Overheating Northstar--Kinda

[Topcat9pet]

Recently bought a '98 DeVille, reluctantly, since I already had seventeen other Cadillacs, The seller said that it was overheating and was losing coolant. It doesn't smoke, no water in the oil and runs smooth. It did have a code set that indicated that it had been hot. I assumed that it was head gaskets/bolts. He said that he had already changed the thermostat and water pump.

When I filled it with anti-freeze-he had been putting water in it- I got no bubbles in the tank and it did not overheat after running for about an hour with the cap off. I let it cool down put a new cap on it, added pellets, and let it run for about forty-five minutes. The temp went up to 222 then dropped back to 212, then it would go back to 222 then drop back to @212-sometimes back to 207, then back to 222, then back to @ 210. On closer exam I noticed the RT. end cap on the radiator was cracked. I changed the radiator, stopped the coolant loss, but it still runs in the 207 to 222 temp range, Temp sensor? Thermostat? No engine codes set. Eighty thousand miles. All of this is at idle. haven't checked it while driving-waiting on a replacement title.

[JimD]

Sitting stationary at idle with the A/C OFF, you are seeing normal coolant temperature swings as the PCM cycles the radiator fans ON and OFF.

Select an A/C mode and see if the coolant temperature gets to somewhere around 200 F and stays right there, rock solid.

When an A/C mode is selected, the PCM has the fans running all the time to be sure there is air flow over the condenser when the car is stopped in traffic.

[Topcat9pet]

Sitting stationary at idle with the A/C OFF, you are seeing normal coolant temperature swings as the PCM cycles the radiator fans ON and OFF.

Select an A/C mode and see if the coolant temperature gets to somewhere around 200 F and stays right there, rock solid.

When an A/C mode is selected, the PCM has the fans running all the time to be sure there is air flow over the condenser when the car is stopped in traffic.

I haven't serviced the A/C yet. It was low on a freon when i got the car and I pulled the radiator and condenser together. The though was, if it was the head bolts I would have to drain it again anyway. I've never had a Northstar that would run in what I would consider a normal temp. range bracket just a little high. I have a '91 Eldo.TC that has been running at 205- 207 since '94, so I guess it's its not hat harmful to the 4.9.

When the rain stops , I'll pull the A/C down and service it to get the Rt. side fan running. Hopefully that will solve the problem. If it does then $650.00 won't seem that bad.

Many thanks.

[JimD]

If there is some reason you can't take it on the street to see what effect a 25 MPH airflow has on the coolant temperature, you could try a large shop fan blowing air at the condenser/radiator area grille opening.

[KHE]

If there was a leak in the cooling system and you fixed that by installing a new radiator, I would say the problemn is fixed. None of the temps youo reported are out of the "normal" range.

[growe3]

The temperatures that you note, are well within range.

That it goes to 222 and then drops (repeatedly), sounds like the thermostat is opening and closing in that range.

If you turn on the AC, both fans should come on, and this might moderate the temperature,down to around 200-205.

Did you put the Bars Leak Gold into the lower radiator hose? If you placed them into the surge tank, they will likely clog the water pump bleed/vent line, and this can cause cavitation; meaning not enough consistent water flowing.

If you haven't already done so, verify that the water pump bleed/vent line is clear, and that the hollow bolt is clear.

Drive the car, you may get a trapped air bubble to clear from the coolant. Temps should stay under 212 most of the time, low 200's is fairly normal.

-George

[Topcat9pet]

Serviced the A/C so the RT. side fan comes on. The temp. at idle is staying between 194 and 212. Now it's on to see why the low oil press light is flashing. It's flashing at a frequency that makes me think that it's probably an electrical problem-sensor- rather than low oil press. First to change the oil and filter and then put a direct reading guage on it.

I did run across a TSB,47-61-32 regarding "low oil press" message and/or "Service Eng.Soon" telltale. This was for the '96 year model, but pertains to other year models of the 4.6

Thanks to all for the input regarding the temp readings.

