Any mechanics in the house?

[Jugernot]

I'm having some problems with my truck oil pressure. I recently had an oil change and now after warming up, my dash shows my oil pressure at 0 at idle. It took it into my mechanic today and they replaced the oil sending unit . This didn't help the problem a bit other than having $150 less in my bank account. They hooked up an external gauge and got the same readings. Also, this is a new dash cluster, so I doubt it's the gauge.

They told me it could be two things. A bad oil pump or bad bearings in the engine. I have two choices, $500 for a high flow oil pump which won't really fix the problem and just kind temporarily covers it up. Two, a new engine. I'm going to get a second opinion before I do anything drastic.

Here is the kicker... this a 1996 Chev. K1500 4.3L with 62,000 miles!:Q

Any ideas?

 

[HappyPuppy]

Your mechanic took you when he charged you $150 for an oil pressure sending unit.

Check your engine oil level. If that is OK, find another shop to give you a second opinion.

 

[Jugernot]

Originally posted by: HappyPuppy
Your mechanic took you when he charged you $150 for an oil pressure sending unit.

Check your engine oil level. If that is OK, find another shop to give you a second opinion.

It was $80 for diagnostics, $30 for sending unit, and $44 for a new dash switch. Oil level is fine.

 

[ThisIsMatt]

I'd be interested to know how bad bearings = no oil pressure?

 

[white]

is your dash meter working properly?

 

[ThisIsMatt]

Originally posted by: white
is your dash meter working properly?

my dash shows my oil pressure at 0 at idle

They hooked up an external gauge and got the same readings.

Also, this is a new dash cluster, so I doubt it's the gauge.

 

[Jugernot]

I'm probably gonna take it into the dealer next week. As much as I don't like paying their prices, they do know what they are doing when it comes to working on their vehicles. More than most anyway.

Jugs

 

They hooked up an external gauge and got the same readings. Also, this is a new dash cluster, so I doubt it's the gauge.

They told me it could be two things. A bad oil pump or bad bearings in the engine.

Did you see the actual reading when he hooked up the mechanical pressure gauge or are you taking his word for it ?

If you had bad bearings in the engine you would know it immediately ;

Bad connecting rod bearings will make a loud and distinct banging noise.

Bad crankshaft bearings will make a dull thud noise.

Do the lifters tick when idling ? <---Sure sign of low oil pressure

Look at the very bottom of the oil pan, is it dented or pushed in ?

What viscosity was the oil that was put in during the oil change ?

What brand of oil filter was installed ?

Is the engine running hot ?

I highly doubt that the oil pump went south, there are many reasons for low oil pressure at idle including the possibilty of a plugged oil pump pick up screen, a oil gallery plug that came loose, a stuck bypass valve etc.

 

[Pepsi90919]

[watch it be a fram filter on there]

 

[psianime]

bump

 

[Analog]

1. plugged or restricted oil filter

2. wrong viscosity oil

3. oil sending transducer failed

4. low oil level

5. combination of the above

 

[Scarpozzi]

This just sounds too odd.... Unless your oil pump has some bad bearings in it or your out of oil, you should have some oil pressure. I assume that there's a problem with the switch and his external reading was wrong. An engine won't necessarily sieze up when the pump isn't working, but it's not exactly good for it. You've got the right idea in taking it to the dealer...but only this once. If nothing else, they should be able to diagnose the problem and let you know exactly what's up.

 

[SuperSix]

I agree with others, I highly doubt your oil pump has failed - the're not that complex, and very rarely (if ever) fail. Even with nearly non-existant bearings, you would still have SOME needle movement.

Was it working fine BEFORE the oil change?

 

[jemcam]

I used to have the same problems with Harleys during the summer in Florida when idling. I put in higher viscosity 50 weight oil and it solved the problem. Doubt it's the same problem, but higher viscosity oil will raise your oil pressure. It's a good temporary fix.

 

[Jugernot]

Originally posted by: Roger


Did you see the actual reading when he hooked up the mechanical pressure gauge or are you taking his word for it ?

Taking their word for it. I told them to let it run before checking idle pressure and I'm 99% they didn't... they quoted me 15lbs at idle. It does read around 15lbs if you don't let it warm up.

If you had bad bearings in the engine you would know it immediately ;

I figured that is the case, it runs like a champ and have never had any knocking or pinging on the engine.

