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I've got a 2003 Deville 4.6 "Y", and I am trying to find the block drain plugs so I can do a complete coolant change. I am also planning to replace the water pump and thermostat. Thank you!

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....I am trying to find the block drain plugs so I can do a complete coolant change.

There are no block drain fittings. The best you can do is remove the bottom trim panel and them remove the drain plug from LH side radiator end panel. A 3/4" socket will fit on the radiator drain plug.

To get even close to a 100% coolant change will require draining the radiator 2 or 3 or more times.

Why are you replacing the water pump (cartridge) and thermostat?


Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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....I am trying to find the block drain plugs so I can do a complete coolant change.

There are no block drain fittings. The best you can do is remove the bottom trim panel and them remove the drain plug from LH side radiator end panel. A 3/4" socket will fit on the radiator drain plug.

To get even close to a 100% coolant change will require draining the radiator 2 or 3 or more times.

Why are you replacing the water pump (cartridge) and thermostat?

The car has 123K on it and it overheated unexpectedly. Could not duplicate the overheating, but found that it maybe had 1% coolant and 99% water. Had lost the coolant and was refilled with water, but found no evidence of leaks. Found no HC in the cooling system and does not build up pressure unexpectedly. My customer requested the water pump change in addition to the thermostat that I recommended. I flushed the system with a cleaning chemical and then ran the car for 15 minutes while putting fresh tap water in as the water drained out of the radiator drain hole. Can't put Dexcool back in because of the tap water and am using a universal coolant, which I have been using for several years without a problem or complaint. I am also putting Kool-It additive in as well as the GM coolant Supplement (12378255)that we started using at Cadillac back in the mid-80's(a real lifesaver). My Cadillac factory manual states that there are block drains on the early Northstars, but I have never found one on the later models.

Thank you for your response an confirmation of no drain plugs.

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What follows is opinion only. Based on many years and miles of Northstar operation and maintenace.

Water pump cartridges do not fail to pump water; the O rings fail and create (very slow) coolant leaks. Sometimes an O ring leak can be seen on and under the drive pulley shaft and sometimes road draft removes all the evidence.

Thermostat failure?? Not in my Northstar experience.

Aftermarket cooling system flush chemicals are not for me.

While distiiled water and Dexcool is the recommended coolant mix, tap water and Dexcool is a very close 2nd.

Universal coolants do not promise to deliver the corrosion inhibitor chemistry included in DexCool labeled products.

You measured 99% water in the cooling system? The coolant is sure enough going somewhere that GM did not intend and shame on the owner for adding water.


Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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There were not any block drains on the Northstar engine - not even the early ones. That is a service manual typo. I confirmed that with the guru several years ago when I went to change the coolant for the first time on my '96 Seville and couldn't find the drains.

Ordinarily, you wouldn't add straight Dexcool to the system but your situation is unique. I would recommend you drain the system, fill with distlled water, run the engine, drain. Repeat until the drainage is clear. Remove as much distilled water as possible and then add straight Dexcool to the system and then run the engine and verify you have a 50% concentration. If you don't have a 50% concentration, use the system capacity and the actual concentration to calculate how much you need to drain from the system and add additional Dexcool to achieve a 50% concentration.

The only supplement/cooling system additive I use is the GM/Bars leaks golden seal supplement.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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What follows is opinion only. Based on many years and miles of Northstar operation and maintenace.

Water pump cartridges do not fail to pump water; the O rings fail and create (very slow) coolant leaks. Sometimes an O ring leak can be seen on and under the drive pulley shaft and sometimes road draft removes all the evidence.

Thermostat failure?? Not in my Northstar experience.

Aftermarket cooling system flush chemicals are not for me.

While distiiled water and Dexcool is the recommended coolant mix, tap water and Dexcool is a very close 2nd.

Universal coolants do not promise to deliver the corrosion inhibitor chemistry included in DexCool labeled products.

You measured 99% water in the cooling system? The coolant is sure enough going somewhere that GM did not intend and shame on the owner for adding water.

I pulled the water pump, and besides being original, I didn't see a problem with it and no signs of leakage. On pulling the thermostat, I found the rubber type seal around the valve warped and loose(possibly blocking the flow of the coolant). The housing seal around the stat was OK. Some foreign cars for years have had the rubber valve seals on the thermostats and I have seen restricted flow and sticking with them in my 30+ years being an auto tech.

