Cadillac struck out with engines in the early 1980s. The V8-6-4 was a good idea in search of the engine management of the future. Despite a diesel-crazy public after a pair of fuel crises, General Motors had so botched the execution of its V8 diesel program that only recently have diesels from all brands been able to shake the severely damaged reputation. It was into this morass of dissatisfaction that General Motors pushed the HT4100 V8 in an attempt to stem the tide of failure.

The HT4100 was a lighter and smaller clean-sheet design built in a new highly-automated, computer-intensive plant. "When the engine works so well for you, it's no surprise," says this GM video, "we knew it would, and so did the computer." That's a shocking disparity compared to the real world experience of HT4100 owners. "We call it high technology, but we hope you'll call it just another pleasant Cadillac experience." The HT4100 was yet another example of GM's ability to engineer but not execute engine-wise, and it was the third failure for Cadillac within a very short timespan. Pleasant is far from what leaking, failing, iron-head, aluminum-block HT4100s were called.

Check out the video below, and remember that Cadillac's next attempt at atonement and a "pleasant experience" was the Cimarron. It's a good thing there's all this past experience for GM to reflect upon, so that it doesn't launch the 2.5-liter four-cylinder ATS with disastrous results or completely alienate the premium European buyers it seeks. Let's hope they're paying attention in history class.



I'm reporting this comment as:

Reported comments and users are reviewed by Autoblog staff 24 hours a day, seven days a week to determine whether they violate Community Guideline. Accounts are penalized for Community Guidelines violations and serious or repeated violations can lead to account termination.


    • 1 Second Ago
  • 76 Comments
      A3TDI
      • 2 Years Ago
      My first job out of college was at Cadillac "Quality Engineering" department at the Clark St Plant, Deetroit, MI, USA. Each week, a train car filled with these iron heads showed up from dealers and 2 or 3 hourly guys and I would unload them and catalog the day's toll. The engine was originally designed with aluminum heads, but the aluminum block flexed and caused the wet-lined cylnders to leak coolant at the top (head). The block flexing also caused the lower main bearings to burn up. In an attempt to stiffen the block up, they put iron heads on the aluminum block; a total patch and It didn't work. It's a very different company that it was when I worked there and they seem to be headed in a good direction (finally).
      SloopJohnB
      • 2 Years Ago
      It was mildly maintenance-intensive...underpowered for sure. There was a GM additive/chemical that had to be added to the coolant system to prevent corrosion. If you didn't do that, then you had problems. But it sure was stupid to make an aluminum block with iron heads.
        carguy1701
        • 2 Years Ago
        @SloopJohnB
        Did they ever say WHY they went with that?
          ss1591
          • 2 Years Ago
          @carguy1701
          They used the Iron head to help stiffen the aluminum block but it didn't work as planned. A relative of mine worked on it and used to laugh at how much extra material Mercedes used adding extra supports in their engines. It had nothing to do with management trying to save money it was just bad engineering and a lack of real world testing. I know a lot of people lost jobs over it and for good reason. They did the same thing with the Quad 4 engine that Pontiac used and GM allowed them to spend whatever they needed to. The real problem was a lack of experience with aluminum castings and how to attach bolts that didn't pull out.
      K.L.
      • 2 Years Ago
      I had two 81' El-dogs with the 4-6-8 6.0 liter 368 cu.in. engines that made 140 hp at 3800 rpm and 265 lb·ft at 1400 rpm. The thing that drew them to me was the fact that the 368 has the distinction of being the last traditional "big-block" cast-iron pushrod V8 engine available in production cars. 1981 was the first year electronic "digital" instrumentation was an available option. They had auto leveling suspensions, auto side-view mirrors with an exterior temperature gauge and chromed out. Those cars stock were faster than my boys 87' G marquis and 85' G Prix with fuel injection (they had throttle body injection) and destroyed the 4100s since they had 75 lb·ft more torque at 600 less RPMs. It was not a move forward in my opinion plus it was fun just looking at the dash waiting for it to drop down to 4 or 6 cylinders.
        jz78817
        • 2 Years Ago
        @K.L.
        the problem with the 368 was that it was 368 c.i. but the block was designed to be 500 c.i. Tons of unnecessary weight in that engine.
          jz78817
          • 2 Years Ago
          @jz78817
          yes. That engine family started out with the 472, which was then stroked to 500, then cut down to 425, then cut down again to 368.
          carguy1701
          • 2 Years Ago
          @jz78817
          It was based on the Caddy 500 big block?
        carguy1701
        • 2 Years Ago
        @K.L.
