99 deville also overheating driving me nuts!!!!

[rev]

hi all, i am new to this board, but i have been lurking and reading for a couple of days now and am impressed with all the great info and knowledge that i have come across on this board.

i have a problem that is driving me crazy, and have tried most of the fixes that i came across on this board to no avail. i bought a used (104,000 mi) sedan deville, w/4.6 L Northstar about 4 months ago and like the car a lot. i've been using it daily back and forth to work (about 6 miles each way) with no problems. I tried to go on a trip a couple of weeks ago and was on the highway for about an hour when she overheated and i had to shut it down. i waited for it to cool and had to add about a gallon coolant (i made sure it was the "compatable "stuff . the car seemed ok, so i got back on the road and about 30 minutes later she started overheating again. this time i decided to abandon the trip and had AAA tow the car back home. i drained and flushed the coolant system, replaced the thermostat, and refilled with dexcool and pellets, only to have the "battery not charging" warning come on. i wound up removing the radiator and replacing the alternator, battery problem was solved. flushed the system real good while i had it apart, refilled it and drove for 1 week without problem. on the way to work on the highway last week, she overheated again. i drained and replaced the coolant, changed the oil, and was fine till yesterday. i was on the highway for 40 minutes, temp started rising, and she overheated again!!!!!! don't quite know what to do now. i just got done checking the "air purge" line, i blew into it at the overflow tank and it was bubbling and shooting out of the 3/8' outlet so it seems clear. any help would be greatly appreciated! i bought the car at an auction, it was a lease turn in originally and seems to run and look fine, but i think i may have gotten duped and need to make this thing work, i'm getting tired of the looks my wife has been giving me for being stranded twice.LOL

den

[PAUL T]

Is there any coolant leaking on the ground? Did you notice any coolant in the oil when you changed it? Have you checked the belt and tension pulley to the waterpump? The belt is on the drivers side of the engine. Are your cooling fans working? Are there any diagnostic codes? Check the codes by turning key on engine off, then press and holding a few seconds the "off" & "warmer" buttons on the climate control panel. Codes will come up in the message center, write them down and post back.

[Cadillac Jim]

We need the codes as PAUL T says. You might have a radiator shop do a pressure test, too, and also test the coolant for combustion products.

[rev]

thank's for the response, i have checked the codes a few times and none of them seem to indicate anything to do with the cooling system, i will get them out and post them in a little while though just in case i'm missing something. both fans are coming on at about 222 degrees, i do have a question though, aren't they supposed to stay running when the engine is hot and the ignition is off? i seem to recall having a car that the electric fans stayed on until the engine was cool, the fans shut off with the ignition. just wondering, other than that, the fans seem to be running ok, sometimes low speed, and sometimes hi. i was reading one of the other posts about the upper radiator hose having to be "hard" when the engine is hot. I can squeeze this one easily when the temp is over 225, is that proper? there seems to be no oil in the coolant or vice versa, no bubbles exept when she's boiling, and there soesn't appear to be any leaks!!! this car seems to be totally different than any others that i have worked on through the years, but then again, the last caddy i had was a '71 !!!!!!!! thank's for the help, i'll post those codes in a little while.

den

[JimD]

I would check the pressure cap and be 100% sure the coolant mixture is 50% Dex-Cool and 50% water. Both of these impact the 'boiling' temperature.

[epricedright]

As Paul T wrote, be sure to check your belt and tensioner pulley for your water pump on the driver side. Seems to be a common problem that exhibits symptoms similiar to yours.

[adallak]

thank's for the response, i have checked the codes a few times and none of them seem to indicate anything to do with the cooling system, i will get them out and post them in a little while though just in case i'm missing something. both fans are coming on at about 222 degrees, i do have a question though, aren't they supposed to stay running when the engine is hot and the ignition is off? i seem to recall having a car that the electric fans stayed on until the engine was cool, the fans shut off with the ignition. just wondering, other than that, the fans seem to be running ok, sometimes low speed, and sometimes hi. i was reading one of the other posts about the upper radiator hose having to be "hard" when the engine is hot. I can squeeze this one easily when the temp is over 225, is that proper? there seems to be no oil in the coolant or vice versa, no bubbles exept when she's boiling, and there soesn't appear to be any leaks!!! this car seems to be totally different than any others that i have worked on through the years, but then again, the last caddy i had was a '71 !!!!!!!! thank's for the help, i'll post those codes in a little while.

den

At 225F your thermostat MUST be completely open and you should not be able to squeeze the upper radiator hose easily. Looks like the stat is your problem.

