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2000 ETC
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46 Posts
Discussion Starter #21
Thank you Submariner, I don't have the instructions in front of me but I recall them stating to test for 2 minutes but will confirm later. The only reason I went 5 was because I kept having to remove the tester to avoid contaminating due to the coolants continuous rising and falling.

I wish I had noted the fans. I didn't even think about that but will make sure they are operating as you stated.

Regarding the purge line, should I simply remove without the engine not running and confirm they are clear and reinstall? If there a chance the nipple is obstructed, can I probe with a thin punch or similar tool to clear or should I attach a hose diverted to a can and start the engine to confirm its open?
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
With the engine idling in P (even cold), the purge line should flow a small, steady stream into the surge tank, increasing flow slightly as rpm is increased a bit. Carefully remove the surge tank end of the line and hold it in the open tank filler neck. DO NOT unduly twist or bend the surge tank plastic nipple.

(In your Eldorado there may not be enough slack in the rubber purge line at the tank - in that case simply use a quart can or bottle. You're not pumping a river here - a healthy trickle.)

If you have no flow or only slight burbly spits then it's time to clean the entire line out as well as use a twist drill in the hollow bolt/nipple to clean it to a depth of 2.5" or so - don't "drill" it - clean it out.

See Post #2.

See Post #20 for your fan sequencing.
 

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2000 ETC
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46 Posts
Discussion Starter #23
No more overheat issues. Thanks a million to all who shared. I traced the purge line as suggested from Submariner in his first response from the surge tank back to the purge nipple where I discovered the nipple was completely blocked. I worked the orange gunk out with very small drill bits until it was 100% clear, put it all back together and the engines heating system ran perfectly again. The fans are operating just as you stated too submariner. After a nearly 10 mile long test drive that included high speeds and heavy slowed traffic I pulled it back into the driveway. I do not know how much money owners have saved over the years with this website but this one alone saved me $5660.00 had I gone that route. At the very least, it saved me from running the car through a local auto heating and AC shop.

Thanks for everything 🍻
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
Thanks for the feedback and the pictures. A perfect example of what Northstar members have been finding over the years. Mainly due to over-use of system sealers and of the long-discontinued GM/Cadillac recommended cooling system sealant tablets. Google "bar's leaks tablets hdc".

A clogged purge line leads to air locks in some small coolant passages as well as in the heater core. After a few days of normal driving, check the cold coolant level again and adjust. Do it again in a week or so. From then on out the coolant level should not change by one drop over a year or so.
 

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2000 ETC
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46 Posts
Discussion Starter #25
Update.

I contacted the service department representative I was working with at the dealership regarding this (left a voice message) and asked if they would consider giving my money back for the misleading diagnosis I received. The service manager called me back within a few hours and apologized for what happened and wanted to refund my money. He was curious how I came up with a conflicting block test result compared to the technician and how I did it, obviously to hear if I had done it properly. He was surprised to learn that a little purge line was to blame however he is not a technician. I offered to come by and introduce myself when I come in for an oil change next time and share the pictures I took. I wanted to share how I had support from this forum but was not sure if that was something that would be ok with the powers that be here on the boards. Truth is, all who chimed in to help me deserved all the credit. All I did was try to keep the details straight as I got them.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
You're in an open, worldwide, public forum. Advice and diagnosis is the product of individual thought and experience and you're free to share it with anyone - as long as it's offered free and clear with no expectation of gain, profit, or liability.

Remarkable that the dealership will eat some of your expense. Show them the pictures and other stuff - maybe a tech will be able to enrich HIS database.
 

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2000 ETC
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46 Posts
Discussion Starter #27
Thanks Submariner.

They are giving me back all of my money. I paid $110.00 for them to diagnosis and quote for repairs as needed. I didn't expect to see dime one as they did invest their labor time to do it and that took away from another paying repair. I consider myself very lucky too. They did not have to do it. Naturally, I am very grateful.
 

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Super Moderator
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86,087 Posts
Imagine that, a Cadillac "tech" not knowing to check for a clogged purge line first, when diagnosing an overheat problem on a Northstar. Part of the problem is that many people (as well as "techs") automatically assume that an overheating Northstar has bad HG's. While that may be true most of the time, it pays to do your homework. At least they are honest enough to refund your money. That's the least they could do the costly mistake they almost caused. Can't help but wonder how many cars went to the crusher or had needless costly repairs because of this.
 

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2002 ETC
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30 Posts
To add to this thread, a couple of months ago while out with my hubby we stopped for some gas. There was a beautiful 02 Deville in front of us with the hood up. While hubby filled up I jumped up to take a look. A very nice older gentleman was scratching his head looking at the motor. I asked him what the problem was, telling him I own a Cadillac of the same vintage. He owned the car since new and always had it regularly serviced where he bought it. It was overheating within 10 minutes of driving into the red with the stop the car overheat message on the DIC.The dealer had replaced EVERYTHING in the cooling system, waterpump, surge tank, hoses, rad you name it. They couldn't figure it out and told him blown head gaskets. He loved the car saying his wife had a bad back and they couldn't find anything as comfortable to replace it with. I asked him if they checked the purge line. He didn't know what I was talking about. Hubby had his tool kit with him and long story short it had a big chunk of orange gunk on the hollow bolt. He cleaned it out and put it back together. We started it up and had a nice chat. Took a look about 10 minutes later and it wasn't overheating. I gave him my number and told him to give me a call and tell me how it went. A week later he called and said it hadn't overheated and was maintaining temperature. He was thrilled. He went over his bill and the dealer had put in those tablets after all that work! Did they know about those tablets or the purge line? Your guess is as good as mine.
 

