Pre '85 Eldorado

[Dkwebb2727]

I have a '94 SLS which I love. I'm thinking about looking for a pre-'85 eldorado or Seville as additional car for fun. Anyone that's owned one have any advice? Thanks.

[KHE]

I have a '94 SLS which I love. I'm thinking about looking for a pre-'85 eldorado or Seville as additional car for fun. Anyone that's owned one have any advice? Thanks.

Evidence of regular coolant changes and use of the GM coolant pellets. It may be difficult on a 20+ year old car.

[jackc]

I had an 83 Eldo for awhile. The 79-85's are beautiful automobiles and they're wonderful to drive. The biggest thing to be aware of in this generation is the different engines. 82-85 had the infamous HT 4100. Its not a bad little engine from a driveability standpoint - although it is somewhat underpowered.

Here is a copy of a post that a member of the Cadillac Mailing List sent me when I was first learning about my car. It pretty well summarizes all of the info I found:

"I have a soft spot for those HT4100 cars

myself, they are such nice cars to drive with the light engine. The HT4100

gets pretty good mileage too.

Frankly, it would be difficult to enumerate every possible HT4100 failure

mode, but here's some common ones-

Failure of the seals at the cylinder bore inserts bottom end, permits

antifreeze to enter the oil pan, and if not caught VERY early, will usually

lead to engine seizure or catastophic damage. This is the big one! You're on

the right track as regards changing antifreeze frequently, and using the

additive. Theres apparently a conflict in that the antifreeze itself

contributes to deterioration of the seals themselves, kind of a materials

incompatibility. GM has recently introduced an altogether new type of

antifreeze (DexCool) which might work better, I'm looking into it presently

to see if theres any conflicts or if it is OK. It likely is fine.

Pretty much every other area of the HT4100 has caused someone troubles, but

the main things aside from the leaking antifreeze is the following;

The Aluminum brackets used up to mid 1985 to hold the rocker arms on can

crack and fail, there is a new replacement that has been redesigned with

considerably greater material that seems ok.

HT4100 versions of the engine break pistons if they are permitted to spark

knock- usually 89 oictane fuel will cure this issue altogether. Retarding

ignition timing is a second possibility, but makes them sluggish.

The distributor gears and oil pumps wear prematurely, particles from them

are frequently evident in crank bearings upon disassembly. Replacement of

the oil pumps at regular intervals might be a worthwhile idea. Pulling the

distributor, and installation of the updated gear might be worthwhile also.

The aluminum engine tends to leak oil and develop intake manifold leaks due

to the larger coefficient of expansion of aluminum. The different parts

expand and contract at about twice the rate iron parts do, which stresses

gaskets, so they dont last quite as long.

Crankshafts and main bearing caps fail suspiciously often, although I feel

this is most likely abuse. It might be possible that premature engagement of

the fourth gear lugs the engine to exacerbate this problem. I would regard

it as a worthwhile practice to drive the car in 'D" under 60 MPH if you

sense the engine is overworking at all.

Overall, I think the HT4100 can be made reliable, I've been trying to see

what could be done to keep them from failing in the first place. The 4.9

liter engine used in the 1994 Cadillacs is a direct descendant of the

HT4100, so there's hope! Best advice I could add to what you're already

doing is think about adding another oil cooler to the factory in-rad one,

check the distributor gear for wear, look into replacement of the oil pump

when you can, and check the oil for signs of antifreeze before driving off

when you can. The antifreeze leaks, when they occur, are quite slow, it

takes a long time to reach critical levels in the oil- however there is no

warning light etc to indicate a problem. Oil and water dont mix as you know,

so it will be evident on the dipstick, or if you take a whiff of the oil

filler cap before driving off. Antifreeze has a sweetish alcohol smell, oil

smells much like wax. Hope your nose is better than mine! You'll see the

milky white contamination on the dipstick easily.

My ultimate ambition regarding HT4100's is to produce a kit of small parts

and seals to bulletproof the main troubles with the engine. Currently, I'm

playing around with metal seals for the cylinder liners, which should be

unaffected by the antifreeze. I'll keep you and the CML posted. If you are

positively rolling in cash, GM still sells BRAND NEW HT4100's for about

$3500- these will be discontinued before long I suspect however.

