What a strange day today was. A little background first; about a month ago, mid-November, I got a "Check Coolant Level" message on my dash. So I checked, and it looked like the reservoir was nearly empty, so I bought some Prestone Gold Pre-Mixed and poured about a quarter of the bottle in, until the coolant level was at the crossmember inside the tank. Everything was copacetic until about two weeks ago, when the message came back. This time I did not fill - I kept an eye on the temp gauge and drove as normal.
Now, being nobody's fool, I had been paying attention to my car since that first message. I noticed a rough idle on cold mornings (sub 30degF, mostly) - it's hard to explain what it felt like, but the tach needle would jump a hair every so often when stopped in Drive, and the car would give an ever-so-slight jerk forwards. If I held my foot on the gas a little, the idle smoothed right out and the jerkiness left. During this whole time, the temperature gauge acted completely normal - no spikes in temp and it never got above 223 degF (I hacked the DIC to give me a digital coolant temp display last year). I also did not notice any excess of white smoke in the exhaust, but I honestly have no idea how much to expect from a N* in wintertime; comparing it to cars around me on the road, it's not any more or any less than the vast majority (including other Caddys). I also have no idea how to tell if the exhaust smells like coolant - exhaust smells like exhaust to me, so short of a side-by-side comparison, I was stymied.
This morning I took the car to Heritage Cadillac in Lombard to have a combustion byproduct and cooling system pressure test done on the Eldorado. The cooling system pressure test came back negative, although the technician said his kit detected "trace, small" (exact words) of CO in the coolant, which was also low. He then told me he found the leak - a hose coming off the interior side of the reservoir had a loose metal clamp, which he then tightened. Sure enough, there was coolant (or something moist) underneath the tank on the interior chassis of the car and some of the components (not electrical) directly under the hose. So, fine, and since it was there, I also had him clean the throttlebody out, and he came back and said there had been a decent amount of gunk in there, coupla years worth at least. The mechanic suggested that I take the car back out, drive it around for a few days, and return if the coolant message came back or something else went awry.
After about 45 minutes of regular driving (some decent passing and one onramp push - nothing extreme like a WOT though) and no coolant message or temp spikes (the car was already warm so I didn't expect - or detect - any rough idling), I parked at Dominoes in Naperville and got a sandwich for lunch. Just as I was about to shut the car off, I got the "Check Coolant Level" message. I turned the car off and gave it a walkaround, and sure enough there was dripping underneath the engine compartment, right where the reservoir is located. Cracked open the hood, and yup, there's coolant dripping from the same damn hose again - and it's not just dripping, it's running like faucet got kicked on real low! That damned technician must have missed something. Also, Yikes!, that had never happened before - never saw any kind of steady drizzle from under my car except when it comes out of the carwash, and never noticed any coolant puddles like the one that was now encircling my shoes.
I get in the car again and set out to the dealership once more, after calling to let them know the situation. I made it about three quarters of the way there - in stop and go traffic, I watched with horror as the digital temp readout climbed steadily from 190 to 240. When it hit 242, I pulled of the road and shut the car down in a parking lot. I got out, opened the hood (after putting on safety goggles because I'm not sure what to expect), and saw what looked like a coolant lake under the car, steadily growing from below the coolant reservoir. The inside of the engine compartment near the leak is sprayed with coolant as well, and the shit is getting all over my shoes. I call Heritage again, and explain that I am two miles away and my coolant is jettisoning with gusto all over my shoes. He says to let the car cool for 15 minutes and then hurry over. I wait until the temp readout says 180, then open the reservoir fill cap: empty, no surprises there. As I pour in coolant, it drains right out almost as fast.
With the traffic on Finley Ave. starting to clear, I decide it's now or never. I hop in, start her up, and take off down the road. I'm trying to coast as much as possible, giving her a gentle kick at the top of the small inclines and using momentum as much as possible. I'm racing against the needle and winning, but barely. I pull into Heritage and shut the car down - the last reading was 250 degF - and immediately open the hood. The coolant is still dripping out, though most was lost en route. I know the N* has a limp-home mode, but fortunately the needle never got into the red zone on the gauge, and it didn't activate. The car also did not get hot enough to reset the oil-life indicator, though twenty more seconds of operation and the ballgame ends differently, I'm sure.
Anyway, they get her into the shop and start fussing over the coolant reservoir. The tech comes back with the reservoir in hand, and points to a small opening (nipple, I suppose) on the outside of the tank, where the formerly loose hose had once been attached. The entire nipple assembly (giggedy) was cracked open, and parts of it looked like crumbled, cracking rubber - perhaps the hose was beginning to melt as well? Anyway, they replaced the entire tank, gave me a new hose and new coolant free of charge, and I also opted for an oil change (the monitor was below 30%, and the last one was over 4500 miles behind me). And though I am perfectly capable of changing my own oil, I hate working on machines when it's cold outside, be they cars or lawnmowers. I can make an exception for snow-blowers.
In conclusion, I want some impressions. The car is running fine again - drove another two hours in stop-n-go traffic (with a few hard passes) with no temp spikes, no temps higher than 223, and no visible coolant loss or warning messages. First, how likely is it that the positive result from the combustion byproducts test was faulty? The car runs perfectly fine, and when the technician changed my oil, he detected no coolant contamination (another reason I had them do it now - all I know about contaminated oil is that it's supposed to look like a milkshake, but are we talking a McD's crapola or a Wendy's Frostie? These things I don't know.). Until today, when the reservoir failed and the coolant was jettisoned, the car has never even approached overheating - not on WOT, not on daily driving, not on long highway trips, and all of these are recent history. Even when the coolant level was low (producing a warning message on the dash), the temperatures never spiked or anything. The car did run an average of 4 or 5 degF hotter when the coolant level was demonstrably low (like after having the message come up a few days in a row), but I assume that could be normal since the cooling system was trying to do it's job with less available coolant as a heat sink. Hell, even when I was losing coolant rapidly today, the temp never really "spiked" - it would climb steadily, but never rapidly, usually 3 or 4 degrees per 90 seconds of driving with the catastrophically failing reservoir.
Second, why did they make the frappin' reservoir black? How the Hell am I supposed to see in there?
Third, are there any other indicators of a failing headgasket aside from the ones I've noted so far? The only symptoms I've had are loss of coolant and rough idle on cold mornings. I'd like to think it was a slowly failing coolant reservoir (with an apparently not-unheard-of problem with the nipple junction [giggedy]) and a dirty throttlebody. I'll know more tomorrow morning when I start her up again to check the idling conditions after a cold soak courtesy of Ma Nature. No temperature issues at all, despite the full range of driving, WOTs and stop-n-go traffic aplenty. These could be explained by a leaky reservoir and a dirty throttlebody, right? The only sticky wicket is the positive result on the combustion byproduct test, and the tech called the amount of gasses detected "small, trace amounts" and mentioned only carbon monoxide by name. How likely is it that this is a false positive and can be dismissed for now?
Any help, advice, or commentary is appreciated.
PS - I spoke to Brad at Wick Automotive in Rockford, IL, this morning while waiting on my first visit to Heritage Cadillac. He seemed skeptical that it could be the HGs, and said the Check Engine (SES) light should come on if this was the case. This was repeated by the technician at the dealership. Anyway, Wick Auto is the only shop in IL listed on NorthstarPerformance.com, Jake's website, as having been certified in using the Suregrip stud kits he manufactures. Has anyone ever used Wick Auto on this forum, and if so, could you share the experience?