[2KEldo]

I am holding my breath while my Eldorado is in a service dealership waiting room to be evaluated why it not running cool anymore. I was on my way home after buying a can of R134a refrigerant to hopefully correct the condition sometimes when cool AC air goes into the passenger side vents but not the drivers side when I noticed my temp gauge started shooting past the normal range. I wasn't even 1/2 mile away from pulling out when I was forced to pull into a parking lot as it got very close to the red zone. I popped my hood and discovered that my lower radiator hose had pulled away from the radiator neck and emptied my system of coolant. I went back and bought more, topped it off, drove it over numerous short distances and waiting to cool to add more coolant until it finally wouldn't take anymore, it still will not run at the proper temp. My heater temp and blower are both set to high but I only get cold air from the defroster. With 95000 miles I am worried it might the dreaded underrated head bolt scenario forcing me into a cataclysmic repair by rethreading the block for the larger head bolts. By the way, this same dealership flushed my coolant system just two weeks ago so hopefully its something they can correct and will hold under some means of warranty.
After saying all that I am going back to holding my breath, hopefully only until tomorrow morning when they call me with their findings. Fingers crossed...

 

[Submariner409]

The reason the heater is blowing cool air is that the circuit is airbound - as well as other low-flow parts of the cooling system. There's probably nothing wrong with the head gaskets and the loss of coolant overheat did no damage to the engine.

Get the cooling system air-free, check the purge line for steady flow. Maintain the coolant at the correct FULL COLD level as marked on the top and side of the surge tank. If necessary, clean the purge line and its hollow bolt/nipple at the water crossover.

The dealership is to blame - bad hose replacement after the unnecessary "flush". Coolant exchange, yes. Flush, no.

 

[2KEldo]

Thank you Submariner, including the helpful diagram. When I picked up the coolant the counter person asked if I knew how to bleed the air out and I said that I was under the impression that it was a self purging system. He said that I might want to double check the radiator to make sure in case there was a bleeder valve or other area within the system. The offerings on youtube sure didn't show me anything so I figured it was self purging. There was however one video of a guy bleeding the air from a DTS but it was only for about a minute. In it he did not show where the long tube connected from that was draining back into the coolant fill reservoir but the area looked to be about where your diagram would suggest. I will be looking for that Coolant Purge Line Connector Nipple when I get my car back.

Thanks again.

 

[Submariner409]

The Northstar (and many other newer) cooling system IS self-purging. That's the function of the purge line/system - but it's often thwarted by deposits from sealants or old coolant in the bolt/nipple or the line itself.

The heater core is supposed to be full coolant flow at all times - there's no coolant throttle valve. Temp is controlled by mixing cold and hot air.

The Devilles used a long purge line/pipe - from the hollow bolt over to the upper side of the surge tank - which often clogs. (Not sure about the Eldorado setup) If it is hopelessly clogged it can be replaced in its entirety by a single length of correctly sized reinforced rubber fuel line and a couple of band clamps from any parts store. Dirt cheap.

Use a correct sized twist drill to "rod out" the hollow bolt to a depth of 2" or so. Note that bolt/nipple is hardened and is one of the bolts that secures an engine lifting strap - it has a specific torque setting. 35 lb/ft.

2001 Deville surge tank ........

 

[2KEldo]

Submariner,

Again thank you for your response. Just so I have it clear, is the "Coolant Purge Line Connector Nipple actually connects by a hose to where the "Purge Line" is in your photo? Up to now I thought the nipple was simply a place to connect a piece of hose to bleed out the air in the system. But now I see that the line is permanently tied back to the surge tank. (Unless that only applies to the Deville?) I missed seeing that when I was looking at it before I took it to the dealership. Of course, it all makes perfect sense now.