Bad connecting rod bearings will make a loud and distinct banging noise.

Bad crankshaft bearings will make a dull thud noise.

Do the lifters tick when idling ? <---Sure sign of low oil pressure

Not that I know of... it's pretty much idling fine.

Look at the very bottom of the oil pan, is it dented or pushed in ?

It's 0F out with snow, I didn't get a chance to check, but since this is a problem only since my last oil change. I'd have to guess no.

What viscosity was the oil that was put in during the oil change ?

I used Mobil 1 5w30 (which I bought myself and gave Sears to put in), which is usually what I use because I live in Alaska which can get very cold during winter.

What brand of oil filter was installed ?

$2 Purilator

Is the engine running hot ?

Nope, totally normal... that was the first reason I didn't take it in immediately. If figured if I was having oil pressure problems my temp would go up pretty damned quick. Though as I said before, it is 0F outside.

I highly doubt that the oil pump went south, there are many reasons for low oil pressure at idle including the possibilty of a plugged oil pump pick up screen, a oil gallery plug that came loose, a stuck bypass valve etc.

From all of the info I've read online, I doubt it's the pump too. I did some testing last night and it's definitely affected by the cold. On cold start, it runs totally normal (around 40lbs idle and cruise) but once it starts heating up, my pressure goes down. Once fully heated up, the cruise pressure is down to 20lbs (1500rpm) and idle reads 0lbs (500rpm). That definitely points away from the oil pump for me, as you said, it's relatively simple and I wouldn't think it would push less oil as it heats up.

Jugs

 

[Thegonagle]

Try a new filter immediately, like, say, a $3 Delco. $25 worth of oil teamed with the cheapest filter you can get doesn?t make much sense in my mind.

 

I suggest that you change your oil again and this time purchase the best filter possible.
If you are going to bring it in to the dealer, have them pull the oil pan first and have them show you in person the unobstructed oil pick up.

 

[Jugernot]

Ok, it's at the dealer now. I took it in a few minutes ago. I told them everything and they said they'd take a look. I also found a TSB that says "Premature main bearing failure" in my particular engine (96 4.3l). I'm hoping that is the problem. If it is, since it was a TSB, they should cover it. At least I'm hoping 62k of the engine would qualify as premature.

Jugs

 

[LAUST]

get a 4.3 shortblock from somewhere, they should be a dime a dozen on any of the GM forums and other GM sites, I've already seen the new 6.0 liter motors selling for $1200

 

[Pepsi90919]

Originally posted by: Garfang
Try a new filter immediately, like, say, a $3 Delco. $25 worth of oil teamed with the cheapest filter you can get doesn?t make much sense in my mind.

Purolator's PremiumPlus filter would be about equal or greater in quality to an AC Delco non-Wix.

 

[Jugernot]

Originally posted by: LAUST
get a 4.3 shortblock from somewhere, they should be a dime a dozen on any of the GM forums and other GM sites, I've already seen the new 6.0 liter motors selling for $1200

If I'm going to end up getting a new engine, I'll get a new GM motor with 3/36 warranty.

Hell, if I end up having to replace it... I might just see what kind of work it would take to put a 5.7l in it. This model year uses a lot of the same parts with all the engines... same air cleaner, tranny, etc.

 

[LAUST]

Originally posted by: Jugernot

Originally posted by: LAUST
get a 4.3 shortblock from somewhere, they should be a dime a dozen on any of the GM forums and other GM sites, I've already seen the new 6.0 liter motors selling for $1200

If I'm going to end up getting a new engine, I'll get a new GM motor with 3/36 warranty.

Hell, if I end up having to replace it... I might just see what kind of work it would take to put a 5.7l in it. This model year uses a lot of the same parts with all the engines... same air cleaner, tranny, etc.

Best of luck to ya

 

[Antisocial Virge]

I've had Chev 305 engines show 0 at idle because of worn bearings and they never made noise at all.

 

[Antisocial Virge]

Originally posted by: ThisIsMatt
I'd be interested to know how bad bearings = no oil pressure?

Try spitting through a sewer pipe. Not able to keep much pressure hun?

 

[ThaGrandCow]

One of my friends had the same general problem. Tell them to see if you have a vaccuum leak (or something along those general lines. When he was idling he had no pressure but since there wasn't very much vaccuum pressure itwouldn't pick up until he gunned the engine)