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99 STS - Another Temp question


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Hello

From doing a google search it looks like temp problems are common for the Northstar, huh?

Please allow me to add another

For the past month my Caddy (4.6L Northstar with 197k miles) has been running "Warm" on occasion. By that I mean the temp guage normally stays at the 12:00 position. But occasionally it would creep over to around 1:00 or so when driving in town,

sitting at a red light ect. but would return to normal when you were moving again.

I have kept a eye on the coolant level and have had to add some a few times. I assumed it was a small leak that I had not found yet.

Yesterday while on the highway it did run hot with me. I stopped the car and let the presure of of the reserve tank so I could fill her back up and make it home. After I got home I let it rest for a hour or so, checked, topped the tank off (with water) and drove it about 5 miles or so. When I got back in to my driveway I let it idel for just a couple of minutes and it began it warm up again.

I killed the engine and started looking at the hoses. The top hose was hot and had pressure on it when I sqwueezed it. The bottom hose was cool and had no pressure, but as I was squeezing it it started to get hot as well. This is also the first time that I have noticed the raesevr tank boiling over as well. But I did fill it completely befor I drove the car.

My first thought was stuck thermostat.

I have repalced it this morning, filled her up with water again. (will replace with coolant after all problems are solved)

Drove it about 5 miles with no problems (temp guage at 12:00 )

Let it sit and idel in the drive way for about 5 min with no problems. (temp guage at 12:00 )

Just as a last resort drove it another 5 miles and it starting warming up a gain ( Temp guage at 1:00 ) and it was boiling over when I killed the engine.

What now?

I see where head gaskets are a common problem but I'm sure hoping that isn't the answer

Oh one other tidbit I did have to replace the water pump belt and tension arm last winter

This is the only other time the car has ever gotten hot

Edit to add

I have seen both of the radiator fans working as well

Edited by FourHughes
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First off, NEVER EVER put staight water into a cooling system, it boils at a lower temp. You might have boiled over because it was water

You will have a hard time now balancing the system to 50/50 as water is in the block, but the next thing I would do is balance the coolant to 50/50

There is an AIR PURGE line that must flow freely, it is at the top of the coolant tank, not the overflow hose the other 3/8" hose at the top of the tank. While the engine is COOL, gently pull the hose off, start the engine, and let it IDLE, go look at the purge line it should stream coolant out in a steady stream, shut engine off.... If no steady stream its clogged and AIR can not get out

Then pressure test your cooling system

Then have the coolant tested for combustion by products to see if a head gasket has been breached

Pre-1995 - DTC codes OBD1  >>

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....the temp guage normally stays at the 12:00 position. But occasionally it would creep over to around 1:00 or so when driving in town, sitting at a red light ect. but would return to normal when you were moving again.

It might help to refer to temperatures rather than analog clock faces. See photo.

....This is also the first time that I have noticed the raesevr tank boiling over as well. But I did fill it completely befor I drove the car.

Completely full of (whatever you put in there) leaves no room for the coolant to expand as it absorbs engine heat. Coolant was being pushed out of the reservoir because it was too full initially. And it would be boiling because instead of being pressurized at 14 or 16 PSI, the coolant was now exposed to atmospheric pressure. Spontaneous vaporization (or boiling, if you prefer).

I see where head gaskets are a common problem but I'm sure hoping that isn't the answer

I will challenge that notion. And that requires a definition of terms.

Do the combustion byproducts test recommended by BBF to answer the question as far as your engine is concerned.

th_Smallertempguagewithnumbers.jpg

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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I'll 3rd the test. Get a block test kit from Napa or rent one from an auto parts store and test the air in the surge tank. Either condemn or rule out the head gaskets before you go one a wild goose chase.

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I agree with checking the air line. Mine would get hot and cool down but could idle all day and never budge off the half mark the higher the rpms the faster it would heat up. Then it started losing all its coolant in 5 miles but could never find any coolant leaking. I checked the line returning to reservior and it was plugged, I took it off found no restrictions then pulled the hollow bolt it connects to. It had a pin hole opening. cleaned it and everything is fine. I was told the retricted opening was causing to much pressure to the resevior tank and causing the cap to release pressure, letting all the coolant out the overflow tube thats why I could not find any coolant leaking.

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I agree with checking the air line. Mine would get hot and cool down but could idle all day and never budge off the half mark the higher the rpms the faster it would heat up. Then it started losing all its coolant in 5 miles but could never find any coolant leaking. I checked the line returning to reservior and it was plugged, I took it off found no restrictions then pulled the hollow bolt it connects to. It had a pin hole opening. cleaned it and everything is fine. I was told the retricted opening was causing to much pressure to the resevior tank and causing the cap to release pressure, letting all the coolant out the overflow tube thats why I could not find any coolant leaking.