[BodybyFisher]

1996 Cadillac Seville STS

LACK OF POWER, LOSS OF OIL PRESSURE

LACK OF POWER, LOSS OF OIL PRESSURE

TECHNICAL SERVICE BULLETIN

Reference Number(s): 47-61-32B, Date of Issue: March, 1996

Superceded Bulletin(s): 47-61-32A, 47-61-32

LACK OF POWER, LOSS OF OIL PRESSURE (CHECK HARMONIC

BALANCER BOLT TORQUE AND FLUSH OIL PUMP RELIEF VALVE)

Model(s): 1993 Cadillac Allante

1993-96 Cadillac Eldorado, Seville

1994-96 Cadillac Concours

1996 Cadillac Sedan DeVille (all above with 4.6L Engine (VINs Y, 9, RPOs LD8, L37)

1995-96 Oldsmobile Aurora with 4.0L Engine (VIN C - RPO L47)

Section: 6 - Engine

Bulletin No.: 47-61-32B

Date: March, 1996

NOTE: This bulletin supersedes Technical Service Bulletin number 47-61-32A, (Section6 - Engine).

CONDITION

Some owners may comment on low oil pressure which may display a "Low Oil Pressure" message and/or a

"Malfunction Indicator Lamp" (Service Engine Soon) telltale. Vehicle owners may comment that these telltale

messages illuminate at engine speeds of 1000 RPM and above.

CAUSE

Lack of oil pressure may be caused by:

z Particles from the manufacturing process sticking the oil pump relief valve, not allowing the valve to seal

to its seat which does not allow the pump to prime.

z A loose harmonic balancer bolt which will result in the oil pump not turning.

CORRECTION

Thursday, February 02, 2006 8:28:42 PM Page 1 © 2004 Mitchell Repair Information Company, LLC.

1996 Cadillac Seville STS

LACK OF POWER, LOSS OF OIL PRESSURE

Ensure the harmonic balancer bolt is tightened to spec. The correct torque value for this bolt is 60 N.m (44 ft-lb)

plus 120° for 1993-95 engines with an M18 bolt and 50 N.m (37 ft-lb) plus 120° for 1996 engines with an M14

bolt.

NOTE: A small number of 1995 engines were built with crankshafts equipped with the

M14 bolt. Identify the size of the bolt to determine the proper torque

specification.

If the bolt is to specification, the cause of the low oil pressure is internal to the pump.

To remove particles from the relief valve in the oil pump, perform the following procedure:

1. Add an ADDITIONAL 10 to 12 quarts (liters) of engine oil to the engine. This will immerse the pump

completely in oil.

2. Start the engine and repeatedly open the throttle (rev the engine) from idle to 3500 RPM. This will allow

the pump to prime; cycling the relief valve forces any debris from the relief valve.

NOTE: Do not operate the engine above 3500 RPM. Doing so will aerate the

engine oil and/or force excess engine oil into the PCV system. DO NOT

DRIVE THE VEHICLE while the additional oil is in the engine.

NOTE: After the engine has sufficient oil pressure, any valve train noise

associated with this low oil pressure condition should not be evident upon

restarting the vehicle and the low oil pressure and malfunction indicator

lamp (service engine soon) messages should not remain illuminated.

3. After engine has sufficient oil pressure, drain the crankcase. Reinstall the engine oil pan drain plug.

4. Add 7 quarts of engine oil and check the oil level. Make sure the vehicle is on a level surface and the

engine operating temperature is 100°C when checking the oil level with the engine stopped for 15-20

seconds.

WARRANTY INFORMATION

For vehicles repaired under warranty, use:

LABOR OPERATION NO.: J0989

LABOR TIME: 0.5 hr

[cardinalsgirl]

I seen on here where you helped someone else about 6months ago with a problem similar to mine. I also have a 98 Cadillac Deville that I recently purchased and I am having issues with it overheating.

I bought it 30 miles away and when I was on my way home it overheated really bad on the highway. But when I finally got it to town it ran fine. So for some reason its only on the highway. I also had a code come up for the engine getting hot which I knew about and I replaced the thermostat. I just curious what you think might be the problem or what my next step should be. I really want to keep the car so I am willing to work on it. Any help you might have is greatly appreciated!

Thank you!

[MrEldo97]

Test the coolant for the presence of combustion gases. You can buy a test kit at NAPA for about $50.00. If combustion gases are present you have pulled head bolts and must Timesert the block. If there are no combustion gases in the coolant your problem is most likely fairly minor.

IMO, as the first generation Northstars age we will see more and more head bolt issues.

[Ranger]

I second that. Rule out the head gaskets before going any farther.

[winterset]

I would bring the car bck to the person who sold it to you & ask for your money back. Ifit happened on your first 30 miles, I'm sure it happened to that person, and they should have let you know. Seems they kept this info from you, and took advantage of you. They will be aware of the overheating problem you are talking about.