Bruce Nunnally

Mailbag: Overheating cured by revving

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From the blog comments:

I have a 2000 Cadillac SLS with a overheating problem. Changed water pump, radiator cap, thermostat, checked purge line fluid flowing. When it starts to overheat if I rive the engine the gauge goes back to normal, then starts to rise again. Secondly, the battery light comes on when I’m at idle for a period of time. Third, the blower for the heater sometimes does not turn on unless I kick the lower panel on the passenger side on the car. Any suggestions on my problem ?

Bruce

2016 Cadillac ATS-V gray/black; 2013 Cadillac ATS 2L Turbo Premium (Wife's)

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I have a general question with regard to the Northstar purge line. Was wondering if anyone has given thought to the cause of head gasket failure on the Northstar, and whether the plugged or partially plugged

bolt with a hole in it maybe be the actual originating cause of head gasket failure? Specifically the build of air/steam pockets in the block, and the much slower then normal release due to the bolt with a hole in it

being partially blocked. This condition creating an overly hot spot, forcing an uneven expansion in the aluminum. Thus causing the unusual stretch on the head bolt, eventually causing the failure of threads in the block. I would like to have feed back, please. Thanks.

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I would like to think that could be possible but I have seen quite a few with failure and the hollow bolt was normal, like my last one.

Failure typically comes from the expansion and contraction of the aluminum over time and the loads applied, eventually the threads will fail and the heads will start to move off of the block


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I would NOT think that overheating of any type, within reason, would cause Northstar head gasket failure. Like most aluminum engines, it uses torque-and-twist head bolts, which means that several inches of head bolt are a tension spring that determines clamping force from that bolt. As the engine temperature cycles, differences in expansion of the block and bolt allow changes in clamping force that are within the design constraints of the engine - again, within limits.

The Northstar, from the first year, has an overheating safety feature that is unique to the Nortstar so far as I know: you can drain out the coolant altogether and run it for 50 miles without voiding the warranty. The PCM puts the driveline into the "limp home mode" where half the cylinders run and the other half pump air for cooling, switching the cylinders back and forth to and from running to cooling duty.

When Car & Driver tested the early STS, they thought that this was great, so the drained the coolant from their test car and ran 0-60 mph and quarter-mile tests with it that way. They estimated from these figures that the car had about 50 hp in the limp-home mode.

To answer your question, of course we have looked at head gasket failure; it's almost always got a root cause of a head bolt pulling out, which in turn is almost always a result of letting the coolant go too long. The problem became common with red coolant, because it is rated at 150,000 miles or 5 years, and since hardly anybody drives 30,000 miles a year, the five years would come and go, the coolant would go acid, and eventually get into the head bolt wells...


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I completely agree with that. I would not trust coolant to last 10 years. In any vehicle


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I read somewhere that you can use the DVM test for coolant. Put it on DC Volts, hold one termina on an engine ground, and dip the other in the coolant (cold, of course). If it reads below 0.7 Volts, you are good, the article says. I would use 0.5 Volts or more as a red flag.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Thanks for the feedback. The Eldo I have has 54000 original miles. Engine cooling has always acted "funny". Never actually overheating, but running hotter then any other vehicle I have owned. Not getting excited about this after doing some investigating. Any way, decided out of the blue to pull the hollow bolt, found red silicone on the end. Now the purge line has always been hot, but I have always felt a gurgling in the top hose. Best of my knowledge, the bolt has never been removed. Now prior to this the engine temp as viewed on the DIC would wander. In traffic the temp would want to go up to the fan turn on point, and then cycle up and down based on fan operation. Once back down the road, engine temp was slow to respond to air flow across the radiator. So now, cleaned the red silicone from the end of the bolt. Reinstalled, filled system

with coolant and headed done the road. Now the engine comes up to operating temp noticeably faster. Gets to about 197 degrees around town and holds the temp without the wandering that it used to do. Now on the highway temp goes to 199 degrees and stays there. No temp wandering on the highway either. Seems more likely that head gasket failure is probably a result of all things listed here, not just the fault of one component in the cooling system. Based on the info read here, I have a few years and a few more miles before I might have to consider TIMESERT work on this engine. Thanks again.

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I just inherited a 97 SLS with 50k. Thinking about keeping it for a time and need to know what to look for. Obviously sits most of the time and there have been battery and coolant problems in the past. I don't know the specifics but would appreciate some suggestions on where and how to start. Thanks.

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I just inherited a 97 SLS with 50k. Thinking about keeping it for a time and need to know what to look for. Obviously sits most of the time and there have been battery and coolant problems in the past. I don't know the specifics but would appreciate some suggestions on where and how to start. Thanks.

The first thing to do is to drain the coolant and refill with fresh Dexcool mixed 50/50 with distilled water. Repeat in 2 to 2-1/2 years.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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In addition to what KHE says (2 years instead of 4 because there may have been green coolant in it at one time), I would do the look-over and maintenance recommended for any used car with lots of deferred maintenance. Change coolant, oil, and check brakes, tires, and all fluids for low levels or contamination. Check the radiator for clogging (easier these days with infrared thermometer inspection guns), the bypass hose for clogging, and all hose clamps for leaks. Check for vacuum leaks and missing or misrouted vacuum hoses and EVAP hoses.