        Your son had a GP with TBI? I thought they were all carb.
        HUMANMPC2000
        • 2 Years Ago
        @K.L.
        Back in 1980 my pop's then a new Eldorado with the diesel engine, i remember having to plug it up overnite to keep the engine oil warm in the winter month's here in Detroit,and before we could drive the car my pops would let me go to garage to start to warm it up..I remember i auto leveling suspension that would light up on the data info dash before you could pull off,But the only trouble we had with the car was it kept getting stolen it happen at least 5 times,with the sim convertible top,vougue tyres and star wire wheels,the last time I remember it got stole I had miss the bus for school and came back home,and I asked my mom's did pop's leave because the garage door was open and the car was gone..!!!! LoL So by then my pop's was sick of that **** by then so he traded it in on the newest model Cadiilac then the Cimmaron..Now the car sucked we went from the top dog Eldo too the Suckaron..but my then pop's used too let me drive it when I was learning to drive...
        K.L.
        • 2 Years Ago
        @K.L.
        Oh, and i was born in 82', I liked Caddies when i was younger and love them now
      Tony
      • 2 Years Ago
      It really wasn't that bad once it became a 4.5 and the 4.9 liters are pretty solid. Having on-board diagnostics was also nice.
        carguy1701
        • 2 Years Ago
        @Tony
        Didn't it still use the aluminum block, iron heads configuration?
      jwoaks
      • 2 Years Ago
      My 87 Deville has 175k and still runs strong. Motor never has been touch except smog pump. It is underpowered but 27 mpg on the highway is nice to have.
      Mike
      • 2 Years Ago
      Great video thanks for posting. The HT4100 was from 1982 to some 1987 Cadillacs. I think the HT4100 was very bold on GM's part. In retrospect it was a transitory engine, having throttle body versus carburetor, digital fuel injection versus port fuel injection, and some aluminum components versus all iron. I think GM and Cadillac get a bad rap from some people because this engine was not as robust as it should have been. To a point this is true. The HT4100 was a turning point in the auto industry. Up until the HT4100 cars were so simple and people worked on their own cars. In the 1950's 60's and 70's it was not uncommon to see someone's dad under the hood of the family car on a Saturday. This was a time before so much pretentious entitlement. But, with the HT4100, if a "shady tree mechanic" did not service the cooling system properly, or the owner did not pay attention to the coolant, they would be in for a big surprise. Truth is, some Cadillac owners at the time had the expectation of greatness based on the following decades and were further enticed from recent new modern Cadillac designs and were so busy raising their families and working a solid job to pay for the top of the American Dream they did not read the owners manual. They were unsuspecting and not the least bit concerned. Cadillac tried to educate the public about this engine. I believe this video was played in dealerships. If people read the owners manual they would have seen the HT4100 required coolant designed only for aluminum engines and it was also necessary to add GM Part # 1825-M coolant supplement (sealant) to prevent damage to cooling system components. As with all cars, you should check the coolant level regularly and if there is a sudden loss of coolant stop the engine and if it is safe immediately open the hood to let it cool quicker. Because Cadillacs are so high tech and sophisticated (like all luxury cars) every luxury car owner should read their owners manual from top to bottom to learn a lot about their car and avoid neglegent operation. There is no such thing as a poor person Cadillac (or any poor person luxury car old or new for that matter). Once GM came out with the red letter HT4100 R (factory rebuilt) they understood what went wrong. The aluminum intake and block were too weak to handle neglegent and or extreme operating conditions (such as flooring it with low coolant on a 100 degree day) so they reinforced them. Bottom line is: Cadillacs evolved with new parts and fluids. They were not owner serviceable and therefore should of had higher heat tolerances. These industry sweeping car and engine downsizing changes were necessary to meet the safety, fuel efficiency, and emissions damands of lawmakers.. too much change imposed too quickly on the American auto industry which didn't leave enough experience or time to test the new designs.. or in the HT4100's case you need to be a GM technician or engineer to know how to properly maintain it.
