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Cadillac Seville / Cadillac Eldorado Forum Discussion, 99 STS Running Hot in Past Cadillac Vehicle Discussion; And here's the latest link to the YouTube. Video just taken by me. Surge hose removed, no clogs at the ...
  1. #31
    maiahsdad's Avatar
    maiahsdad is offline Cadillac Owners Fanatic
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    And here's the latest link to the YouTube. Video just taken by me. Surge hose removed, no clogs at the opening, and no fluid shooting out. Engine is currently cold. I am wondering if the engine needs to be warm? Check out the link.

    http://www.youtube.com/watch?v=nn05z...e_gdata_player

  2. #32
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    Re: 99 STS Running Hot

    Quote Originally Posted by maeng9981 View Post
    Northstar thermostat is very reliable and it should be the very last thing to check. You cannot flush the inside of the engine and you are not having problems because of it.

    Water pump drive belt is located at the rear side of the engine (driver's side near your oil dipstick). There should be only one belt on that side so it should be easy to find. Does everything look good? No funny noises or smell around the belt? Is it spinning well?

    When the heat becomes cold, it means the heater core is airbound. This means you have air in the cooling system and air will not cool down the engine. Water pump will cavitate and will pump air - no circulation leads to overheating. Also that "air" in the system is likely to be so hot; it is going to show you a false temperature gauge reading. Have you checked your purge line for blockage? Pull out the hose that is attached to the top nipple of the coolant tank. Point it towards to the coolant filler neck and start the car. If you have a steady coolant flow, it's good. If not, either the hose and/or the hollow bolt at the other end needs to be cleaned.

    Is the coolant level going down?
    WHAT? really? Northstar thermostat, the last thing to check? Thats very obserd to me. My northstar started running warm and i changed that first thing, and it was the issue!

  3. #33
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    Block test link with engine idling and temp at noon position. Fluid remained blue color. See my block test YouTube video take. Few minutes ago.

    Drove to Auto one and left idling. Never heated past 12 noon position. Drove back to friends house, and never heated past noon. Drove it a little hard down street and back and stopped on a hill. Temp raised to 1pm and then went right back to noon while I sat idle. Then drove harder around 4 blocks and back. Heated to 3pm and held there. Eventually after another 5 minutes idling in gear, ran hot ( I didn't let it go into the red).

    Surge tank was bubbling up so I couldn't do another test at that temperature.

    I'm all out of ideas.

  4. #34
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    Re: 99 STS Running Hot

    Quote Originally Posted by maiahsdad View Post
    And here's the latest link to the YouTube. Video just taken by me. Surge hose removed, no clogs at the opening, and no fluid shooting out. Engine is currently cold. I am wondering if the engine needs to be warm? Check out the link.

    http://www.youtube.com/watch?v=nn05z...e_gdata_player
    No. Coolant should flow from the purge line cold or hot. Makes no difference. Stick a stiff wire like a 12 or 14 ga. electrical wire down the fitting where the purge line attaches to the engine to clear any blockage that may be in there. It tends to get plugged with sealant tab residue.

    Surge tank was bubbling up so I couldn't do another test at that temperature.
    THAT is not a good sign. Does the tank smell like exhaust gas (when you are able to open it)? After it cools down a bit would also be the time to do the block test.

  5. #35
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    Re: 99 STS Running Hot

    The location where the hose connects to on the engine end of the hose in that video is not where the purge line is suppossed to be connected to. That looks like some kind of vacuum connection into the throttlebody. The hose that connects to the surge tank should be connected to the lower connection that sticks out of the crossover/thermostat housing pointing towards the drivers side fender right below the two fuel lines. My 2000 doesn't have a metal line next to the throttle body like the 99s do, so I don't know what line you disconnected. You have another video where you point to the fitting with a hose on it, but say that it doesn't go to the surge tank. Thats the correct connection for the purge line.

    ----------

    Check this picture in Submariner409s photo set. It shows the purge line connections quite clearly.

    http://www.cadillacforums.com/forums...air-box-2.html

    Still need to find a picture of the what line the hose is connected to now.

  6. #36
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    Re: 99 STS Running Hot

    294335124.png

    Think I found it, that line is the inlet (or outlet) hose for the throttlebody heating circuit, there is another connector underneath the throttlebody that lets coolant out (or in). It does carry radiator coolant thru the throttlebody to keep it warm. I suspect the the hose that is presently on the purge line bolt is suppossed to be connected to one of these throttle body lines. Now just need to find where the other one goes.

  7. #37
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    Quote Originally Posted by Ranger
    No. Coolant should flow from the purge line cold or hot. Makes no difference. Stick a stiff wire like a 12 or 14 ga. electrical wire down the fitting where the purge line attaches to the engine to clear any blockage that may be in there. It tends to get plugged with sealant tab residue.