Your feeling regarding failure to maintain the HT4100 leading to engine

failure are largely correct. They really are fussy about being heavily

serviced, this tends to extend life but is by no means a certain cure, many

very well kept ones have failed prematurely. Its all the insurance you have

right now however. If you're a tinkerer, a blown up HT4100 engine core is

very cheap, you might want to watch your local free ads paper etc. for one

to take apart at home to see for yourself whats inside. Its a beuatiful

little engine, just flawed in some ways. When they are working as intended,

they're unbeatable, a model of smoothness and refinement. "

I never had any major problems with my 4100. But mine was an extremely well-maintained 1 owner with 95k miles when I got it. So I don't know how my experience compare to others'. I do know that wrecking yards were full of nice 4100 cars with bad engines.

Regarding engines in the other years - Most 79's came with the Olds 350. Great engine. Most 80's had the Cadillac 368. Also a great engine. 81 was the V8-6-4 year. The engine was also the Cadillac 368, but it was equipped with valve deactivation solenoids that had ongoing problems. Its my understanding that the 8-6-4 system can be disabled though, leaving you with a 368.

Based on all of the above, if I got another one of these cars, I'd want a 79 or 80.

From 82 to 85, the Seville was basically a 4 door Eldo, with the "ramp-back". So the above applies to them too.

Pre-82, the Sevilles were basically 4-door Novas with a fuel-injected Olds 350. These are also among my all-time favorite cars. Very good styling, good power, and a great size for the practicalities of daily driving.

There are alot of folks on the Cadillac Mailing List that dabble with cars of this era. Here's a link to their archives:

http://bluedog.cc.emory.edu/archives/cml/

Hope this helps....

Jack

[95concours]

I have always liked the 80-85 seville, I don't know why but I really like how it looks, esp with some of the 2 tone paint schemes they offered them in back then. The fully optioned ones have some of the most comfortable seats I've ever sat in as part of the Elegante package. I believe they also had a digital speedometer as an option too. I also think but I'm not sure that there was a 4.1L buick v6 also offered as an option in the 81-82 Sevilles.

As with any car of that vintage I think rust would be something to look out for too esp on the bottoms of the doors where u don't really see it from the outside.

[KHE]

Don't use Dexcool in an engine that has been using green coolant - there is absolutely nothing to gain as the silicates from the green coolant that are plated in the coolant passages will deplete the corrosion inhibitors in the Dexcool.

If I were to buy a HT-4100 car, I would immediately drain the coolant, add the coolant sealant, and refill with fresh coolant mixed 50/50 with distilled water. I would also change the oil and use 15W-40 diesel oil such as Rotella, Delo, or Delvac. That oil has more antiwear additive that will keep the distributor gear, etc. from wearing.

FWIW, my Dad had a 1985 Fleetwood Brougham d'Elegance (RWD) with the HT-4100 and he never had any engine issues - he maintained it per the recommended service intervals in the owner's manual. He sold it with 191,000 miles on it and two years later, the guy who bought it said it had 250,000 on it.

[Dkwebb2727]

Thanks for the feedback. I'll let you know what I find.

[HT4100 Whiz]

HT4100 Miscarriage of the Millenium

To those of you who "love" the 1982-1987 Caddies underpowered by the most unmerchantable mill Cadillac ever frankensteined, the supposed "High Technology" HT4100 metal-aluminum engine, I suggest you swap it out. The HT is absolutely the greatest single disaster in GM's engineering history, held together with spit and glue. The engineers started out with good intentions but went to hell in a handbasket due, in part, to prematurely releasing it. The rationalization I see on some threads that it was compliance with C.A.F.E. standards es el caca del toro. It was negligence.

That engine was fatally unmerchantable out of the gate. The 350 swap out seems to be working well. Go to: http://www.eldocountry.com/eldo/swap.html for the details. It's no piece of cake but if you want to keep your Caddy, check it out. The major problem with the HT4100 is glycol-antifreeze intrusion, a condition for which the HT4100 is both infamous and notorious. In addition, the engine is a bi-metal engine (aluminum and iron) which vibrate at different rates and cause the engine to virtually vibrate itself loose. This, in conjunction with the antifreeze results in a self-destructing vicious cycle (some fancy schmancy physics known as variable "coefficients of expansion.") There were also problems with the engine's gasketing being able to cope with all the block and manifold movement. The antifreeze wipes out the lubricating properties of motor oil which accelerates wear and tear on all moving parts including the cam, wormgears, and so forth.

