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2016 SRX Performance, 2006 STS 4,
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Discussion Starter #1
Hi I have a 99 seville which has hit 100k

I am planning to change the following:
Plugs
Wires
Air Filter
Flush Coolant

I am curious if I have the coolant flush, do I need to replace the t-stat or does that not matter?

Does anyone else suggest I should do anything else?
 

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Cadillac Owners Connoisseur
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1,164 Posts
CadillacEtc said:
Hi I have a 99 seville which has hit 100k

I am planning to change the following:
Plugs
Wires
Air Filter
Flush Coolant

I am curious if I have the coolant flush, do I need to replace the t-stat or does that not matter?

Does anyone else suggest I should do anything else?
CadillacEtc - Glad to hear you're on top of the maintenance! To answer your question, the plugs are AC-Delco part number 41-950, the wires are AC-Delco part number 748Q. The air filter is AC-Delco part number A1096C. Air filters are not quite as important as plugs and wires, so other brands will probably work fine, but I don't recommend any Fram products at all. The Delco plugs and wires cost a few bux more, but they are known to work very well on Northstars and people have had problems with some other brands, especially Bosch. Bosch plugs suck big time. It may be worth investing in a torque wrench to install the new plugs. If installed too tightly, the threads can strip. Using a torque wrench will ensure you don't overtighten them. The plugs are usually pre-gapped, but the correct gap is 0.050".

As far as coolant, your car uses Dexcool coolant. It shouldn't be flushed, just drained and refilled. When the coolant is done draining, with the drain plug still open, pour about 1/4 gallon of distilled water in the surge tank to help flush out any leftover coolant still in the radiator. When it stops dripping, close up the drain, install the supplement in the radiator hose, NEVER PUT THE SUPPLEMENT IN THE SURGE TANK, then refill the system with a 50/50 mix of distilled water and Dexcool coolant. Don't use tap water, and don't put any flush chemicals in the system, no matter how tempting it sounds.

The coolant supplement required on Northstars is one of three products:

* Six of the GM Cooling System Supplement pellets (available at any GM dealership)

* Six of the Bar's Leaks HD Tablet Stop Leak tablets (Bar's part number HDC)

* Two tubes of Bar's Leaks Golden Seal Powder (Bar's part number G12BP)

You can probably find a good price on the plugs and wires at www.rockauto.com. The coolant and supplement are fairly inexpensive at Walmart.

As far as other maintenance work, you should probably clean the throttle body bore and blade. Use some carb cleaner (or TB cleaner) and a toothbrush and some rags. Remove the air filter box and hose, remove the MAF (three small bolts), open the throttle blade, spray some cleaner on the blade and around the perimeter, and scrub that thing up as well as you can, ensuring you get around the edges of the blade and as far into the bore as you can reach. This will help prevent idle problems and a sticky accelerator.

Do the tires need to be rotated? Now is a good time to put a little silicone grease (also called dielectric grease) on the door seals to help prevent them from getting dry-rotted and cracked, which will lead to more wind noise. When you're done with the throttle body, disconnect the battery for 60 seconds, clean up the terminals if needed, and reconnect. This will clear out the learned idle data so the computer can start fresh with new idle values since you cleaned the throttle body.

If I think of anything else, I'll post it. Others may join in the action here with other ideas and suggestions. Let us know what you do and how it turns out. Good luck!
 

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'98 STS (RIP @ 206,xxx miles)
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In addition to the steps already mentioned, I would (and did) replace both drive belts just for insurance. At the same time, check that the belt tensioners move freely and rotate smoothly.
 

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JimD said:
In addition to the steps already mentioned, I would (and did) replace both drive belts just for insurance. At the same time, check that the belt tensioners move freely and rotate smoothly.
Excellent advice, JimD... Totally forgot about the belts... :thumbsup:
 

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White Diamond '03 DHS (with DTS floor shift)
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At 100K it would not be a bad idea to drain and refill (DO NOT flush)the trans. Don't forget the hidden drain plug under the side cover up inside when you drop the pan. Screens and gasket are reusable.
 
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