1996 Chevy Tahoe changing engines

the reason i felt i needed to change the engine is because,.when i start the truck it has a knocking sound that strart about (30sec)after the engine strarts running if i press on the gas pedal and raise the r.p.m,s the noise kind of dies down ,also if i put the truck in drive the noise is not as loud as it is in park . i.ve checkedthe oil ,not water is in it ,l.ve changed th oil too.also i,ve checked the spark plugs.the look fine..the check engine, service engine lwarning lights are not on ,it has around (40psi) oil pressure,..so i really cant find anything wrong ..

ok, well ill give you a few things that can cause a knocking sound like you described and are relatively easy to check, and probably save you the trouble of the new engine.

I would eliminate the valves clicking because sounds like you got sufficent oil.

A torque convertor that is loose on the flex plate or a cracked flex plate will cause a knockiing sound like that, usually mistaken for a main bearing going. its normally most noticable in idle when speed is low and no engine load.

next thign to do is ground out one cylinder at a time and see if the noise stops. do this by putting a piece of vaccum hose in the spark plug wire and on the spark plug then grounding it out with a grounded test light, if noise stops when one cylinder is disabled it could be a piston pin that knocks, it also usually gives off a double knock sound.

i would eliminate timing chain noise as if the vehicles chain is worn that badly your vehicle will be running poorly. with main and rod bearing noise it depends on speed and engien load the noise it will make so i dont think that would be the problem.

If you have a heat riser remove the vaccum line from it and remove the drive belt, does noise stop when this is done?

so ,when i ground the spark plug and wire with a test light and the engine noise stops what is causing the problem? and if it,s a piston pin who will i know? also i put a wrench on the belt tensioner(which is so weak i could have held it down by hand) and let slack in the belt and the noise is still the ..does this mean any thing...PS I ONLY GET PAID ONCE A MONTH(1st-3rd) I,LL BE SURE TO SEND YOU A DONATION YOU HAVE BEEN A REAL HELP IN TIME OF NEED AND I WANT TO SAY THANK YOU!!!

are you saying the noise stops when you ground out a cylinder? which one?

take the drivebelt completely off and see if the noise still continues, a defective belt can cause a knocking type noise and is often mistaken as something much more serious.\

and i would like to thank you ahead of time for the donation, it is very helpful!

get back to me.

if it stops on a particuallar cylinder you can suspect a worn rod bearing on that cylinder or piston slap on that cylinder.

if it dont stop on any cylinders yoiu can suspect everything else i listed.

id like to ask some more questions bout the sound

is it a clicking noise like clicking a pen?
a clanking noise such as tapping on metal?
clunking like shutting a door
clatter, like marbles rolling around
knock, such as knockign on a door
or rattle type noise.

i,am sorry!! my question was (if) the noise did stop what was causing the problem? also if it didn,t stop what was causeing the problem? the noise i hear is that of a metal clanking sound..just a regular clank,clank,clank as in it something metal with a hammer

as i said above if the knocking stops then either you have a case of piston slap or rod bearing on that cylinder, even a hole in the piston!

when grounding out the cylinder where shoul i ground the clip end of the test light on,..and what do i touch with the probe end of the test light the spark plug wire or the spark plug itself

hook the groudn on a good engine ground on the block, touch the probe on the vaccum line you put on the spark plug tip and into the spark plug wire.

to ground it out simply touch th eprobe part of the test light on the vaccum line.

and since you said its a clacking noise, then the most common causes of that are, a worn pison pin, a broken piston even valve clearence that is out of specs will cause that noise due to the slack.

after i put the radiator back in , the hoses and all electric connecters that i hade disconnected (i was going to change the engine) the exact way they came off ,because i labeled each piece. now i got in the truck and turned the key and to my suprise it wont crank.. the dash lights come on and they stay on while i turn the key but the starter dont engage the engine wont turn over..do you have an idea of what,s going on ,...also i took a good hot battery out of my car and put it in the truck , but it still will not turn over

does it attempt to crank? crank slowly fastly? or does it crank normally jsut not start?

it dont even etempt to start,..it dont make a sound when i turn the key the only thing that happens is the dash lights and radio lights up also the interior lights

when key is turned to start do the dash lights go out like normal or stay on? turn on the headlights and attempt to crank it, anything?