There are a few things you can do to decrease the above self-destructing scenario, 1) under absolutely no conditions, do not wait for 3,000 miles to change your oil! - do it a lot earlier; and 2) use GM Part No. 3634621, coolant pellets, which act as sealants to forestall antifreeze intrusion. Use the recommended dosage but no more because they have been known to seal other voids such as heater and radiator cores. Change the water at least annually.

P.S. There is an incredible, almost completely unknown book on the HT4100 entitled, "The HT4100 4.1 Liter Digital Fuel Injection Metal-Aluminum V8 Gasoline Engine - Cadillac's Miscarriage of the Millenium." The book contains an incredible wealth of information on the design, manufacturing and engineering problems/defects of the engine. It is an eye-opener and a rare book and is somewhat difficult to obtain. If you want to try to obtain a copy, the distributor can be reached at APNEWSLETR@aol.com.

Thank you Jack - your assessment of the HT is very good. However, a miss is as good as a mile. Check out the above-referenced book for at least 20 times more dirt on that piece of crap of an engine.

Sincerely,

HT4100 Whiz!

I had an 83 Eldo for awhile. The 79-85's are beautiful automobiles and they're wonderful to drive. The biggest thing to be aware of in this generation is the different engines. 82-85 had the infamous HT 4100. Its not a bad little engine from a driveability standpoint - although it is somewhat underpowered.

Here is a copy of a post that a member of the Cadillac Mailing List sent me when I was first learning about my car. It pretty well summarizes all of the info I found:

"I have a soft spot for those HT4100 cars

myself, they are such nice cars to drive with the light engine. The HT4100

gets pretty good mileage too.

Frankly, it would be difficult to enumerate every possible HT4100 failure

mode, but here's some common ones-

Failure of the seals at the cylinder bore inserts bottom end, permits

antifreeze to enter the oil pan, and if not caught VERY early, will usually

lead to engine seizure or catastophic damage. This is the big one! You're on

the right track as regards changing antifreeze frequently, and using the

additive. Theres apparently a conflict in that the antifreeze itself

contributes to deterioration of the seals themselves, kind of a materials

incompatibility. GM has recently introduced an altogether new type of

antifreeze (DexCool) which might work better, I'm looking into it presently

to see if theres any conflicts or if it is OK. It likely is fine.

Pretty much every other area of the HT4100 has caused someone troubles, but

the main things aside from the leaking antifreeze is the following;

The Aluminum brackets used up to mid 1985 to hold the rocker arms on can

crack and fail, there is a new replacement that has been redesigned with

considerably greater material that seems ok.

HT4100 versions of the engine break pistons if they are permitted to spark

knock- usually 89 oictane fuel will cure this issue altogether. Retarding

ignition timing is a second possibility, but makes them sluggish.

The distributor gears and oil pumps wear prematurely, particles from them

are frequently evident in crank bearings upon disassembly. Replacement of

the oil pumps at regular intervals might be a worthwhile idea. Pulling the

distributor, and installation of the updated gear might be worthwhile also.

The aluminum engine tends to leak oil and develop intake manifold leaks due

to the larger coefficient of expansion of aluminum. The different parts

expand and contract at about twice the rate iron parts do, which stresses

gaskets, so they dont last quite as long.

Crankshafts and main bearing caps fail suspiciously often, although I feel

this is most likely abuse. It might be possible that premature engagement of

the fourth gear lugs the engine to exacerbate this problem. I would regard

it as a worthwhile practice to drive the car in 'D" under 60 MPH if you

sense the engine is overworking at all.

