Anyone else currently own a 78-85 Cadillac diesel?

[TJ Hopland]

Just wondering how many people here currently own a diesel Cadillac?   

I still have my 80 Eldo but after a deer hit have not been driving it.   Sort of replaced it with an 81 Riv diesel but its just not a Cadillac.

There has to be some others out there still running.       

[Barry M Wheeler #2189]

Lars has a nice one.

[TJ Hopland]

I know there are a few.   I occasionally get an email or PM from someone asking questions.  Just for some reason they don't seem to want people on the board to know they have one and like it.   Lately I have noticed a lot more people with 4100 era cars 'coming out' so I thought maybe some more diesel folks would appear.  Maybe they are just that rare today?    I suppose you take the number of 4100 people here vs the number sold and apply that same formula to the diesels it makes sense that there are none here.   Then you could factor in the 'survival rate' and none should still exist. 

[David King (kz78hy)]

I would love to have Seville diesel.  Back in '84, I had a '81 Sedan DeVille diesel and loved it.  The car was stolen and I replaced it w/a gas Seville, but I would not be afraid of the later designed 350 diesel.

David

[bcroe]

I drove a few of those diesels, 3 are still here (converted after the diesel died). 
If you convert a RWD to a switch pitch trans, you will be amazed at the
improvement in performance.  That, because it gets the engine into its power
band far sooner.  The only reason a 120 hp engine can't move a car smartly
around town, is poor gearing.  Bruce Roe

[Eric DeVirgilis CLC# 8621]

Diesels are definitely scarce today; many were traded, converted and/or scrapped while in their prime. The few owners who followed all maintenance directives to a T had far better service from their diesels than those who didn't.

The fact that gasoline powered Cadillacs up until 1980 required very little by way of conscientious & deliberate care probably did not help matters any: Newbie diesel owners were unprepared - more or less - for the special needs of their machines.

Probably the rarest of the rare in diesel Cadillac is the 1986 FWD DeVille/Fleetwood. I only saw one in my entire life - a 1986 Fleetwood Sedan, brown with beige leather.

[Walter Youshock]

Former owner of a funeral home I worked at bought a new early '80's diesel.  The car was so loud, he said he had to dump it after about 6 months.  Families were complaining about how noisy it was.

I went to college with an older lady who's husband bought her a ne '81 diesel sdv.  She said the car left her stranded so many times, she dumped the car AND the husband!

[bcroe]

Diesels are definitely scarce today; many were traded, converted
and/or scrapped while in their prime. The few owners who followed all maintenance directives
to a T had far better service from their diesels than those who didn't.

The fact that gasoline powered Cadillacs up until 1980 required very little by way of conscientious & deliberate care probably did not help matters any: Newbie diesel owners were unprepared - more or less -
for the special needs of their machines.   

My first diesel was an early 80 model; next was a replacement engine in an 81.  As I recall
we put a special pickup (recall) in the 80 tank; about the only maintenance was oil changes
and oil & filter changes done religiously.  At about 40K miles the (now notorious) poor quality
injection pump developed a problem.  The dealer managed to fix that, but the engine now
had what sounded like a rod knock.  The (either incompetent or completely dishonest) dealer
informed me I needed to put in a new engine and trade in the car on a new one.  After telling
him where he could go (trade my NEW car??), I put in a gas engine.  Seems I created a car
with lots of extra sound proofing, super duty electrical system, hydro boost brakes, 28 gallon
gas tank with no gas restrictor, high flow exhaust with no cat converter, and no emissions
testing ever.  Currently my best car ever at over 300K.   I eventually took the the rods off
the diesel engine crank; the bearings were like new.  Reading the manual revealed the noise
was caused by a defective fuel injector (put in by the dealer).  The engine is still here too,
just in case. 

So I could pick up great diesel cars for a song when the engine or (crappy) TH200 trans
failed.  I had and converted a few to gas back then.  The second engine in the 81 eventually
failed too.  By now the price of diesel was far above gasoline, instead of far below; I saw no
reason to try and keep the diesel going.  That Cutlass with 403 engine and a mere 220,000
miles is still here too, for reasons mentioned above. 

Perhaps the diesels were just about upgraded enough when they were dropped; too bad.  The
V6 I took apart had a lot more reinforcement in the block than the first V8s.  Still needed a
better injection pump.  Maybe some owners were lax, but even those who were meticulous
experienced failures.  The way to go is the turbo diesel.  Bruce Roe

[Big Apple Caddy]

Probably the rarest of the rare in diesel Cadillac is the 1986 FWD DeVille/Fleetwood. I only saw one in my entire life - a 1986 Fleetwood Sedan, brown with beige leather.

