Help with my overheating 4.9!!!
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Help with my overheating 4.9!!! in Past Cadillac Vehicle Discussion; I recently bought my car from my sister in law who bought it from an elderly couple down south. Anyways, ...
  1. #1
    MrFlippers is offline Cadillac Owners Member
    Automobile(s): 1994 Cadillac Deville 4.9
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    Help with my overheating 4.9!!!

    I recently bought my car from my sister in law who bought it from an elderly couple down south. Anyways, there are 2 main problems one of which is scaring the S*** out of me. When I went to pick the car up it had overheated on her, I put a new thermostat in and filled it with coolant (and Bars Gold), drove it 150 miles back to Phoenix, ran 195-203 the entire way

    However...

    I drove it home from work today (a few weeks have gone by with no problems including lots of idling and few full throttle runs) and all of a sudden the readout says 250, I immediately get off the freeway and hit the street and the temperature drops to 190, then 180, then 170, then 160 all the way down to 150. Obviously none of this seemed right to me, I figured hey bad coolant temp sensor, sweet.

    Opened the hood when I got home and noticed coolant spill on the passenger side that appears to have come from the reservoir. I check the reservoir and surprise, empty. I know it had coolant in it because I was messing with changing some bulbs on it at work and checked all the fluids

    Obviously now I am worried, I know head gaskets on the 4.9 are rare to go out so I am straying away from suspecting that it is the culprit. Any thoughts???

    The other problem is an INCREDIBLY long time to cold start it, when I say INCREDIBLY.... I mean INCREDIBLY. The starter appears to not hit properly all the time (no big deal) but even when it does I can crank and crank and it will take close to a minute and a half before I get the thing started (not cranking the entire time due to the starter) but still in short bursts it should only take 2-3 times max. There is no loss of power at all, the thing gets up and hauls butt.

    Any help is greatly appreciated as I have proceeded to park it until I can get this figured out. Thanks Guys.

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  3. #2
    amunderdog is offline Cadillac Owners Connoisseur
    Automobile(s): 1994 SLS x 2 ---- 1993 Eldorado Sport ----- 1994 Deville 4.9
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    Re: Help with my 4.9!!!

    Check the water pump.

  4. #3
    bigm57ict's Avatar
    bigm57ict is offline Cadillac Owners Connoisseur
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    Re: Help with my 4.9!!!

    Yup. Sounds like a leak. As amunderdog said, the WP is a likely culprit. Rent a pressure tester from your local auto parts store and check the system with it.

    As to the other issue, have you pulled your codes yet? There's a Sticky at the top if you don't know how to do this through your dashboard.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Help with my 4.9!!!

    Maybe a cracked coolant reservoir?

    Not sure what to say about starting based on what you said. Sounds like an intermittent starter and maybe an ignition or fuel pressure problem.

  6. #5
    bigm57ict's Avatar
    bigm57ict is offline Cadillac Owners Connoisseur
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    Re: Help with my 4.9!!!

    A cracked reservoir would lead to low coolant, but I don't think that alone would make it go low enough to cause overheating.
    The water pump is located right next the the reservoir. The water pump, itself, may be okay, but the water pump cover is quite large, held on by at least 15 screws/bolts/nuts. It is not uncommon for the gasket on the cover to fail.

  7. #6
    onecool is offline Cadillac Owners Fanatic
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    Long crank time, might want to check your "FPR/Fuel Pressure Regulator" pull off the hose to the FPR see if you got a little bit of fuel if so then the FPR might be bad. Also check your fuel pressure.

    But look in to that over heating that could be causing it too.

  8. #7
    MrFlippers is offline Cadillac Owners Member
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    Re: Help with my 4.9!!!

    So I looked into everything today. I did not see a leak from the water pump, all of the coolant that has come out appears to have boiled out of the reservoir. I had a gallon of 100 percent Prestone that I added along with the second tube of Bars Gold I picked up. Have not run it yet however has anyone here encountered a problem like this due to a radiator cap? I looked at my cap and not only does it appear to be old but I did notice one crack around the outer gasket and some more hairline fracture cracks. I do know that not pressurizing correctly will cause the boiling temp to decrease. Also due to the fact that I am sure my sister in law added water instead of coolant possibly this car could not have the proper mixture which due to improper pressure would cause a 226ish boiling point which... yeah.

    The only reason I haven't thought about it that way is I sat in line at emissions (it failed) for 30 minutes with the vehicle idling and watched the temp go to 226 then down to 205 which indicated the fans were turning on and all was fine then, this was 5 days ago.

    My Boss is lending me his fuel pressure tester tomorrow so I will post back with results on that.

    On a final note has anyone here ever had a sporadic water pump that would randomly cease proper function???

  9. #8
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Help with my 4.9!!!

    The radiator cap could be the problem based on your description.

    Where did you put the Bars Gold powder? Not in the reservoir tank I hope.

  10. #9
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: Help with my 4.9!!!

    So far, what's been said is textbook hg problems on a 4.x (and they aren't as rare as this forum likes to brag - there's just not as much drama associated with it like other examples...read N*). However, there isn't enough info to confirm. I would think that a rad cap not holding pressure would have presented itself real quick on your highway road trip, but it's so cheap, it's worth a shot if yours is showing cracks. Coolant boiling from lack of pressure is different than totally pushing it all out of the reservoir...there's a large mass displacing A LOT of volume somewhere in the cooling system, and if it's not solid or liquid, it's a gas. Does the coolant "boil" when the engine is cold?

  11. #10
    MrFlippers is offline Cadillac Owners Member
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    Re: Help with my 4.9!!!

    Bars leak went into the radiator as it should. Fired it up after adding a gallon of prestone and watched it climb to 226 and it proceeded to drop back down to 200. I also felt the upper radiator hose while it was at 226 and there was no pressure at all in the upper hose. I also opened the reservoir and noticed no boiling or air of any sort.

  12. #11
    brougham is offline Cadillac Owners Master
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    Re: Help with my 4.9!!!

    Try changing the rad cap. Cooling systems do strange things when the cap isn't maintaining the right pressure.

  13. #12
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: Help with my 4.9!!!

    Quote Originally Posted by MrFlippers View Post
    I also felt the upper radiator hose while it was at 226 and there was no pressure at all in the upper hose. I also opened the reservoir and noticed no boiling or air of any sort.
    That's good info. I agree at this point, definitely try a cap

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