Overall, I think the HT4100 can be made reliable, I've been trying to see

what could be done to keep them from failing in the first place. The 4.9

liter engine used in the 1994 Cadillacs is a direct descendant of the

HT4100, so there's hope! Best advice I could add to what you're already

doing is think about adding another oil cooler to the factory in-rad one,

check the distributor gear for wear, look into replacement of the oil pump

when you can, and check the oil for signs of antifreeze before driving off

when you can. The antifreeze leaks, when they occur, are quite slow, it

takes a long time to reach critical levels in the oil- however there is no

warning light etc to indicate a problem. Oil and water dont mix as you know,

so it will be evident on the dipstick, or if you take a whiff of the oil

filler cap before driving off. Antifreeze has a sweetish alcohol smell, oil

smells much like wax. Hope your nose is better than mine! You'll see the

milky white contamination on the dipstick easily.

My ultimate ambition regarding HT4100's is to produce a kit of small parts

and seals to bulletproof the main troubles with the engine. Currently, I'm

playing around with metal seals for the cylinder liners, which should be

unaffected by the antifreeze. I'll keep you and the CML posted. If you are

positively rolling in cash, GM still sells BRAND NEW HT4100's for about

$3500- these will be discontinued before long I suspect however.

Your feeling regarding failure to maintain the HT4100 leading to engine

failure are largely correct. They really are fussy about being heavily

serviced, this tends to extend life but is by no means a certain cure, many

very well kept ones have failed prematurely. Its all the insurance you have

right now however. If you're a tinkerer, a blown up HT4100 engine core is

very cheap, you might want to watch your local free ads paper etc. for one

to take apart at home to see for yourself whats inside. Its a beuatiful

little engine, just flawed in some ways. When they are working as intended,

they're unbeatable, a model of smoothness and refinement. "

I never had any major problems with my 4100. But mine was an extremely well-maintained 1 owner with 95k miles when I got it. So I don't know how my experience compare to others'. I do know that wrecking yards were full of nice 4100 cars with bad engines.

Regarding engines in the other years - Most 79's came with the Olds 350. Great engine. Most 80's had the Cadillac 368. Also a great engine. 81 was the V8-6-4 year. The engine was also the Cadillac 368, but it was equipped with valve deactivation solenoids that had ongoing problems. Its my understanding that the 8-6-4 system can be disabled though, leaving you with a 368.

Based on all of the above, if I got another one of these cars, I'd want a 79 or 80.

From 82 to 85, the Seville was basically a 4 door Eldo, with the "ramp-back". So the above applies to them too.

Pre-82, the Sevilles were basically 4-door Novas with a fuel-injected Olds 350. These are also among my all-time favorite cars. Very good styling, good power, and a great size for the practicalities of daily driving.

There are alot of folks on the Cadillac Mailing List that dabble with cars of this era. Here's a link to their archives:

http://bluedog.cc.emory.edu/archives/cml/

Hope this helps....

Jack

[GreenMachine]

I'd see if you can find one with an old's 350 or Cadilac 368. Much better than the HT4100 in power and reliability from what I have heard.

[scottshoe]

I love those 80's Eldo's and Riv's. I think the term "it rides like a Caddy" was termed after people rode in one of them. I have a 1983 Riviera T-Type (turbo V6, not V8) that has been in my family since it was new. It's my favorite car to just go for a sunday drive in. It's not a rocket, but it sure is smooth! My Dad ordered one after seeing a Riv that GM had done up at the Milford Provings Grounds, it was dark blue with blacked out trim and the turbine wheels that had the black inside the fins... It was so 80's!

[coolnesss]

I had an 84 Eldorado that I got with 28k miles and drove for 10 years. I only had trouble with the motor one time.

I'm a fast and hard driver. It lacked power, similar to the feeling of a plugged catalytic converter. After many trips to mechanics, one finally said: I heard from a cad mechanic that Marvel Mystery Oil can cure the problem - and should be used regularly in the gas. I forgot what the problem is that it remedied. Anyway, I started pouring it in, and in a few tankfulls of gas, the problem was solved. After that, I added MMO to the gas according to the can's instructions, and had no more problems at all.

I had to replace the trans at about 70k miles, which I thought was premature - but I live in the hills and we tend to have more trans repairs as a result - other repairs on the car were consistent with its age and mileage - but - overall, it was one of the most comfortable, stylish, cool cars I have ever owned. I LOVED it. Let my god-daughter borrow it for awhile and she trashed it . . .

