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Project thread: 1979 Coupe DeVille Phaeton (a thread 7 years in the making... kinda)

22K views 115 replies 26 participants last post by  guyrobert 
#1 ·
Welcome!

So, I decided it would be a good idea to start an official, consolidated "project thread" for my Phaeton. Until now I had just started separate threads, or posted bits in the picture threads. The only problem with doing that, is that you'd end up with entire threads for simple questions, and all of the smaller details & triumphs slipping through the cracks. I'm thinking of wrangling all the old threads I can find that are relevant, & posting links here, thus keeping everything together except special concerns / slightly unrelated content. I'm going to do a quick summary of my history with the car, then probably do featured posts with greater detail about specific old & new subjects as time goes by. I'm hoping this will be a thread with lots of useful information about the sleek modern classic 1977-79 425 Cadillacs that are still favorites for so many of us.

...You might want to make a drink & get comfortable, we may be here a while.

Personal History:
Before watching the movie 'Goodfellas', I had no idea what a Phaeton was. When I first saw it, I just thought "oh hey, someone put a full cloth top on a '79 Coupe DeVille... that looks kinda badass!" A couple months later I was looking around online & stumbled upon a description of what the Phaeton was. Right then, I knew I wanted to find one. I started looking officially in 2005, but most of the ones I found were white with the blue top (apparently referred to as the "Nautical look"), and I was already set on 'Western Saddle Firemist'.

So naturally, when my friend Chad found this one on eBay, I jumped on it. The downside was a well traveled 216,000 miles on the original engine and rebuilt trans, and that the car was in California... while I'm in Tennessee. But who has time for such trivial details? So... another $1000 in shipping later, on June 7th 2006, I took delivery of my new iron muse. I also have to thank our very own Craig (77CDV) for driving up and inspecting the car in Ventura, CA before it was delivered, and taking more pictures for me. A computer crash ate the pics from him, but I still have the eBay pictures.
(eBay pictures)








Love at first sight






So there it was! Unfortunately, the seller didn't mention to me that the battery was dead, alternator belt not included, and alternator itself on life support... I was just sad I didn't get to drive it home yet. One pensive night later, I had it towed to a shop two blocks down. Shop replaced the missing belt, put on an Interstate battery, replaced a sketchy freeze plug, repacked a front wheel bearing; and on June 8th, 2006, I drove home deliriously happy with my new time-machine. The fact that the seat was stuck 8 inches too far back, and that I had to keep my foot slightly on the throttle at all times to stay running had no apparent effect on me. You'd think I was driving a Ferrari by the look on my face. Details were trivial, I was still too busy cranking Frank Sinatra through the 8-track & marveling over guide-matic headlamps.




My Phaeton came with it's original dealer invoice (From Hillcrest Motors, Beverly Hills, CA.) with a note scribbled about the custom "Classic Cadillac" grille and it's price of $1250 (I'll never understand the appeal, so I replaced it with an original version & sold the Rolls knockoff on eBay). Even the original owners manual was there, with a note about "Only 2,400 Phaeton Coupes" above A Cadillac customer-service number, with the name "Chuck". There was also a fascinating chromed, extendable, cross-car, hook-to-hook clothes hanger (There's a good idea... just block the rear view completely with a nice wall of leisure suits... Safety first!); One set of dark brown velour seat covers, probably left from before the seats were recovered in 1998; and a cheap cloth car cover, among other things. The California plates that were on it dated back to 1989. I've often wondered what the original plates might have been & where they went (vanity plates perhaps?). I was very lucky that it still actually has the original plate frame from the factory, as mentioned on the invoice. The grippy steering wheel cover & tan super-store floor mats were the first things to go...




Annual summary:
2006: Carb rebuilt (twice... Horribly, by a very bad, BAD mechanic); new power steering pump; replaced a weak freeze plug; first set of spark plugs, dist cap; front brake pads; first new starter; misc other.

At cruise-in, the first week I had it.


________
2007: Original alternator rebuilt; New 215-75-R15 Dimension IV 1.3" whitewall tires; Urethane clear coat paint job & bodywork; replaced dealer-installed grille with a stock one; headlight short fixed;
A.I.R pump replaced (didn't know at the time that I could just bypass it, or that it came with the California emissions kit); rear springs & shocks replaced with Impala SS springs, and Hijacker air shocks (details in thread); blinker module replaced; installed a set of Lloyds Ultimat floor mats. The cardboard trunk walls were looking a big saggy, so I carpeted them with some of that grey roll up carpet you can get at about any super-store or parts store, and some spray adhesive. Six years later, they are still holding up well.



