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2002 5.7 Vortec Tough Questions !


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#1 2002gmcvan5.7

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Posted 23 June 2008 - 08:41 AM

hello.
i am new to this forum.

i purchased a 2002 gmc savana van 3500 about 6 months ago. i has a 5.7 liter vortec engine.
mileage was 104,000 when i bought it...and now it is 110,000.

it was formerly a computer business van in south georgia. the former owner seemed very tidy....and had service records and maintenance records etc... and everything he owned besides this van seemed very neat and orderly.

that being said,....

ok. the gauges act funny sometimes. when i idle...sometimes the check engine light will come on...or kinda flash in and out... but if i just touch the gaspedal...it stops.
in my mind...seems like it is related to the output of the alternator? any ideas? and most important...the oil pressure drops first.....

the oil pressure is super low. almost down to the red when idling. when driving...it may go up to 30....sometimes not. it somtimes varies for no reason at all.

i asked the former owner...he said it always did that..and the dealer said there wasn no way...or need to replace or fix the gauges because its a common problem with gm trucks and van of this style.

so i let it go...

but now...i heard a ticking sound when i first cranked the engine one morning. i checked the oikl. it was barely touching the stick! so i add 3 quarts!!!!!
i never saw smoke. i never saw a leak on my carport. where does it go?

i have been adding oil a few times lately. sometime i check it..its fine. then all the sudden...its a little low. just random.

i crawled under it...what i see is.... some oil around front of oil pan and around a sensor. it looks like some sort of crank sensor???
and on two lines..running closeby and beside the oil pan i see some oil "caked" over....not as freshly wet..as much as the oil pan is and around the sensor. what is that sensor? does it seal anything also? are those oil lines? do the oil pans leak much around the front? can i pull the oil pan off with the engine still in the van to put new gaskets? seals? oil pump? or even crank bearings?

i read all kinds of horror stories about the vortec 5.7 motors leaking....having bad bearings..intake leaks...distributor leaks..lifter ticking...etc.

can i put an extra mechanical oil pressure gauge somewhere just as a backup to make sure the oil pressure is correct after i fix all this stuff? maybe a tee" in the oil sending unit output for a mechanical and also keep the gauge in the dash working too? a dual setup?

i am scared to ruin the engine. what do i do?

its runs sooo smooth..and perfect..otherwise!

the gauge is just crazy as heck too!

sorry this message was sooo random....i am tired..its early here!

#2 98silvz71

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Posted 23 June 2008 - 09:03 AM

my 98 5.7L Vortec had really low pressure on idle and had about 30-40 when I was running down the road. It wouldn't help to T off the sensor because whatever that sensor is sending you will see the same value on both of the gauges. As for the SES light, you might try to get a code reader on it to see what it says before it goes off. It could be something simple. It probably burns off oil and you just arn't aware of it. My 98 did but at a slower pace. And the only thing that I ever had problem with was the intake gaskets leaking and right before I traded it the distributor started to also. Hope this helps.

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#3 smartcat

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Posted 23 June 2008 - 02:00 PM

if the check engine lite is coming on , get it checked, many times auto zone can do it for free. Gm dealership cost me $35 to check mine, was having transmission problems.

I have a 2000 model 2500 series with 350 engine, 81k miles.

I run about 40 psi of oil pressure at idle
at 60 mph it runs about 55 psi of oil pressure.

so you could have sensor or gauge problems.

I use 10w40 valvoline oil with wix filter and add 1qt of lucas oil stablizer at every oil change, i change oil at 5k intervals.

I would add a direct connect manual oil pressure guage, you must know you have oil pressure before you run the engine,
quickest way to ruin a engine is lack of oil pressure.

change oil put in 10w40 or 15w40 and 1 qt of lucas will not hurt your engine. use good quality oil filter like a wix or napa gold, not cheap fram

good luck

#4 2002gmcvan5.7

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Posted 23 June 2008 - 03:09 PM

thanks so far for the info.

what is that sensor located at the very bottom...front of motor....? does it seal from oil? crank sensor? are they expensive? i see oil around it. can i just put new o-rings around it?

where is the oil sending unit? r they expensive?

i do have a leak...dont know how bad....but as i said above...its around the front bottom of motor. could be oil pan gasket...crank sensor? seal....or an oil line that runs by the oil pan! i just dont know. but it doesnt leak on the carport when sitting. must be leaking only when engine runs and getting burned off or something. maybe i should leave it idling for a while while sitting still.

does anyone know if i can pull the oil pan off and repair gaskets...bearing and such while the engine is still in the van?

#5 98silvz71

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Posted 23 June 2008 - 11:22 PM

I put 10w40 in with a Wix filter, and also added Lucas. I would get the nice 40 psi idle and 55 down the highway until the engine heated up fully and then it would go down to about 30-35 psi idle and about 40-45psi running down the highway.

It seemed to burn less with the higher weight oil. Give that a try before trying to tear into the thing.

The best way to get help is take pictures of where the oil is coming from so we can see what you see.

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#6 2002gmcvan5.7

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Posted 24 June 2008 - 02:40 PM

wow. thicker oil to get better pressure? i can see how it would "read" more pressure. but i dont see how its really good. but i am gonna try it!

does anyone know if i can pull the oil pan off this van with the engine still in the van? in case i wanna put a new oil pump...and bearings?

also...where in the world is the oil sending unit? expensive?

what is that sensor on the bottom front of the motor? crank sensor?

if these engines burn oil. where does the oil go? is it blowby from the piston rings????

