96 Deville 4.6 North* overheating problem
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Northstar Engines and System Technical Discussion Discussion, 96 Deville 4.6 North* overheating problem in Cadillac Engine Technical Discussion; I am looking for a little direction here. All of a sudden, the engine started overheating on occasion. I dont ...
  1. #1
    richbanta is offline Cadillac Owners Member
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    96 Deville 4.6 North* overheating problem

    I am looking for a little direction here. All of a sudden, the engine started overheating on occasion. I dont seem to be losing coolant anywhere. It would overheat, then run fine for a couple days, then overheat again. The temp would flucuate wildly from 202 to 248, go down rise, etc. I changed the thermostat and coolant, ran good for a couple days, started running hot on occasion again. Changed water pump, old one seemed good, still seems to run hot. (BTW, forget about the head gasket, if that is it then I am getting rid of car but it only has 94,000 miles, and runs fine otherwise)

    I read somewhere about some tube that goes from one side of engine to the coolant tank should be checked. What exactly is that? and how do I check? Shoulod I check it with engine running and warm? Should fluid squirt out when I disconnect it from coolant tank?

    Also, how do I check to see if the radiator is any good? Do I have to remove it from the car? Is it difficult to change? (trying to save a little money!)

    Also, assuming no head gasket problem, is there any preventive maintenance that can be done to forestall any head problems?

    Thanks
    Rich

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    Ranger's Avatar
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    Re: 96 Deville 4.6 North* overheating problem

    The "tube" you are talking about is the purge line. It enters the surge tank on the side near the top. Start the engine (cold so as not to burn yourself) and pull that line loose. If there is coolant flow (there should be) quickly plug it back on. If there is none, remove it, locate the obstruction and clear it.

    If the purge line is clear, do a cylinder pressure test to confirm or rule out head gaskets. Also when you first start the car and it is cold, you could remove the surge tank cap and look for bubbles. You will have a few min. before the stat opens and you have to close it up. If you see bubbles, the head gaskets are going.

    Regular cooling system maintanence is the best preventative maintanence for head gaskets.

  4. #3
    richbanta is offline Cadillac Owners Member
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    Re: 96 Deville 4.6 North* overheating problem

    Follow up. I had radiator flushed and new coolant with tabs added. It seemed to take forever to get all of the coolant in! Now what happens is when I drive it, it seems to get kinda hot, up to 240, and then when I am idling at a light, it cools off rather quickly. If I just let it idle, it seems to cool off to about 212 or so and stays there. I wonder whats going on?

  5. #4
    Ranger's Avatar
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    Re: 96 Deville 4.6 North* overheating problem

    Did you check the purge line like I told you to? How about the water pump drive belt tensioner? Have you checked it to be sure that it is providing enough tension and not allowing the belt to slip?

  6. #5
    richbanta is offline Cadillac Owners Member
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    Re: 96 Deville 4.6 North* overheating problem

    Hey, thanks for the input. As far as the purge line, I blew air through the line and coolant squirted up through the overflow tank. However, when I started the car up in the morning, disconnected the purge line at the coolant tank and revved the engine up a little to see if coolant was coming out of the line, it wasn't. It doesn't make sense. If I blow into the line air goes through the one way, but coolant doesn't flow out when I start it. Its like there is a valve or something that allows it air to go one way but not the other. BTW, do I need to have the rad cap on when I pull the line from the overflow tank? The reason I ask, is that I had the rad cap off when I revved the engine to make sure there was no exhaust gases leaking into coolant system. I read a thread that said one way to check if the HG may be bad is to take off the radiator cap and start and rev engine to see of it bubbles or blows any coolant out. (It didn't)

    As far as the water pump pulley, when I changes the pump, the pulley seemed fine and I did change the belt too.

    Thanks alot for your help in this Ranger.

    Rich

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    Re: 96 Deville 4.6 North* overheating problem

    Ok, seems like you have found the problem. You have confirmed that the line it clear. Sounds like the blockage is where the line connects to the pump housing. Makes no difference whether the cap is on or off. When you pull the line at the tank, you should get a coolant flow and it should be much stronger as the RPM is raised. Either pull the line at the engine side and clear the obstruction where it mounts or try blowing air in from the tank side of the line. Whatever is blocking the line (cooling system suppliment probably) will go back into the water pump and get chopped up. Then check the line again for flow.

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    Re: 96 Deville 4.6 North* overheating problem

    Don't waste any more time. Just check all the entries on this formum regarding the same problem and you will see that the only, repeat, only solution is to replace the head gaskets. I just went through months of grief and had everything changed except the air in the tires and it all came down to head gaskets. They were just changed and guess what? Problem gone! Save yourself a lot of time and BS. Get them done now and don't play around with a lkot of other "maybe" solutions.

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    Re: 96 Deville 4.6 North* overheating problem

    Doing a head gasket job without proper diagnosis is like having open heart surgery because you have heart burn.

  10. #9
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    Re: 96 Deville 4.6 North* overheating problem

    Quote Originally Posted by Ranger View Post
    Doing a head gasket job without proper diagnosis is like having open heart surgery because you have heart burn.
    Good One!

    I'll remember that next time I have heartburn!

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    Re: 96 Deville 4.6 North* overheating problem

    Quote Originally Posted by Ranger View Post
    Doing a head gasket job without proper diagnosis is like having open heart surgery because you have heart burn.

    LOL good one!

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    Re: 96 Deville 4.6 North* overheating problem

    Quote Originally Posted by Ranger View Post
    Doing a head gasket job without proper diagnosis is like having open heart surgery because you have heart burn.
    Dam Ranger I can't resist to post because that is one hell of a statement. I hope you don't mind if I use it .

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    Re: 96 Deville 4.6 North* overheating problem

    Quote Originally Posted by ALBUNDY View Post
    Dam Ranger I can't resist to post because that is one hell of a statement. I hope you don't mind if I use it .
    Be my guest. It just seemed so appropriate.

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    Re: 96 Deville 4.6 North* overheating problem

    Quote Originally Posted by Ranger View Post
    Doing a head gasket job without proper diagnosis is like having open heart surgery because you have heart burn.
    Wow! That is deep man!

    David

  15. #14
    richbanta is offline Cadillac Owners Member
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    Re: 96 Deville 4.6 North* overheating problem

    Follow up. I removed the purge line where it goes into the water pump housing and blew everything out forwards and backwards. Seemed clear. The nipple that the hose connects to on the housing shoots out coolant when the engine is running but it doesnt seem to go all the way through the hose to the overflow tank. I took it into a shop recommended by a friend to chek the head gasket. They swear its the head gasket based upon what it does now. That is when idling, the temp is fine but when driving, it heats up to 250, and when idling again cools down. The upper radiator hose also gets hot and rock hard. They said they didnt do the heads on this engine so I thought I'd call a couple dealerships. They said it would take 40 or so hours and cost over $4,000.00! I called a couple other shops and most wouldnt even consider doing it. My understanding that it is the same as any other head job, with the exception of putting in the timeserts. Anyone know of a dependable shop in the Detroit area who will do the job for a reasonable price. I hate to get rid of car, its in grat physical shape with 95,000 miles. BTW, the dealerships all called it a very high mileage car not worth fixing! I dont know, I had Cadillacs before that ran great with over 200,000 miles. Thanks

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    Re: 96 Deville 4.6 North* overheating problem

    Have you seen this link?
    cadillac46northstar

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