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08 CTS with Sports Package and 165k miles
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Discussion Starter · #1 ·
My '08 CTS 3.6DI engine was not happy today. On the way to work, I noticed reduced power and got P0305 (misfire in cylinder 5). After work about 3 miles from home the temps shot up and the ECU shut the engine down to (hopefully) prevent damage. The computer showed P1258 (Engine Coolant Over-temperature) and P2601 (Coolant pump "A" Control Circut Performance/Stuck off) which leads me to believe the water pump died. There was still plenty of coolant in the system, so I didn't have a coolant leak. (Coincidentally, I was planning on replacing the timing chain this weekend and I had just ordered a new water pump along with all the Timing Chain stuff yesterday.)

When I'm in the engine replacing the timing chain, are there things I should check to ensure there is no additional damage beyond the water pump?
 

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08 CTS DI
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My '08 CTS 3.6DI engine was not happy today. On the way to work, I noticed reduced power and got P0305 (misfire in cylinder 5). After work about 3 miles from home the temps shot up and the ECU shut the engine down to (hopefully) prevent damage. The computer showed P1258 (Engine Coolant Over-temperature) and P2601 (Coolant pump "A" Control Circut Performance/Stuck off) which leads me to believe the water pump died. There was still plenty of coolant in the system, so I didn't have a coolant leak. (Coincidentally, I was planning on replacing the timing chain this weekend and I had just ordered a new water pump along with all the Timing Chain stuff yesterday.)

When I'm in the engine replacing the timing chain, are there things I should check to ensure there is no additional damage beyond the water pump?
I believe your problem is with the auxiliary water pump just in front of the engine instead of the engine mounted pump which does not have any electrical connections.

 

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2011 SRX4 3.0 4WD, Luxury
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When I did my SRX i did the thermostat and all the hoses and new Cap, I also did the serpentine belt and Idler pully as well....since your in that deep.... pay close attention to torque spec's....there is a helluva difference between inch and Ft pounds

Steve
 

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I believe your problem is with the auxiliary water pump just in front of the engine instead of the engine mounted pump which does not have any electrical connections.

Agreed- this aux pump was only used in '08-'09.
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2013 Black Diamond CTS4 Premium Coupe (sold-09 CTS4 DI Black Raven/Ebony)
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I know that the aux pump is called into action when the car is shut off and the coolant is still too hot. It allows the coolant to by cycled without running the engine. I don't know how it is used when driving though. It's not expensive and easy to replace.
You did not mention if your fans were running properly when the car shut down. Malfunctioning fans would contribute to an overheating situation too.
 

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2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
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Failure of the auxiliary pump wouldn't have caused overheating under normal conditions and it is likely the pump has had this issue for some time but your driving conditions haven't caused it to be activated in some time.

How far had you driven before you got the overtemp warning? What was going on with the surge/recovery tank at that time. With a true overheat, the coolant should have either been boiling in the recovery section OR there was no coolant in it indicating you are low on coolant.

I would carefully test to see if the car is actually overheating and if so run down the reason why (failed pump etc.) or if it is a sensor issue. But do be careful, the 3.6 isn't prone to head gasket issues but seriously overheating any engine can result in that problem. My 2008 CTS RWD premium was my favorite Cadillac and the 3.6 is a great engine. My experience with the 3.6 in the 2008 CTS is why I ordered the same powertrain in my 2014 ATS that my HS daughter now drives and the 2021 Camaro RS I bought as my curent daily driver.

And on a related note, I nearly bought a 2008 BMW 335i instead of the 2008 CTS because of a issue in GM's build preference system that caused my order to go into purgatory for a few months. I decided to stick with my CTS order and through one of my consulting contacts, I got in touch with the executive suite at Cadillac division that took care of the issue and issued a $1,500 credit because of the bad order experience. Two strikes against the BMW were its slightly smaller back seat which was an issue with my then 5 year old daughter still in a car seat AND the 335i had an issue with overheating and at the time I test drove one the current BMW fix was to aggressively reduce engine power when engine temperature rose and they also had the oil temperature gauge displaying a false lower reading. They finally corrected the problem of insufficient cooling for its twin turbo engine by adding another oil cooler in one of the front wheel wells.