First & only car show to date.



2008: New fuel pump, 2nd new starter.

2009: Alternator replaced with rebuilt one. (and probably other stuff that I don't remember)

2010: Transmission rebuilt after it decided it was done with all of this 'shifting' business. Unrelated front-end collision & repairs. (details in thread)





2011: New alternator drive belt after the old one shredded & wrapped itself around the fan.

2012: New 120 amp alternator (that makes 3); new starter (...also 3); new battery (2nd one).
New exhaust pipe & muffler; front end alignment & center-link replaced; new spark plugs, more plug wires, cap & rotor; installed rear-window 3rd brake light; coolant flush, correct 195 degree thermostat, replaced heater core & hoses; new windshield-wiper motor (Yet my delay function still doesn't work right).

2013: I replaced the distributor with a re-manufactured 4-pin federal version in order to bypass the Electronic Spark Selection (aka E.S.S) box, which is an annoying CA emissions feature that had WAY to much authority over engine timing advance.
Lots of vacuum hose replacement & routing corrections; new ceramic brake pads, flex hoses, master cylinder & power booster. I replaced the anemic, lean-jetted & generally toasted California carburetor with one from a federal '78 DeVille that I rebuilt specifically for this. Rather proud, it's my first carburetor. But more on that later..

Pictures from around April, 2013.








now, if I don't go ahead and post this, I might never finish! I'm already avoiding the urge to divide this first post into separate chapters, lol. Sorry for the pic spam. Possible sub-topics might include things like shock replacement, front end rebuilding, sway bars, AC work, valve cover gaskets, carburetor rebuilding, federalizing a California Cadillac, & much more. Stick around and ask questions!
 
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#3 ·
Outstanding write-up. I still think of your Denise (sp?) story, too.

Is that a tach or temp guage? Did you install it or was it installed prior to your acquisition? I see you've changed up the hood ornament too (standalone crest vs. wreath-and-crest), what is on it presently? (I know it is not original, yet I like the wreath and crest ornament on the DeVilles.) I sorely miss my '79 Brougham. I'd happily surrender my '92 Brougham d'Elegance to have another '79!
 
#20 ·
Blower motor? Have you checked the relay? That is the only chronic issue I have with my 79 and I keep a stock of the relays since they regularly melt down. :)
Cadillac_Fan: Thanks! What you see under the ashtray is a temp gauge. It was installed when I bought the car. Power to the light + ground is split off of the ashtray light. Power is supplied by a wire running to the fuse panel. It stopped working soon after I bought the car, when investigating, I found that the wire had come unplugged because it was just stuck in next to a fuse. Open question What would be the best way to supply power to the gauge?

It actually caused me a bit of trouble, because whoever installed the gauge put its temp sensor in the hole for the vacuum switch of the heat riser (EFE) valve, and rerouted the vacuum lines so that the heat riser was held SHUT whenever the car was running blocking the exhaust, & creating a hot running condition, as you could imagine. I ended up just bypassing the whole heat riser system.

The hood ornament has indeed switched back & forth, good eye! The Phaeton came with it's original crest, but the plastic was peeling from one corner, and it was badly faded/yellowed. I decided I wanted to replace it with a fancier wreath version, and justified it because I had already put wreaths around the door locks (like the one in Goodfellas had). This was in 2006, and it was on there until Feb '13. Suppose I just got tired of it.. I'd ended up with a couple of new looking crest versions, so I switched it out again.

I actually removed the plastic from the original, and repainted it to go on Denice (she had none of her own). It looked good for a summer or two before it faded out again. Ahh well.

Original



Painted for Denice



NOS wreath & crest from a Brougham




Bro-Ham: Thanks for the reminder on the blower relay! You're probably right. I replaced a couple years ago, but forgot how common it is for them to blow on these cars.
 
#5 ·
Thanks guys! I'll be delighted to answer questions very soon, but for now, I have a pressing "riddle" that I need some ideas on:

I've been having a strange issue... Most of the time, the car has a predictable amount of throttle response, however I've been noticing for quite some time now the following issue:

In the course of a day, if I take the car for a long enough drive to reach & hold full operating temp for a while, then drive home & park it for a while (maybe a few hours), when I go back out for the second drive of the day, the car has a VERY noticeable power increase for a while after startup.

