We return to the saga of GM’s High Technology engine today, after taking a diesel detour in our last entry. Concurrent in the High Technology engine’s timeline, the Oldsmobile diesel’s failure was quick, but certainly not painless. It put the majority of American consumers off the idea of a passenger car equipped with a diesel engine. And by the time GM pulled the diesel from its various brand lineups, there was a strategy change over in HT4100 land: Not calling the engine HT anymore.
Though the engine was full of designed-in mechanical issues and failures, cars with the Cadillac-exclusive HT4100 sold well. It was the days when American buyers were loyal to domestic offerings, and usually loyal to one brand in particular. Even through a swap to front-wheel drive, downsizing, poor quality, and styling that was lacking in 1985 terms, Cadillac sales increased. The brand sold around 300,000 cars each year from 1983 through 1986, riding on a wave of consumer loyalty built in the Sixties and early Seventies. For a modern times sales reference, Cadillac sold 156,246 cars in the Most Recent Normal Year, 2019.
Even though buyers weren’t put off by the HT branding, Cadillac’s marketing people were eager to get away from it. Sales fell by around 14 percent in 1987, a drop to 261,284. Keep in mind, even with HT and diesel woes, Cadillac was still trouncing Lincoln’s 1987 sales figure of 166,037. HT4100 disappeared from all Cadillacs after 1987, save for the Allante with its special high-powered version which lasted through 1988. For all other cars, the ’88 model year introduced a new power plant for Cadillac Style, the 4.5.
The 4.5 was in fact an enlarged and improved version of the HT4100 but was never referred to as an HT4500. At 273 cubic inches, the “new” 4.5-liter offered a modest power increase over the 4.1, at 155 horsepower versus the 135 horses of its older sibling. More carefully engineered than before, Cadillac knew a rushed repeat of the HT4100 wouldn’t cut it. Compression on the 4.5 was higher than on the HT at 9:5:1, and premium fuel became a requirement.
Carried over from the 4100 were the throttle body fuel injection system, as well as the aluminum block and cast iron head combination. This meant that the cooling system still required regular and careful maintenance. Intake and head gasket failure were still factors in the 4.5, ideally mitigated through regular coolant changes and the addition of GM’s cooling system sealant tablets.
The tablets were (are) manufactured by AC Delco, and were meant to correct leaks that already occurred, and prevent leaks in the future. Said leaks were caused by the aluminum block and coolant components becoming porous over time, which isn’t the best outcome for critical car components.
Sales improved in 1988, up slightly to 266,548 cars. Cadillac sold the 4.5-liter engine for a shorter time than the HT4100, as it continued to develop the series after the 4.5 went on sale. DeVille, Seville, Eldorado, and Fleetwood models between 1988 and 1990 used the 4.5-liter. Sales in 1989 remained steady at 266,899 cars and dropped in 1990 to 213,238.
The Allante joined the 4.5 fold in 1989, and once again received its own special version of the engine. Called the LW2, the Allante’s 4.5 implemented the ever-important multiport fuel injection. The modern fuel system upped the power to 200 horses, but only for the LW2. Given the Allante’s flagship status and outlandish asking price ($57,183, or $132,757 adjusted), it was important that it received new technology first.
Multiport was added to the standard versions of the 4.5 for 1990, where it meant 180 horses and 245 lb-ft of torque. Huge “4.5 PORT FUEL INJECTION V8” badges were emblazoned on the back of every Cadillac on the lot. Unlike the HT4100, all applications of the 4.5 were front-drive as Cadillac shifted from its prior rear-drive identity, and chased after the “younger European car buyer” General Motors was so obsessed with between 1986 and about 1998.
Cadillac was ready with its final iteration of the HT for the 1991 model year. The 4.5 was upsized again and became the L26 of 4.9 liters. Horsepower and torque both increased with the 4.9, up to 200 horsepower, and 275 lb-ft of torque at 4,100 rpm. Never mind that this figure was attained earlier by the high-po LW2 4.5-liter, as the L26 was generously applied to the entire Cadillac lineup – apart from the Allante. Allante soldiered on with the 4.5 for 1992 and received the all-new (and not ready) 4.6-liter Northstar for its final outing in 1993.
Elsewhere in the lineup, the 4.9 remained in use through 1992 in the front-drive C-body Fleetwood, 1993 in the Eldorado, Seville and Sixty Special, and through 1995 in the DeVille. Notable in the Deville’s usage, the ’94 and ’95 models with the 4.9 were base versions, as upscale Concours used the Northstar. Guess which trims are still running today?