1986?  Did you mean 1985?  I thought production of the 4.3L V6 diesel used in the FWD Electra, 98 and DeVille/Fleetwood models ended in late 1984, maybe early 1985.  Too early to be available in a 1986 model.

[Dr. John T. Welch]

There are only two kinds of GM 5.7L diesel engines:  those that failed catastrophically between 75K and 100K miles and those that will. Any exceptions are just that: random good fortune. I've owned ,used and converted several of these diesel powered vehicles in various GM platforms.

In correspondence with the Oldsmobile Division Chief Engineer  during  the heyday of the 5.7 diesel engine experience, I was assured of GM's commitment to customer satisfaction and the solid warranty provisions covering the powertrain. Here are the empirical facts about the 5.7L  and derivative 4.3L  engine programs:

The engines were developed to allow an accelerated compliance with emerging EPA corporate average fuel economy (CAFE) statutes. This was a major cross divisional program including passenger cars and very light duty GMC and Cheverolet pickup trucks. This was no small feat from an engineering and manufacturing standpoint for GM.

The program was not viable financially within the proscribed time frame without using existing  manufacturing resources for the major cast engine components: block, cylinder heads, camshaft, crankshaft. An existing engine architecture was chosen after evaluation of several possibilities: the Oldsmobile Division "small block" V-8 whose development and manufacturing costs were already fully amortized. The machining of these major  components occurred on the same lines as the conventional gasoline engines, minimizing manufacturing costs.

The main problem with the service life of the engines derived from the vibrations and related harmonics  inherent in  diesel combustion.
The block/head assembly did not fare well with vibration propagation through it, resulting in broken headbolts and cracked cylinder heads that led to catastrophic hydrolocking and engine destruction. Early indicators of the problem were coolant in the oil and white smoke out the exhaust that masqueraded as simple headgasket failure.  A particular concentration of severe second and third order harmonic phenomena occurred at the lower left area of the block at the starter mounting boss. GM went through three designs of the starter motor cast aluminum end housing attempting to defeat the fracture of this piece from vibrations transmitted to it during normal engine operation. Also afflicted in a similar way were rocker arm pedestals and some accessory mounting brackets in the front of the engine.  No amount of customer compliance with recommended maintenance schedules would defeat these inherent destructive forces.   
 

[TJ Hopland]

What I have found since I have become a diesel enthusiast is that about 95% of what I have always heard about diesels (especially when it comes to the early 80's) is just not true.   Some of it was never true and then the rest was mostly related what was available for fuel, oil, and service at the time.  If you think back to 1980 there just was not a lot of diesel stuff around especially at the average consumer level.  Lighter construction equipment was all gas, heck even some of the bigger stuff was still gas.  Only the larger farm equipment was diesel.  City delivery trucks were gas, some 'semi's' were even gas.  The GM ads from the era told you to stop by and get a pamphlet showing you where you could buy diesel fuel so just finding it had to be a big issue for some buyers if gm bothered to print those and advertise / distribute them.   

The fuel at the time was prone to algae growth and gelling in cold climates.   Factor in how leaky a lot of underground tanks were at the time you also got a lot of water issues which is a much bigger issue for diesels than gas engines.   Take a leaky tank in a low volume gas station and you could be lucky to get any actual diesel fuel out of the pump.  EPA has taken care of the leaky tanks.  Fuel formulas have improved so you typically don't have gelling or algae issues.   The engine oils have dramatically improved.   I heard often times in the 80's a Cadillac dealer may not have had diesel rated oil in stock.  You often had to run out to a 'truck stop' or an ag (tractor) dealer to get a diesel motor oil (maybe that is also where you had to go for your fuel?).   Today I would say 1/2-3/4 of 'gas' stations have diesel.   Many of them have at least one option for a diesel rated oil and fuel treatment on the shelf.   You can go to a walmart and have a dozen options for a diesel rated oil.    My 2013 Jetta looks, sounds, smells, starts, and drives like any other 2013 Jetta, only difference is I typically go over 600 miles without having to stop to fill up.   My Suburban can go 800 miles but that is a 42 gallon tank, vs the 12 ish of the Jetta.   