It's as if my throttle input is being amplified, and the car feels extremely responsive & peppy. If I keep driving, this phenomenon slowly goes away within about 5-10 minutes of driving, and I'm left with the performance level that I've come to expect as normal. It's like while the power influx is happening, the engine isn't working nearly as hard to accelerate, and there's a big difference in that "butt-to-the-seat" feeling of propulsion.

Facts:

I don't get any kind of power flux during the 1st trip of the day, ever. It's only after it's been heated up fully, and cooled down to some extent.

This problem has transcended a carburetor swap, and full ignition system replacement. Meaning that unless the carb I rebuilt has the same theoretical problem that I'm somehow overlooking; carb adjustments make no difference in this erratic performance. Choke, linkage & all other variables have been adjusted according to the factory service manual.

The car still wears what I believe to be the original catalytic converter, which makes me wonder about heat sensitive back-pressure fluctuation of some kind?

The engine has 234,000 miles on it, with no known complete rebuild. Could this be some kind of compression issue or other internal disturbance?

I've had a long running off & on battle with detonation. I think I have it solved, but that is to point out that the detonation would also come and go seemingly randomly. However, the pinging always seemed to vanish while the car was having a "power influx"

________

Any ideas, guys?
 
#6 ·
Sorry I can't offer any advice on your engine problems, but I wanted to give a big thumbs up for your persistence. I also have a Coupe De Ville ( a 78 in my case ) with but 44,000 original miles on it. It is sitting in my garage, waiting for the next year ( I hope ) when I will repaint it and once again get it on the road. Last year I replaced the original radiator, hoses and belts, along with a new battery, and it starts and runs amazingly well for a car that has been largely unused for the last 20 years. I still open the door and marvel at the beautiful, comfy whore red leather seats, and look forward to the day once again when it is a running and driving car. You are an inspiration!
 
#7 ·
Hey Ben,

Nice job you're care looks great! When is the last time you have changed the EGR valve on it? If it has been a long time it would probably be a good proactive option to try which could rule out some stuff. They're fairly cheap and easy to change. That may be contributing to some of the detonation issues. Also there is a thermal switch that is in-line from the carb to the EGR valve. It opens at a specific temp when the engine is warmed up and closes when the engine cools down. If it's opening or closing at the wrong times this could be the problem. It is not electronically controlled but just has some sort of metal spring that opens in it when the temp rises. That might be another thing to try replacing especially since the engine has that kind of mileage on it. I would also bet if that's the original converter it may be getting plugged up causing power issues. One common issue is the advance weights sticking in the distributor but that shouldn't be a problem for you since you've replaced it fairly recently with a rebuilt distributor.
 
#8 ·
I checked & cleaned the ERG valve a few thousand miles ago, everything seems fine there.

I didn't think to mention, the vacuum advance is run direct manifold vacuum. This is a change I made. The car was originally from California, with all the special equipment, so the vac advance ran through a thermal vacuum switch (TVS), disabling cold operation advance. The same TVS also cut cold operation of the EGR valve. I eliminated the TVS entirely & ran the EGR valve direct from the carb, as the federal versions were routed.

Here's the original pinging thread
, started back in May of 2012. It starts at the absolute beginning, and is quite a book:
http://www.cadillacforums.com/forum...ging-detonation-timing-chain-seafoam-etc.html

And another thread started further along, with more knowledge of the problem, started (OFF-SITE) in March of 2013:
http://forums.cadillaclasalleclub.org/index.php?topic=123917.0


So, anyway... I made a discovery earlier. I was out re-checking vacuum lines for leaks, because I had this idea that perhaps an intermittent vacuum leak was causing engine vacuum at idle to fall lower than that required for the vacuum advance can to properly seat all the way, & throwing off the advance amount. In the process of testing this theory, I discovered that my 8-month old distributor's vacuum-can has, at some point in the recent past, gone belly-up, and is now a giant vacuum leak. Now... Though this is not the main culprit for the situation at hand, it might explain a dieseling (run-on) problem I've had the last couple of weeks, assuming the vacuum advance broke at the same time the dieseling began.

In light of this discovery, I've been trying to determine what vacuum advance I should replace it with. I've heard that most generic non-adjustable replacements pull too much advance, around 22 degrees, where as my service manual says the original only pulled 16 degrees on federal cars, less on CA. However I've also heard that the adjustable ones have to be adjusted to extremes to get the advance curve close to GM's original, because they pull full vacuum too soon, at too few hg, possible causing part-throttle-detonation. I have no proof of either of these statements. For now, I'll see if the advance-can on my original distributor is still holding air, and if so; put that on until I choose a replacement.


