info. on car-related problems...

RLLOVETT
07-02-04, 01:54 PM
And here's a link to a 93 N* engine for sale in Maine, FYI:http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7908062900

Crouter
07-02-04, 01:59 PM
After pressure test on each cylinder, #3 has a problem. Mechanic also noticed ocassional puffs of blue smoke from exhaust while running. He does not want to do a "head job" because of unknown "liability." I think he means he is afraid to warranty the work because of unknown possibilities. He suggest replacing engine.

Do I want a "long block" & where do I get one & how much should it cost? How many hours to replace the engine?

Anthony Cipriano
07-03-04, 12:31 AM
Find another mechanic.http://cadillacforums.com/forums/images/smilies/ill.gif

94CaddyConcours
07-16-04, 08:55 PM
When my engine overheat and it goes to the home sump(protective mode) where only 4 cylinders work. Will my engine still run in the same mode after it cool down or I have to punch in a code to overide it.

Ranger
07-16-04, 09:51 PM
When it cools down it will return to normal.

pos2nat
07-17-04, 11:19 PM
[QUOTE=Rhuiefn]I am still yet to get the cylindar pressure test done on mine but the Cadillac dealer here said ballpark figure of $3000 for the headgasket. I could probably get a new engine for that much... Its just insane. When I told them what it was doing (see thread 1996 Eldorado ETC Overheating for the details) they said "yeah... you are looking at a head gasket replacement." I know this has been discussed a lot on this board and I am still new but it seems like this is fairly common. I do understand that people usually come to this board to discuss problems but there just seems that too many people have this. A engine that has been well maintained and has 100k miles on it should not be blowing a head gasket. I would like to get another Cadillac in the future, I just don't know if I want to spend $3000 every 100k to replace the headgaskets. Do the dealers just like to say "headgasket" so they can make money?[/QUOTE

When I bought my 93 last year with 120K on the clock, the temps were running 228 to 239 in 90 degrees weather, I spoke to a cadillac dealership mechanic, who regularly worked on Northstars and he immdiately said head gasket, and replace engine. I listened to Anthony Cipriano and replaced my tstat, now 30000 miles and many WOTs later I see temps from 217 to 234 in 90 degrees weather. Too many people jump to the head gasket failure solution, have someone else do the required pressure test to diagnose head gasket failure.

I_Need_a_Northstar
10-21-04, 01:40 PM
I just purchased a '96 Deville that did exactly the same thing (display-wise) and when I stopped, the coolant was extremely low. I just checked it yesterday and took about a 50 mile trip in the vehicle, and the display had the same overheating message and change oil, A/C shut down and went into "limp" mode. Do these engines protect themselves via PCM from a "melt-down"?...


Our 97 caddy did that too then we took it to the shop and the mechanic says its a blown head gasket. That is a total engine replacement.

outlaw1369
10-21-04, 04:07 PM
Local mechanic quoted 1300-1600 for the head job with timeserts. I used the stopleak pellets (6) and have not had any colling issues yet. Funny how 6 pellets (5$) made from some sort of vegtable can fix a car.

No More Cadillac's
10-23-04, 09:35 AM
If Cadillac will repair the engine make sure you ask about the warranty. These repairs if not done properly are known to come undone. Read the thread No More Cadillac's.
I found after some research and the advice of my mechanic as well as a Cadillac head service technician the best solution is to find a used engine.
A used engine that does NOT have a blown head gasket and or a oil consumption problem may be hard to find.
I was not able to find a reliable and reasonable rebuilt engine although there is a shop in Canada that I was referred to.
I just got my car back with a used engine and it works fine Cost was $4300 with tax in New York

Dooman
10-25-04, 09:48 AM
New head gaskets, water pump, all brakes and rotors, new GM starter, all hoses and seals ran me $3900 in Mass. Total engine-out and a full week of time...My 99 STS had 125k miles..