      Mike
      • 2 Years Ago
      GM and Cadillac were experimenting with a lot of new things and they rushed to create the 4100 because the 1981 model year V8 6 4 was notorious with it's slow Eaton Corp. computer (which in short electronically activated and deactivated the cylinders). To Cadillacs credit, anyone remember how slow and primitive 1980's DOS and Apple computers were? My aunt had a 1986 Coupe DeVille with the HT4100 that pioneered present OBDII and it was very sophisticated for it's time and made it to 175k before the cooling fans didn't work one summer day in traffic and that was that. But, she did replace the whole car over in parts and rebuilt the transaxle many times to keep it going a decade. Those front drivetrains were designed for GM 4 and 6 cylinders and could not handle the torque of the 4100 V8. If you ask me a lot of new "blank sheet" designs different from 70 years of traditional Cadillac building went wrong. New front drive unitbody. Iron heads with aluminum block. Didn't they learn from the Chevy Vega engine? Ideally they probably thought most Cadillac owners would keep up with regular maintenance but this was the era when Cadillacs became non owner serviceable. Even still, they knew these engines would be sensitive to heat. All the early 80's Sevilles and Eldos had a specific light to the right of the speedo to warn the driver of coolant temp. Vulcanized rubber gaskets under controlled heat are safe, but once the engine heats up from lack of coolant or any problem that would cause runaway heat those gaskets would melt like a chocolate bar on a hot day. Any engine would fail without the correct coolant / mixture, proper level, cooling fans, etc, and the 4100 needed a coolant flush and vacuum hose check every 30,000 miles. Do a degree even they were unsure so at the end of the line they checked those 4100's to make sure they ran ok but that is Not enough time or World testing because they were in a rush. Everyone was paranoid about gas since 1973, the CAFE numbers demanded more mileage, and Federal Laws and Emissions Laws permanently changed the auto industry dynamics. Plus I read GM received info in the late 70's / early 80's recession that gas was (speculated to be) $5 a gallon by 1985 and this is one of the (probably big) reasons why the GM unitbody front drive "corporate car cousin" regime took over. Regardless I still love Cadillacs. Owning a Cadillac is still and always will be "The Penalty of Leadership." I've driven everything and I'd take a Classy Caddy over anything but a Rolls. GM and Cadillac in those days (hindsight is 20/20) I think had new designs and had a lot of emphasis on electronics, technology, and computers versus more concentration on tried and true (like now) robust mechanical designs preventing / factoring well in worst case situations. The 1980's mistakes by GM sadly paved the way for competition to perfect upon and this is still unfortunately evident to the present day. GM, Cadillac needs young buyers!
      Mike
      • 2 Years Ago
      To understand why the HT4100 failed you have to understand the safety and risk variabilities in the design. Perhaps the single biggest design flaw was the Stop Engine Temp. or Coolant Temp. / Fan Warning Lights. Unless there was the correct coolant level and proper 50/50 to 70/30 mixture, the computer would not have the correct coolant temperature (which is what turned on the warning lights). The common misconception to the average consumer then was this modern and high technology car would tell you when there was a problem (as indicated through hidden panel lights and very few or no analog gauge instrumentation). The HT4100's all new engine specifications and maintenance requirements and big panels of cluster lights were also relatively new and not yet fully understood by the average consumer. The irony was if a light came on, you took it to your Cadillac dealer for service.. you were not expected to get under the hood and try it was too modern and complex. But, if the HT4100 got low on (usually dirty and corrosive or unsealed coolant) and the engine got hotter than normal you would have no idea unless you saw the coolant reservoir level (the owners manual says to check this at fuel stops). If left uncheked low coolant would cause a runaway situation. As the operating temp. increased the aluminum block would slowly warp away from the iron heads and over time more and more coolant would seep through the gasket. When it overheated a rush of coolant would blow through the head gasket and seize up the engine (and to many this came as a total surprise). Perhaps if people understood then the many limitations of the panel warning lights, or if there was a dash engine temp. gauge, many GM and Cadillac owners would have noticed the temperature was above normal and done something about it before it got too late. By comparison, the 1981 Cadillac 368 (L62) V-8-6-4 iron block ran at 180*f for emissions and the HT4100 ran at a much hotter 210*f and was made from a weaker aluminum. If the HT4100 reached 250*f or more it was done. That is not a big margin for error and a low / coolant problem exasperated quicker overheating (such as climbing a long hill on a hot day, or idling for long periods in traffic, or water pump or electrical fan failure). Unfortunately the only examples of these cars still in existence today are running because their owners understand the trouble areas and keep their HT4100 extremely well maintained; -and even that is no 100% guarantee. But, when running propery the HT4100 has a very distinctive note upon startup and a high torque muscular growl during acceleration. For it's time it was very innovative, refined, and sophisticated. If the HT4100 was durable like it's iron ancestors and had a driver viewable temperature gauge versus a warning light it would have been better and many more might have survived. It's too bad the 1980's and 90's saw some of the best looking and last traditional Cadillacs ever produced.