i would double check all connections and grounds might have knocked one loose, make sure you hooked up wires properly also.

the dash lights stay on when the key is turned

sounds like a bad ignition switch to me.

would the ignition switch go out just like that, i nver had any problems out fo it before..,also i took the starter back off and the little bolt that the (purple) wire goes on which would be the stud for the starter (s) has broken in half do to rust ,..but it,s not enough left to put a nut back on it with the terminal on the purple wire. so i wrapped the wire around what little bit of stud is left sticking out .and put the starter back on and when i turned the ignition switch this time it clicked so i turned the switch off ,then i tryed it agian and it clicked again as in the battery post was loose or something!! so i checked the post they both are tight and the starter wires are tight .got in the truck and tryed again and nothing,s happing now no click or anything so i know i need a new starter because the terminal is broken do i need to purchase a ignition switch as well

hmmm, sounds like the ignition switch is good since it clicked like that. still could be a error with it but i wouldnt buy one till hte starter is replaced, also have the solenoid looked at also whle your there.

i, grounded the cylinders out like you told me to./the noise is still there.i performed this test with the serpintine belt on the engine ,did i do this correct..also i took the belt off and started the truck and the noise is still there also,but i didnt perform the grounding cylinder test with the belt off,was i suppose to? i let the truck run for about5-10 minutes and the noise sounds like it,s at the top of the engine alsoit kinda sounds like a lifter clicking orvalve noise i really dont know ,i,am nota mechanic so can you to me what i should do next

after 5 or 10 mins it starts making that noise not when cold?

if you shut it off and then restart it right away does it take 5-10 mins to reapear or does it start right away?

are you planning on switching the engines out or no?

maybe you can take the valve covers off see if theres any wear on the pushrods or lifters. indicating a lack of oil to them or too little oil.

no ,i,am not planning on changing the engine..if i can save it ,,i really dont have the money for another engine.. what are the procedures for checking to see if the push rods and lifters are worn andto see if they are getting enough oil . i know i take the valve cover off ,what do i do next?

check for oil at start up, then see if the oil stops or drastically decreases in ammount when noise appears, take the rods out and check them for being bent, do this by rolling on a table.

check the rocker arms for excessive wear also.

i romoved the valve covers on both sides and i noticed they both have water deposits in them also little spots of water around inthe top of the head,but none on the dip stick!!, it,s really very little water i see ,but i know i should,nt be seeing any (right)...so could this be and intake problem or head gasket problem..also i removed each spark plug and thers no water present on them.now do i still remove the push rods to check and see if any are bent or do i need to check something else at this point

now were getting somwhere, first thing to do is check for a bad headgasket, get the compression guage out and start compression checking all cylinders.

post back after the test has been done and what you have concluded.

does it have a antifreeze smell or taste?

do you mean does the water i found in the valve covers smell or taste like antifreeze

yes, which would indicate a bad headgasket, cracked block, or intake manifold gasket instead of simple condensation caused by different means.

i checked the valve covers out they dont smell like antifreeze and they dont have that sweet antifreeze taste..they got that old ,need a oil change oil change bad taste

so it was just regular water? in the combustion chamber also?

is the noise any louder with cover off? try oiling the pushrods rockers and other components with engine take note of any differences between no noise and when it starts.

by the way you run it without the drivebelt yet when the noise appears?

something else can you get the transmission bacj iff and examine the thrust/flex plate for cracks with the flywheel off also check it over for cracks take your time an make sure you clean it.

then pry the flywheel towards front of engine an engine rear, notice excessive okay? time to check the crank jounals and main bearing for wear

i checked the push rods and rocker arms for oil ,they are getting plenty of oil ,also i poured oil on them while the truck was running ,but the noise didn't stop ,also do i still need to do the job with the transmission ,the flex plate and flywheel? because i'am really gonna need you to stick with me on this one.. because i though the flex plate and the flywheel where the same thing but i guess they are not ,.. can you explain that procedure one more time ,you left out a few words on your reply and i want to be sure i do the job right the first time,..also when i had the truck running the noise sounds like it's under the intake manifold ,i didn't have a peice of hose to hold to my ear and the other end on the manifold to try to pinpoint the location of the noise,. i just wanted to mention this to you ,,.also i know for a fact you are exellent with what you do(IN MY BOOK ) a MASTER,MASTER MECHANIC .. thanks for helping me.