Despite how the 4.9 was the best engine Cadillac had used in some years, sales continued to decrease from their Eighties high. Seventeen percent fewer Cadillacs were sold in 1991 than 1990, 213,238. A slight increase in 1992 was followed by another drop in 1993 to 204,159. The HT series ushered in a damaged era at Cadillac, where the brand decided to pursue a different front-drive and Euro-centric imaginary customer that was much different from its traditionalist domestic rear-drive buyer. Cadillac lost over 100,000 annual sales from the time the HT was introduced to the time the 4.9 finished its run.
Through three generations and nine model years, the HT4100 was reworked, upsized, and generally improved to a decent reliability standard. Horror stories about the 4.9 are much scarcer than in the 4.5, and especially the 4100. The HT line would be the last engine exclusive to Cadillac for over 20 years, until the debut of the Blackwing V8 in 2018 (RIP 2020).
Unfortunately, the HT engine was a case of the fix-then-drop operating procedure that GM used so many times before. By the time the 4.9 arrived at dealers, Cadillac was already well into development of its next V8, the much-heralded Northstar 4.6. But that’s an Abandoned History for another day.
[Images: Cadillac]
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The C-body should have been designed with rear wheel drive along with its independent rear suspension if they wanted a Autobahn cruiser European competitor. In typical GM form they finally got it right with the Seville replacement STS and the CT6 before unceremoniously dropping them.
A great uncle of mine, a life long Oldsmobile 98 buyer who was disenchanted with the redesign went for an 89 Sedan DeVille with the 4.5. He enjoyed it until his driving days ended. It ended up with a relative where it proceeded to leak and have electrical issues.
That stretch in the whichever model year in the Eldorado, Toro and Riv finally put them where they should have been in 1985, instead of the Calais/Grand Am/Skymorset lookalikes! Of course, the damage was done by that point.
It’s funny how Craigslist ads for Cadillacs of this vintage always tout the 4.5 or 4.9 as a major advantage over the Northstar.
And they’re right!
It’s really unfortunate that the earlier Northstar tended to blow head gaskets. The later version solved this problem and the engine finally met expectations. ARP makes a head stud retrofit for earlier Northstars that addresses the problem. Of course, while the heads are being serviced, it’s a good idea to change the starter as well since it lives in the vee between the heads.
One cool fact about the Northstar is that it’s split block design gives it an exceptionally strong bottom end as it permits very little crankshaft whip resulting in very few issues with main bearings.
To this day, I miss my 2006 Northstar STS. It was a great car.
N*, worse or better than HT4100?
STS, worse or better name than Seville Touring Sedan?
I’ll take the first-gen RWD Seville with the 350 all day, every day. When Iacocca decreed that Chrysler would go all-FWD, dropping the similar-to-Seville RWD M-body, Maximum Bob Lutz argued against it, pointing out that MB and BMW still had top-of-the-line RWD models, and Chrysler should too.
Iacocca won that one, but Lutz persuaded the engineers to use a longitudinal engine in the LX platform for “future” AWD, but it could have allowed for RWD alone. Lutz left after the “Merger of Equals” takeover and moved back to GM, where he’d started in 1963, and the LX remained FWD.
You mean the LH platform, not the LX which later replaced it and was RWD/AWD.
Most of what I’ve read is that the LH cars used longitudinal engines (and FWD) because their basic design was an evolution of the Renault-based Eagle Premier which also had a north-south engine and FWD.
Oh good. We finally got to some stuff I like.
If Cadillac had managed to anticipate a bit more and the first twice-downsized DeVille had been the ’89 (with the stretched body and the 4.5), there would have been no problem for Cadillac in the ’80s.
Of course, by the time it was actually 1989 or 1990, they needed a step further ahead still. There was a missed opportunity for a new kind of Cadillac between the ’92 Seville, which just gave up all Cadillac-ness to be more like the Germans, and the ’93 DeVille, which was far too conservative for younger buyers.
That 92 Seville really looked nice, especially the new direction with the interior. It was a major hit at the NYIAS. Sadly, it was let down by some serious assembly issues. While the car show display had perfect fit, the models at the dealers were loaded with ill-fitting trim and misaligned panels. No surprise I guess but a disappointment.
It was a nice car, but it was more of a proof of concept that, yes, Detroit really honestly could compete with Lexus and the Germans if it wanted to than a statement of what Cadillac should be in the future.
They needed to do it, but they also needed to update the brand. That should have happened through (1) putting a bit more Cadillac-ness in the Seville and (2) making more of the DeVille’s transition to the new platform, even if it forced the old guys with WWII hats to adjust a bit.
My mom had a base ’94 Deville with the 4.9 back in the late ’90s. It was dorky but comfy and never any engine problems over the 10 years she had it. It was helpful for my driving skills to learn how to parallel park (and drive in general) using that car.
Had a guy at my bus stop that had his father’s 94 Deville teal colored with tan leather seats who Cash for Clunkers it for a new Ford Focus which he let his kids drive (he drove the Focus some). It was in good shape but he put a lot of miles on it. A lot of these were CC’d along with Crown Victorias and Mercury Marquis. Most of the cars and trucks CC’d around me were used up but there were a few with good bodies with high mileage. The salt and road chemicals where I live eat up the bodies.
Tablets? Was there a prescription interval for them?
Grandfather to that that prestone quick radiator repair product at the local autoparts store?
Believe it was 60k intervals.
Coincidentally, I just ordered a jar (100 tablets) of these to try a couple weeks ago:
http://www.amazon.com/Bars-Leaks-J-100-Professional-Treatment/dp/B003RGBUTE
Here’s the ‘Genuine GM’ version [note the slightly different per-unit pricing – lol]:
http://www.amazon.com/Genuine-GM-12378255-3634621-Cooling/dp/B000QIH3C4
I am interested to see how these compare in use to the ‘liquid’ products which I have used before. (Might let you know; will probably forget.)
In the Cadillac forum the use of the coolant tablets for the HT series is a whole thing. I guess GM put out a TSB in 2003 advising to discontinue their use in all historical models but it’s hard to ignore the original service procedure.
Some people swear by the coolant tabs stating you need to use 4 every 24 months. Then others state to just do a coolant replacement by the book and as long as the coolant is fresh the tabs aren’t needed. Their feeling is that the tabs could do more harm clogging things than good and GM only originally advised them to help lower short-term warranty claims.
Personally, with my 4.5L I used 1 tablet but I also only put about 8k miles on it during my ownership period.
Hmm. I can see where they’d gum up the works over time. And the short-term fix for GM to avoid warranty claims sounds JUST HOW THEY’D OPERATE. I didn’t have my 4.9 long enough to mess with any tablets.
Was this issue mixed in and/or compounded by the Dex-Cool stuff later on?
I believe they were separate issues. I remember when the tablets were announced and it was stated that it was to address porosity issues with the casting of the block. DexDeath was an incompatibility of OAT coolants and the existing materials used for the intake gaskets. I got the joy of paying for gasket replacements twice – the first repair did not hold and the independent shop refused to do the right thing and fix it without charge. They said it failed 13 months after the repair which is correct. However, the factory gasket lasted 80K miles. The repair lasted 4,500 miles. My only recourse was to find another shop and to post my experience on Yelp. Hopefully that cost them some business.
Ouch.
Couldn’t you plop-plop a few of the tablets into a coffee can filled with coolant, then dump it in the radiator?
Here’s Ed’s Auto Review on Cadillac https://www.youtube.com/watch?v=WSIRkKb3wJQ&ab_channel=Ed%27sAutoReviews
Worst GM engines
https://www.youtube.com/watch?v=eaRLUyOSxgk&ab_channel=RareClassicCars Best GM engineshttps://www.youtube.com/watch?v=6fRs1uhhg_M&ab_channel=RareClassicCars
It is funny but Youtube app on Roku offers me to watch exactly same videos last couple of day. How they know?
That guy really knows his stuff, and he seems to have, and be able to find, normal, commodity vehicles that are true time capsules!
The weirdest one I’ve seen so far is the Galaxie 500 hardtop which literally didn’t have a factory radio, but was ordered with the Ford automatic climate control!
He does know his stuff. Look at his more recent purchase of a 70 Caprice Classic loaded with 454 V8 power everything but no ac custom ordered as a flower car by a funeral home in Ottawa. The car is black with a beautiful blue interior. He has some unique and interesting old cars and he tells you how he gets them.
I owned a ’87 FWD Fleetwood d’Elegance for a couple years I bought from the leasing company that my dad got his cars from. Ran the 4100 up to 100k miles with no trouble and really don’t recall servicing the cooling system, although that may have happened before I bought the cars. The 4100 was weak on power however and as a result didn’t get great mileage as it was foot to the floor most of the time. A few years later I rented a brand-new DeVille sedan with the just introduced 4.9L and was astonished how much better that car drove than mine. The 4.9L was smooth, quiet and almost vibration-less. It also had plenty of torque and moved the big Caddy smartly. Finally, on a trip from Jacksonville to Virginia it got about 27 mpg at a steady 80mph. The 4.9L was the engine the car needed all along. GM Kept the 4.9L for 2 more years is all then dumped it for the Northstar, just to continue their vicious cycle of using the customer for R&D on their product.
I came hear to say the same thing about the 4.9. It was a good engine, GM finally had everything sorted out. So, wisely, they embarked on the Northstar fiasco.