      Joe Y
      • 6 Months Ago

      I always found it bizarre that with all the engineering that went into these and Digital fuel injection and fast burn combustion chambers etc that the 4100 engine could only muster a very weak 125 horses and 190 torque when introduced four 1982. Compare that with the credit option Buick 4.1 liter 4 BBL V6 which made the same 125 HP and a full 20 more torque at 210 or the Olds 307 which was making between 140-150 HP and 240 torque. Even the underpowered Buick 231 2BBL V6 made the same torque as the 4100 at 190. 

      Somehow for 1983 the power and torque went up through detail internal modifications according to Cadillac to 135 HP and 200 torque which still was less than the Buick 4.1 V6!

      It seems that Cadillac would have been far better off giving this engine further development, introducing them instead on the downsized 1985 C-body cars they were intended for, and instead continued producing the superior 6.0 liter V8 coupled with the then new 200R-4 overdrive transmission for better highway mileage figures. Of course the ever interfering government and Cafe was the instegating factor in pushing the HT 4100 development forward early along with the 8-6-4 woes and less than expected mileage. The interesting thing was that the 8-6-4 did live on until the 1984 model year in the limos and by that point was reportedly much better as time went by.

      Walt
      • 2 Years Ago
      More weekend domestic hateraid from (Import) Autoblog. Of course, being an arm of the socialist Huffington Post, it only makes sense. When American companies fail the capital that built them is lost. Lose enough capital and capitalism fails which will hopefully usher in your dream of a socialist utopia. We've had a taste of what a socialist utopia might look like for the past for years. Only the die hard, committed socialist would continue to push that failed agenda. Capitalism will rise again if for no other reason because it is the only system in the world that has ever produced the most good for the most people.
        Ryan
        • 2 Years Ago
        @Walt
        DUDE, it's AUTOblog, not POLITICSblog. This engine and this era of Cadillacs are known to b sub par at best! I think the comment at the end may b a little much, I believe GM and Cadillac are completely different then in the 80's both in quality and as a company, but nothing in this blog shouts politics and nobody wants to hear this bs. Talk about the engine. There's no conspiracy at autoblog.
        carguy1701
        • 2 Years Ago
        @Walt
        You clearly know nothing about cars. The HT4100 WAS a failure.
        Walt
        • 2 Years Ago
        @Walt
        Re-read my comments. DId I say anything about the HT4100? No. And are we're going to have a replay of every failed engine for the past 30 years? Then let's see an in depth article on Toyota sludge engines. An improperly designed PVC system was the culprit, yet Toyota (as usual) denied there was a problem because fixing it would have resulted in having the engines re-certified by the EPA. Newsflash - poor design is not the exclusive domain of any one manufacturer, yet domestic vehicles are continually singled out on this site even if it takes going back 30 years to dredge up some fresh domestic hateraid to quench (Import) Autoblog's insatiable thirst. And what does democracy and the constitution have to do with this discussion?
          Ryan
          • 2 Years Ago
          @Walt
          Show us a documentary that preaches great design when it's actually horrible. Oh wait, foreign automakers didn't do anything that stupid. Honestly, the only person singling out ANY brand, domestic or foreign, is you. Stop. Jeeeezzz man jus go on to the next blog and make an intelligent comment and leave this stupid argument of yours behind you.