[Patrick7997]

Obviously, the HT4100 is to be avoided... some good posts in this thread breaking that down very nicely.....

I had a 79 Eldorado. It had an Olds 350 in it, with fuel injection. The concept was remarkably similar to a modern setup.

The problem with THAT is that the computer goes out, and the car is dead. Last I heard, there was 1 company in California who could fix it, but it was expensive, and took 6 weeks. You send yours in, they send it back in 6 weeks. So, no car for awhile....

I loved the car... I bought it with 120k on it, drove it to 160. The engine was tired, and had problems. Oil & radiator were swapping both ways freely. Leaking oil... frame rails rusting badly... I wanted to restore it, but it was not a candidate for restoration.

I have considered exactly what you are considering many times.... if I was to do it, I would look real hard, and try to find a 79-81 Eldo, no HT4100, in real good shape. It will cost more, but save you a fortune down the line. There are examples out there, with real low miles, all original. Prices really vary.

Good luck. I still think that particular Eldorado was one of the sharpest cars Cadillac ever made. And as far as owning it & riding in it, it was a great ride. Drove super nice. Very very comfy. Zero effort steering, Lazy Boy seating... You could drive 300 miles in utter and complete comfort.

[KHE]

HT4100 Miscarriage of the Millenium

To those of you who "love" the 1982-1987 Caddies underpowered by the most unmerchantable mill Cadillac ever frankensteined, the supposed "High Technology" HT4100 metal-aluminum engine, I suggest you swap it out. The HT is absolutely the greatest single disaster in GM's engineering history, held together with spit and glue. The engineers started out with good intentions but went to hell in a handbasket due, in part, to prematurely releasing it. The rationalization I see on some threads that it was compliance with C.A.F.E. standards es el caca del toro. It was negligence.

That engine was fatally unmerchantable out of the gate. The 350 swap out seems to be working well. Go to: http://www.eldocountry.com/eldo/swap.html for the details. It's no piece of cake but if you want to keep your Caddy, check it out. The major problem with the HT4100 is glycol-antifreeze intrusion, a condition for which the HT4100 is both infamous and notorious. In addition, the engine is a bi-metal engine (aluminum and iron) which vibrate at different rates and cause the engine to virtually vibrate itself loose. This, in conjunction with the antifreeze results in a self-destructing vicious cycle (some fancy schmancy physics known as variable "coefficients of expansion.") There were also problems with the engine's gasketing being able to cope with all the block and manifold movement. The antifreeze wipes out the lubricating properties of motor oil which accelerates wear and tear on all moving parts including the cam, wormgears, and so forth.

There are a few things you can do to decrease the above self-destructing scenario, 1) under absolutely no conditions, do not wait for 3,000 miles to change your oil! - do it a lot earlier; and 2) use GM Part No. 3634621, coolant pellets, which act as sealants to forestall antifreeze intrusion. Use the recommended dosage but no more because they have been known to seal other voids such as heater and radiator cores. Change the water at least annually.

P.S. There is an incredible, almost completely unknown book on the HT4100 entitled, "The HT4100 4.1 Liter Digital Fuel Injection Metal-Aluminum V8 Gasoline Engine - Cadillac's Miscarriage of the Millenium." The book contains an incredible wealth of information on the design, manufacturing and engineering problems/defects of the engine. It is an eye-opener and a rare book and is somewhat difficult to obtain. If you want to try to obtain a copy, the distributor can be reached at APNEWSLETR@aol.com.

Thank you Jack - your assessment of the HT is very good. However, a miss is as good as a mile. Check out the above-referenced book for at least 20 times more dirt on that piece of crap of an engine.

Sincerely,

HT4100 Whiz!

HT4100 Whiz,

Thre have been a few changes to the gaskets in the last 20 years or so as gasketing technology has advanced. The replacement head gaskets and intake gaskets from the GM are FAR superior to the original designs from 25 years ago. Any Goodwrench 4100 engine incorporates the latest engineering changes to the gaskets and other areas of the engine and the reliability is good. In 1998, JD Powers published a listing of the most reliable cars after 10 years on the road. A 1988 Sedan de Ville with the 4.5 engine scored #1. The 4.5 engine is a bored 4.1 and the 4.9 engine is a stroked 4.5.