News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

1985 Eldorado - HT4100 Engine Problems?

Started by gofast123, October 28, 2012, 06:27:57 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

gofast123

I've heard the stories about this engine many times (iron heads / aluminum block).  I'm looking at an '85 with 25,000 miles on it.  Did GM (Cadillac) have this problem corrected by the 1985 model year?  If not, is there any way to tell if I'm walking into a problem?  Is this a car to stay away from?

Opinions Welcome!  Thanks in advance...

austingta

IMHO, the ONLY years to buy that body style are 1979 and 1980. And then, not the diesel. The HT4100 is better than the V8-6-4, but only barely.

I would like to hear other opinions.

936CD69

IMHO the V8-6-4 was INFINITELY better than the early HT like up to 87. In the early 90,s I had to rebuild a 29K HT in an 85 Eldo..two weeks after I bought it. And I would do it again...rather underpowered but the Eldo was a sweet driver
Craig Brillhart CLC# 26217
1993 Sedan deVille Spring Edition Carmine Red White Top-SOLD!
1993 Sedan deVille Spring Edition Triple Black
CLCMRC Benefactor #302

Dave Shepherd

As mentioned 85 was probably the worst version of the HT, I was a field troubleshooter for Cadillac back then, yikes, we couldn't keep them running, camshafts and subsequent internal engine damage were the #1 issues.

cadillactim

Dave

Why was 85 the worst? I thought they had improved them in 85. I rebuilt a 83 one time, and even though the engine ran fine afterwards, I traded it shortly thereafter once I saw firsthand how the engine was designed. Before that I had a 82 that was running fine, then just locked up solid on the interstate. Couldn't turn the crank in either direction. But what were the design changes from 82-85?

My big concern would be the age of the sleeve O-rings at this point. Just being 27 years old would worry me.

Tim
Tim Groves

76eldo

79 had an Olds 350. 1980 and 81 had a Cadillac 368, same engine family and dimensions as the 472, 500, and 425.  In 1981 they tried a version of variable displacement and called it the V-864.  Solenoids controlled the variable displacement and were generally disconnected due to the problems encountered and then then you had a 368 inch motor with no computerized wizzardry.

In 82 and 83 the HT4100's were really bad.  Not that 84 and 85 were that much better, but at least they knew they had a clunker of an engine and started to do updates and modifications.  1985 was the best of the bunch of the 4100's.  Later in the 80's the punched them out to 4.5 and 4.9 but they were designed for FWD and mounted transversely.

1980 is the best of the bunch in my opinion, but a low mileage 4100 is possibly a safe bet, but always keep in the back of your mind that you can have sudden catastrophic failure and will have to dump 4K to 5K in the car to keep it running with a new or rebuilt engine.

Keep that in mind when you buy one.  There are some engine swap possibilities but they are difficult and require some engineering and parts from earlier models.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

waterzap

Pm me your email. Will send you some articles on the HT4100. They made a lot of changes in 85. The pre 85 and post 85 blocks are very different. Check the oil, check the coolant. Intake manifold failure corresponds with milkshake oil. Drive the car and see how it feels. These aren't fast cars, but they aren't dead slow either. If it can barely climb a hill, the engine might have problems. Do you see any oil leaks?

Like anything, these engines can be fixed. A few thousand probably at most. A friend of mine had a VW Passat, and I think when his engine died it was going to be between $6k and $8k to fix. This won't be that much.

Where are you located? Just like the N* motors, you need someone that knows these engines if you ever want it rebuilt.
Leesburg, AL

waterzap

#7
As a side note. Have had my 87 Deville with the HT4100 for a few months now. So far so good. Actually put around 300 miles on the car the last week. Not planning to drive the car that much, but taking a bit of a trip this weekend. Changed the coolant, oil, hoses, belt and a few other things, and so far the car hasn't missed a beat. Probably the nicest riding car I own. If I had the space and money and got offered a nice 85 Eldorado, would not hesitate.
Leesburg, AL

TJ Hopland

My questions would be:

What condition is the overall car in?

What do you plan to do with the car?

What sort of money are they asking?