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Super Moderator
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86,087 Posts
Pretty sure GM issued a TSB a LONG time ago (somewhere around '02 or '03) advising dealers to quit using the sealant tabs as regular maintenance.
 

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2002 ETC
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30 Posts
Right. But you would think there would be some knowledge of that purge line and possible overheating. I mean, I know they haven't been making Northstar Cadillacs for a while now and 02-03 is ions ago in model years but still.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
Dealerships are very close to the cuff when it comes to talking about TSBs. MOST Northstar owners that come here have never heard of 95% of the later series bulletins issued for their cars - the purge line thing is one problem, the discontinued use of the sealant tablets in another, the loose steering rack bolts is another, the correct Northstar oil level is another, and the list goes on.

Other fixit forums, even BITOG, are filled with hearsay, incorrect info, magic potions, spammed "performance modifications", and just plain dangerous advice. At least CF has a long history of good advice. But we need a continuing influx of good wrenchers, drivers, and tuners to continue the tradition.
 

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2000 ETC
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46 Posts
Discussion Starter #33
Per Rangers comment...

"...Imagine that, a Cadillac "tech" not knowing to check for a clogged purge line first, when diagnosing an overheat problem on a Northstar. ..."

I need to make mention that, well, for what its all worth, I took my Eldorado to my local Chevrolet dealership who was only about 4 miles away versus the nearest Cadillac location at about 16 miles. I reasoned that considering the situation (An overheating engine) and the fact that I didn't want to subject the engine to any more overheating time as possible, it would have been ok to take it to them instead. Sorry if I misrepresented that somewhere. Had I known my cars situation was deeper that meets the eye I absolutely would have had it towed to the further distance.

Just felt I needed to clear that part up.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
Makes no difference for that diagnosis - many different vehicles - my 2014 Explorer included - use sealed surge tanks and purge lines as part of the newer no-vapor-loss cooling systems. Our 2004 F-150 4X4 V8 does, also.

Older, unsealed systems with coolant expansion tanks vented off coolant vapor to the atmosphere, thus the "green" sealed systems. Yes, they all develop leaks and weeps over time - we're talking "green" on the showroom floor to satisfy snowflakes.
 

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2000 ETC
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46 Posts
Discussion Starter #35
Well its been nearly a week and the car was running like its old self until on the drive home from work today. Got about 11 miles into my commute when I noticed the temp gauge flirting at about 12:30 (about 220 degrees?) and then slipping back to normal. It normally is just slightly to the right of 12. It continued this for the remainder of the drive or 11 more miles. After a 2 hour cool down I removed the radiator cap and seen the level at 3/4 full. After that I went straight to the purge nipple and it flows freely from static pressure without the engine on. I will keep an eye on this for the next few days.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
Cross your fingers - maybe just burping out the last of small air pockets.

During the commute - did the temp gauge variation occur on the open road at speed or did it occur during stop & go traffic conditions? Was the HVAC set to some A/C function (fans in SLOW at all times) or was it OFF (fans controlled by the ECT/PCM)?
 

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2000 ETC
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46 Posts
Discussion Starter #37
It didn't seem to matter that I was driving at posted speeds. I was expecting the temp to rise at the red lights but it didn't seem to care and just stayed within the same area. I had my AC on recirc blowing high as it was nearly 90 outside.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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66,321 Posts
In a correctly functioning Northstar cooling system if the HVAC is set to some A/C compressor function the fans run in SLOW all the time. Under those circumstances the temp gauge should stay at or near the 12 o'clock tick mark.

Post #20
 

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2000 ETC
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46 Posts
Discussion Starter #39
Thank you Submariner409. Today I did not drive it to work because I couldn't risk being late or worse yet, missing 2 scheduled doc appointments my wife has this afternoon. (She is not cleared to drive yet) But I will be driving it the rest of the week after today. I will pay close attention to the fan speed as I get to my destinations where I can listen while in parking lot.
 

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1997 SLS
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28 Posts
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.

View attachment 571501
Sorry to interrupt this thread, but I wanted to thank you for this graphic. My 1997 SLS runs in the green-dot-marked areas, either just a centimeter over 12-o'clock, or at the third green dot shown above (it moves back and forth, I think, depending on whether or not I'm idling). I've always been fearful that it's running hot. I've always believed, perhaps erroneously in hindsight, that anything over 12-o'clock was "running hot", that normal temperatures should be just below 12-o'clock.

I'm considering taking a quick drive and taking some pictures to post in a new thread. This issue has kept me awake since I got the car in February. The water pump has been replaced (2017, I believe), and it's been flushed twice in the past year or two (I was just looking at my records on Carfax....curse my short memory!). Perhaps I too have a clogged line?

(EDIT: coolant and antifreeze was flushed in February of this year, as was the water pump replaced as well).

Thanks again for the photo. No joke: the heat gauge has really bothered me for a while now; especially with the head-gasket issues, combined with the water pump being replaced and the coolant flushes.. I've always thought it was running hot. Am I wrong?
 
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