1980 Cadillac DeVille Diesel

[Parkis Waterbury]

Does anyone have any idea what a 1980 Cadillac Sedan Deville with a Good Wrench Diesel Motor Might be worth? Is the good Wrench a better motor? The car has only 59000 and is part of an estate. It needs headliner repair (typical) and the trunk needs some attention to whatever allows it to keep open as well as the A/C is at best cool not cold. Seats are like new. I drove it and seeemed to run well although no powerhouse. Do you think this may be collectable? Oh by the way considering we live in the 'rust belt" the body is in great condition.
Thanks for any ideas.
   

[TJ Hopland]

I just bought an 80 Eldo diesel.   For the most part a 77-90 sedan is a pretty ho hum car that not many people are looking for.  The coupes do a little better because most people looking for a 'fun' extra car are looking for a 2 door, not a 'practical' 4 door.  To make that even worse you got what almost everyone says its the worst engine GM ever made.  The second worst was only 2 years later and in the same cars (the infamous HT4100).  As for the cars in my area at any given time you can likely pick one up for anywhere from $100 to maybe $5000 for a low miles original that has hardly ever been outside.    There was a 82 sedan for sale in my area a few months ago.  I think it started at $3500.  Last time I saw the ad it was $2000 obo and that ad stayed up for several weeks.  It looked fairly clean in the pictures I think the only thing that stood out was cracked armrests.   Mine was pretty clean except for a few rust spots and the famous flaking paint in a few spots.  Someone had put new batteries in it and some brake parts.  It seemed to run good.  I paid $1600 out the door from a dealer and it was probably too much but I really wanted a diesel to play with and had the cash.  

80 was one of the transition years for the diesel.   Earlier cars had what they called the pencil injectors.  The pencil injectors are held into the head by a clip and a bolt.  They also have a return line on them.  Mid 80 they went to what was called a popit injector.  They thread into the head and do not have the return lines.   The popits were considered better for this engine but are very hard to find because they were not used on many other engines.  The pencil style was much more common on other engines. The pumps are slightly different between the popit and pencil injectors.  In 81 they added a cold start advance to the pump so 80 is a odd year because of the popits and no cold advance.  The internals of the pumps are pretty standard so rebuilding one is no problem for just about any diesel shop.  The 6.2 chevs and the 80's fords used pretty much the same pump as did many of the American farm tractors of the 60's and 70's.  80 still had the external egr which was a pipe up from the exhaust manifold that then connected to the intake crossover just under the air cleaner.   The 78-81 should have had the external EGR and 1 bolt in the air cleaner.  The 82-85's had internal EGR and 2 bolts on the air cleaner.   I think around 81 or 82 they went to what they called the DX block.  All the remans I have ever seen have been DX's.  If you want to know for sure its cast into the sides of the block below the heads.  Its pretty big raised letters so even with some goo you can usually see it.  At the top center is 350 and centered below it is DX.  The DX block was beefed up slightly in some areas and had deeper threaded holes for the mains.  The big improvement was it had a roller cam setup that almost eliminated the cam wear issues that were even a problem on the gas engines in the late 70's.    Apparently the remans were long blocks with the heads to match your system so you kept the rest of your original system.   The people that like these engines dont really care which block it had.  The people that dont like the engines dont think the DX or remans were any better.

The starting procedure is to turn the key on.  There should be a wait light on the dash.  While you are waiting you should step down on the 'gas' pedal and release it just like you did for a carburetor.  This allows it to set the fast idle if its still working.  After 5-20 seconds depending on temps the light should go off and you then crank the engine.   It should pretty much start instantly just like a modern EFI car.  Its pretty normal to get some bucking and chugging for the first 30 seconds especially if ambient temps are cool and the engine has some miles on it but after about a minute it should be pretty smooth and pretty much quit smoking.  If you then drive and put it to the floor it will likely puke out a ton of thick black smoke but for the most part even that should go away after the engine fully warms up.  You may get a noticeable bit of smoke while driving but you usually dont see it looking in the rear view unless its night and there is a car behind you.  If you were following the car you may notice it but it should not be bad.