-Ben
 
#14 ·
So I installed the original vacuum advance can again, and haven't notice any power changes since then. Dieseling seemed to be caused by a slightly high idle speed.

Next issue up, my blower motor stopped working. I know the ground wire connector is a bit wonky on mine so that's where I'll start. I also need to replace the compressor, and have someone find a possible refrigerant leak. I don't mind not having AC, but no defogger is just a hazard when it's cold out.

Rear window defogger has never worked either. Would love to fix that, but electronics really aren't my strong suit. All I've checked is the fuse. I've dreaded having a go at the back window, because a previous owner had the three rear windows lightly tinted, and I'm not sure how to go about removing the tint without breaking the defogger strips.
 
#15 ·
So I installed the original vacuum advance can again, and haven't notice any power changes since then. Dieseling seemed to be caused by a slightly high idle speed.

Next issue up, my blower motor stopped working. I know the ground wire connector is a bit wonky on mine so that's where I'll start. I also need to replace the compressor, and have someone find a possible refrigerant leak. I don't mind not having AC, but no defogger is just a hazard when it's cold out.

Rear window defogger has never worked either. Would love to fix that, but electronics really aren't my strong suit. All I've checked is the fuse. I've dreaded having a go at the back window, because a previous owner had the three rear windows lightly tinted, and I'm not sure how to go about removing the tint without breaking the defogger strips.
Blower motor? Have you checked the relay? That is the only chronic issue I have with my 79 and I keep a stock of the relays since they reularly melt down. :)
 
#17 ·
Dimension IV size of whitewall 1.3"
Have the same tires. :)

----------

So I installed the original vacuum advance can again, and haven't notice any power changes since then. Dieseling seemed to be caused by a slightly high idle speed.

Next issue up, my blower motor stopped working. I know the ground wire connector is a bit wonky on mine so that's where I'll start. I also need to replace the compressor, and have someone find a possible refrigerant leak. I don't mind not having AC, but no defogger is just a hazard when it's cold out.

Rear window defogger has never worked either. Would love to fix that, but electronics really aren't my strong suit. All I've checked is the fuse. I've dreaded having a go at the back window, because a previous owner had the three rear windows lightly tinted, and I'm not sure how to go about removing the tint without breaking the defogger strips.
Tint can be removed with a hand held steamer. My brother-in-law bought one at walmart and add water, plug it in, wait till warmed up, and hold
up against glass and it'll release steam/vapor and it'll loosen it and you can peel it off.
 
#19 · (Edited)
Thanks for the tip! I have one of those Shark steamers at my parents' house. I'll try that.

Yes, the tires in all of those pictures are a set of Dimension IV 215-75-R15 1.3" whitewalls. I absolutely loved those tires. I bought them new off eBay in late 2006 for $300 + shipping. The whitewall was dead-on correct for 1979, they made the car a time machine! By the summer of '13, they were dry-rotted, and the front tread had taken a hit due to an unnoticed worn-out center link.

This was taken right after I repainted the crests in '07.



Right after the tires were installed



I replaced them with the set of Runway Enduro 75s that are on there now. (below) The Runway's whitewall isn't the same, it's about 1.1" wide, and drawn about 3/16th closer to the rim. They also have the wide serrated band in the sidewall just outside the whitewall, which catches the light, and is anachronistic for 1979. It dulls over time, but is very noticeable when the tires are new, or you ever put tire dressing on them. Painted crests faded in the six years since they were touched up.



The Enduros are also discontinued now... They were about $350-400 installed, and have great traction. Yet, when you compare it to the picture above this, it's just not the same for me. The only place to get correct 1.3" whitewall tires at the time of writing this, is Diamondback Tires, which are about $920 for a set..Ouch! Do not buy the American Classic 1.3" whitewalls if you want a factory correct look. The whitewall is much too far out on the sidewall to be correct. It changes how the proportions of the wheel/tire combo work together visually.
 
#21 ·
I'm having a problem with the remanufactured brake master cylinder I had installed last summer. Pretty much the whole time it's been on there, it has leaked an increasing amount of brake fluid from around the resevoir cover gasket. Especially towards the rear. At first, it was just an annoying thing in the back of my to-do list. I'd add a bit of brake fluid now & then, and kick myself for having a shop install a reman unit when I was crunched for time, instead of rebuilding the old one myself!