they arnt the same but pretty close, flywheel is related to manual, flexplate to automatic, sorry i typed wrong i meant block plate.

block plate is the plate on the rear of the motor behind flexplate or flywheel :P.

you gotta check for cracks in the flywheel really well orflexplate, because the cracks expand when hot.

sorry bout my reply was early morn and i was in a hurry lol.

well back to the subject.

pry the flywheel/flexplate forward, and pry it back, you should have hardly any play, if it goes forward and backward with excessie play chances are the journals are worn.

i had edited my other post but i think you had read it before i reposted it ,. but the question was ,that the noise sounds like it's under the intake manifold ,.and when i let the truck run i didn't see any water in the oil,and i have'nt checked the compression yet ,but i'll get on the job the first thing monday morning

if you can use a piece of hose to listen to this would be great because it can help pinpoint where its coming from, its not backfiring through the manifold is it? can you get an audio clip of the sound? thing with a manifold it can pick up sounds deep in the engine and echo them out and make it easier to hear, noise travels so its hard to pinpoint.

only thing that doesnt add up here is usually when something is wrong the noise goes away when the engine is warmed not the other way around. im thinking maybe something has excessive clearence and when it heats up it expands away from the other part causing this noise.

best bet may be to pull the engine, strip it down and look for wear, manifold, upper and lower will have to come off, then engine can be turned upside down after lifters are removed and marked and you can check the journals with oil pan off.

but get the compression done first.

also i asked about a question for your engien previously and you didnt answer i belive.

here it is.

when you shut the engine off and restart after clanking noise begins, does noise still appear?

does it go away only after engine has been allowed to cool? how long? notice any change in anythign when engine starts to clank or right before it?

no,it does'nt backfire through the maniflod,and yes i can get a audio clip of the sound on a cassette tape ,i'll mail it to you if you like (i'amm just following the rules) .the noise starts after the truck has been running for about ten seconds(it;s like plapp,plapp,plapp)and it's there every time i start it and i can shut it off and crank it up again and it's there, buti notice if i put the truck in reverse the noise is'nt as loud , and if i put it in drive it's not as loud ,iguess the engine idles down once it's in gear, and idles faster in park but i do know it's idleing correct

so now im thinking possible piston slap issues. really would like a compression test here, or get the engine out of the vehicle to work on it better. might have need that flexplate to be checked again also and pryed on to see if the vehicles journals are worn.

i talked to a few friends that own them and they said that its normal to make a noise like that, not horribly loud, but should have a bit of noise, how loud we talking. with 200k miles man, im surpised it lasted that long might be time for a rebuild. you can do a decent rebuild for about 500-600 bucks.

the noise is loud enough to hear 2 houses up the street from my house ,also my wife said she hears the noise in the house when i start the truck up and thetruck is in my driveway and my beedroom is on the back of the house , so i think it's pretty loud ,also if i can fit a rebuild in my budget can you tell me how to go about ordering the parts i'll need $500.00-$600.00 is good price ... as soon as my son get my compression tester back to me ,i'll let you know the readings i come up with

have you tryed the thickest oil you can find?

dependent on the machine shop, a basic one will hone and bore your block for 100 bucks but a rough honing if the cylinders arnt shot should use just a simple honing and call it a day, put on new piston rings, talk to a auto value part store or equivilent. so for about 150-200 bucks you can have a honed or bored out block with new rings on it..

when you have the pistons out, look for bent connecting rods, cracks cracked pistons, pistons scuffed, melted and such.

next get new journals for the crankshaft, and those are relatively cheap 40 bucks most.
check the crank shaft for damage cracks and stuff, a cracked crank can still run the engine just fine.

basically checking specifications and wear, all can be done in one day of hard work.


check camshaft for wear, lifters, pushrods and such. exhaust leaks.

what weight engine oil do you recommend as being the thickest oil i can buy