Overheating
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Overheating in Past Cadillac Vehicle Discussion; So a couple of weeks ago I posted regarding my overheating issue with my 99 deville and was frantic about ...
  1. #1
    Sheryllynne is offline Cadillac Owners Member
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    Overheating

    So a couple of weeks ago I posted regarding my overheating issue with my 99 deville and was frantic about my heads, did the block test, pressure test and tested the cap all a-ok, Im feeling very optimistic again. But still don't know why she overheated, I had the low coolant light start coming on last year had cross over valves replaced still happened and they said radiator hose had leak, so replaced. Ran her like crazy today with the tests and everything ok, don't know what her issue is, but again I'm crossing my fingers. Tomorrow taking in for an oil change since my daughter and I bought synthetic thinking that's what we had, guess not, it was time for 1 any way.

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  3. #2
    basscatt's Avatar
    basscatt is offline Cadillac Owners Master
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    Re: Overheating

    check the PURGE LINE -

    the PURGE LINE is the only way of expelling air from the Northstar cooling system -

    it is a 3/8 diameter hose that goes from a hollow bolt in the thermostat/waterpump housing area of the engine - and plugs onto a nipple on the side of the SERGE TANK -

    with the engine running - there should be a gentle - constant flow of coolant - from the engine - to the serge tank -

    if there is no flow - the most likely cause is a blockage in the hollow bolt -

    follow the hose towards the engine - with the engine OFF - remove the hose - use a straightened metal coat hanger - or something similar - and poke it into the hollow bolt -

    the coat hanger should go in about 2 1/2 inches -

    once the hollow bolt is cleared - you can briefly start the engine to verify coolant flow - be sure to use some sort of container to catch the coolant so you don't make a mess -

    check the hose and serge tank for blockage -

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Overheating

    Are you saying you are still overheating and still having to add coolant?

  5. #4
    Sheryllynne is offline Cadillac Owners Member
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    Re: Overheating

    actually no it hasn't overheated, but we haven't really driven either. during the test we tried to get it to overheat and couldn't. and it has maintained its coolant, but again we haven't really driven it.

  6. #5
    Sheryllynne is offline Cadillac Owners Member
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    Re: Overheating

    well a 2 trip and no overheating. Im really hoping. Now to try to get our money back from the guy who did nothing and said it may or may not be heads, and ending with I don't work on Cadi's because of the Northstar, maybe he should have said that before we gave him a hundred dollars to put water in my car,

  7. #6
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    Re: Overheating

    OK, not overheating is good. Check the coolant level each time you drive it. Remember, the level will be higher when hot due to expansion so check it cold (before each drive). If the level goes down, post back and we'll have to figure out where it's going.

  8. #7
    Sheryllynne is offline Cadillac Owners Member
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    Re: Overheating

    so we drove today out of the county ran a little warmer at 224, it used to not get over 199. Before we left I of course checked the level and was fine, but of course check coolant level showed on DIC again which is how this all started so first thing tomorrow I'll be checking again. When I took it to a local shop for diagnostic and they did nothing in fact we asked them to put the Dex cool that was in trunk in it and they put water so I actually hope its a little low so I can put some in, it hitting the 90's here, don't know if it makes a big difference but will make me feel better. Changed oil sunday was perfect, never has a leak under, seems like it would have to go somewhere that fast, but all pressure tests and block have been good.

  9. #8
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Overheating

    224 is just a tad on the hot side. That's where the PCM says turn on the auxiliary cooling fans. Have you checked the purge line to verify coolant flow?

  10. #9
    stoveguyy is offline Cadillac Owners Connoisseur
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    You or shop keep adding water only? What is your coolant concentration now? Do you hit 224f at hwy speeds? Idling you may see 220 spikes. But you should drop to 200f as you get going. My thermostat always yo-yos. I stay at 200 on hwy. it hits 210-215 while stopped and than as soon as I am up to speed it drops to 195 and than stabilizes at 200 or so. Always has done that.

  11. #10
    Slipgate is offline Cadillac Owners Enthusiast
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    Re: Overheating

    Is mine an oddball? I run at 190 all day long - sometimes in the 180s. Highest it ever gets in traffic is maybe 215.

  12. #11
    Ranger's Avatar
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    Re: Overheating

    I'd say yes (not that that means much). My '97 ran a reliable 205 (summer) - 215 (winter). Now having said that, I have heard others say that they run in the 190 range.

  13. #12
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Overheating

    It all comes down to how much goose grease is stuck in the radiator fins...............

    Mine runs at 195 at a steady 65 mph.

  14. #13
    Sheryllynne is offline Cadillac Owners Member
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    Re: Overheating

    yes at idle it was 224 then did cool as we went even at the end of driving in 90 degree temp outside had to sit at a drive thru for 10 min and didn't go over 219. Coolant is low this morn, and at this point I'm not sure of my concentrate since the mechanic put in only water, today I will be adding my 50/50 dex. Purge line a-ok. You know we always use Lucas and 1 day they were out and my daughter grabbed this goo be gone or gunk something, anyway trouble ever since, it was a sealant I thought it was just like my Lucas, I don't think so, I'm not saying that's it, just weird. LOve my car but boy its giving me a headache.

  15. #14
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Overheating

    I wouldn't loose any sleep over 219 as long as you are not overheating.

    Since the "mechanic" used straight water, you add straight coolant this time. That should get you pretty close to 50/50 again.

    Never put any of that snake oil crap in your cooling system. That might be your problem, especially if your problems started right after that. We usually don't recommend flushing anything but toilets, but You might be a candidate at this point.

    Did you ever check the purge line to confirm it is not clogged? That would be the first thing to do, especially since you added snake oil and had problems immediately afterwards.

  16. #15
    Sheryllynne is offline Cadillac Owners Member
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    Re: Overheating

    really you guy don't use Lucas? I mean I put prem gas in it I guess maybe that's all the additives it needs. Checking purge line today, I have been getting help and they looked at me like I was dumb so I printed the diagram and step by step directions from I believe submariner. So we'll see. I have learned a lot that is for sure.

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