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Thread: new radiator, now engine overheats

  1. #1
    starfox86's Avatar
    starfox86 is offline Cadillac Owners Fanatic
    Automobile(s): 1998 deville, 2000 sls, 2006 cts-v
    Join Date
    Feb 2005
    Milwaukee, WI

    new radiator, now engine overheats

    I just put a new raditator in my 94 sls, my old one had a leak where the trans fluid goes in and the trans fluid was getting into the coolant. but even with that the engine was staying around 200-215, but sitting still, it would raise up to as much as 234, but not any higher. I was going to get it cleaned but i found the leak so i jus got a new one. with this new one that i purchased from perfomance radiator, the temp rises like crazy, I flushed it with a hose before i put the anti freeze in it. it seems as if the top hose isnt getting much pressure. and the bottom is geting alot, almost too much. and I filled it up with 50% distilled water and 50% autozone coolant. i know the thermostat isnt acting up because when i pulled the valve release on the tank and the coolant was boiling. so, im in need o some help here!!!

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Woodstock Ill.

    Re: new radiator, now engine overheats

    First off, if you were getting trans fluid in the coolant, you can get coolant in the trans. Drain it and refill it, then do it again.

    You said "when i pulled the valve release on the tank". I assume you are talking about the cap? That is not an OEM cap. Not even the correct type. That may be your problem. Was it a recent replacement?

  4. #3
    Res STS is offline Cadillac Owners Fanatic
    Automobile(s): 1998 Seville STS
    Join Date
    Feb 2005

    Re: new radiator, now engine overheats

    The surge tank is conected to the heater hose circuit so boiling in the surge tank does not mean the thermostat is working properly as you think.

    Further to Ranger, if you have trans oil in the coolant, and you should if you also had coolant in the trans, things could be pretty gooped up. I don't think a water flush would get the sludge out of your cooling system. Sludge may be plugging up your t'stat and vapor bleed lines. If vapor bleed lines are plugged, you will have pockets of air in your cooling system that prevent proper flow through the system. I'm not sure of the best way to flush out the sludge, but antifreeze/distiiled water mix may work better than other concoctions that might foam, corrode etc. You'll probably need to flush several times. For sure, take out the t'stat and inspect it for sludge fouling and test it on your range with a soak in a pot of boiling water. If the t'stat looks goopy, you may need to rod out some of the vapor bleed lines and fittings .

    Also, the N* cooling system is different from older designs. The thermomostat is on the inlet side of the engine, not like an old Chevy small block where the t'stat is at the engine outlet and feeds the top radiator hose. So the N* lower radiator hose is actually feeding the thermostat inlet. Takes a little getting used to but this concept is also used on the fine 4.7 liter Chrysler V8 OHC engine used in Jeeps, Dodge Dakotas and Durangos.


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