Rodger
 

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08 CTS DI
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Failure of the auxiliary pump wouldn't have caused overheating under normal conditions and it is likely the pump has had this issue for some time but your driving conditions haven't caused it to be activated in some time.
Per CTS shop manual:
P1258, engine coolant exceeded a specified temp. The PCM detected that and shut off half the fuel injectors and associated cylinders to reduce temp (reduced power).
P2601, auxiliary pump is activated after engine shut down if coolant temp is above 230 deg F for 4 to 30 seconds. If the pump circuit has the appropriate fault, this code sets.
P0305, cylinder #5 misfire, possibly one of the disabled cylinders that was inadvertently counted, despite programmed shut down.
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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First thing, pressure check for leaks. The engine internal cooling in the engine block will see more than the pressure cap is rated at when the engine is running so pump it up to 20PSI.
 

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08 CTS with Sports Package and 165k miles
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Discussion Starter · #12 ·
Failure of the auxiliary pump wouldn't have caused overheating under normal conditions and it is likely the pump has had this issue for some time but your driving conditions haven't caused it to be activated in some time.
Quite possible. This was the hottest day of the year so far (97F)
How far had you driven before you got the overtemp warning?
About 40 miles. Warning (AC shutting off due to hot engine) and codes happened with about 7 miles to go. The electronic engine shutdown to prevent damage happened 4-5 miles later.
What was going on with the surge/recovery tank at that time. With a true overheat, the coolant should have either been boiling in the recovery section OR there was no coolant in it indicating you are low on coolant.
After about 20 minutes, I used a thick rag to slowly loosen the cap. I got a bit of pressure, but nothing extreme. The surge tank was full.
 

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08 CTS with Sports Package and 165k miles
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Discussion Starter · #13 ·
Parts just arrived for the whole job. I'll be replacing the power steering pump (Unrelated to this. It was worn out), oil pump, mechanical water pump, auxiliary 12v water pump, spark plugs, and all the timing components.

My current working theory/plan (Let me know if this doesn't sound reasonable.)
1) The old timing chains finally stretched enough to cause the misfire in cylinder 5.
2) The other 5 cylinders worked much harder than normal, causing the engine to heat up ahead of what the radiator could handle, causing the overheat.
3) I will pull the radiator to both give me additional room in front to access the front of the engine** and to clean the radiator and do basic checks for a clogged radiator***.
4) I will dismantle the front of the engine, following the service manual for replacing the timing chains and timing parts.
5) While there, I will replace the oil pump, water pump, and gaskets.
6) I'll reassemble according to the service manual, replacing the spark plugs and power steering pump on the way out****
7) Reassemble cooling system with new auxiliary pump.
8) The cooling system needs to be fully flushed out filled with water and then pressure tested. (This should let me know if there are additional problems.)
9) Drain water and replace with coolant/water.
10) Start car with fingers crossed, and make any adjustments needed, including purging air from the PS and cooling system.
11) Contact a dealer to see if my car needs the software update for TSB #07-06-04-024, have installed if needed.

** How much more can I easily remove in the front to make room for myself? Is the CTS one of the cars I can take the whole front bumper off in under an hour to have easy access?
*** How can I check for a partially clogged radiator? I know the trick of filling a good radiator, draining it and making sure the old one can fit all the coolant that came out of the new one. However, I'm not going to have a new radiator, because I don't want to spend $300 if it isn't bad.
**** Is there any reason to change the power steering pump when I first get to it versus changing it while I am reassembling things?
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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14 year old car, NEW radiator $80.
 

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08 CTS DI
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After about 20 minutes, I used a thick rag to slowly loosen the cap. I got a bit of pressure, but nothing extreme. The surge tank was full.
The auxiliary pump only operates after engine shut off (confirmed by factory shop manual), so although it's coding, that should not be the cause. It is also unusual for an overheat to occur at speed on just a hot day if that was the circumstance. The info I provided above is from the GM shop manuals, P1285 and reduced power is stated to be half of the cylinders shut off to reduce temps, so it's unlikely 5 cylinders driving 1 would result in an overheat, as this car has a tow capability that would deliver a much greater load than that. I have the same year and cooling system and never had a problem with engine cooling on long trips, or around town in 90+ degree weather in FL/GA.

Proper coolant level, and cooling fan operation would make me highly suspicious of the thermostat.
You can remove the radiator, but it is not necessary, I never felt the need when I replaced my timing components. It is recommended that the oil pump not be bothered as it is a flush mount seal-less pump that must be carefully centered and torqued. I've read a couple of "Oil pressure was fine until the pump was replaced" stories associated with timing chain installs.
If a decision is made to replace the radiator, check Rockauto, there is a Spectra radiator (Make that TYC now) offered for the CTS that has the CTS-V 1" thick core instead of the stock ~.5" core. You'll have to check the info buttons for spec confirmation.
 

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2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
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You would be very wise to follow Joseph's advice and only fix what is known to be broken, each part replaced creates possibilities for other problems and mistakes. And unfortunately new production part doesn't always mean not defective from the start and that is even more of an issue with the pandemic supply chain problems.

A stuck (as in partially open) thermostat is a great call by Joseph. I had to replace the thermostat in my low mile 2016 Corvette Z06 earlier this spring because on cooler days it was allowing the coolant temperature to drop too low while cruising on the highway bringing up the lowered "red line" on the tach. I would rather have it sticking open than closed but neither is good.

An older radiator hose can both delaminate internally and also become soft/weak enough to be pulled partially closed due to the suction action of the water pump so keep that as a possibility also if the thermostat isn't the cause.

Rodger
 

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Discussion Starter · #17 ·
Great tips, guys!

I spent 3 hours getting the intake, cam covers, and several plastic shields off and called it a night. Underneath the cam covers showed exactly what I expected for a car needing the timing chains done: The left side was clean as a whistle, and the passenger side was much darker and got darker towards the rear. There was a few mm play in the right side timing chain and none in the driver's side chain.

When I get the thermostat out, how will I know if it was stuck closed and was thus the problem?

Also, how do you read the "full cold" line on the surge tank? The words are next to a line on the top that goes up and down, rather than next to a horizontal line like every other surge tank I've ever seen.
 

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Great tips, guys!

I spent 3 hours getting the intake, cam covers, and several plastic shields off and called it a night. Underneath the cam covers showed exactly what I expected for a car needing the timing chains done: The left side was clean as a whistle, and the passenger side was much darker and got darker towards the rear. There was a few mm play in the right side timing chain and none in the driver's side chain.

When I get the thermostat out, how will I know if it was stuck closed and was thus the problem?

Also, how do you read the "full cold" line on the surge tank? The words are next to a line on the top that goes up and down, rather than next to a horizontal line like every other surge tank I've ever seen.
You can boil the stat in a pot of water along with a thermometer to see if it functions properly.

The full cold mark on the coolant tank is the horizontal seam where the two halves (black & clear) join together.
 

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Great tips, guys!

I spent 3 hours getting the intake, cam covers, and several plastic shields off and called it a night. Underneath the cam covers showed exactly what I expected for a car needing the timing chains done: The left side was clean as a whistle, and the passenger side was much darker and got darker towards the rear. There was a few mm play in the right side timing chain and none in the driver's side chain.

When I get the thermostat out, how will I know if it was stuck closed and was thus the problem?

Also, how do you read the "full cold" line on the surge tank? The words are next to a line on the top that goes up and down, rather than next to a horizontal line like every other surge tank I've ever seen.
The discoloration of the passenger side cylinder head likely has all to do with the fact that it is on the "dirty" side of the motor and the end of the valvetrain valley is partitioned off from PCV flow, resulting in poor air flow over it and long standing exposure to spent gases and oil mist allowing more time to stick and coat. The driver side head has air flow entering at the rear flowing over the head to the front keeping it fresh.

You can't get an accurate assessment of chain play by feel. Both sides will show slack dependent upon the position of the camshafts relative to the valves as tension on the springs change load from one side of the cam lobe to the other. If you continue to turn the crank you will note that the condition observed will change to the opposite.

The chains elongate from wear at the pivot pins and the sum of thousandths of an inch at each one adds up to several tenths. When you hold a new chain along side the old you might see as much as .5" difference in length, or more.

I'd put both the old and new stat in water side by side, heat and observe. Water boils at 212 deg F so they should both be fully open by that time. If there is no rust, or debris in your coolant system, I doubt there is any blockage in the radiator.
 
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