The markings on the surge tank are a little unclear: ENGINE COOLANT, FULLY COLD & ?? I guess my real question is how to tell where the liquid in the tank is if you cant see through the black molded tank? The thin lines that run away from the words would likely be to an area to clarify but I cant see them. I thought that as long as the coolant was midway on that slanted bar feature just below the radiator cap that was where the cold level was supposed to be. When I get my car back I will examine all of this more closely.

Thanks again for your help. I knew I should have come here first before I went to youtube. Next time I will not even think twice about it.

Kind regards.

 

[Submariner409]

Yes, the (all Northstar) purge line is a constant bleed hose/pipe that is connected at all times and is used to remove any air/gases from the cooling system high point in order to assure "solid" coolant to the water pump. The pump is a centrifugal type, so if it "sees" air bubbles then flow stops and overheats occur.

The flat molded arrow on the surge tank goes over and down to the midseam. Check the level, cold (ambient temp cold) using a SWAG (Scientific Wild Ass Guess) - maintain a couple of inches of airspace below the filler neck.

Install a new Stant, DAYCO, or Gates pressure cap.

I posted a picture of the Deville surge tank on the opposite side off the engine compartment from the water crossover.here's a 2002 Seville setup - short purge line.

 

[Submariner409]

Here's your 2002 Eldorado - long purge line - the black rubber/plastic one that runs under the A/C refrigerant line into the top front corner of the tank.

 

[2KEldo]

Yes, that 2002 looks just like what I remember. When I took the car in for the flush the first time, I was told they found a small leak at my water pump and would not be able to flush until it passed the pressure test. I since replaced this including the thermostat, upper and lower radiator hoses. For a week later I had no issues or leaks so I then took it back and they did the coolant flush and replaced with new coolant. That was two weeks ago. Is there a chance that they would have to disconnect the radiator hoes to perform a flush? My guess is that at this point the techs will close in on something that's obstructing the flow at the purge line and the problem will be solved.

Great information Submariner. The photos are a big help. Thank you very much.

 

[Submariner409]

Several hoses were disconnected if they did a thorough flush.

These Northstar cars are now 18 or so years old. Many techs were still in grade school when they were built. Their diagnostics and repairs are done using computer screens and printed directions. NOWHERE will you find reference to purge line clogging in any GM/Cadillac service manual. Most of the current techs do not know that Cadillac discontinued the use of the recommended cooling system sealant tablets back in 2006. All the pre-2006 Northstar radiator sight shield information stickers are wrong - they were never updated.

 

[2KEldo]

Just spoke to the contact at the dealership. The tech is on lunch break so I could only speak to the customer contact. They said that pressure from a blown head gasket was why the lower radiator hose pulled away. I do not understand that but is one of many questions I have. They said that it would require another engine of which they can order one from a yard with 120k miles on it, installed in about a week at the cost of $5660.00. I asked if there was something else in the form of a crate engine and they said no. I then went online to check for rebuilt Northstars and found one for $3399. I could probably add $2k for the labor I guess too.

Before I get ahead of myself, shouldn't the replacement of the head gasket come in significantly less and the more feasible option? I guess I am still very numb over the conversation I just had and was not thinking clear enough to ask. If you could perhaps arm me with some questions and counter questions to the responses I should anticipate when I talk to the tech it would be greatly appreciated.

 

[Submariner409]

"Excess pressure from a blown head gasket" - does that factor in the 18 psi relief in the surge tank cap ? Heh, heh.......

The dealership has absolutely NO idea of what they're talking about.

If the spirit moves you, ask the tech whether they use TimeSerts, BigSerts, or studs for cylinder block head bolt hole thread repair - it's not the head gaskets - it's the cylinder block bolt hole failures = loose head bolts = leaking gaskets.

Even to truck it from Waterford to Palatine, IL and have Joe Blau at Midwest Cadillac repair the engine would be less than half of that dealer's estimate .............

Find out if Jake (Northstar Performance - excellent stud work) still has a shop in London, Ontario.