[Ranger]

There is no need for the fans to run after shutdown as there is no coolant circulation so it can't cool the engine anyway.

[JohnnyG]

What most of the post WON'T tell you, and I'm really surprised that nobody else has figued it out yet, is that the design of the Northstar is such that coolant will not go into the oil when a headgasket lets go. That is a great thing! That means you will not have to deal with rings and main bearings and connecting rods, and all the other stuff inside the engine that can be damaged by coolant getting in there.

There is a downside to this however.

You have a headgasket leak.

The reason you can go a few days without seeing the effects is that combustion gasses will go into the cooling system when a headgasket lets go. First, you may notice it as loss of heating capacity on cold days. Maybe refill the surge tank a few times, hoping that there is some air left in the system that you did not get out when you, so correctly, changed the coolant. If in hot weather, you may not notice it at all on short trips, the air (actually combustion gasses) can be purged from the system by the line you have so prudently checked. BUT, as the trips get longer, and the air in the system builds up, eventually, coolant will be displaced by air (gasses). We all know how poor a conductor of heat air is, otherwise there wouldn't be such things as insulation or double pane windows!

End result, something gets REALLY hot. Sooner or later, you see it on the temp gauge, and you get that sinking $4000.00 feeling. Codes or not....headgasket time.

Now keep in mind that this is pure cojecture on my part. I have been on this board for many years. I have never once seen this "theory" of mine posted by any authority on the subject, whether self proclaimed, or blessed by the General himself. Nor have I ever posted it before. It is gleaned from the many posts on the subject, and based in experience and common sense. You however, have done your homework, and have spent many hours trying to fix your problem as you have seen it presented on this forum. For that I commend you! You have done everything exactly right, and should be spared the anguish of thinking that you have screwed it up somehow.

If you want a second opinion, take it to a dealer and have the surge tank sniffed for hydrocarbons.

Sorry to be so gruff, I've been told that I could be a bit more diplomatic, but that's my problem, not yours.

[BodybyFisher]

The fact that your upper hose is soft at 225 degrees concerns me as you are not building up pressure to raise the boiling point. It is possible that your purge/bleed line is clogged and you are unable to evacuate air from the system..

With the engine idling, remove the 3/8" line that leads to the surge tank and verify that a stream of coolant is coming out of the hose.

If you look at this thread by rollingthunder he came close to thinking he had headgasket problems and it was the bleed/purge line.. My name was Scotty back then... This is an extensive thread on overheating > http://caddyinfo.ipbhost.com/index.php?sho...ic=5012&hl= On page 4 the problem was solved!

Check the waterpump belt tensioner for free movement - lube the pivot point if it is sticking check the belt for cracking and missing chunks.

[JohnnyG]

The others have all posted great suggestions. Check everything that has anything to do with the water pump or water circulation, that would be the perfect fix.

Remember though, air is compressable at 225°F, water is not.

[rev]

ok gang i finally got a chance to grab the codes, JohnnyG thank's for the great info, but i'm gonna exhaust all other possibilities first because if it's the HG, i don't think i'll be wanting to tackle that!

the codes that came up are;

P0440 current

0742 history

PCM P1258 history

NO IPC

ACM B1350 history

NO SDM

NO TCS

NO PZM

NO IRC

NO RFA

NO MSM

MMM 2146 current

again thank's for the help guys!

by the way, bodybyfisher, where is that hollow bolt located and what does it do ?