In my area of CA, we have chlorine in our water and as we all know, chlorine and Dexcool don't work, besides all the minerals in the water. I have seen GM cars with chlorine contamination of the Dexcool so bad, that the engines had to be pulled and the core plugs removed to wash out all the Dexcool gel. I had a heater core a couple of years ago that was 2/3 plugged with Dexcool gel(we sliced it open cross-ways in three sections.

I have used a universal(also called Complete) coolant manufactured by ServicePro in virtually all the cars that I have worked on for several years now and have had absolutely NO problems with it. It is also an extended life 5/150K coolant. It is almost identical to the factory Mercedes-Benz coolant, but at 1/3 the price. In MB, BMW and Toyota I used their proprietary coolant. The customers request this. I only use Dexcool on GM cars that are still under factory warranty, and like many GM dealers, the first chance to get rid of the Dexcool outside the warranty period, they take it. As an added precaution, as I stated before, I add the GM coolant supplement, made by Barsleaks for GM, #12378255. This additive has been put in virtually every new car for at least 20 years. Not only is it a stopleak, but it contains rust inhibitors and soluble oil. I also add Kool-it to the mix. It is a water wetter and helps to eliminate electrolysis in the cooling system. Again, I have been using this additive for many years with NO problems.

Thank you again!

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Not sure what the need for soluble oil is in a cooling system. The Northstar powertrain engineer who used to frequent this board used to say if that was the only bars leaks youcound find, it was OK to use but to pour as much of the oil out before adding it to the cooling system.

The powdered bars leaks or the tablets were added to the factory fill but that stopped in the late 1990s or so. I still use it though.

I have Dexcool in all of my Northstar Cadillacs, two of which have 150,000 miles on them and have never had any issues with it.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Not sure what the need for soluble oil is in a cooling system. The Northstar powertrain engineer who used to frequent this board used to say if that was the only bars leaks youcound find, it was OK to use but to pour as much of the oil out before adding it to the cooling system.

The powdered bars leaks or the tablets were added to the factory fill but that stopped in the late 1990s or so. I still use it though.

I have Dexcool in all of my Northstar Cadillacs, two of which have 150,000 miles on them and have never had any issues with it.

The soluble oil is an oil that dilutes with water and helps to lubricate and preserve seals that keep the water out of the sealed bearings of the water pump and any other moving parts like valves, shafts and thermostats. A little goes a long way, so the extent that I go to is one card of the GM coolant supplement tablets for an average capacity cooling system. Many engine rebuilders, including those for GM, pre-install the cooling tablets in their rebuilt engines. Sometimes they glue them to the inside of the core plugs.

As to the engineering of the Northstar engine, as usual it falls short of more advanced worldwide engineering. As an example, since the 70's, world makes such as Honda, BMW, Mercedes-Benz, Porsche, Jaguar, etc., have successfully made all-aluminum cast engines for years, but GM's last attempt was the Vega engine. As with the 215 V-8 from the early 60's to the 70's Vega, they just couldn't get aluminum cylinder walls to work. Starting with the Vega "Dura-built" engines, as the engine remanufacturers had already been doing, GM started integrally casting castiron cylinders into their aluminum blocks, as is the case of the Northstar. Cadillac's attempt with a sealed castiron sleeve in their HT-4100's was again disasterous, let alone with the crankshaft knocking problem.

Out here on the West Coast, where our temperatures get over 100 degrees frequntly, has not been a great experience for owners of Northstar equiped cars. Possibly due to a problem why they can't manage to have a successful aluminum cylinder wall engine, leads to the problem of the head bolt threads pulling out of the block. It had to be a Canadian company to come up with an aftermarket solution for this.

As I've stated previously, we have water with chlorine and high mineral content out here in California. Chlorine causes a chemical reaction with the Dexcool and problems result. Unless they know about the problem with chlorine, car owners and uninformed technicians just pour in tap water into the Dexcool systems. When used correctly, Dexcool works great. When NOT used correctly, watch out!

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Never had a cooling issue in my 1996 STS, and I live in Tucson, where summer temperatures have reached 112 -116 degrees in my experience.  In fact, I thought the gauge was broken for a time.  Because we don’t worry much about freezing around here in the winter, I use a gallon of DexCool, combined with 3 bottles of Purple Ice and bottled drinking water.  I used to use distilled water, however an engineer at Royal Purple told me deionized or plain bottled drinking water was preferable.  He said distilled water naturally tries to replace the dissolved minerals, and attacks engine/ radiator components to replace them. I’d be interested in other points of view, however, in the mean time, I think I will reserve my distilled water for my battery (yes, no gel cell for me!) and my CPAP machine.

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Welcome to the Forum.


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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