1998 Deville overheating problems?
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1998 Deville overheating problems? in Past Cadillac Vehicle Discussion; Help please! 1998 Deville with 65,000 miles. Lately, the temperature seems to be climbing a little. With the Climate Control ...
  1. #1
    MATTYL88 is offline Cadillac Owners Member
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    1998 Deville overheating problems?

    Help please! 1998 Deville with 65,000 miles. Lately, the temperature seems to be climbing a little. With the Climate Control on and in 75-90 degree weather, temperature reaches about 212-222. On the highway, it cools to a low of 196. In Economy mode, it can climb as high as 233-238. I changed the thermostat to a 180 and put in a 70-30 ratio of the factory spec coolant. Still running about the same after the thermostat change.

    I heard putting 4-6 tablets of bars leaks in the radiator may help. I've also heard of running a switch so both the primary and secondary fan come on together. Does anyone know how to do this and do you have a diagram I could use and a possible place to put the switch?

    I have not replaced my radiator, and also there is no oil in the coolant, so I hope and pray I do not have head gasket problems at such low miles. Otherwise, the car runs like a champ.

    Any help is appreciated guys!

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1998 cadillac deville overheating problems?

    Are these temps higher than you normally see?

    DO NOT use the bars tabs. They just tend to clog purge line and heater cores, which could be your problem. Check the purge line.

    Jury rigging the fans is a band aid. Forget it. Find and fix the problem.

    DO NOT start replacing parts. That will get expensive and put the proper thermostat back in.

    Also forget about coolant in the oil. Northstars don't do that when a HG fails.

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    MATTYL88 is offline Cadillac Owners Member
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    Re: 1998 cadillac deville overheating problems?

    The temps are ab little higher than I normally see. Where s the purge line? The thermostat I put in was what the auto parts people at O Reilly showed me in their catalog. Is the 180 degree wrong?

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    MATTYL88 is offline Cadillac Owners Member
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    Re: 1998 cadillac deville overheating problems?

    Is the purge line the one that connects to what looks like a coolant overflow tank on the passenger side with what looks like a big radiator cap on top? The line extends vertically down and is about 12-14 inches long and open at the bottom

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    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    The purge line does connect to that tank )surge tank), but the open one is the overflow hose. There's another one.

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    The Donald is offline Cadillac Owners Fanatic
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    Re: 1998 cadillac deville overheating problems?

    Quote Originally Posted by MATTYL88 View Post
    Help please! 1998 Deville with 65,000 miles. Lately, the temperature seems to be climbing a little. With the Climate Control on and in 75-90 degree weather, temperature reaches about 212-222. On the highway, it cools to a low of 196. In Economy mode, it can climb as high as 233-238. I changed the thermostat to a 180 and put in a 70-30 ratio of the factory spec coolant. Still running about the same after the thermostat change.

    I heard putting 4-6 tablets of bars leaks in the radiator may help. I've also heard of running a switch so both the primary and secondary fan come on together. Does anyone know how to do this and do you have a diagram I could use and a possible place to put the switch?

    I have not replaced my radiator, and also there is no oil in the coolant, so I hope and pray I do not have head gasket problems at such low miles. Otherwise, the car runs like a champ.

    Any help is appreciated guys!
    Dont think those temps are high at all fans dont come on until 224 deg (except when the a/c on) then they come on immediately. I really dont think you have a problem.......

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: 1998 Deville overheating problems?

    The fans always run together in either FAST (236 degrees) or SLOW (224 degrees) speeds. Go to the Engines, Northstar Performance forum and read the 3 sticky threads on cooling system, gauge, and fan operation. You appear to need that knowledge. DO NOT listen to "wire this and wire that" - it's all witchcraft and hearsay: In proper condition the cooling system, all of it, will operate perfectly whether the car is in Alaska or the Sahara.

    The Bar's Leaks tablets #HDC or the equivalent powder #G12BP were used on the assembly line to prevent nuisance weeps and warranty comebacks. They were discontinued in ?? 2005 - 2006 ?? and unless you had weeps and drips, there is/was NO sense putting more ground up walnut shell, wood pulp, and ginger root into your cooling system.

    The correct thermostat is set to begin at 188 and fully open at 206, so the normal running temps of the engine are from about 193 - 210 all day/night/week/year. With no A/C function set, temp WILL go to 224 in traffic before fans go to SLOW. the engine cools to 213, fans turn OFF, the cycle repeats. With an A/C function set, fans run in SLOW all the time, so you should see temps of 195 - 210 all the time. Fans are never needed above about 35 mph.

    Several recent cooling threads have a temp gauge picture with annotation - the ticks correspond to your gauge ticks. Copy it to your car files. You're welcome. Go to the Engines forum and read those cooling stickys - and study the entire Cadillac Technical Archive way up ^^^ in the top black bar.

    Surge tank .................. proper cold fill level is down at the other end of that arrow molded into the tank top/side.

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    Re: 1998 cadillac deville overheating problems?

    Quote Originally Posted by MATTYL88 View Post
    The temps are ab little higher than I normally see. Where s the purge line? The thermostat I put in was what the auto parts people at O Reilly showed me in their catalog. Is the 180 degree wrong?
    I thought they had a 200 degree thermostat, but I could be wrong.

    ----------

    Quote Originally Posted by Submariner409 View Post
    The Bar's Leaks tablets #HDC or the equivalent powder #G12BP were used on the assembly line to prevent nuisance weeps and warranty comebacks. They were discontinued in ?? 2005 - 2006 ?? and unless you had weeps and drips, there is/was NO sense putting more ground up walnut shell, wood pulp, and ginger root into your cooling system.
    I think they where discontinued in about 2002. None in my '03.

  10. #9
    MATTYL88 is offline Cadillac Owners Member
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    Re: 1998 Deville overheating problems?

    Thanks for the info. I looked at that other forum and your profile. My gauges are digital and display actual numbers only, but I may be running normal temperatures after reading the replies. I'm going on a 1000 mile trip this week and will let you know how it performs. Thanks!

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