Head gasket issues were common with these.   If its real bad you will get steam out the tail pipe.  The 'regular' diesel smoke sort of hangs in the air if its a calm day.  The 'smoke' from a head gasket issue disappears quickly.  If its that bad you will likely hear it bubbling in the engine / radiator / overflow tank when you shut it down hot.   Minor issues will usually also tend to cause bubbles in the cooling system.  

Another thing to look at if everything else seems to check out is the timing marks on the injector pump.   Pull off the air cleaner housing.  Its just like the carb ones with a vacuum line and and a hose clamp holding an elbow to the inlet.  With that out of the way you can get a better look at the injector pump.  Part of its hidden by the intake cross over but thats not important now.  Where you are looking is where it goes into the intake manifold.  You will see a flange with 3 bolts in it that mounts the pump to an aluminum housing in the intake.  There should be a notch on the pump and on the housing and they should be within 2 line widths of being aligned.  If there is more than one set of marks its a sign that its been apart several times.   The reason you are checking is sometimes when these engines start having issues people will adjust the timing to keep it running but it wont last long that way.  While you are looking around there look for pools of fuel.  Diesels tend to be a little on the messy side but you shoudl not see pools of fuel anywhere.  There is supposed to be a drain hole in the back of the valley where the pump is but its often plugged with goop so if there is a leak it just pools up there.  Its common for there to be oil leaking down the sides of the engine.  I found out this was due to the breather filters being full of oil and the grommets in the valve covers being dried out and not sealing well.   The filters and grommets are easy to get and cheap and seem to eliminate all the oil mess from the top side of the engine.

Its normal for the oil to be jet black.   Even a clean engine will turn the oil black in a few hours.  

There should be a water in fuel light near the wait light that you see when you first turn the key on or start the engine but it should then go off.  I think this came in 80 so if yours was an early car it may not have it.  If you dont see it look close at the dash in the sun or with a bright flash light to see if you can see it.  If its there its possible that the bulb is burnt out.  If that light comes on that means there is something like 2 gallons of water in the fuel tank.  The fuel pickup is above this point so the theory was that you would not be able to get water to the engine.  The way you drain the water is to remove the return line up by the engine and suck it out.  The return line is at the very bottom of the tank.  The return line comes out of the top of the injector pump and usually transitions to a steel line down to the frame where there is another junction of rubber to the steel line that goes back to the tank.  

Driving around town it should feel very solid and responsive  power wise.  Getting on the highway you have to put er down and hold it there and hope for the best.  Passing, forget it.   MPG on mine has been around 24.

The other bad news is the transmission.   Its also infamous.  Its the THM200 'metric'. The only good thing most people had to say about it is it was the same externally as the 350 so lots of then got junked in favor of 350's.

As for what holds up the trunk if its the same as the 80 Eldorado they are those shock sort of things like modern cars use.  They just loose pressure over time and need to be replaced.   They are a little odd because they use a peg instead of a ball joint like most of them but I got both the hood and trunk ones for my eldo locally.   One of them was at the local parts warehouse and the other ones were at a regional one and came in the next day.  I think they were around $20 each.  Before you order them unhook them one at a time, you may find that only one is bad.  A bad one you can compress with you bare hands.  A good one will be difficult to compress without leverage.  

I have always been interested in diesel engines and these.  I have learned a lot more about them in the last few months owning this one so let me know if you end up with the car and I will pass on more of what I have learned.  

[bcroe]

I also have an early 1980 diesel (Olds 88).  Yes the trans blew in no time.  I can tell you, putting in a THM400 switch pitch trans will really wake up this engine, by getting it into the power band far sooner.  It will also end trans problems.  The vacuum modulator can be connected to that mechanical vacuum switch on the end of the throttle shaft, seems to work fine.  Check a regular cad for a trans support.  Getting a switch pitch THM425 into a 1980 Eldo isn't easy, but I have one in my 79.  Pictures on PHOTOBUCKET. 

     http://s93.photobucket.com/albums/l71/bcroe/

(that is a lower case "L"71, not an upper case "i"71)

  click on an Album
  click on a picture to enlarge + explanation

Bruce Roe

[Parkis Waterbury]

Thanks for your help-will let you know what happens.