my 425 is pretty dirty inside.....
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500, 472, 425, 368 Discussion, my 425 is pretty dirty inside..... in Cadillac Engine Technical Discussion; I bought the car with 84k miles, now it has a hair under 90k. Anyway, when I bought it the ...
  1. #1
    Night Wolf's Avatar
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    my 425 is pretty dirty inside.....

    I bought the car with 84k miles, now it has a hair under 90k.

    Anyway, when I bought it the guy said it had a recent oil change with 10W-40 oil, so in either case, I did my own when I got it home. My father had alot of Castrol Syntec 10W-30 left over, so he let me use that, so I did.

    That was in there for about 2,200 miles and I did an oil change, I switched to Mobil 1 synthetic that I use in my '93 DeVille.... this was back int he summer.

    The car dosn't get much use (compared to the '93 DeVille and Oldsmobile) so in about 6 months, the oil change only had 2,500 miles on it. I must say though, the oil was black.... it looked dirty.

    So I really can't see myself keep running the expensive Mobil 1 synthetic on a stock 425, so I decided to save some money and switch. I picked up Castrol GTX High mileage 10W-30, I was gonna get regular Castrol GTX, but the high mileage was only like $3 more for 5 quarts, and it seems to have extra stuff for older engines.

    So I put it in drive the car off the ramps etc.... check the level.... but the oil on the dipstick has some black (dirty) oil mixed in with the clean oil... so I mess around a little more, drive 4 miles to my fathers place, shut it downa nd check the oil again... and the new oil is already kinda tinted black from the old oil/inside of the engine.

    When I remove the oil fill cap and look in the valve cover, it is gunky, sludgy and dirty... not very pretty.

    How can I clean it up short of removing anything from the engine? will any of those engine cleaners work? the ones you put in before an oil change etc? I'd like to do something, as I know it can't be pretty inside, let alone good for the engine.

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  3. #2
    lux hauler is offline Cadillac Owners Connoisseur
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    Re: my 425 is pretty dirty inside.....

    I would think twice before doing anything to try to clean it. If you use a cleaner in it and it loosens the sludge, it could break loose and clog oil passages.

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    Night Wolf's Avatar
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    Re: my 425 is pretty dirty inside.....

    yeah, thats what I was also thinking....

    I mean, it runs great, lots of power, dosn't burn oil etc.... has a slight leak at the rear main (I think)... maybe due to syntehtic? I'll see if it goes away now that I am not using it anymore... either way I don't care....

    I just keep thining that is can't be good for the engine... my 4/9 with 103k is squeeky clean inside, my '89 Oldsmobile (3800 V6) isn't as clean, it has a small layer of grime... whatever it is, but the 425 is the worst of my 3 engines... also the lowest mileage, but oldest....

  5. #4
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    Re: my 425 is pretty dirty inside.....

    Don't worry about it - unless you plan to rebuild it there's not a lot you can/should do.

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    Re: my 425 is pretty dirty inside.....

    Let 'er be...don't fix what ain't broke...it runs great, you say, so leave it alone...just use decent oil, non synthetic, and drive it!

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    Re: my 425 is pretty dirty inside.....

    Someone probably decided not to change oil when it was due. Those engines usually stay very clean inside. Not much can be done for it. Stay away from 10W-30. Stick with 10W-40 as mentioned in your owner's manual.

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    Night Wolf's Avatar
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    Re: my 425 is pretty dirty inside.....

    it says 10W-30 in the owners manual... I read NOT to use a 40 weight oil in the BB Cad as some oil passeges are small and it can starve the lifters of oil.... don't remember the exact reasons though...

    it was owned by an old lady in FL for the first 20 years of its life... I think the oil was changed as it should have been, but it was a grocery getter... never had time to get to proper temprature, probably only ran wide open once a year when she got in a frantic situation and had to pull out quick etc.....

    If I was rebuilding it, then yeah it would be all washed and everything, but I was just thinking if anything could be done as it is... but I guess I am better off leaving it alone.... like I said, besides the way it looks under the oil cap and in the valve cover, there is no other way to tell somethig is "wrong" (if you can call it that) as it runs great, idles fine, powerful, no oil leaking/burning etc...

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    Re: my 425 is pretty dirty inside.....