Just for fun when you are out driving start looking close at all the VW's you see, look for the TDI badge on the back.   I bet you will be amazed how many are actually out there.  I never really noticed till I started thinking about buying one.   Some parts of the USA it almost seems like half the ones you see are diesels.   The current $1 ish spread between gas and diesel is not an incentive at the moment but the previous 9 months it was a lot closer so you had a pretty good shot and some savings for many applications.

The 80's ones were loud on the outside so I can see where an application like the funeral home was maybe a problem.   Amazingly Cadillac and Olds really did an excellent job of insulating all that noise from the interior.   Going down the highway in my 80 you would not know its a diesel.   I am not sure if the lower models got the same treatment, the few Chev's I have been in were kinda loud but that could also have been an age thing. 

The Rosamaster (now Stanadyne) injection pump basic design I think dates back to the 1930's or 40's.  Got to be commonly used in the 1950's I think.   Same basic pump was used on several smaller tractors including John Deere and International.  Was used on all the GM light diesels through 2000ish.  Used on all the US light us military vehicles (I think it still may be used). Used on all the Ford diesel pickups till the mid 90's.         

The 85's apparently had a lot of changes so it really appeared they thought the program was going to continue even though it looked like sales had fallen pretty badly, likely a combination of the reputation and raising fuel prices.   Also don't forget that the early 80's a full size car with the Chev or Olds 5.0 could see 20 mpg.  When the program started you would be lucky to see mid teens from your full size car and small cars were really terrible so the prospect of getting 20's for MPG from a cheaper fuel and keep the comfort of you land yacht really appealed to a lot of people. 

I have never heard of any actually titled as 86's.   Have heard of fairly late build date 85's but that was likely due to all the problems they had getting the FWD C's into production, I would imagine they focused on the gas ones first since those were likely bigger sellers.   People also said the had seen a diesel option listed in many of the 86 parts manuals at the time. 

[TJ Hopland]

I was curious and looked up the 86 passenger car VIN chart and the only diesel listed there was a 4cyl produced in Japan.  Apparently they knew they were giving up by the time they produced the VIN charts.   I also didn't know GM had a plant in Japan in the mid 80's. 

[Eric DeVirgilis CLC# 8621]

1986?  Did you mean 1985?  I thought production of the 4.3L V6 diesel used in the FWD Electra, 98 and DeVille/Fleetwood models ended in late 1984, maybe early 1985.  Too early to be available in a 1986 model.

I did. Thanks for the correction.


I've known a number of people over the years who positively swear by the 350 diesel - but these were people intimately familiar with these engines as well as which years were the best and which to avoid.

Supposedly the Goodwrench "Target" replacement engine had been thoroughly reengineered to address the maladies for which the 350 became infamous. The injection pump was also a well known weak point.

Despite the many myths surrounding the diesel's kinship to its gasoline counterpart, there was very little in commonality between the two other than displacement and V-8 configuration. Recently I had read a detailed article on the subject but I cannot recall where I saw it.

[bcroe]

Despite the many myths surrounding the diesel's kinship to its gasoline counterpart, there was very little in commonality between the two other than displacement and V-8 configuration.   

I have spent a lot of time 5.7L diesels and Olds gas engines, and swapping their parts.  The
350 Olds is a direct bolt in; essentially everything fits.  Sure the power producing internal
parts are all reworked for the diesel.  But all the geometry is the same, including all the
common accessory mounts.  Valve covers, oil pan, oil filter mounting, oil pump, and more
have been swapped here.  An Olds 425 crank drops in. 

AND the worlds biggest small block, Olds 403, also drops in, with even more in common with
the gas 350.  I know they only claimed some 160 hp from the 403.  But with the right spark
advance curve (not that emissions version) and a really good exhaust, my measurements
calculate out to 260 hp.  My "diesels" surprised a lot of people.  Bruce Roe

[936CD69]

.  My "diesels" surprised a lot of people.  Bruce Roe
LOL sounds like the 403 I pulled from a 77 88 freshened up, with a mild cam, standard intake and carb and headers for a 260, dropped into a 78 Cutlass. Wasn't much around that could touch it in the 1/4. With 3.73 posi it was out of breath at 85 turning about 6000....

Bruce can you give an explanation of your "switch pitch" trans conversions..or perhaps have it on your website?

