Question about 1999 Cadillac DeVille

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1999 cadillac deville overheating

So far I have replaced the engine temp sensor,thermostat, checked hoses and radiator replaced surge tank,and verified cooling fans are coming on, replaced waterpump and block tested the engine for combustion gasses. The vehicle runs ok at idle but overheats while driving, return to an idle and it will cool off again. Any suggestions?

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  • pemayer54 Oct 10, 2008

    I block tested the engine cooling system for a head gasket/crack etc. I comes up negative. There is no water in the oil or coming out the exhaust. I flow tested the radiator and it is good also.

  • Anonymous Nov 14, 2008

    car will over heat when drove in the hwy



  • pemayer54 Nov 20, 2008

    The pellets you speak of are an inhibitor to keep the aluminum form deteriorating from electolisis, and also a stop leak. I did finally fix the problem, these engines run close to boiling temperatures so the system has to hold presure. I found a couple of small leaks from hoses that had the factory clamps on them. After presurinzing the system and repairing all of the small leaks the overheating has stopped. Thanks for the feedback.

  • lconway80 Jan 03, 2009

    i have a 2001 dts. i changed the thermetat, water pump, and radiator. the car can idle for 2 hours without over heating. but once driven it over heats about 10-15 minutes whille driving. i have no leaks, no engine knocking.

  • regis84 Jan 04, 2009

    Overheats after about 15min...

    that smoke comes out of the hood

    changed gasket, and thermostat....

    if you have an idea on what it is let me know

    thx

  • Anonymous Mar 02, 2009

    water is dripping from tailpipes (more than usual) and over heats

  • Anonymous Apr 28, 2009

    Engine is losing coolant> I can drive about 25 miles before the engine begins to overheat I then will need to put in a little less than a quart of coolant. If it is a headgasket. What is the best, most affordable and efficient way to resolve the leak problem. Tanks for the assistance.

  • markeibren96
    markeibren96 Sep 12, 2012

    call 1-718-316-5935----i ask a few questions and the problem is solve --garanteed

  • Anonymous Mar 12, 2014

    My 1999 Cadillac deville was overheating. I replaced the thermostat and the waterpump and its still overheating. What is my next solution?

  • Anonymous Mar 12, 2014

    On my 1999 cadillac deville the waterpump and thermostat was replaced, but there was coolant mix in with the engine oil. What can i do to get this resolved?

  • Anonymous Mar 29, 2014

    THE CHECK COOLIANT KEEP COMING UP I CHANGE THE WATERPUMP AND THERSTAT AND IT NT OVER HEATING BUT THE RADATOR HOSE FEEL TIGHT

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My husband did everything that everyone else did that had this overheating problem. It was so weird that my engine cooled at a light and heated up going down the road. I have a north star 4.6 engine and this is natorious for happening. my check engine light also came on and so I had a diagnostics done which told me my #1 injector wasn't firing , car ran like **** as well. After putting in a new water pump and plugs,ect. and realized injector was good a friend told him we could have a blown head gasket. So just to see if this was the problem I went to buy a bottle of glassbeads and the auto parts guy told us to purchase a bottle of BARS STOP LEAK BLOCK SEALER NOT RADIATOR BUT BLOCK SEALER $31.99 . He followed the directions and we waited 24 hrs. before driving it. What ever the problem was has stopped my car runs like brand new and I am loving it again. no over heating no injector problem, runs great.......I hope this helps. I know its probly a temperary fix but its a fix and now we know what the problem was. SASSY

Posted on Mar 19, 2009

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That sure sounds like a headgasket failure even if the engine recovers at an idle. It seems you have done the likely suspects already.
If you haven't done it, check coolant overflow tank for exhaust fumes and discolored or oily coolant and engine oil for any cream-colored effect.
Neither of these missing means the headgasket is good but they are sure clues if you see either fouled. 
You could also start cold, leave the radiator cap off (if you still have one) and watch for bubbles as the coolant starts to circulate.
If this problem has been coming on gradually, your radiator may be limed too far closed especially if anyone has used tap water in it for years. If you can reach it, check the radiator to see if the temperature is roughly the same from top to bottom; that will tell you whether the coolant is passing through all of it. You wouldn't have to wait for it to get scorching hot for this.        

Posted on Oct 09, 2008

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Pellets. read owners manual

Posted on Nov 19, 2008

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I have replaced radiator,thermostat,water pump,fans and fan relays.does fine sitting or even at low speeds until get 55 or above then overheats.1 thing i noticed is my fans are blowing air into the radiator from ingine bay to outside grille so when get to high speeds air going in through grille to the ingine bay is fighting the fans and not cooling the radiator and overheats until i slow down or stop.atleast what i have found so far with my 99 deville.still trying to find out how to solve the problem

Posted on May 02, 2014

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Call 718-316-5935-----your car will be fix

Posted on Sep 21, 2012

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99 cadillac deville engine overheating an loosing coolent couple times a day.Replaced thermostat, water pump ok, cooling fans on at 217deg.,radiator pressure tested an holding pressure.engine still keeps...


Check to see if you have flow through the entire radiator.If part of the radiator core is cool to the touch when the engine is at operating temp, this indicates restricted radiator flow. If the entire radiator core is not allowing water to flow through, cooling will not be at all efficient. Also a good idea would be to purchase a block tester. available at napa and other reputable parts houses for around thirty dollars. You remove a small amount of coolant, and put the tool in the radiator, or pressure tank opening. If there are any combustable gasses present, i'e' exhaust, this would indicate a head gasket breech, (or maybe worse) and would indicate that it's time to stop looking for a simple problems, and get proffessional help. Good luck to you!

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Are you sure the thermostat was in the wrong way ?.

The thermostat is located in the bottom hose unlike most conventional cooling systems.

The thermostat in the Northstar engine is a dual action device.
One end of the stem is the Thermostat(obviously) and at the other end is a spring loaded pressure valve(the thinner end).

Make sure the thermostat end is nearest the rubber hose and the pressure valve end is in towards the engine.

Also note that the cooling fans don't come on until the coolant temperature hits around 225 degrees.
During normal highway driving the fans will very rarely come on(if at all) due to constant air flow through the radiator.They will only usually come on in heavy traffic conditions on a hot day.
But......if you have the Air Con switched on, the fans will run all of the time.

For overheating problems consider the following......

The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.

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The normal operating temperature for the Northstar engine is around 210 degrees.
The fans will not come on until the temp hits 225 degrees.

The thermostat in the northstar engine is located at the bottom radiator hose (unlike most conventional cooling systems).

The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.The hose goes in to the engine to a crossover and comes out the other side to near the thermostat housing,the blockage may be there.

If the other end of your purge line is not connected to anything then that is the problem......it must be reconnected otherwise the cooling system is not pressurized.

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The most common overheating problem with the Northstar engine is a blocked purge line. It's job is to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.The hose goes in to the engine to a crossover and comes out the other side to near the thermostat housing,the blockage may be there.
Also note that the cooling fans don't come on until the temp hits around 225 degrees.
During normal highway driving the fans will very rarely come on(if at all) due to constant air flow through the radiator.They will only usually come on in heavy traffic conditions on a hot day.
But......if you have the Air Con switched on, the fans will run all of the time.

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