Im looking at a 4100 car. I have owned them before.  Im not afraid of them.  Im getting it cheap enough that I dont care how long it runs.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Dave Shepherd

#9
I was stuck trying to keep the dealers and shops happy keeping these engine/cars going, no HT 4100 came up to accepted standards back then, Cadillac tried their best to make them " tolerable". I am not even bringing into play unreliable sensors, gaskets, multiple oil leaks and low power complaints. So now everyone is so wary of the issues with that generation that a decent running one comes to the top of the heap like it was representive of all of them, not! On the other hand any of these cars still running today more than likely have have had major repairs already done or new engines sometime in the past.

Scot Minesinger

Aside from reliability problems the 4.1 is underpowered.  The way people drive today, even with my 472 you have to get into it a little to keep up with modern traffic at stop lights sometimes.  I would say that even with a perfect 4.1 you will not enjoy the driving experience if power is something you appreciate at all in a car.  If you buy the car and enjoy a little bit of pep, I would save for the installation of a 1979 drive train.

My Grandmother owned a 1982 Sedan DeVille with a 4.1 and she did not suffer any reliability issues during the first year they made them.  I drove the car on a 100 mile trip in 1983 at age 22.  It seemed that the throttle was set up so that at about one third depression of the accelerator you were at full throttle, giving the impression of more power than there really is at takeoff from a dead stop.  There is no good power on the open road.  She offered the car to me in 1990 as a gift and I passed due to the 4.1 under power issue.  My Dad eagerly accepted as the second alternate on the gift.  When my Dad picked up the car, he said "I wonder what engine this has?" with excitement.  Not surprisingly, within six months he sold the car because it was not fun at all to drive.

There are a lot of people who enjoy the 4.1, but I'm just not one of them.  For people who do not expect power from the standard of the world car manufacturer, then it could be just fine.  The 1985 Eldorado is a beautiful looking car from a non-mechanical perspective to me.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Guidematic

 There were many improvements made by 1985. Once they had the sore spots identified, the updates began. Generally the '85 are OK, but they do suffer the same maladies of any aluminum engine if it hasn'r been properly cared for. You've heard mention of other Cadillac engines and the timing mchains, the nylon coming off and plugging the oil pick up. Same issue with these.

You want the coolant to be clean, the oil to be clean. And see of you can obtain the maintenance records. Proper maintenance is very important, even if the car has low miles.

Many of these cars have replacement engines too. GM replaced them with Goodwrench motors well into the 90's. These engines have the updates already incorporated into them, and they are good engines. They are a couple of quick giveaways to identify one, the easies is the cast aluminum rocker covers. The real identifier is the additional ribbing on the block.

These are beautiful cars both to look at and drive. And they can return some pretty good fuel economy numbers. They are not fast by any means, but can cruise pretty effortlessly at 70-75 MPH once you get there.

Mike
1970 Fleetwood Brougham 68169
1985 Eldorado Coupe 6EL57
1988 Eldorado Biarritz 6EL57
1990 Brougham d'Elegance 6DW69
1994 Fleetwood Brougham 6DW69

Guidematic


Oh, BTW, I p;urchased a used Goodwrench engine for my '85 Eldorado. I removed the pan, rocker covers and front cover to inspect the internals. I elected to replace the crank due to some scratching. The timing gear on this one is all metal. So I think It's safe to say the Goodwrench engines have steel gears.

At the time, the HT4100 was considered to have a pretty competitive specific output. The power seems very low by today's standards, though. Also, originally this engine was designed to go into the lighter FWD cars that debuted a year late in 1985. These cars perform much better. This engine in the full sized C/D cars really taxes them. The lighter E/K cars also have slightly better performance than the full sized cars.

Mike
1970 Fleetwood Brougham 68169
1985 Eldorado Coupe 6EL57
1988 Eldorado Biarritz 6EL57
1990 Brougham d'Elegance 6DW69
1994 Fleetwood Brougham 6DW69

Eric DeVirgilis CLC# 8621

#13
Agreed with the posters who feel the 4100 had improved in reliability through the successive years. I once had an out-of-towner stop in with a '84 Brougham he had purchased new. The car had just shy of 400,000 miles. When I asked him what number engine he was on, he replied with a laugh that everyone asks him the same thing. Amazing isn't it?