    Quote Originally Posted by Night Wolf
    it says 10W-30 in the owners manual... I read NOT to use a 40 weight oil in the BB Cad as some oil passeges are small and it can starve the lifters of oil.... don't remember the exact reasons though...
    I have a '77 owner's manual here which does not specifically state 10W30 or 10W40 so my previous statement was incorrect. It shows them as interchangable.
    Back when those cars were new 10W40 was what everyone used unless you lived in an extreme climate. There were many millions of trouble-free non lifter starved miles enjoyed by owners who allowed 10W40 to be poured into their 425's. Maybe the guru who wrote what you saw was talking about high performance drag strip only situations.

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    kjc
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    Re: my 425 is pretty dirty inside.....

    If you happen to have the valve covers off at some point in the future, you might want to make sure the oil drainback passages in the heads are clear, other than that, I agree with what everyone else said.

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    bryan1970 is offline Cadillac Owners Fanatic
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    Re: my 425 is pretty dirty inside.....

    i've ran both 10W40 and 10W30 in mine and had no problems as far as no oil getting to the lifters. i also agree that if you do decide to doa ynthing the most you should do without a rebuild is make sure the oil can get back down from the heads.

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    Re: my 425 is pretty dirty inside.....

    What are all the products that say they will clean the engine out, put it in before oil change, run engine etc.... what do they do?

    I have no intention of using any of them, but there seem to be alot of them at the store...

  13. #12
    kjc
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    Re: my 425 is pretty dirty inside.....

    I've tried Berryman B-12 on a couple of engines and I won't bother trying it again. You pour it in your engine and let it run about 2500 RPM for around 20 minutes, then drain the oil. It didn't seem to cause any problems but it didn't change anything, either. The oil still gets black soon after an oil change. I've used Marvel Mystery Oil on the same engine, and it may have clogged or restricted some oil passages by breaking loose some large particles, it developed a knock and I pulled the oil pan and it looked like red and black clay had been dropped into the engine- it was bearing babbit, copper-lead-tin. All five main bearings were worn down to the copper, the rod bearings weren't much better, I replaced them all, and after all that, the oil STILL gets black right after a change!

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    Caddy112 is offline Cadillac Owners Member
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    Re: my 425 is pretty dirty inside.....

    I have a 77 Coupe De Ville which had 57,000 old lady short trip miles on it. After the first oil change, the lifters were noisy, and I cleaned them out by running 4 quarts of Kendall 10/40 and one qt of Marvel Mystery Oil for 1000 miles at a time. I did this for several thousand miles, and they finally cleared out enough to get enough oil in to operate quietly. Now I use 5 qts of regular 10/40, and I hardly ever hear the lifters. Under the valve covers was a slight coating of grime, not black, and the oil stays clean. It does'nt burn any oil in the 1000 mile oil change intervals. 1000 miles, or one year, whichever comes first. Yes, it's garaged, and always gets a good highway run to burn off any moisture whenever I use it.
    I don't think you can thoroughly clean an engine without taking it apart. Too bad some people did'nt and still don't change their oil enough. On my every day cars, I do them every 2-3000 miles.
    An old timer once told me they used to do kerosene washes, where they would drain the oil, put in one or two fresh qts of oil, and then fill the rest of it with kerosene, and run it for a while, then drain it all out and refill with fresh oil. He was'nt convinced that it was very helpful, and that was in the early 60s, I guess before good detergent oil.

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    Re: my 425 is pretty dirty inside.....

    Thats the thing, I don't have any lifter noise or any bad noises...

    just on startup after it has been sitting for awhile, for the first 5 seconds or so it will "knock" it isn't a knock, but I think the lifters just getting oil... its tap, tap, tap, tap then fades away after a few seconds...

    I have pics looking into the valve cover, but none of them came out very well...

  16. #15
    jk1000 is offline Cadillac Owners Member
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    Re: my 425 is pretty dirty inside.....

    Just my 2 cents:

    It's clear the previous owner(s) did not change the oil frequently. I find it really irritating when people do that.

    If you don't have a problem, there is no need to tear down the engine. However, I would keep changing the oil frequently, say every few hundred miles, perhaps more often at first.
    I would not use a heavy oil during this "cleaning up" process. Be sure to reach full operating temperature and forget the short drives. This conservative approach and will gently clean the engine to some degree. How much remains to be seen.

    I've also heard about the use of kerosene from old timers. It must have been a popular thing to do in the old days. I believe it works, but I also believe there may be a small risk involved. The same goes for mystery oil. A little bit, say a cup or 2 with the next oil change should not be a problem. Another thing, change the oil filter with every oil change.

    Good Luck.

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