[Ranger]

Decifer codes here.

http://myweb.accessus.net/~090/dtcobd2.html

[BodybyFisher]

ok gang i finally got a chance to grab the codes, JohnnyG thank's for the great info, but i'm gonna exhaust all other possibilities first because if it's the HG, i don't think i'll be wanting to tackle that!

the codes that came up are;

P0440 current

0742 history

PCM P1258 history

NO IPC

ACM B1350 history

NO SDM

NO TCS

NO PZM

NO IRC

NO RFA

NO MSM

MMM 2146 current

again thank's for the help guys!

by the way, bodybyfisher, where is that hollow bolt located and what does it do ?

There is a pipe that crosses the engine at the top of the front head/cam cover. Take off the beauty cover to see it more clearly. Follow the hose from the surge tank across the engine and I believe it goes to the rear of the water pump housing, but someone else will need to confirm that.. I will look at my engine in the morning. But if you read rollingthunder's post it stays this:

Last night after work, i decided to change all the small coolant hoses. I took off the metal line that runs from the surge tank to the water pump, no blockage. I then decided to take out the hollow bolt that is in the water pump housing. There was my problem. There was a piece of hose stuck in the hole, which was blocking correct coolant and air flow.

[KHE]

What most of the post WON'T tell you, and I'm really surprised that nobody else has figued it out yet, is that the design of the Northstar is such that coolant will not go into the oil when a headgasket lets go. That is a great thing! That means you will not have to deal with rings and main bearings and connecting rods, and all the other stuff inside the engine that can be damaged by coolant getting in there.

Not always so - My '97 STS that I bought in March with bad headgaskets had coolant in the oil - it looked like coffee with cream. I changed the oil and added GM EOS and then drained the coolant, then ran the engine with no coolant for a few minutes and then changed the oil again and ran the engine for a few minutes to circulate fresh oil through the bearings. After I replaced the headgaskets, I changed the oil again and used Rotella 10W-30 with a pint of GM EOS. I ran the car for 300 miles and then changed the oil. After that, I began to use the oil life monitor. I have put about 4000 miles on the car since the engine repair - the bearings are fine.

[Cadillac Jim]

P0442 - Evaporative Emission (EVAP) System Small Leak Detected

P0740 - TCC Enable Solenoid Circuit Electrical

P1258 - Engine Coolant Overtemperature - above 268°F - Protection Mode Active

B1350 - Engine Coolant Over-Temperature

B2146 - Left Front Mirror Horizontal Position Sensor Circuit Low (?)

The leak DTC is current. This is a fuel leak. You should find it and fix it ASAP because it can cause an engine fire.

The overheating codes are significant, and shows that the PCM cut off the A/C and left a message, as you stated. The others may be transients and can be ignored for now.

[rev]

is there any easy procedure to definately rule out the head gasket?

[adallak]

is there any easy procedure to definately rule out the head gasket?

I would first rule out the easy and inexpensive stuff. Have you replaced the stat?

[PAUL T]

.i decided to abandon the trip and had AAA tow the car back home. i drained and flushed the coolant system, replaced the thermostat, and refilled with dexcool and pellets, only to have the "battery not charging" warning come on. i wound up removing the radiator and replacing the alternator, battery problem was solved. flushed the system real good while i had it apart, refilled it and drove for 1 week without problem. on the way to work on the highway last week, she overheated again. i drained and replaced the coolant, changed the oil, and was fine till yesterday. i was on the highway for 40 minutes, temp started rising, and she overheated again!!!!!! don't quite know what to do now. i just got done checking the "air purge" line, i blew into it at the overflow tank and it was bubbling and shooting out of the 3/8' outlet so it seems clear. any help would be greatly appreciated! i bought the car at an auction, it was a lease turn in originally and seems to run and look fine, but i think i may have gotten duped and need to make this thing work, i'm getting tired of the looks my wife has been giving me for being stranded twice.LOL

den

Since you replaced the thermostat, I would check the waterpump BELT and hollow bolt to the purge line. Then we can talk headgasket.

