4.5 head gaskets
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HT4100 4.1, 4.5, 4.9 Discussion, 4.5 head gaskets in Cadillac Engine Technical Discussion; My 88 Coupe DeVille 4.5 TBI, 135,000 mi. got driven several weeks with the radiator cap loose. The driver said ...
  1. #1
    raymondk is offline Cadillac Owners Fanatic
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    4.5 head gaskets

    My 88 Coupe DeVille 4.5 TBI, 135,000 mi. got driven several weeks with the radiator cap loose. The driver said he had added several gallons of water several times and the heater kept quiting. I figure it got run very low on water several times but he said the stop engine light never came on. When I got to it the engine was full of water-oil mix and had blown a substantial amount out of the valve cover vent connector. I refilled the radiator and drove it easy to the shop about 20 miles. Next day I changed the oil and filter. I idled it with the cap on and it ran OK and the oil cleared up. It would idle fine with no bubbles and if sped up gradually ran fine but a sudden throttle opening would belch water out the radiator (cap off). I drove it easy about half a mile and it took about 2 quarts of water into the engine and the oil was like mayonaise. I changed it again and ran it a few minutes. Then pulled the heads off. I never ran any tests because I was sure with the huge leaks that the failure would be obvious. It isn't. There is no sign of compression leaking past the fire rings. I have flushed new oil through the engine with the pan off and dried it out with infrared heat lamps. Was the leakage so wide spread that it didn't damage the fire rings? The head bolts all felt perfect and everything looks almost new. Is there some other failure I am missing or can I just put it back with new HG's and cruise on.

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    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: 4.5 head gaskets

    First, one of the easier things:

    One area often overlooked on these engines is the timing cover gasket. Coolant passes through the timing cover to/from the water pump. If it leaks, it will dump coolant straight to the oil pan. This is unlikely however.

    Now for the bad:

    If the engine has been severely overheated, you may be looking at cracked or warped head and block surfaces, prohibiting head gasket seal even if new. Did you check the gasket surfaces for flatness or did you just replace the gaskets and button it up?

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    Ranger's Avatar
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    Re: 4.5 head gaskets

    Weren't they known for intake manifold gasket leaks or am I thinking of something else?

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    drewsdeville's Avatar
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    Re: 4.5 head gaskets

    Yes ranger they are, but if he replaced the head gaskets already, that means he replaced the intake gaskets as well. Unless everythign wasn't torqued down correctly, gaskets are no longer in the equation.

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    Re: 4.5 head gaskets

    Quite true. I overlooked that part.

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    steelybill is offline Cadillac Owners Enthusiast
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    Re: 4.5 head gaskets

    What about a leak in the bottom seal on one of the cylinder liners where they sit in the water jacket? Just an idea......

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    raymondk is offline Cadillac Owners Fanatic
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    Re: 4.5 head gaskets

    I've inspected all the gasket surfaces mentioned and I don't see any obvious leaks. There is a heavy deposit of gooey crud in the rear corner that may be the result of some leakage over a long period of time but nothing like quarts a minute. It dribbled water out the tailpipe idling and I probably added 2 gallons in the hour I ran it. I have some pix but I have to resize them.

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    raymondk is offline Cadillac Owners Fanatic
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    Re: 4.5 head gaskets

    As the pix show there doesn't appear to be any single major gasket damage. Could it have leaked by the fire rings and not show? I believe if the cylinder barrels leaked it would be visible, but there is a nice undisturbed layer of mud at the bottom And I doubt that much could leak around a barrel. They would all have to leak. If the fire rings leaked, it would have had to suck the water into the cylinder while idling, that wouldn't add water to the crankcase and surely it would leak combustion gas into the jacket and blow bubbles and expel water. Could the black crud along the top of the block and around the bolt holes be from water/AF leakage?
    Attached Images

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    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.5 head gaskets

    First let me start by saying that just about the same thing happened to me, except the gasket let go between cylinder and water pocket.