The time and expense comes from opening up the cylinders and drilling/machining the 20 block bolt holes to accept new, beefy thread inserts or studs. Lots of info in the stickies in Engines; Northstar.

Homework - - -

www.northstarperformance.com

www.huhnsolutions.com

 

[bjc789]

While it is possible they are right (all Northstars are suspect, though later ones its less common) I would want to confirm that there are combustion gasses getting into the coolant before I went down that road. So do a “block test” as described on here many times.

 

[2KEldo]

Thank you. bjc789. I have since picked up car and contacted a few local shops regarding the repair based on the tech's "Blown head gasket" analysis. By the time I picked up my car, he had left. Here's the weird part. I live about 4 miles from the dealership and before I brought the car to them, I could only drive 1-1/2 miles before the temp started creeping beyond the normal range. After another mile it would be nearing the red zone. Also, when I dropped it off last Friday, it had begun leaking coolant in the check in bay. When I picked it up yesterday, I drove it straight home without having to pull over for a cool down period. There were no leaks and it never went past the normal range. So yeah, I will be calling to talk with the tech and inquire on how the blown head gasket diagnosis was reached. If nothing else, I want to be able to better isolate the forensic history as best I can when I decide on a shop for the repair. By the way, his report noted that the earlier coolant flush had been hooked up at the Upper radiator hose. He then stated that the lower radiator hose clamp was not tight and that the petcock drain was slightly open. I suppose that could have been possible as I used the screw type. I never was able to find that petcock drain when I replaced the pump, thermostat and hoses. I drained all of my coolant by collecting it in a large clean plastic garbage bag routed from the upper hose connection at the thermostat thus not having to worry about it being contaminated.

Submariner, Thank you too for the links. I did find the website for the Ontario shop as well as the thread repair kit. I spoke to some local shops and 1/2 had extensive experienced repairing the Northstar engines with the head bolt history of which is suspect but not confirmed. Northstar Performance clearly are specialists and I will be reaching out to them. I just hope that at the end of the day the costs of transporting will not inflate my budget beyond reach.

I will update as soon as I have something new. I cannot thank this forums support enough.

Kind regards, 2KEldo

 

[Ranger]

Here's the weird part. I live about 4 miles from the dealership and before I brought the car to them, I could only drive 1-1/2 miles before the temp started creeping beyond the normal range. After another mile it would be nearing the red zone. Also, when I dropped it off last Friday, it had begun leaking coolant in the check in bay. When I picked it up yesterday, I drove it straight home without having to pull over for a cool down period. There were no leaks and it never went past the normal range.

Consider the possibility that someone forgot to tighten the hose clamp on the radiator. THAT would be enough to allow the cooling system pressure to blow the hose off. As Sub has eluded to, even with the excessive pressure added by a failed HG, the pressures should NEVER exceed the cap pressure (16-18 psi) and rest the cooling system is designed to handle pressure far exceeding that.

If you seem to be running normal now, sit back and take a deep breath and see what happens. Your problem may have been a simple mistake, that was either covered up or not noticed, thus the "need" for a HG job or replacement engine, or it was discovered and fixed (either knowingly or unknowingly) at the last shop visit. Bottom line is drive it and see if the problem reoccurs BEFORE throwing any more money at it.

 

[2KEldo]

Thanks Ranger. That is about where my head is at too. Feeling better for now. I know I need to put it through a normal run when I get off work today and check where any potential strike zone is. If's is still problematic, I need to get an appointment at a place ASAP as the backlogs at the places I called on yesterday are at about 3 weeks just to start on it. I am using my wifes 2014 Impala for now but when she gets back to work in a month (Shes on workman's comp recovering from a broken arm) she will need her car back. Last night I didn't have the time to drive it around due to commitments already planned for the evening. Still waiting to hear back on what method the tech used to diagnose as a blown head gasket. One more question, though I didn't share the entire report from the tech, he also stated in it : "...ran car to operating temp. Hose was super hard, checked temp it was a little above normal. Started to back out and temp climbed. Car has blown head gasket causing over heat condition. ..."