You can start by checking the OBD codes and see what the car sees.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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In addition to what KHE says (2 years instead of 4 because there may have been green coolant in it at one time),

Nope - It is because the Northstar engine does not have block drains so by draining the coolant only half the coolant is able to be changed. Dex is good for 5 years/100,000 miles whichever comes first so it could go 2-1/2 years between coolant changes.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Thanks Jim and KHE. Is there any flushing procedure to follow? Any useful publications or sites that are model specific like a Haynes or Clymers? I saw that the hose clamps on the soft hose sections on the driver's side of the engine are wet and I have run it for a time looking under for leaks but I am not seeing any puddles. Could it be pushing out coolant at highway speeds? Is it advisable to change the hoses and clamps before changing the coolant to eliminate that as a leak source? Is there a link to the OBD reading procedure? Thanks for helping a noob.

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No need to flush the system - it will be very difficult to get the concentration 50/50 on the refill. Just drain what you can and refill with fresh Dexcool mixed 50/50 with distilled water every 2 to 2-1/2 years.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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So I spent a couple hours last night reading horror stories about Dexcool, class action laws suits etc. I know I saw green coolant in the tank. So where to go from here? Still recommend drain and refill with Dexcool? If so why? Is there no validity to these claims? I'm just trying to make sense of it all and don't want to make things worse. Thanks.

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All the horror stories are from the Dex in an IRON engine that was run low on coolant. The Northstar is aluminum and won't have that issue. Most but not all coolant is silicate free these days - even the green stuff. That said, you can't tell if the green coolant had silicates in it but you need to assume it does. The silicates plate the internals of the cooling system and will deplete the corrosion inhibitors from the Dexcool so if you go back to Dexcool, you'd need to change it out at half the interval anyway. Since the green coolant is only good for two years, you're looking at 1 year change intervals.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Thanks KHE. This Sunday I will see what codes might be there and start a list of to do's. Already gearing up for potential head gasket/stud replacement and have looked at the links onCCC web site. I really want to keep this car if I can.

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Ran the DTC yesterday and go the following codes; P0108 History, P0135 History, P0155 Current, P1106 History, PZM B1983 History, IRC B1740 History, IRC U1255 History, RFA B2560 History, PCM? What am I dealing with? Thanks.

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P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage
P0135 Heated Oxygen Sensor (HO2S) Heater Performance Bank 1 Sensor 1
P0155 Heated Oxygen Sensor (HO2S) Heater Performance Bank 2 Sensor 1 CURRENT
P1106 Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent High Voltage
B1983 Driver’s Door Unlock Relay Circuit Short to Battery
B1740 Driver Seat Front Down Switch Circuit Malfunction (IRC?)
U1255 Class 2 Communication Malfunction (Serial Data Line Malfunction) (IRC)
B2560 Aux A/C Blower Motor Relay Circuit Short to Ground (RFA?)

The P0155 will turn on the MIL. It's the oxygen sensor on the front exhaust manifold near the flange where the crossover bolts to it. The code indicates that the heater is generating bad output. The FSM says to check the PNK wire and make sure that it draws between 0.9 and 1.5 Amps with the key on. This code won't throw unless the problem is detected in two consecutive driving cycles, and it will go away if the problem is NOT detected for three driving cycles, so if it is CURRENT, then either you have a wiring/connector problem or the sensor is bad.

You also have a P0135 so I would check the fuses (OXY SEN 1 and OXY SEN 2, 10 Amp, in engine compartment fuse/relay center).

I would also check the battery cables, particularly corrosion on the positive battery cable at the battery terminal, because you have a lot of HISTORY codes. Disconnecting the battery will reset the codes. If the battery is good and the cables are clean, you can look at which codes come back as showing what needs to be done first.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Thank you Jim I start on that this weekend. This car is my mother's and she gave it to me, which is why I would like to try to keep it running. They had a "friend" with his own shop work on this car for years and sadly I have no confidence in their work other than very basic parts replacement. It would be nice if this doesn't get too ugly but we shall see what is yet to come.

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A lot of friendly neighborhood mechanics will do what needs to be done to keep the car running with no real consideration of its future. Most often this means that minimal repairs are done using the cheapest parts available. Conventional wisdom is to treat repair and maintenance decisions on the basis of assuming that the car is going up for sale or trade Monday morning, not on the basis of thinking of what you want to be driving for the next year or more. I feel your pain.

The simplest way to avoid the pain is simply to take the car elsewhere, hopefully to someone the "friend" doesn't know. Look for ASE certification; small, usually framed certificates on the wall with this logo on them:

showGif_ASE.png

Check the dates on the certificates and the names, and see if the people named will work on your car if you bring it in.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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If the p0135 pops up only on cold mornings, then that means the o2 sensor internal heater is going bad, and the entire sensor needs to be replaced. Mine was bad for a while, and when the code would come up every once in a while, i would just clear it, and the car would run fine. My inspections were in the summer, so in the warm weather, the code will not set.

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Unfortunately the P0135 refers to Bank 1 Sensor 1 which is between the engine and the firewall, so it's quite hard to change as a DIY job. You're getting a P0155, the same code for the front H02 sensor, so would replace both, if the P0135 doesn't go to HISTORY once the weather warms a bit.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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