Monte Carlo Forum - Monte Carlo Enthusiast Forums - Info: FWD Monte Maintenance at 100,000 miles

This applies to ANY FWD Monte hitting 100,000 miles (as they are all built of products that last a similar life span).

So you just bought a Monte with about 100,000 miles on it, give or take or you have owned it for a long time and are approaching the big 100,000 mile marker. With that, you want to keep things running smooth, then this reading is FOR YOU! Here are things that COULD help you avoid up coming issues by doing a little maintenance ahead of a potential break down.

100,000 Mile Maintenance:

Transmission Fluid and Filter Change - Please verify with your owners manual as well as your driving conditions! If you are in a location that is really hot temps most of the year or lots of up hill climbs, consider this sooner (more frequently is never harmful). This is a topic of lots of debate AND is a commonly overlooked maintenance. First, I do not advocate having a shop flush the trans fluid. When a flush is done, you are still riding on an old/used transmission filter!!! People with high miles cars getting a flush shortly after complain of trans problems. Stick with dropping the pan and changing the filter. While the pan is down, wipe it as clean as possible, including the pan magnet. Replace the filter seal and the filter. I believe most or all GM v6 Montes recommend doing this at 100,000 miles. I have done this with all GM v6 cars I've owned (heck, twice on a '94 3100 powered car that I sold with 215,000 miles) and never a problem with the transmissions, they all performed perfectly.
Spark Plugs and Plug Wires - Cars previously used copper plugs, good for about 40,000-50,000 miles. Today, many GM v6 powered cars since about mid-to-late 90's use platinum or irridium spark plugs. The advantage was a lifespan of about 100,000-150,000 miles. Even though 150,000 is the max rated life, the plugs are still worn, MPG and performance can be negatively affected, honestly, after 100,000 miles, look at it as being on "borrowed time". The plug wires also degrade in some respect, cores get brittle, sheathing weaken. I say this from much personal experience, stay away from BOSCH spark plugs (they don't run as well and have had faster fail rates in GM v6 engines). I recommend using AC Delco or NGK plugs (fun fact, some plugs from the factory are stamped AC Delco on the ceramic, but have NGK scribed on the metal). I've used NGK Platinum plugs in a bunch of GM v6 cars now and they work great. Even if the plugs claim to be pre-gapped, re-check the gap and make sure. BOSCH and AC Delco plug wires are just fine. If you have a 3100 that came with copper, consider upgrading to at least platinum for the longer life.
LIM Gaskets - The GM v6's have been hurt by nylon LIM gaskets. They tend to fail on average between 80,000-120,000 miles. Best ways to check for this possible failure, look at the oil cap for milky residue (looks like a "milk shake" or tan hand lotion). With the car off, you can also swipe your finder on the inside of the valve cover through the hole for the cap. If you want to go a step further, get a hold of a radiator pressure tester, pressurize the system, look and listen around where the LIM and heads meat for hissing or bubbling around the gasket edges. This is a good time to consider inspecting them before a failure.
Coolant Elbows (3800 Owners) - These are made of nylon, same as the LIM gaskets and subject to cracking. Consider inspecting and replacing. Dorman nylon replacements at one point had been known to have issues due to incorrect o-rings and pushing out (I assume that has been resolved, but I fell pray to that mess and currently have GM elbows in my Monte). Dorman now makes aluminum replacement elbows. I believe these have been in the market 1-1.5 years. So far no complaints, but the longevity is still being proven. Based on people currently using them, I would recommend replacing with the aluminum ones. If you don't replace the elbows at this time, consider at your next coolant flush.
Throttle Body/IAC Clean Up - Consider removing the throttle body (on a 3100/3400, if the gasket does not separate, stays in one piece, you can can typically re-use it, on the 3800, due to coolant flow, replace it). Remove the throttle body and the IAC from the throttle body (if the MAF is in the throttle body, remove it as well), using carb clean, small brushes, like an old tooth brush, and clean the gunk and carbon from it. I have seen some people use Berryman's Chem Dip (sold at the auto parts store) to clean these like new.
EGR/UIM Passage (3100 and 3400 Owners) - It's not as bad since GM switched from an analog 3 solenoid EGR to the digital one they use now (I believe since '96), regardless, this is a good tip. The EGR sits on a pedestal that is part of the UIM, and that is a cast aluminum passage way from the pedestal to the inside chamber of the UIM (which ends almost directly behind the throttle body, as a result, removing the throttle body is recommended). Remove the EGR and throttle body. Using carb clean, a piece of wire, or a thin bottle brush stiff enough, spray that passage from the EGR side and scrub it. It has had a history of building up "gunk" that later causes problems. You may even need to grab the gunk from behind the throttle body.
Fuel Filter - Fuel today is FAR cleaner then it was 20-30 years ago. But regardless, this is a good idea. Down side, GM likes to place it in an area that the fitting may rust up. I've been advised by former mechanics, after you change the filter, clean the fitting area up as best you can with a rag, get a tub of bearing grease and coat the fitting with it. The grease will help protect it from corrosion promoting elements.
Power Steering Fluid - Most people over look this one, but it is a lubricant and with heat and use, it does degrade. I don't go crazy here. Just get yourself a cheap turkey baster (lots of dollar stores have them). Use that to remove the old fluid from the reservoir, then simply top-off with new fluid.
Brake Fluid Fluid - This is a REALLY over looked one, it too degrades. Plus can begin containing contaminants that may promote break line corrosion. I also don't go crazy here. Get that turkey baster again. Use that to remove the old fluid from the reservoir, then simply top-off with new fluid. If you want to go a step further, after topping off with new fluid, re-bleed the brake system.
MAF Sensor - The part store sells a spray for this purpose. Follow the instructions on the can to clean it.
O2 Sensors - These have a heated element in them that weakens over time (among other aspects). In most GM v6 cars, the Upstream O2 (the one in the rear exhaust manifold) has impact in the fueling of the car and the downstream one after the cat does not (this is not the case in all GM v6 Montes, but is with some). Replace at minimum the upstream. Brand can be critical here with stricter EPA guide lines, as the calibrations between the O2 and what the PCM may not align well with some brands. Best successes have been with AC Delco and Delphi O2 sensors.
Radiator and Heater Hoses - This is a great time to inspect them for dry rot/cracking signs or abnormal "bubbling"/swelling. If they show any signs of weakness, then replace them to avoid a road side burst later.
Wheel Hubs (specifically the fronts) and tie rods - Simply inspect the hubs and tie rods for play in them. If so, replace as needed. It is possible to have a hub exceed expectations (I had a factory front hub on a '94 Grand Am make it to 200,000 miles before requiring a change).

Regular Maintenance:
Note: If you DON'T know the vehicle's history, then it is heavily recommended you do these.

Coolant Flush - Regardless if you have Dex (orange/pink coolant) or the ol' green coolant, I believe this should be done about every 30,000 miles give or take (or about every other year). Note: Dex has this stigma of being acidic and harmful to the engine and gaskets. This is true of ANY coolant you are running and NOT maintaining. The reason Dex got this rep is do to LIM gasket failures in GM v6 engines. Piece of information most people don't know, those LIM gasket failures also happened in vehicles that came from the factory with ol' green coolant and never saw a drop of Dex. The root cause here was that nylon was a horrible gasket material.
Oil and Filter Change - If you use conventional oil, I have proven on more then one GM v6, changing oil and filter at 3,000-5,000 miles keeps things running great (and past the 200,000 mile marker). I do not recommend going past 5,000 miles between changes. Note #1: Do not motor flush type products. These can remove lubricants from aged parts that rely on them and are difficult to re-lubricate. Note #2: If you opt to use synthetic oil, this should further extend your oil change intervals. I do not have experience with synthetics, so I cannot recommend an interval at this time. Note #3: MAMONTE shared some input of his experience with synthetic oil in a Monte he has owned since day one and is now a very high miles car. Please click this link for his input ---> https://montecarloforum.com/forum/ge...78/#post584285
Chassis Lube - Inspect your car for grease fittings on anything for your suspension that has a ball joint or bushing. If it does, get the grease gun out at least every other oil change and give them a squirt. Helpful Tip: The same dust/protective caps found on the bleed screws for brake calipers work great as dust covers on almost every grease fitting on a car. This allows for preventing debris to enter through the fitting when re-greasing. Sad Note: modern car manufacturers have gotten away from greasable joints that would help prolong the life of the joint. These are things like tie rods and lower ball joints.
Inspect the Belt - Check the serpentine belt for wear and tear, unusual cracking. If it's looking worn, replace it. Helpful Tip: If the belt is not broken or hanging by a thread, when you replace it, take the old one, tuck it in the sleeve the new one came in and put it in the trunk with the spare tire. It's out of the way, but now you have an "emergency" spare if something happens on the road.
Air Filter - If you are using a simple paper air filter, this should be changed about 30,000-50,000 miles. Some filters on the market are re-usable (such as K&N). Just be careful with oil-ed air filters when cleaning and re-oiling (as too much oil can cause MAF problems).
Supercharger Oil (3800 Supercharged Owners) - As I understand, the GM owner's manual claims this is a sealed unit, no need to change the oil. Not true. It's a lubricant that breaks down with heat and use. I don't have experience with the Superchargers, but I've heard members on MCF here recommend doing this about ever 30,000 miles. A method explained to me that sounds easy is to remove the fill plug from the Supercharger, using an empty bottle of hand lotion, take the pump of the bottle out, stick the straw in through the fill hole, activate the pump and squirt the old supercharger oil into the bottle. Once completed, refill with the oil specific for the supercharger and put the plug in.

Now, if you don't intend to do all of these items at 100,000 miles or around it, I would recommend a top priority being your transmission and your spark plugs/wires. These are two very critical items. But everything listed is good to consider to ensure you keep a well maintained Monte :thumbsup: