Thoughts on the 4.5
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HT4100 4.1, 4.5, 4.9 Discussion, Thoughts on the 4.5 in Cadillac Engine Technical Discussion; I have a chance to buy a 1990 Eldo with the 4.5 engine. 81K miles. The car is very nice ...
  1. #1
    leftoverture is offline Cadillac Owners Fanatic
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    Thoughts on the 4.5

    I have a chance to buy a 1990 Eldo with the 4.5 engine. 81K miles. The car is very nice but I do not have access to the service records. How reliable is the 4.5? Anything particular I should look for when I examine it up close?

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    awadecki is offline Cadillac Owners Enthusiast
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    Re: Thoughts on the 4.5

    4.5 is a great engine. Make sure the car doesn't have a rough idle. The 4.5 PFI and 4.9 PFI engines like to eat fuel injectors, a symptom of which is a rough idle. Check the coolant bottle and see if the coolant looks a bit gray, instead of pure green...gray means that coolant tabs have been added, which is a good thing. Also look at the water pump housing on the accessory drive and see if it looks newer, these have a tendency to go our around 60-80k miles.

    That's about it though...the 4.5 is an excellent engine.

  4. #3
    noahsdad's Avatar
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    Re: Thoughts on the 4.5

    The 4.5 is everything the 4100 should have been. It addresses all the weak points of it's older brother, while offering more power at the same or better fuel efficiency. The 4.5 and 4.9 engines remain one of the lowest warranty claim engines Cadillac ever built.

    Having said that, ALL aluminum engines suffer from gasket sealing issues. It is essential that the cooling system be maintained as GM prescribes to avoid major problems like head and intake gasket failure, and the subsequent cam lobe and bearing destruction that takes place with coolant intrusion into the oil.

    Check the oil for any milky color or lumpy consistency. Then draw some coolant from the rad. If it's oily or smells of exhaust, that's not good. If it's a dirty brown color (see picture below) and smells sweet - that's very good. That means the system sealant has been used, which generally indicates a properly maintained cooling system.



    Best of luck!

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    Re: Thoughts on the 4.5

    Mines been indestructible at 225k she's still going like new. The most common thing I've seen is intake gasket leaking oil.

    They're a great engine with gobs of low end torque.

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    Night Wolf's Avatar
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    Re: Thoughts on the 4.5

    Quite a nice enigne, I've seen many with over 200k

    a buddy in my class just bought an '89 Eldorado with 122k.... 4.5 TBI, 155hp and 245ft-lbs torque.

    I did some work on it today... the darn thing moves, and moves very good.... in that Eldo, it seemed nearly as powerful as my '93 Coupe... though it's been a while on that car....

    the 4.5TBI just works well... one of the rare and few TBI systems that works very good, IMO, the best application of TBI. The throttle response is awesome too, it revs quick and the 4.5 TBI is designed in a way, that they just feel faster... a light throttle imput makes a huge difference.

    This was with really old and bad spark plugs and origanal plug wires too.... never got around to changing those yet.

    The car runs nice. 1990 4.5 had PFI and 180hp/255tq. 4.9 had 200hp/275tq.

  7. #6
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    Re: Thoughts on the 4.5

    From my experience (one '89 Sedan deVille with the TBI, not MPFI), loads of low end power and great throttle responce. Reliability seems to be about as good as any Cadillac engine after the HT4100..which is good for Cadillac but not as good as the 350 or 3800. Overall I'd say it's a decent motor, I give it a 7/10.

    Does the 4.5 have the main bearing thump the 4.1 and some 4.9's have?
    "They call Alabama the Crimson Tide, call me Deacon Blues."

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    Re: Thoughts on the 4.5

    Mine is quiet as a mouse. Always has been so I would have to say no.

    Quote Originally Posted by I~LUV~Caddys8792 View Post
    Does the 4.5 have the main bearing thump the 4.1 and some 4.9's have?

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    Re: Thoughts on the 4.5

    No noise at all from the 4.5 I worked on....

    I'd say they are very reliable.... very strong enignes.

    my friend back in high school was driving his grand parents '89 DeVille... 4.5 TBI... that car had 230k and still ran great.

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    leftoverture is offline Cadillac Owners Fanatic
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    Re: Thoughts on the 4.5

    Thanks for all the responses. I am going to buy this car but I have to sell my snowmobile first, it's for sale now and hopefully will go soon before this car is sold. I had a 83 Coupe DeVille before, with the HT4100. Frankly, the 4100 worked great for me (other than being underpowered). Mine was well-cared for and never gave me too much trouble. Sold it to my son and he's still driving it.
    But if any of you are in MN and want a snowmobile. . .let me know!

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    Re: Thoughts on the 4.5

    Would you 4.x experts say that the 4.5 is a more reliable, trouble free engine than the 4.9?
    "They call Alabama the Crimson Tide, call me Deacon Blues."

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    2003 Mercury Marauder (4/12-10/13)
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  12. #11
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Thoughts on the 4.5

    I would say that the 4.5 TBI is more trouble free than the 4.9 PFI. You don't have to worry about the thump or bad injectors.

  13. #12
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Thoughts on the 4.5

    To supplement the previous post, I think the transmission backing the 4.5 TBI can also handle its lower torque better than the 4T60E can handle the 4.9's. I've never heard of a trans burning out that backed a 4.5, but we've all heard of 4T60E's kicking the can around 130k.

  14. #13
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    Re: Thoughts on the 4.5

    The FWD 4.1 and 4.5 TBI engines have the same transmissions, My 4.1 hasn't given me trouble at all, runs great, smooth, quiet and is quite powerfull. I do regular maintenance and just drive my car without worrying about anything happening.

  15. #14
    90Devillex32 is offline Cadillac Owners Member
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    Re: Thoughts on the 4.5

    I know PFI means "port fuel injection" but what does TBI stand for.

  16. #15
    leftoverture is offline Cadillac Owners Fanatic
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    Re: Thoughts on the 4.5

    Throttle Body Injection. Fuel is injected into a throttle body on top of the intake manifold. Sort of between a carb and port injection.

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