[adallak]

.i decided to abandon the trip and had AAA tow the car back home. i drained and flushed the coolant system, replaced the thermostat, and refilled with dexcool and pellets, only to have the "battery not charging" warning come on. i wound up removing the radiator and replacing the alternator, battery problem was solved. flushed the system real good while i had it apart, refilled it and drove for 1 week without problem. on the way to work on the highway last week, she overheated again. i drained and replaced the coolant, changed the oil, and was fine till yesterday. i was on the highway for 40 minutes, temp started rising, and she overheated again!!!!!! don't quite know what to do now. i just got done checking the "air purge" line, i blew into it at the overflow tank and it was bubbling and shooting out of the 3/8' outlet so it seems clear. any help would be greatly appreciated! i bought the car at an auction, it was a lease turn in originally and seems to run and look fine, but i think i may have gotten duped and need to make this thing work, i'm getting tired of the looks my wife has been giving me for being stranded twice.LOL

den

Since you replaced the thermostat, I would check the waterpump BELT and hollow bolt to the purge line. Then we can talk headgasket.

It is not clear whether he could squeeze easily the upper hose at 225F AFTER he replaced the thermostat...

[rev]

yes i can easily squeeze the upper hose at 225 degrees, it is definately NOT "rock hard". also, i put a new thermostat in the lower hose, then boiled the old thermostat just to see if it was opening, and it seemed normal, as the water heated up the thermostat opened. the pump belt and tensioner appear to be working fine. i had the car idling for over an hour with the air cond. on and it stayed right around 207 degrees, couldn't get it to overheat

[KHE]

is there any easy procedure to definately rule out the head gasket?

Yes, there is. Take an old spark plug and grind off the flange that retains the insulator and porcelain. Tap the I.D. of the remains with an 1/8 pipe tap. Buy an assortment of 1/8" pipe nipples and an air fitting. Assemble them as shown in the photo below. I loctited the fittings together with Loctite red and cured it in a 200 degree oven for 1 hour.

Remove the surge tank cap. Remove each spark plug and insert a wood dowel into the spark plug hole. Turn the balancer bolt to bring the cyliner up to top dead center. Remove the dowel and install the adapter. Connect 120 psi shop air to the adapter while holding a breaker bar on the balancer bolt. If you hear air rushing out the exhaust, all four valves are not closed - remove the adapter and insert the dowel and rotate the balancer in the same direction until the dowel is again at top dead center and then install the adapter and pressurize the cylinder. If you see bubbles in the surge tank or hear gurgling or thumping, the head gasket is leaking. You will need to repeat this for the other 7 cylinders.

[BodybyFisher]

If you don't feel like going through the above process of making a compression fitting from the spark plug, you could buy this Combusion Leak Detector from Napa Parts also:

http://www.napaonline.com/MasterPages/NOLM...k&VehCode=N

In addition, many radiator shops have the ability to test your coolant for combusion gases..

However, I still feel you have something wrong if the upper hose is soft, you seem to have air in the system. In addition, check the cap on your surge tank, if it is not holding pressure it will release to the overflow. Have you disconnected the purge line yet to see if you have coolant flowing?

[rev]

thank's guys,

bodybyfisher how do you use that kit?

i just got back from taking a ride in my car, i drove it hard and soft for over an hour, speed ranges from 20 (got stuck in a small traffic jam) to 85 on the thruway, at one point the temp went up to 239, for a couple of minutes, and then went back down to 215, no problems, i tried with the air on and with it off, i would say the temp stayed at about 201 for the first half hour at least, then hovered at about 215 on average (until i got that one spike up to 239) i thought she was going to go all the way up, but it came back down on it's own!!!!!!! i am totally stumped!!!!! oil looks as good as new, it isn't even dirty!!!!

[BodybyFisher]

Understand that the AC forces the COOLING FANS on immediately, with the AC off, you believe it or not will see wider temperature swings as the fans don't come on till 228 I believe...

Marika recently took her car to a shop and they used that kit on it. I believe you set up the tester and suck in some coolant, if it turns a certain color you have combustion gases. I am sure its easy and comes with directions.. What were you doing when you hit 239 degrees? Traffic, high speed? What is your outside temp?