          Ryan
          • 2 Years Ago
          @Walt
          the reason the video was posted is because it's ironic. they preach the engines high tech design and production, and the facility it's made in in this video. Yet, the engine was a flop, having multiple problems and being a perfect example of bad design, worse performance and a company where quality obviously wasn't a priority at the time. Nobody is being singled out, domestic or otherwise. If Toyota had made a video like this praising an engines design then had it fail, I'm POSITIVE Autoblog would hav found it and posted it. Relax. Nobody at Autoblog is conspiring against our domestic brands.
          carguy1701
          • 2 Years Ago
          @Walt
          You were the one who brought up politics. Also, PVC stands for polyvinylchloride. You mean PCV, and I have not heard anything about any such problems on Toyota engines. Provide some evidence for your claims, otherwise you will be dismissed as a conspiracy theorist.
          carguy1701
          • 2 Years Ago
          @Walt
          You'd do well to be more specfic about WHICH Toyota engines have sludging problems (they kinda have multple engine families, you know). As for documenting the mistakes of the domestics versus those of the Europeans, Japanese, and Koreans, the mistakes of the Big 3 tend to be more hilarious from an engineering standpoint, and the HT4100 is a prime example of that. IRON heads on an aluminum block? That's bound to fail. Even most sensible GM fans (which you clearly are not) would agree that this was a bad idea. Moving on to your claims about Toyota engines sludging, the engines involved appears to be the MZ V6 (specfically the 1MZ-FE) and the S 4-cylinder (specifically the 5S-FE). Both of those engines have been out of production for some time, replaced by the GR V6 and the AZ and AR 4-cylinders, respectively. A class action lawsuit was filed and settled in 2007, with Toyota agreeing to repair sludged engines for up to eight years from the time of purchase.
          Walt
          • 2 Years Ago
          @Walt
          Toyota sludge? 764,000 Google hits - http://lmgtfy.com/?q=toyota+sludge+engines Chances of reading about Toyota sludge here on (Import) Autoblog? Zero. And to be clear, I'm not the one who turned this site political. (Import) Autoblog did that, going all the way back to an article years ago by Johnny Liberman - who has since gone to Motor Trend - taking a shot at the National Rifle Association to more recent attacks on Republican nominee Mitt Romney. You start it, you can bet I'll finish it for you.
          carguy1701
          • 2 Years Ago
          @Walt
          Walt: I've heard of the Civic Hybrid issues, and I find it hilarious, as I'm not a fan of Honda by any means. I think you are making too big a deal about the Toyota engines, especially since they DID eventually change the design for the 1MZ at some point during 2002; the 5S was phased out. Ryan hit the nail on the head. Take off the tinfoil hat and actually use your brain.
          j0nny5
          • 2 Years Ago
          @Walt
          > More weekend domestic hateraid from (Import) Autoblog. Hateraid? Are you one of those people that only wants failures pointed out for those you dislike? I just looked back at the archives and see no pattern of "weekend hateraid" on this site. But you go on believing that "they" are out to get you. > Of course, being an arm of the socialist Huffington Post, it only makes sense. I didn't realize that there was a vast conspiracy by a blog to spread a political ideology by... pointing out... that an engine that sucked... sucked. An engine assembled by UAW "thugs" most likely. In Amurrka. But you hate the UAW, and in another breath will talk about how Toyota is doing things right by discouraging unionization. You are the *worst* kind of hypocrite: one that votes. > When American companies fail the capital that built them is lost. Lose enough capital and capitalism fails which will hopefully usher in your dream of a socialist utopia. That's a mighty long jump to a bizarre conclusion there, chief. Newsflash: GM made some sh!tty, sh!tty cars during the malaise era. They make much better cars now. This article serves to contrast that. But... you probably didn't read all of it. Like the rest of your voting base. > We've had a taste of what a socialist utopia might look like for the past for years. Only the die hard, committed socialist would continue to push that failed agenda. Funny, in a socialist "utopia", I would have at least expected to have my medicine, food and shelter provided for. Those things got *harder* to come by. Mostly because a bunch of greedy capitalists decided to gamble on whether people were too misinformed to take out a good mortgage. Where does socialism figure into that? You ask others to google things... why don't you google "socialism"? Then you could actually talk about it with authority, instead of as a straw-man for idiot(s). > Capitalism will rise again if for no other reason because it is the only system in the world that has ever produced the most good for the most people. I think your confusing a system of trade and wealth distribution for one of technological and social progress. Saying "capitalism will rise again" is like saying "one day Christianity will finally become the dominant religion". I know that F*cksNoose has alarmed you into believing that we will be in line for scraps of bread soon, and that's very scary to you, because you're an anxious person (the perfect target for disinformation). Calm down, step back, and take a deep breath. No one is trying to destroy your way of life. Rabid dogs snarl and bite when you try to give them medicine and care, and as you've proven, they will continue to do so, until Generation Scared is finally gone.
