: Suggestions for keeping 05 4.6L in mint condition?

12-01-10, 11:04 PM
Hey guys, I don't have a Caddy per-se, but a Pontiac with the heart of its Cadillac bretheren, an 05 Bonneville GXP. I keep her lubed w/ Pennzoil Platinum 5W-30 and Wix oil filters every 6k-7500 miles, and keep a close eye on coolant consumption, etc. I'm planning on having the coolant flushed this winter (she's at 75k and 5 years) and I keep fresh air filters on it, and will be cleaning the TB and MAF this winter as well. What else can I do to keep her in tip-top shape? This includes the trans. I'm doing a pan drop and filter this winter as well.

12-01-10, 11:16 PM
Exact ditto here - just drive it fast and hard once in a while.

Coolant and transmission - let me spend your money: Take the car to a GM dealer and finagle a "Fall Special" - coolant exchange, transmission fluid change to DEXRON-VI, and a brake fluid exchange.

"Brake fluid exchange" ??? Yep - the stuff loves to suck up moisture and should be completely changed every 3 - 5 years, just like coolant.

12-02-10, 12:30 AM
Yup, I know all about brake fluid. I'm new on here, but not to cars.

I honestly don't like trans flushes. I'm going to do a pan drop and filter. I have a Bend Pak 2 post asymmetric lift at home, so I'm equipped to handle it. My plan is to put in Amsoil Synthetic Trans fluid. I trust myself more than anyone else with our vehicles.

The GXP is my dad's car (I'm in college and maintain our rather large fleet) and whenever I drive it it gets hammered on, LOL.

12-02-10, 02:05 AM
Don't flush the cooling system; drain and refill is enough.

Flushing is for toilets.

12-02-10, 10:43 AM
Why no flush? I also have heard that as per GM's procedure they're supposed to put the cooling system tabs into the lower hose when refilling. Is that correct?

12-02-10, 11:24 AM
GM quit using the tabs in '02 or '03.

The no flush is more for transmissions than cooling systems, but you cannot get all the coolant out, so if you flush it, you won't get all the water out. Now you have to run through the mathematical gymnastics to get it back to a 50/50 mix or use a refractometer.

12-02-10, 05:38 PM
pontiaced25, If you're dead set on doing a "flush", take the car to the Pontiac (GM) dealer and ask for a "coolant exchange": let them obsess over "how" and "why". They'll hook it up to a vacuum machine, suck it all out, blow in new 50/50 (no air bubbles or voids) - you'll have another 3 years of driving and a dealer to fall back on if you're not happy.

"I've also heard that........................" Heard what? From who? Is the GM supplement tablet question discussed in your GM/Helm Service Manual for your car ?? As Ranger posted, the tablets were discontinued some time ago.

Transmission pan drop and filter - the only time you can replace the filter in a 4T80E transmission is during overhaul - there's a screen in there, yes - but it's seldom dirty. At 75K miles the filter is the LEAST of your worries. Have the same dealer do a fluid exchange to the new (2006+) DEXRON-VI synthetic fluid - now used for ALL GM transmission service (as old stocks of obsolete -III run out). Unless you plan on driving the car in Saudi Arabia or doing extensive trailer towing, while AMSOIL fluid is the top of the line, it is entirely unnecessary.

12-03-10, 12:09 AM
I just want to get all the old dex-cool out, and put a fresh mix in.

It was posted on www.pontiacbonnevilleclub.com about the tabs.

I understand most of the people on this forum merely drop the keys in the box at the dealer, and that is one perfectly acceptable method of doing things. However, I have the investment in tools, equipment and I'm willing and able to do the job myself. I do not have a FSM for this car yet, but it sounds like I am going to have to purchase one.

12-03-10, 09:43 AM
I understand most of the people on this forum merely drop the keys in the box at the dealer

WRONG !!!! Most of the people in CF DIY to a great extent - me included.

Your first post -

".....planning on having the coolant flushed......" - doesn't sound like DIY. 2.5 quarts of some liquid remains in the block, no matter how you drain it: there are no block drains on a Northstar. Thus the coolant mix exchange system.

".........pan drop and filter.........." - The filter is serviced only at transmission overhaul. You mentioned nothing about the transmission side tank drain plug - and the fact that it's a dry sump unit: there's very little fluid in the pan with the engine off - you also check the fluid level with the engine running, hot, in P.

Based on that info, your knowledge of the Northstar system appeared limited, so my suggestion to let a dealer do the coolant exchange and transmission fluid exchange/upgrade was offered as a quick, relatively inexpensive way to get the job done, done correctly, and have some insurance to fall back on.

If you have the equipment and understand the necessary steps and procedures to work on a Northstar cooling system and transmission, by all means have at it.

johnny kannapo
12-03-10, 12:18 PM
When I say coolant flush, have done this several ways.

1)I have simply drained the radiator, added fresh 50/50 Dex.

2)I have drained the rad then flushed with the small coolant hose out the 3/8 line on the reservoir as I matched the flow with the garden hose in the reservoir running the engine at 1800 rpm for 15 minutes. The cold water from the garden hose flowed slow enough that it was hot when it came out the 3/8ths TB hose. After it was clear water I drained the water, closed it up, then added 1 gallon full strength Dexcool, and what amounted to about a gallon of 50/50.

3)Recently I repaired the crossover and was able to directly flush both sides of the block, heater core & reservoir, Rad radiator under garden hose nozzle pressure.

This last flush crossover removed, is the only flush that will get out any heavy sediments in lower sections of the cooling system. If sealants are added as all cars get from the assembly line there is crud in there that will not come out with a regular flush or drain.