    If you look on the first picture of the head gasket, you'll notice a slight discoloration around the ring of the cylinder side and the face of the gasket seat; same on mine. What I believe happened was that the head bolts failed ( in my case the fuel injector stuck open and flooded cylinder) and pulled the head bolts up and out, sucking in water (and in my case fuel) and dispersing it back into the cooling system (in your case possibly the oil return) where it will of course froth and foam with the crank.

    I come to this conclusion based on the fact that I found those particular head bolts relatively easy to remove and the amount of threads still stuck to the bolt as I removed them. I had to helicoil the whole block.

    My car would run "fine" at idle, but real crappy at WOT and wreak of raw fuel in the cooling reservoir.

    Just my 2 cents, and I may be off a bit in my assumptions, but I'm on my way to getting mine back together again soon (hopefully).

    If yours turned that much water in the pan the one thing you can count on is a new motor

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    Re: 4.5 head gaskets

    If all if the gasket surfaces are within spec for flatness, I'm at a loss as well.

    The sleeve o-rings mentioned are a possibility, but rarely if at all fail unless disturbed. Since you had a problem before disassembly, I'd say the chances are slim.

    Many people check for cracked blocks and heads, but one often overlooked area is checking the sleeves themselves for cracks...If you are losing that much coolant to the pan, I'd take a look at them.

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    raymondk is offline Cadillac Owners Fanatic
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    Re: 4.5 head gaskets

    I had the heads checked for cracks and warpage. They were perfect so I had the valves done. I'm ready to install the heads but I ran across a referrence in the FSM to use cam and lifter prelube GM #1052356 or equivalent. Anyone know of an equivalent? The head bolts all felt right on removal and there was no sign of any thread damage. I cleaned the holes thoroughly and they are clean and dry.

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    drewsdeville's Avatar
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    Re: 4.5 head gaskets

    Recluse brought up the head bolt thread problem that could be a concern. You never helicoiled/timeserted the block? You are sure that the top 3 bolts that get the 3rd 90ft/lb pass are holding?

    I don't even mess around anymore when doing 4.X headgaskets. I use helicoils every time. I learned the hard way, on two engines, that the headbolt threads are not reusable.

    Who knows, maybe I just had bad luck or maybe you just had good luck. Perhaps that's not your problem. Either way, the strange fact that the threads on yours held up is disturbing to me...

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    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.5 head gaskets

    ^^^Agreed.

    With the stresses put on the block I would definitely at least do the center 3 on right and left bank (the ones that require the last 90 ft lb pass). Of all the holes, those are the easiest to reach.

    As far as GM equivalent, I would just pick up some Royal Purple Synthetic oil (15w30 or 15w40) and coat everything with that for reassembly, then top off reservoir with oil of your choice. I think they make an engine assembly lube also, but either way you only need a quart.

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    raymondk is offline Cadillac Owners Fanatic
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    Re: 4.5 head gaskets

    When I removed the heads, I inspected every bolt for signs of block thread material and found none. The bolts were all so tight I had to use a long pull handle to loosen them. I did not detect the extra torque on the three top bolts, but then that extra torque may not prevail. Has anyone measured the torque on one a year after installation? The perfect appearance of the head gaskets, and the heads not being warped lead me to believe that the problem must have been the intake manifold gasket. Anyway I'm going to try it with the original threads. The coefficient of friction of steel bolts in steel is around .2, I believe. I don't know what it is with steel to aluminum, but the wrong lubricant could be the difference between success and failure. The heads have never been off, and the driver says that the stop engine light never came on and there was never any steam. I guess it's possible that there was so much water in the engine that it stayed cool enough from ebulience.

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    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.5 head gaskets

    You should know even before the engine ever runs, as usually the blocks fails the 90 lb pass almost immediately. The biggest problem is paying the $250+ dollars for the head gasket kit again when it does.

    Good luck....

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