But the leak seems to be getting worse. I was extreamly displeased recently, to discover a puddle under the car, and a good portion of the chassis under the master covered in brake fluid. I took the car out this evening, and in the space of less than an hour it left a 8" puddle in the parking lot.

The strap seems to hold it down tightly. Gasket is present & intact. The resivoir casting is a little corroded at the seal, but not bad where it's leaking, and the leak started before the rust formed.

What I can't figure out is; if it's the top gasket, how is it leaking when I'm not driving the car & using the brakes? I wonder of it's also leaking where the master meets the booster, but I can't tell because there's so much fluid coming down from the gasket, lol! Ugh...

Anyone have an idea about why ths is happening or how to fix it? I'm probably going to replace the whole cover next. Because this one is an oddball, the gasket attaches differently than my stock one, and I can't find any gaskets that attach the same way.

Because this is not ok...




 
#24 ·
I think what you're seeing is actually in the casting, but i'm not sure why it's there... take a look at the top, you can see the line I'm taking about. The center of the rear actually worries me a bit, it looks bent slightly. Regardless, I'm going to replace the cap with one that has an original type gasket retention system, and take it from there.



This is actually the way the gasket was installed when I bought the MC... I'm pretty sure that's upside down. Definitely didn't help the leak, nothing to catch the geysers that come up.

 
#25 ·
You're last pic suggests the problem. The gasket isn't seated correctly and so isn't sealing. Remember that brake fluid is hygroscopic (it absorbs water), so if the reservoir isn't sealing, air and moisture are getting in there, and the fluid is expanding in volume, even at rest, thus overflowing through the poorly sealed gasket. Return the gasket to it's original orientation, flush the system, and then see. Bet your leak goes away.

Good luck, Ben! :)
 
#26 ·
You may be right there. Although as a good sign, I haven't noticed the level of brake fluid fluctuate any after I've been driving, or sitting hot, etc. Meaning I don't think it's expanding / contracting other than the obvious slow leak depleting it. If I pop the cap off right after I've been driving, it's the same level as if it was cold.

I ordered a new cap & gasket that have the original gasket retention system, and a new bail wire. It's a chrome cap... only kind I could find. I don't mind the chrome, just hope it isn't flimsy. At least it looks more like my original in the pic.

In the research I've done, apparently it's pretty common for remanufactured master cylinders to have gasket leaks. Has anyone else found this to be true? This one is a Bendix From O'Reilly. I thought Bendix was good. Seems like it rusted pretty fast, too.
 
#27 ·
Well, new problem.. Yesterday the phaeton rolled over 235,000 miles & promptly had a "mental breakdown". We think the flywheel may be the culprit. I was driving around running errands, and I started to notice the engine making a slightly pronounced grinding whine under throttle. as I was pulling through a parking lot, it got louder, and started making a scraping noise even at idle. I looked under the hood, thinking it was probably a pulley or something, didn't see anything so I went inside & let it cool down for about half an hour. when I came back, I checked the fluids, belts, etc, and started it. I didn't hear anything so I drove away. it soon started making the scraping noise again. I was at a light & heard little pops and clicks coming from under the hood. got a block down, pulled into a parking lot. while looking for a spot, it started shuttering constantly & sounded pretty rough. I got out & listened around. sound was coming from the lower end, near the back of the engine / front of trans. I had it towed home, and here we are.

I bounced ideas around with ga_etc (Austin), and the tow truck drivers. general consensus is possibly flywheel / flex plate. trans was rebuilt less than 10,000 mi ago. engine never as far as I know...

I'm thinking this might be the red flag that convinces me to get the whole engine yanked out and rebuilt with cad company / mts parts. however there's no way I could do that myself due to a lack of skill & tools. so I'd have to go about finding a shop I can actually trust... which is no small undertaking. any thoughts on any of this are highly welcome! what would you do?
 
#28 ·
Remove dust cover/shield under the trans and you can visually see if the the flyweel is cracked by turning flywheel with the use of a screwdriver amd you'll see where its bolted to if there's any cracks around that area. My 79 has it, check youtube, I posted a video of the sound. Is it like that?
Search 1979 cadillac flywheel, or something like that. Lol
 
#29 ·
1980Coupe,

I found your video. Mine sounds different, it has more of a constant whining / scraping sound. Here's a video I shot to try and diagnose it. You can hear the noise very well close to the end, when I shoot the camera under the car. Does this help?

LINK TO ENGINE NOISE VIDEO

https://www.youtube.com/watch?v=70wdzM0x5_Q
 
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