Hello. I have a 1995 chevy blazer 4.3 vortec 4 door 4x4 automatic. 191,000 miles

I got it last night (4-16-11) knowing it had an constant hard engine knock. It seems to be coming from the back or the bottom of the engine. I have checked the oil, its fairly new, and is still at the right level. But I needed to get it home.

When driving on the freeway, going about 55-60 mph, the knock fades away for about 30 seconds then the oil pressure drops and the knock comes back for 30 seconds, then disappears for 30 seconds and so on and fluctuates as the oil pressure falls and rises. Oil pressure stayed between 0 and 20 psi

I drove it 45 miles home last night, almost made it home but the knock got so loud and started knocking faster so we decided to tow it the last 1.5 mile home.

There was a check engine light on but it only stayed on for about 5 minutes then went off and never came back on.

There is of course the possibility of bad motor.

But I was wondering if there is anything I can do to save my motor?

My husband said he thinks that its the oil pump and that adding a thicker oil and oil additive to every oil change afterwords will make the knock fade away.

Any suggestions would help


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desolate_dreamer@yahoo.com

 

i dont think that its the oil pump itself, i think these pumps are mechanically driven, im not sure, but if it was the pump locking up i think i would cause the truck not to run at all, i heard the pump suction hose tht draws up the oil on 4.3ls was a common thing for them to fall off into the pan, umm oil additive and oil will not make a knock due to a bearing go away(ever), but there are a few things you can do to prolong the life of an engine thats going to go in just a matter of time thickter oil will prolong the life of a knocking engine, was you dashboard light Service Engine Soon or Check Gauges, is it was SES you can have it scanned for trouble codes, if it was Check Gauges(like mine) that was only indicating your oil psi was dangerously low, try getting under the truck and listening to your oil pump, you may or may not hear anything out of the normal, and when the truck hasnt been ran for a while what does the oil psi look like at start up and untill the engine is warm? mine would start as 30-40ish and then as the truck warms up, drop down to 0, ummm also these trucks take sea5w-30, so there is the possibilty the owner put something like 0-20 or something in it for some dumb reason, doubtful but, if that were the cause 0-15, 0-20 are very thin oils, almost like water in a way, so that would cause improper lubrication and very low psi, also when you take off dont gun, take the rpms up slow and gentle(even if that makes you the slow poke on the road) this puts less stress on your engine, also do you have any visible leaks?(mine didnt)ill try to learn more about these pumps and touch back up with you, i know the situation you in first hand, its not fun lol, and what other informatiom did the seller give you? like how long(time/miles) its been knocking, when did it start, what happen when it started(did a line blow or over revved one to many times, or did it just "show up")

 

I hope you didnt pay much for the truck. Im am surprised it lasted as long as it did. Are you prepared to put a motor in the truck? If everything you say is true, 99% chance the engine needs to be either rebuilt or replaced. Hate to be the bearer of bad news. As for saving the motor? Dont even start it. It isnt going to heal. It needs to come apart.

 

Sounds serious to me also. 0-20 psi isn't enough especially the 0.

 

yeah, thats the exact thing mine was doing before mine finially blew, sad to say, but on the flip side! the good news is, you can get a used engine in great condition for around 600 if you look in the right places, like i said i got mine off of ebay, as far as knockin engine goes, no knocking engine is realiable as a vortec, 2500 miles and red-ling on the highway(being stupid could've been a big towing cost lol) but yeah the shop i had mine done at cost 675 for the swap, plus 200 in gaskets and motor mounts and other parts that they didnt charge me labor to do

 

A rod knock means that there is a lot of space between the rod and the crank pin it rides on. That space is typically taken up by the rod bearing. When there is too much clearance, you will lose a lot of oil pressure right there. Sooner or later, you'll destroy the engine if left unrepaired.

 

Danb2760 - Is that the same shop that cant diagnose the problems you're having?

 

i didnt buy it, i traded my 99 saturn that needed 230 dollars in back tags and an egr for it. I desperatly wanted a blazer, i didnt care what condition it was in and i already had another engine anyway. and the previous owner said the knock started as a low ticking and slowly and gradually got louder. the check engine light went off after it warmed up, i do have a scanner to read it but i didnt hook it up because it went off. yeah everytime the oil pressure drop the check gauses light would come on. i do already have a motor lined up waiting to go in it, its just a matter of getting it here from my friends house now. I was just looking for any other possible causes. finally when i was off the freeway the oil pressure stopped going up at all i had to stop and have my brother tow me home.

the motor i have to go in it is a 4.3 out of an 80's older truck.

the only leaks i saw was a transmission leak coming from a hose that needs replacing
i dont think there was/is any other leaks

 

Im glad to here you are prepared to replace the motor. I was really afraid you got yourself in over your head. I am unfamiliar with the late 80's motor vs 1995 motor. I do not know how compatable they are. Where i live we must meet emissions so swapping different year motors is tricky business. Good Luck!

 

2 cents worth: You obviously have a replace/rebuild in the near future. 190K is a lot shy of normal life of these motors,but then,who knows what the previous owners did or did not do! I nursed a rod knock on a previous 4.3 for almost 60k! Also babied a 78 305 for 300k with the same issue!