Checking the purge line!!!
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Checking the purge line!!! in Past Cadillac Vehicle Discussion; I have a 97 Cadillac Deville. As soon as it get to operating temp, the coolant rises up and out ...
  1. #1
    adamsjw2 is offline Cadillac Owners Member
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    Checking the purge line!!!

    I have a 97 Cadillac Deville. As soon as it get to operating temp, the coolant rises up and out of the overflow tube. I checked the thermostat and it is working. So I read about the purge lines sometimes causing problems, went out this morning and determined it to be clear. However, from what I read, when the car is running, water should come out of this line steadily? Is this water supposed to flow from the engine side, or the coolant reservoir?

    Thanks,
    John

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    1BadCadSTS's Avatar
    1BadCadSTS is online now Cadillac Owners Connoisseur
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    Headgaskets
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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Checking the purge line!!!

    Coolant is supposed to flow from the metal nipple/bolt to the surge tank. Steadily. With the engine cold, remove the line at the tank, open the tank, and hold the end of the line in the open filler neck. Have an assistant start the engine normally. A small but steady stream should flow.

    Proper coolant level in the tank is half full, cold.

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    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Yes, I did that and no water came out of the metal line. I did put some air through the line and could hear it coming back to the reserve tank, so the line cant be clogged?? right?

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    The Donald is offline Cadillac Owners Fanatic
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    Re: Checking the purge line!!!

    Quote Originally Posted by adamsjw2 View Post
    Yes, I did that and no water came out of the metal line. I did put some air through the line and could hear it coming back to the reserve tank, so the line cant be clogged?? right?
    Its probably not the line itself but that infamous bolt with the hole in it that the hose is connected to. it may be plugged,however as badcad says
    sounds like a bad head gasket..Good luck with this one and hope it is'nt

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Checking the purge line!!!

    Pull the hose off the metal bolt/nipple and rod out the bolt with a straightened coat hanger. The coat hanger should have free opening to a depth of 2.5" or so. That system is a high point bleed that is used to keep air and gases out of the coolant - any bubbles find their way back to the surge tank airspace. The surge tank is part of the pressurized system so there is no loss there.

    IF there is air trapped in the main coolant system it causes water pump cavitation - low or no coolant flow - with the resulting overheat and coolant blowoff - which compounds the problem. In some cases you can hear bubbles moving through the heater core - a gurgling noise in the center dash area.

    Troubleshoot the cooling system before condemning the head gaskets - or water pump or thermostat.

    IF your engine has a pair of lines that go to the throttlebody
    - from the bolt/nipple to the throttlebody then to the surge tank - that may be your problem. Bypass the throttlebody coolant lines with a suitable length of proper ID reinforced rubber hose - go straight from the bolt/nipple to the surge tank side. (That throttlebody circuit was designed to heat the bore in order to prevent cool, humid days from icing the throttle blade. Not needed - the aluminum water crossover heats the throttlebody quite well.)

  8. #7
    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Yes there is a line coming from the surge tank to the throttle body, and then one from the "hollow bolt" to the back of the throttle body. So I should try running a hose from the surge tank to the hollow bolt, right?

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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Checking the purge line!!!

    Yes - eliminate the throttlebody circuit - and make sure that hollow bolt/nipple flows coolant - rod it out as insurance.

    The reinforced fuel hose - any large parts store - cheap - and use a couple of screw band clamps - proper size. Make sure there is no strain on the new hose - a bit of slack at the surge tank will be fine.

    Here's what it looks like on a 2000 Deville ..............

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    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Thank you! I am going to try this and will let you know what happens. Would be nice if it works as I really like the car!

    John

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    Re: Checking the purge line!!!

    .......... and here's your throttlebody - eliminate this coolant circuit. THAT may be what's (if ?) plugged up and MAY be your problem .................

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    Re: Checking the purge line!!!

    Quote Originally Posted by adamsjw2 View Post
    Yes, I did that and no water came out of the metal line. I did put some air through the line and could hear it coming back to the reserve tank, so the line cant be clogged?? right?
    Putting air into the line and hearing it return to the surge tank would lead me to believe that the line is clear. If it wasn't, you cleared it (I assume you used compressed air). The fact that you get no coolant flow out of the open line leads me to think there is "air" (exhaust gases) in the cooling system. Couple that with the fact that it overheats and blows coolant out of the overflow is not a good sign. Does the surge tank smell like exhaust? Might be time for a block test.

  13. #12
    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Well, I went and got a hose and did the bypass. I have been driving the car for about an hour now and there is NO overheating at all!!!!! It appears to have worked, but I am going to keep a close eye on it!!

    Thanks to everyone for your help!!

  14. #13
    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Day 2
    I changed out the coolant and put in the correct mixture of ant-freeze. I have driven the car several times today (quite a few miles) and it has done well. Coolant level is still where it should be and the car is running great!!
    98eldo32v likes this.

  15. #14
    adamsjw2 is offline Cadillac Owners Member
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    Re: Checking the purge line!!!

    Well, it has been several days since I followed Submariner's advice and by passed the throttle body with a new hose. I am glad to say that this has worked and the car is doing just fine. We have drove many miles now with no trouble. If any of you have similar problems, I would try this same thing before assuming that you have a blown head gasket!

    Again, thanks for the good advice!

  16. #15
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    Re: Checking the purge line!!!

    Quote Originally Posted by adamsjw2 View Post
    Well, it has been several days since I followed Submariner's advice and by passed the throttle body with a new hose. I am glad to say that this has worked and the car is doing just fine. We have drove many miles now with no trouble. If any of you have similar problems, I would try this same thing before assuming that you have a blown head gasket!

    Again, thanks for the good advice!
    ----------------------
    yep - MANY misdiagnosed "failed head gaskets" turn out to be simply a blocked purge line -

    glad you are one of the lucky ones -

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