    THAT is not a good sign. Does the tank smell like exhaust gas (when you are able to open it)? After it cools down a bit would also be the time to do the block test.
    possibly. I will check again. But why would it pass the block test that I've just done repeatedly?

  8. #38
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    Re: 99 STS Running Hot

    Dammit, dammit, dammit! Boy do I feel stupid. Mark, you are right on. Something just did not look right in that video, but it did not hit me until you mentioned it. The line you are pointing to in this video http://www.youtube.com/watch?v=zuQ08...e_gdata_player is where the purge line should be connected to. The one at the base of the engine lift bracket, next to the radiator hose. The way it is hooked up now you are just recirculating air through out the system. No damn wonder it's overheating.

  9. #39
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    Re: 99 STS Running Hot

    OK had to go dig out my 98 Service manual to get this straight. Your hoses are connected correctly. The purge line from the crossover manifold with the bolt (that you want to clean out) facing the drivers side fender connects to the rear tube on the throttle body, the front tube on the throttlebody connects to the surge tank, just as your does. Apparently the pre 2000 cars have the throttlebody in the purge line loop, water and any non condesable gases flows thru the bolt, thru the throttlebody and into the surge tank when the engine is running. Eitherway there should always be water flowing thru that line whenever the car is running. Pull the lower line below the fuel lines and rod the hole out with a 6 penny nail, a peice of weed wacker line, anything you can stick in there. You need to get in pretty deep to clean out any plug, probably at least 2" deep. If need be make sure water can pass thru the throttlebody as well. Blow thru the line with it disconnected at the hollow bolt and the surge tank before hooking it back up to make sure there are no other plugs in the line.

  10. #40
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    Re: 99 STS Running Hot

    Well, now I am totally confused. Mine is connected as I mentioned above. Maybe it is correct as Mark says. Definitely rod it out.

  11. #41
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    Re: 99 STS Running Hot

    Here we go, to make things clear here. This is for pre-2000 with coolant-circulating throttle body (Thanks Mark C for the water pump connection pictures!):




    Definitely pull the hollow bolt side hose out and clear that up. My Deville was clogged at the hollow bolt AND the hose as well.

    ----------

    Quote Originally Posted by nelson480 View Post
    WHAT? really? Northstar thermostat, the last thing to check? Thats very obserd to me. My northstar started running warm and i changed that first thing, and it was the issue!
    In one of your posts, you said you replaced the thermostat because the car ran at 220F. A happy Northstar will run anywhere between 188-224. Fans don't even come on until the temperature hits 222-224.

    There was nothing wrong with your previous thermostat.

  12. #42
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    Re: 99 STS Running Hot

    Quote Originally Posted by Ranger View Post
    Well, now I am totally confused. Mine is connected as I mentioned above. Maybe it is correct as Mark says. Definitely rod it out.
    The Pre-2000 engines have a separate throttle body and had external heating lines connected to them unlike the 2000 up cars which have the heating circuit internal to the crossover pipe. I had a couple of 97s that had these hoses but I forgot about them until I went digging thru my old service manuals. There is definately a plug somewhere in that circuit, could be at the hollow bolt, inside any of the rubber lines, or even inside the throttlebody coolant passages. If its inside the throttlebody and you can't clear it, connect the surge tank line directly to the hollow bolt, until you can get it cleared. At least that way you can drive it while figuring out how to unplug the blockage.

  13. #43
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    Re: 99 STS Running Hot

    I had a '97, but it was a while ago and I don't remember the differences. Where ever the blockage may be, it can always be cleared with compressed air if it can't be reached with a wire as it will almost always be noting more than s soft sealant tab residue (muck). Bottom line is maiahsdad MUST clear that line and get coolant flowing to the surge tank before he can turn to the HG's.

  14. #44
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    Quote Originally Posted by maeng9981

    Definitely pull the hollow bolt side hose out and clear that up. My Deville was clogged at the hollow bolt AND the hose as well.
    pulled the hollow bolt side of the hose out and it was clogged. But not with any solid matter. Took an ice pick and riddled it about an inch in where it elbows. If that little bit could make THAT big a difference, I'll be amazed.

    Next, I can't see the coolant level when looking from the outside of the surge tank because the bottom half of the tank is black. When I look inside the top of the tank, I can see a seemingly plastic, round, rod-like piece running across. Should I use that as a mark?

  15. #45
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    Re: 99 STS Running Hot

    Just use some sort of a dipstick like a piece for dowel rod. Stick it in to the bottom. Mark the bottom of the filler neck on the rod and then make a mark about 2" below that. That is a good ball park coolant level.

    pulled the hollow bolt side of the hose out and it was clogged. But not with any solid matter. Took an ice pick and riddled it about an inch in where it elbows. If that little bit could make THAT big a difference, I'll be amazed.
    What was it clogged with? Might try rodding it out with something that will get past the elbow like a piece of wire. That's why I suggested wire.

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