Craig

[bcroe]

.  My "diesels" surprised a lot of people.  Bruce Roe
LOL sounds like the 403 I pulled from a 77 88 freshened up, with a mild cam,
standard intake and carb and headers for a 260, dropped into a 78 Cutlass. Wasn't
much around that could touch it in the 1/4. With 3.73 posi it was out of breath
at 85 turning about 6000....
Bruce can you give an explanation of your "switch pitch" trans conversions..or perhaps
have it on your website?  Craig   

You would be far ahead of my 2.41 cruising axle in the 1/4 mile, but the car measured
a 91.2 MPH quarter and still climbing (would do 100 in second). 

All big block 65-67 Buick, Olds, and Cads used a switch pitch trans, other years can be
converted.  A normal torque converter gives about a 2:1 torque increase stopped,
gradually decreasing to a straight 1:1 fluid coupling over some 3000 rpm.  So it stretches
the useful range of each gear, compared to a stick.  A 3 speed TH400 has a great advantage
over a 3 speed stick. 

Normally with the car stopped, the engine is limited to some 1500 rpm "stall" speed,
below its best power band.  Racing "high stall" converters will allow the engine to rev well
above 2000 rpm, getting at more power to begin with.  But racing converters are dogs on
the street, since the car won't move till 2000 rpm. 

The switch pitch converter allows changing any time between low stall and a modestly
high stall operation.  This comes with somewhat more than initial 2:1 torque multiplication. 
This is useful in getting any vehicle going, I used it for diesels and late 70s with 2.41:1
"gas economy" rear axles.  WIth a properly running engine, it reduced the 0-60 time
of my Olds by a full second, and it will do the same for a 70s Seville.  Meanwhile the gas
mileage is the same or just a bit better, with a 2 state converter instead of a single
compromise.  I use electronic pitch control, the OEM control wasn't very effective. 

Bruce Roe

[TJ Hopland]

The Olds museum has a V5 diesel on display.   It was supposed to be the diesel engine option for the small and mid size transverse FWD cars.  It never went into production because they pulled the plug on the whole program.  Just one more thing they were spending money on and then abandoned when they maybe finally got it right. 

Apparently the transverse FWD 4.3v6  cars has some major overweight weight issues.   I read that they had a lot of lightweight body parts up front to try and lighten things up.  Compared to a 4100 or typical V6 I suppose they were a little on the heavy side.  I never looked close, I would imagine the had two batteries like the 5.7's did which is just more weight and space.

There is a guy on one of the diesel forums that is on his 3rd or 4th 85 diesel coupe deville (or maybe they were Fleetwoods?).  I think total Cadillac diesel production for 85 was only around 1000 cars so a coupe has got to be rare.  He thinks maybe as few as 100 were made. 

I have dealt with Olds 403's and they really should not have been a good engine but they seemed to be reliable and you could get some good power out of em.  Most of the other engines they squeezed that size bore in had lots of issues.  Lots of those ended up in Firebirds as well as your full sized land yachts.     

[wrench]

I don't know about any Caddy's still running diesel, but I had one of those in a 82 Olds Cutlass Cruiser wagon...got to the point i could replace the head gasket blindfolded. I still have that special wrench for the injection pump...jeez that motor was a boat anchor...but I did run it on free sumped jet fuel with a little bit of marvel mystery oil and that thing ran like a locomotive and got great gas mileage...just the head gasket would blow every 15k miles or so...

I remember going to the local Olds dealer and asking for a new set of head bolts...the parts guy says 'Set?'...'There's no set. You have to look up each bolt as a separate line item AND pay freight in for each one'...Now that's customer service...bah!

And the torque on the head bolts was what? 160 foot pounds? Or some ungodly amount of torque you could barely apply...

[TJ Hopland]

I have heard a lot of stories about diesel wagons.  They must have sold quite a few.  There does not seem to be a lot of survivors.  I suppose it was the mileage appeal there too, 9 passengers and decent mpg for the big family vacation. 

[Eric DeVirgilis CLC# 8621]

I have spent a lot of time 5.7L diesels and Olds gas engines, and swapping their parts.  The
350 Olds is a direct bolt in; essentially everything fits.  Sure the power producing internal
parts are all reworked for the diesel.  But all the geometry is the same, including all the
common accessory mounts.  Valve covers, oil pan, oil filter mounting, oil pump, and more
have been swapped here.  An Olds 425 crank drops in. 

Correct, externals are the same.

Internals are very different - and the diesel weighs 500 lbs more than the gasoline version.