Still no word back from Northstar Performance at this time.

2KEldo

 

[Ranger]

One more question, though I didn't share the entire report from the tech, he also stated in it : "...ran car to operating temp. Hose was super hard, checked temp it was a little above normal. Started to back out and temp climbed. Car has blown head gasket causing over heat condition. ..."

Hmm, that does not sound good, BUT based on that hose problem, I'd still drive it and let the car prove that it is still overheating. A block test would be the decisive HG test. I guess they just figured that they had enough evidence to preclude doing it.

 

[2KEldo]

Sorry so late getting back to this with updates. Am buried in training at work all this week and minimal time at home. Got 3 hours sleep last night. Ugh...

Dealer tech confirmed that a block test was conducted which showed exhaust gases in coolant. Was decided to stop any further evaluation and diagnosis after that. I did drive the car around for about 20 minutes and it never got above the normal temp zone. After that I went to my local auto-parts store and rented the OEM Engine Block Test kit but the car was too hot for me to open the radiator cap after driving around. I plan on doing this after work today but am uncomfortable removing some of the coolant from the surge tank considering all that has happened for fear I may get air back into the system but I need to see it for piece of mind. I also will be testing my wife's 2014 impala while I have it. It has 107k miles on it and am curious on the condition.

Finally, after considering the costs of repairing the Eldorado I have been looking at a few DTS models starting in the 2006 year. For another $1500 over the head repair I can get into a 2006 or 2008 with less than 75k miles. The NorthStar head issue has long since been resolved by then but am also going to study up on what models Cadillac offer in a 6 cylinder for that would ease my fuel costs driving to work. Also no word back from Northstar Performance yet. Looks like I am now on the fence anyway about what I am going to do...

 

[Submariner409]

Remove coolant ? The surge tank should be about 1/2 full cold (ambient) and about 3/4 full hot. Let it cool until the upper radiator hose is squishy.

You sample the airspace - not the coolant - if any coolant gets into the test tube you wash it all with fresh water and start over.

 

[2KEldo]

I did the block test last evening. Attached is a photo of what I ended up after warming the car per the instructions. When the car was cold before I started, my coolant was about 1/2 full in my surge tank. As it warmed it rose to about 3/4 full. When it got to the normal temp I started the test. But a minute into the test it sucked a little coolant so I shut the car off, cleaned the tester and started again. This time I noticed that the coolant would rise and fall very close to the top (Is this normal??) so I bailed out coolant (about 1-1/2 cups) from the surge tank until it was not going over. I did the test again and after about 5 minutes squeezing the ball pump I had to stop as the fluid was continuing to rise and boil over the top. The photo represents the results I had at this point and the liquid did not change color at all. But during the test and to keep from contaminating the fluid with coolant I had to constantly pull the tester out and wait for the fluid drop down again. It would almost immediately drop down when I pulled the tester out at which time I would put it back on and squeeze it some more.
Maybe this was not the correct way to test for this and the idea is to keep the tester in place throughout the test. Whatever the case I had to stop because the car began to over heat. See temp gauge photo. Today when I get home I will return the coolant and start the car again to see if it over heats. But before I do that, I will be checking the purge line to confirm that its not obstructed.

 

[Submariner409]

The tester fluid is still clear blue - No exhaust gas in the coolant. The temp gauge is at the fans to FAST temp - 236 degrees. Warm, but not overheating. Do the fans run in SLOW ?

Overheat occurs above 260 degrees.

Your coolant rise/fall sounds suspiciously like a clogged purge line.

The bubble test takes about 30 seconds - DO NOT try to make it better with excessively long bubble times. When all else fails, read the directions.

Here's a Seville temp gauge - the tick marks are the same temps as your slightly smaller sweep gauge. All these engines use the same coolant temp sender.