#7 2002gmcvan5.7

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Posted 25 June 2008 - 12:44 AM

i did the oil change. put in the lucas.

it does show a little higher oil pressure. but i swear....the gauge isnt consistant. but the gauge doesnt just drop to zero.....just up and down. weird...weird....

oh...and i think the oil lines that run from the oil filter housing to the oil cooler have a leak. but the leak is next to the front of the oil pan...... and it almost also looks like a sensor....that is going up into where the front crank seal is between the harmonic balancer and the oil pan is leaking. i cant pin it down....which one is leaking. one may be spraying the other.....

#8 Wingnut

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Posted 25 June 2008 - 01:42 AM

Just some thoughts.

A pic of this "sensor" would help to determine what exactly it is, I know that the older 5.7's had the knock sensor down on the block by the starter, but in my '02 (pickup though) the knock sensors were under the intake manifold.

If ALL your gauges are erratic, I would suspect electrical problems, and I'd start with the positive battery cable. VERY common for it to look great on the outside and be completely rotten on the inside. Nothing but powder.

That MIGHT cause the oil pressure gauge to be spotty, but you're also losing oil, so I'd be leaning towards something else there...

Not sure about dropping the pan, you'd have to get under there and look around to see for yourself if it will come off without pulling half the frontend off with it.
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#9 2002gmcvan5.7

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Posted 25 June 2008 - 12:28 PM

Just some thoughts.

A pic of this "sensor" would help to determine what exactly it is, I know that the older 5.7's had the knock sensor down on the block by the starter, but in my '02 (pickup though) the knock sensors were under the intake manifold.

If ALL your gauges are erratic, I would suspect electrical problems, and I'd start with the positive battery cable. VERY common for it to look great on the outside and be completely rotten on the inside. Nothing but powder.

That MIGHT cause the oil pressure gauge to be spotty, but you're also losing oil, so I'd be leaning towards something else there...

Not sure about dropping the pan, you'd have to get under there and look around to see for yourself if it will come off without pulling half the frontend off with it.


the oil sensor is close to the starter. or i think it is the oil sensor?(sending unit)

but there is another one at the bottom front of the motor between oil pan and harmonic balancer. what is that one?
it almost looks like i could get the pan off the bottom.

if i could get the pan off the bottom. can i change pistons...rings....rods...bearings....oil pump..and all? how do i compress the piston rings from the bottom?

#10 Texas Jim

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Posted 25 June 2008 - 09:20 PM

if i could get the pan off the bottom. can i change pistons...rings....rods...bearings....oil pump..and all? how do i compress the piston rings from the bottom?




No.
If you are going to overhaul the engine.... pistons, rings, bearings etc etc ...
it needs to come OUT of the vehicle.

The pistons come out the TOP ... AFTER you have pulled the heads.
You can not compress the rings from the bottom.
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#11 2002gmcvan5.7

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Posted 26 June 2008 - 02:28 AM

ok.

but what if i skip the pistons and rings. can i get the pan off with the engine in the vehicle? replace the bearings and oil pump on crank and rods?

#12 Wingnut

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Posted 26 June 2008 - 03:18 AM

Wow...I've never heard of anybody doing THAT particular maneuver. Be a neat trick though. :lol:
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#13 2002gmcvan5.7

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Posted 26 June 2008 - 02:03 PM

yes. well...i have heavy equipment. we have dropped the pan on equipment....and replaced crank bearings...and rod bearing...and oil pump before while an engine is still in a machine. but you were right...we didnt pull the pistons out. i was just wondering if they make something new to compress the springs from the bottom side up. but it would be too hard anyways.... and with the head on the block...i would have to remove the spark plugs to not trap air inside some of the cylinders.

so...does anyone know if the pan can be removed with the engine in the vehicle?

how hard is it to just remove the whole engine?

my engine runs fine...just cant pinpoint if i have a leak(i do...just dont know where or how serious)..or am using oil.

i can rebuild heavy equipment engines. and i have rebuilt many ford engines. it would be cool to find a used engine...and rebuild it...to have ready for when i need to replace this one.

#14 doompir8

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Posted 05 June 2010 - 06:56 PM

as far as the oil pressure it could be worn bearings a bad oil pump or just running too thin an oil for the engine. the sensor between the oil pan an the balancer is the crank sensor bolted by a 10mm bolt into the timing cover. the oil sending unit is on the back of the motor directly behind the intake it is a larger unit that screw into an l shaped tube coming directlt off the block. you can pull the oil pan with the engine in the truck although it might be required to raise the engine just a couple of inches however to change the main bearings (highly recommended if you change the rod bearings) you will have to at least back off the tranny to remove the flywheel. pulling this engine is a royal pain (at least it was for me) took a few days but a fairly simple and straightfoward rebuild and fairly cheap the cheapest rebuild kit was napa premium for like 300 dollars. hope this helps you some. The mud jumpin tapeworm

#15 shadetree25

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Posted 23 September 2010 - 04:34 PM

The sensor in the front is either the cam sensor or the crank sensor. Both are in the front. I would replace the oil pressure sensor first. It is located in the rear to the left of the distributor. You could probably get to it from the inside of the van. Just remove the cover below the instrument panel.
It the oil pressure was really that low the lifters would be rattling and the fuel pump would shut off.

Edited by shadetree25, 23 September 2010 - 04:36 PM.





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