engine oil flush

[joe f malone]

I have a 1998 Chevrolet Truck K1500 1/2ton P/U 4WD 5.7L SFI 8cyl. This truck has been setting for a couple of years and i would like to flush the oil from the motor. What would be the safest way to do this ?

Topic

[Mike]

Just change the oil and filter 3 times in a row with maybe a 20 minute run time between oil changes. Before that would be a really great time to pull the oil pan and clean all the ooze out of the bottom of it before it gets stirred back up. You can bet that every piece of crap that ever will drain back down into that pan has done so after sitting so long. Using a couple quarts of ATF in that second oil change is safe and would get some extra cleaning power in there.

[Daniel]

I would just throw a couple quarts of trans fluid in it, run it for 20 minutes, change it with reg oil, run it, change it once more. You’re probably going to have to change the lifters and adjust the valve lash. You should probably spray the heck outta the throttle body with cleaner. If it’s been more than 2 or 3 years expect oil leaks.

[Nick Warner]

I’m going to have to respectfully disagree with you guys on this one. This Vortec motor wasn’t built with the sloppy tolerances of the old school stuff. Its just been sitting parked and no evidence has been given that it has some sort of sludge problem. I’m not really a fan of putting anything but engine oil into an engine. If it is sludged, the ATF could break loose way too much at once. On something that’s been neglected, I change the interval to every thousand for a few changes and swap filters every 500 to be sure I’m getting all the crap out, but on a gradual scale.

One thing I would say to do if this was otherwise a good running truck when it got parked is that you should pull the plugs and give a quick shot of fogging oil in the cylinders. Then put your plugs back. Not a bad idea to install new ones since you have them out, but do not use anything but OE grade Delco plugs in this. Change the oil and filter with some fresh stuff and unplug the fuel pump relay. Crank over the engine for long enough that you actually get a good reading on your oil pressure gauge. This way the oil galleries are primed up prior to starting.

You need to get the old fuel out completely. Two year old gas is garbage. Change the fuel filter, drain out the tank completely and unhook the return line. Stick some tubing onto it to go into a jug. Now pour in some fresh fuel with some seafoam added to it. Jump across the load terminals of the relay to energize the pump until what is coming out of the return hose is clean fresh fuel.

Now one thing to think of prior to the first time you crank this motor is that two years is plenty of time for mice to take a liking to your truck. Open the airbox up and look for nests. You do not want to suck that into your motor. Look around for chewed wires, anything indicating they have been in there.

Get the engine up to running temp and be looking all over for leaks. Coolant hoses get soft, gaskets dry up and all fluids need to be checked. Also bear in mind that the brake rotors will have a healthy coating of rust on them and this thing isn’t going to stop like normal at first. Might even hear a grinding noise while driving until they clean up. If the rust is heavy enough, it might be better to just have them turned and throw on fresh pads. Worth making sure all your caliper slides and such get some lube, as they haven’t moved in 2 years.

[Ingvar]

My 99 Silverado Vortec was one hell of sloppy engine. If you want to hear about piston slap, or general rockers noise – I’m your man.

[Daniel]

I agree with the oil in the spark plug hole and draining the gas. You may want to change the fuel filter and add some injector cleaner for a few tanks.
These engines are, pretty much, identical to the older ones. The only difference is the fuel delivery system and the heads are a little different. Most American engines, up until recent years, are sloppy junk.
There is going to be a sludge issue. Oil is hydroscopic so it has been absorbing moisture and breaking down for the last few years. ATF won’t hurt anything. There are going to be leaks, it’s unavoidable. The truck is almost twenty years old and the seals are probably all dry rotted.
Typically I agree with not using additives, but this is an extreme case that requires extreme measures. I have done this with a lot of engines and have a few regular customers that add a bit of ATF before oil changes and have had no “out of the ordinary” results.

[Author]

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