The sad fact remains, and as I've said it before many times, this is hardly a robust engine. The problems that plague aren't just limited to an area or two, but many. Compounding the problem is that this is not an engine that likes to be tampered with as it ages. That means that if you go to do a head gasket job on your 30 yo 4100, chances are you'll find the steel bolts have electrolically "welded" themselves to the aluminum casting resulting in chunks of your engine block breaking off when you try removing them. Such occurred in my case resulting in a $2.200 Jasper reman engine plus another $800 in labor. External fasteners were no easier turning the simplest and most routine of tasks into a series of nightmares.

Personally I never had a problem with the lack of performance the 4100 is so noted. In fact they've always seemed quicker than the 307 Olds V-8 to me.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

waterzap

#14
400,000 miles? Thats amazing. Just amazing.

All very good points about the HT4100, but it all really comes down to how much you spend on these cars. I think the HT4100 engine problems are built into the price of the cars by now.
If you can get one for $2,500, and spend another $3,000 for a new engine, you have a great looking, great driving car for $5,500. New shocks and a few other things, $6,000

Not much you can get out there for $6,000
A few months ago I rented a Hyundai Elantra for a cross country trip. I wasn’t impressed at all. I think they cost around $21k -$25k new for the one with AC and auto transmission.

The car was loud and the ride wasn’t as very nice. The $6,000 Eldorado with the new engine will probably ride better, be just as reliable, and look better. Bit worse MPG, but not that bad. You can buy a lot of gas for $14k.
Just my opinion.
Leesburg, AL

xcaret

Being an ex auto wrecker and driving an 1982,1985 and 1983 Eldo in the past ,Plus parting a few out , the thing I noticed besides not a lot of power was when the eng started going bad you could often hear a dull thud,thud sound coming from the engine at an idle. Being that I was only selling them used for $600.00 I never thought of repairing one ,just sold them to the core eng buyer. My 83 and 85 started doing the same thing. As for the rest of the car I have no complaints   

Eric DeVirgilis CLC# 8621

Quote from: austingta on October 28, 2012, 07:08:12 PM
IMHO, the ONLY years to buy that body style are 1979 and 1980. And then, not the diesel. The HT4100 is better than the V8-6-4, but only barely.

I would like to hear other opinions.

Sorry to differ but the V-8-6-4 is far superior plant than the 4100. There's really no comparison.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

Tim Pawl CLC#4383

1985 Eldorados after VIN FE623772 and 1985 Sevilles after VIN FE812094 had improved intake manifold gaskets and block casting changes.   Anything before that and you are at risk. We had a 1985 Eldorado Biarritz convertible with VIN after those shown and put 146,000 miles on it without issue, but changed oil every 2500 miles and coolant change with pellets every two years.
It is still around, saw it on the road this summer,  we sold it in 2003 , often wonder how many miles are on it now.   Tim Pawl CLC#4383

Dave Shepherd

Quote from: ericdev on November 21, 2012, 09:05:03 AM
Sorry to differ but the V-8-6-4 is far superior plant than the 4100. There's really no comparison.
Agreed, basically the engine was an 80 368 all steel engine, the computer and rocker solenoid devices were the issue as the transition to 8-6-4 was very slow and caused customer complaints. Mileage was not as good as the HT series, but no engine issues at all.

Eric DeVirgilis CLC# 8621

The transition between active cyliders was far less perceptible than an automatic transmission shifting between gears. Biggest annoyance I always thought was 6-cyl mode which was very rough. 8 was smoothest and 4 was okay. One of the "green lights" for variable cylinder operation was the transmission needed to be in 3rd gear so we'd just pull the plug from the transmission so they'd always remain in 8 cyl mode.

The primary issues the V-8-6-4 had nothing to do with its mechanical integrity which was excellent but with early electronics and/or the primitive connectors that were used. These issues had been addressed and sorted many years ago when '81s were active in the field. Unfortunately to this day, many still equivocate unreliability of 4100s and diesels with that of the V-8-6-4. Even diesels (1981-up or Goodwrench replacements) can get 100,000s miles of reliable service- properly tended.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute