Question about 1998 Cadillac DeVille

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Water leaking and engine heating up in 1998

Water leaking and temperature heating up in 1998 cadillac deville . can't find out where the thermostat is. no info in manual. please help- disabled mother who can't afford to take to repair shop.

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I asked about the water housing unit!

Posted on Oct 21, 2011

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The thermostat can be traced by following the top (usually) radiator hose to the block. On some engines it is located by tracing the bottom radiator hose. There will be the thermostat housing unit (top most part is rounded between the size of a golf ball and a tennis ball. There will be either two or three bolts. Here are the steps for removal and installation.

1. Drain radiator. (if you cannot do this, take the cap off to release any pressure and allow for draining; i.e. will explain further) Check both radiator hoses (replacing is a good idea since draining the radiator is necessary (and if this is a possible for you to do, but not necessarily a must in the event you cannot.

2. After draining radiator (have new fluid and filtered (best, not necessary) water (about 3-4 gallons{sometimes more}, available for refill), remove the hose connected to the housing (thermo). Sometimes this is not possible and you may need to unbolt housing first (as well as remove any parts that may be in the way). Once hose (and/or housing) is off, clean off old gasket on both the housing and the block (housing bolts up to) and remove the old thermostat. Be sure the new thermostat is inserted correctly (most go in one way so this isn't usually an issue).

3. Once the housing and block area are clean, put the new thermostat and gasket in (if one did not come with the thermostat, a "gasket sheet" will need to be purchased). It is a good idea to use gasket sealer to hold the gasket in place on either the block (best) or the housing. Make sure both sides are clean and free of any high areas such as bumps as these can cause leaks. Also, when cleaning (use a straight razor blade if availble or a flat head screwdriver) make sure not to score or gouge the housing or block as they are aluminum. A straight raiser (new) is necessary, and sometimes two are necessary as they dull quicly during this process, depending on how badly the gasket sticks to the surfaces.

4. Once the thermostat and gasket are in place, bolt the housing back to the block and put the hose (clamp) back in place. Add 1 gallon of 50/50 pre-diluted anti-freeze (or recommended amount per manual/repair manual); then add water until radiator is full and level does not go down. Let the thermostat sit for about an hour (for drying and sealing purposes); then, with the radiator cap off, start the engine and let the water begin to circulate (may take 4-5 minutes or longer) until engine is at operating temperature (watch temp gauge). Once this point is reached, watch the water level and add water as needed until full. Also check and make sure the "overflow" resevoir is full (not overfilled) with coolent fluid (anti-freeze only; water if no coolent is available); you can mix part of the gallan of antifreeze with water to make this happen if need be.

5. Let engine idle and watch for leakes around thermostat area. Sometimes you will see small bubbles or very small amounts of water at gasket area. This is normal if only very small amouts are seen. If none are seen then you're in good shape. Do not drive the car until no leaks are visible, and you are confident that there are no leaks at the thermostat area, and while car is idling, watch the temperature gauge. If it reads normal and is steady, good. If it starts to go up again, turn on the heater and wait only about 2 minutes to see if it goes down, but no longer. It may go up while the gasket is sealing. If it is normal still after 2 minutes, let the car idle for about 10-15 minutes while the water continuously circulates. DO NOT REV THE ENGINE.

6. Once the temp gauge reads normal after this amount of time, take the car for a short drive, keeping an eye on the temp gauge. Start small by circling the block a couple of times (2-3) and then slowly venture out further.

7. After returning home, take a look unde the hood and under the car and look to see if you see any leakage.

6. If you were requried to purchase a "gasket sheet", make sure the gasket is cut for the entire area of the housing (bolts and all) so that the entire unit is sealed.

Please let me know if you have any further questions.



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Posted on Apr 24, 2010

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The thermostat in the northstar engine is located at the bottom radiator hose (unlike most conventional cooling systems), the hose connects into the housing where you will also find the water pump.
Remove the hose from the housing,then remove the two bolts on the flange,the thermostat can then be pulled out.
Take note of the orientation of the thermostat as you remove it.
Don't forget the new gasket when you install your new stat, you may have to order this separately.

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.

Posted on Apr 26, 2010

  • Ninja Oct 18, 2011

    I asked about the water housing unit not the thermostat. I am not disabled. I don't know what it up with this site, but it completely reworded my question.


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