          Ryan
          • 2 Years Ago
          @Walt
          http://i.autoblog.com/2012/05/10/the-case-of-heather-peters-and-the-honda-civic-hybrid-sets-an-al/ There it is, and it we actually brought up on 3 separate occasions altogether. This site has NO bias toward ANY company's.
          Ryan
          • 2 Years Ago
          @Walt
          the reason the video was posted is because it's ironic. they preach the engines high tech design and production, and the facility it's made in in this video. Yet, the engine was a flop, having multiple problems and being a perfect example of bad design, worse performance and a company where quality obviously wasn't a priority at the time. Nobody is being singled out, domestic or otherwise. If Toyota had made a video like this praising an engines design then had it fail, I'm POSITIVE Autoblog would hav found it and posted it. Relax. Nobody at Autoblog is conspiring against our domestic brands.
          Ryan
          • 2 Years Ago
          @Walt
          WALT, the post about the Civic Hybrid wa on this site within the past 2 weeks. Give up.
          Antonio K. Piech
          • 2 Years Ago
          @Walt
          where about Saab sludge? Got a failure on my 9-5 because of that and also because,and the Impala recal that they dont want to fix because I was the old GM? Or the Cruze fire?
        carguy1701
        • 2 Years Ago
        @Walt
        Also, as an FYI, the word 'democracy' does NOT appear in the Constitution. You would do well to brush up on things before you open your mouth.
        Antonio K. Piech
        • 2 Years Ago
        @Walt
        Research,GM spend more and more money on export than here,check Korea,China and brazil,Domestics like the Camry,Accord and Sonata are the way to go,my uncle was fired when the Factory close in the 90's that move to another country
        Antonio K. Piech
        • 2 Years Ago
        @Walt
        Domestic?,search and for your information GM spend more money in China and Korea than in USA car plants,my uncle was fired from them,they move to another country
      Josie
      • 2 Years Ago
      hey, lets tall about bad products more than a generation ago and try to raise some poser fan domestic car hatred tops to stir up the blog. lets see, what about the 1984 audi? how about the 1986 hyundai, how about the 1981 vw rabbit? how about the 1981 datsun 2000? no, lets just pander to the undereducated conventional cool poser fan crowd and get some real blog action!
      j1935waspm
      • 2 Years Ago
      Yes Cadillac has fallen a long ways from where it used to be the preferred car with selective buyers. Before the HT4100 there was the 368 CID engine that was another pile of junk. But the HT4100 and its successors was the worst. Cadillac is no longer the prestige vehicle for upscale buyers because now they look just like all the others on the road. Really sad.
        mchlrus1
        • 2 Years Ago
        @j1935waspm
        Buick is the new Lexus killer
          l9t8z
          • 2 Years Ago
          @mchlrus1
          Not really, but thats not a knock on Buick. I think they have a nice crop of cars, but GM is still has got teething problems. If Buick was the Lexus killer GM claims it wants to be, the new XTS with ALL its Cadillac specific features would have all been wrapped into a freshened LaCrosse. XTS price tag and all. The Malibu LTZ is actually using the same interior materials as a top line Regal, the new Impala will be nicer than the LaCrosse, a top trim Cruze LTZ is just as nice inside as the Verano. Too much similarity between Buick and top trim Chevys. As much as I hate Toyota and Lexus, you go from a Toyota to Lexus at any trim level, you damn well know it. Cant say the same between Chevy and Buck . I do think GM will eventually get it sorted though once Cadillac has fully broken away and has a full RWD line-up.
          • 2 Years Ago
          @mchlrus1
          [blocked]
        Antonio K. Piech
        • 2 Years Ago
        @j1935waspm
        Lexus is the cadi killer
    • Load More Comments