You are correct for the wrong reason, you said,

I was told the retricted opening was causing to much pressure to the resevior tank and causing the cap to release pressure, letting all the coolant out the overflow tube thats why I could not find any coolant leaking

A clogged purge line does not 'cause too much pressure in the coolant tank, it stops AIR from getting out of the system. With AIR in the system the water pump cavitates and circulates coolant poorly if not at all

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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First off, NEVER EVER put staight water into a cooling system, it boils at a lower temp. You might have boiled over because it was water

Normally I would not but I was on the side of the road and H2O was all I had at the time

I intended to do a complete drain and refill after I was sure all my problems were fixed

There is an AIR PURGE line that must flow freely, it is at the top of the coolant tank, not the overflow hose the other 3/8" hose at the top of the tank. While the engine is COOL, gently pull the hose off, start the engine, and let it IDLE, go look at the purge line it should stream coolant out in a steady stream, shut engine off.... If no steady stream its clogged and AIR can not get out

Thanks

I checked this and there was a steady stream about 1/2 - 2/3 the diameter of a pencil

Then pressure test your cooling system

Then have the coolant tested for combustion by products to see if a head gasket has been breached

Looks like these will be next....

Looking ahead for the worst ('Cause I just feel sooooo lucky )

Can anyone advise if you are able to replace the gaskets with the engine in the car or do I need to pull it?

It looks like space will be very tight on the back head against the firewall

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....the temp guage normally stays at the 12:00 position. But occasionally it would creep over to around 1:00 or so when driving in town, sitting at a red light ect. but would return to normal when you were moving again.

It might help to refer to temperatures rather than analog clock faces. See photo.

Sorry

You lost me here...

My temp gauge does give me a read out in degrees

What am I missing?

th_Smallertempguagewithnumbers.jpg

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It's more like what am I missing?

If we are both discussing a non-modified 1999 Seville, your temperature gauge does not give you a "read out" in degrees. And if your temperature gauge did show you coolant temperature in degrees, why did you convert that information to an anolog clock face?

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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The engine must be pulled from the top or the carriage lowered. But even worse than that, the block MUST be either timeserted or studded, as the cause of the head gasket failure is the bolts pulling out of the block

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

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....as the cause of the head gasket failure is the bolts pulling out of the block

Mike:

You and I have to schedule a two or three hour lunch meeting.

I disagree with your "bolts pulling out of the block"

as the cause of a head gasket failure.

To the original poster, please excuse my taking this thread a little off-topic.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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[

You are correct for the wrong reason, you said,

I was told the retricted opening was causing to much pressure to the resevior tank and causing the cap to release pressure, letting all the coolant out the overflow tube thats why I could not find any coolant leaking

A clogged purge line does not 'cause too much pressure in the coolant tank, it stops AIR from getting out of the system. With AIR in the system the water pump cavitates and circulates coolant poorly if not at all

It did cause a pressure problem in the resevior tank because if you took the engine to anything above 2000 rpms the coolant would start flowing out the overflow tube and the cap tested out at 15 lbs so pressure was above that.

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I disagree with your "bolts pulling out of the block"

as the cause of a head gasket failure.

To the original poster, please excuse my taking this thread a little off-topic.

Divert away

I'd like to hear (read) your thoughts

It'll be something else to chew on as I get set for what will likely be a weekend full of wrenching, cussing, and knuckle busting! :(

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I agree with having a combustion byproduct test done. I feel the need to emphasize what BBF said about getting your coolant to a proper 50/50 mixture FIRST. Then drive it a bit. If you do the test on fresh coolant, then you are most likely going to get a negative result even if the head gasket(s) are shot because the coolant hasn't been in the car long enough for any combustion gases to build up in it and cause a positive result.

big4870885.jpg

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Good advice Carla, I like your logic.

As to the picture of that gauge, my '99 didn't have the numbers. This must be a Canadian or export model.

Never underestimate the amount of a persons greed.

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[

You are correct for the wrong reason, you said,

I was told the retricted opening was causing to much pressure to the resevior tank and causing the cap to release pressure, letting all the coolant out the overflow tube thats why I could not find any coolant leaking

A clogged purge line does not 'cause too much pressure in the coolant tank, it stops AIR from getting out of the system. With AIR in the system the water pump cavitates and circulates coolant poorly if not at all

It did cause a pressure problem in the resevior tank because if you took the engine to anything above 2000 rpms the coolant would start flowing out the overflow tube and the cap tested out at 15 lbs so pressure was above that.

