i just got this blazer, has 200,000 miles on it, original motor. It makes its fair share of noises as any high mileage vehicle does but this one in particular scares me. After leaving it sit overnight when i start it in the morning there is a fairly loud knocking sound for about 10 seconds or so and then it clears up. My first thought was a rod, but when it cleared up i wasn't sure. i'm leaning toward lifter i guess, but i wanted some feedback first.

-Thought i might add that sometimes it takes several cranks to start.

 

heavy things make heavy noises, little things make little noises. Lifters make little noises, I'm assuming you live somewhere where it's cold at night, or colder then 50 F. What you are hearing is called piston knock, the cylinder walls and the pistons expand at different temperatures. Meaning the piston is ratteling against the side of the cylinders. It's not great for the engine but you can't do anything about it, my truck does it too, and yes it's annoying.

 

I have the same noise in my 97. Piston knock or piston slap would be accurate. As an engine wears the cylinders will wear in a taper and the piston skirt will wear too which increases the gap between the two. As the piston is driven down in the cylinder it will rock to one side (the thrust side) and will knock. As the parts warm up the gap closes and knock goes away. Stay easy on the gas pedal while it's cold and it will be fine. I switched to 10w40 and it quiets down a little quicker.

 

was considering changing oil weight and filter company at next oil change. is it safe to switch from 10w30 to straight 30weight in a high mileage engine? I also added a quart of lucas oil stabilizer to the motor at the last oil change and didn't help any.

 

I would never put straight 30w in an automotive engine. Not a good idea.

 

Changing oil viscosity is a hit and miss solution. How heavy the viscosity is will depend on driving conditions, engine condition, average outside ambeint temps and so on. If you're looking for an oil that will completely remove the cold knock, I'm not sure that gear lube would do that. But of course that would not be practical.

I just happened to see that using high mileage oil at a 10-40 rating helped mine. Heavier engine oils on a high milage engine helps fill those widening gaps and might just add some miles to a worn engine. What could hurt ? Will it fix every noise in an engine ???? Don't think so....

 

I wouldn't say that my motor is noisy. It only makes the noise every so often, and clears right up after 10 seconds or so. I believe i'll go with a 10w40 and not straight 30. after some research straight 30 is just oil without the detergents that keep your motor clean and whatnot.

 

mine was doing the same thing and i tried changing the oil mine calls for 5-30 and wasn't due for a change but i figured it was worth a try it did not help
within a week the 10 sec. ticking became a minute a nd then a few minutes and finally constant with 170,000 miles i figured it was a lifter so we pulled the motor and are now doing a longblock lifter and cam were smoked