A clogged purge line causes the water pump to cavitate, and either circulate the coolant poorly or not at all. THAT causes the engine to overheat, overheating causes the coolant to BOIL, boiling causes more pressure, that is released by the cap... so in a way, you are correct, I suppose... But its a domino effect

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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As to the picture of that gauge, my '99 didn't have the numbers. This must be a Canadian or export model.

That picture is the gauge in my domestic '98 Seville.

I added the number ranges on the picture according to the temperature values retrieved from the OBD connector under the dash.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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....as the cause of the head gasket failure is the bolts pulling out of the block

Mike:

You and I have to schedule a two or three hour lunch meeting.

I disagree with your "bolts pulling out of the block"

as the cause of a head gasket failure.

To the original poster, please excuse my taking this thread a little off-topic.

I'd love to hear your reasoning, please elaborate Jim. I know the coolant gets acidic, rots or corrodes the bolt threads, then the bolts pull, but from what I understand the bolts pull, either from corroded threads or aluminum that gets soft from heat and the bolts pull the threads out.. That is my understanding

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'd love to hear your reasoning, please elaborate Jim. I know the coolant gets acidic....

Number one:

DexCool is acidic right out of the container from Prestone or Texaco or whomever. The corrosion inhibitor chemical additive in DexCool is acidic by design. The following is from the Chevron Texaco web pages;

Havoline Extended Life Anti-Freeze/Coolant DEX-COOL is a universal

engine coolant that incorporates patented organic acid corrosion

inhibitor technology. This coolant meets both ASTM D 3306 for

automotive service and ASTM D 4985 for heavy-duty diesel service. It

is a nitrite-, nitrate-, phosphate-, silicate-, borate and

amine-free formulation which uses Texaco’s patented carboxylate

technology to provide maximum protection of the six basic metal

alloys found in most heat transfer systems. Since the coolant

contains no phosphates or silicates, hard water deposits in the

cooling system are almost eliminated. The low level of abrasive

dissolved solids in Havoline Extended Life Anti-Freeze/Coolant

DEX-COOL results in improved water pump seal life.

Number two:

The head bolts and the bolt hole threads in the block are intended to be "dry". The head gasket design prevents coolant from coming in contact with the bolts or bolt hole threads.

We all realize there is a galvanic reaction between ferrous bolt threads and an aluminum threaded hole in aluminum. That reaction can be controlled by the factory coating on OEM head bolts.

If and when the head gasket fails to seal the bolts and block threads from coolant is the beginning of a spiral toward block bolt hole thread failure.

The (acidic) coolant acts as an electrolyte at the ferrous bolt to aluminum block thread contact points and the galvanic reaction quickly gets out of control resulting in failed bolt hole threads.

This is not my reasoning. This comes from reading between the lines of all the cooling system posts that I saved from (you know who).

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Ahh but the bottom line is, the bolts pull out of the block.

The guru thought it was from corrosion, my discussions with the timesert people disclosed it was from heat which softens already soft aluminum causing a bolt pull. As we note, most of the time the rear head gaskets go first, due to the heat by the firewall.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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You are ducking under ths issue of the head bolt threads being the cause of gasket failure with your "bottom line" position.

We are not likely to see a metallurgical engineer's report on the question, but that is what would provide the definitive answer.

If the Northstar was an air cooled engine, I might give the rear bank gasket failure theory some serious consideration. Otherwise, it's a coin toss. Using a 1909 penny!

As it is, I agree that we disagree. :)

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Oh I see what you are getting at, but from whatever the cause, the bolts pull from the block, that is what I see, but something caused the bolts to pull. The problem is, that does not make it much better for me, the bottom line is, the bolts pulled and I just junked a 96 Deville, if it was from me driving too hard, soft aluminum or acidic Dexcool, it doesnt matter. The fact is I have recorded every coolant change since about 35000 on my Deville and no coolant change went longer than 25000 makes me wonder what caused the bolt failure. I no longer subscribe to acidic Dexcool as the sole cause

The reason I always make that the bolts pull clear is because, I dont want anyone to think you pull a head, replace the head gasket and torque the bolts back down again. Timeserting or studding is necessary as the threads are compromised. Furthermore, its not the head gasket itself that causes the problem, so sealant will not work as many have tried as the head moves from combustion.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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This is the old chicken or the egg question. Have you guys seen AJ's "root cause" sticky at CF? personally I am leaning more towards metallurgy and the threads pulling as the initial cause.

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