GM Truck Club Forum banner

21 - 38 of 38 Posts

·
Registered
Joined
·
637 Posts
Some one said if I changed everything and it starts and pressure jumps up to 60 then after it warms up drops to zero probably the cam or main baerings
That could be, I can tell you that when I installed a new cam in my 5.7L a couple years ago, I gained 10LBS pressure when cold and hot (went from 60 cold, ~10 hot to 70cold, 20 hot @ idle). Using the same Mobil1 10W-40. I didn't even change the cam bearings or touch the rotating assy, LOL. I know we're talking about a different gen engine but, it would still apply.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #22
That could be, I can tell you that when I installed a new cam in my 5.7L a couple years ago, I gained 10LBS pressure when cold and hot (went from 60 cold, ~10 hot to 70cold, 20 hot @ idle). Using the same Mobil1 10W-40. I didn't even change the cam bearings or touch the rotating assy, LOL. I know we're talking about a different gen engine but, it would still apply.
I guess we going to pull it out and put new bearing all through it see what happens I know the guy that had it before me didn't change the oil it was really gumed up we cleaned it when we put oil pump and timing chain in it plus pulled the valve covers cleaned top of motor and heads then oil pan out new pick up tube and cleaned all that
 

·
Registered
Joined
·
13,592 Posts
I don't think it's bearings, your getting a rattle (lifters) not knocks (bearings).

If it's bearing, try some heavy grade convention oil.

The thicker regular oil will hold the pressure and not drop to zero.

If it drops to zero (and it rattles) you have plugged passages not bearing problems.
 

·
Registered
Joined
·
637 Posts
I guess we going to pull it out and put new bearing all through it see what happens
Do you have the necessary tools i.e. micrometers, dial indicator, feeler gauges, ring cutting wheel (if you do the bearings you might as well do the rings), bore hone, torque wrench, etc? Do you know what the crank end play needs to be, tolerances for journal to bearing clearances yada, yada, yada? What about the heads, are you going to have them magnafluxed (magnetic particle testing). Sometimes it's just better to get a long or short block, maybe a used junkyard one. Years ago I built a few engines from 283 - 327 SBCs, Mopar 360 & 440, and even farm tractor diesels and enjoyed every minute (well almost) of doing it. That's why I did my 5.7 top end recently but, I'm retired now and have time on my hands (if I choose to). Good luck, hope you're successful!
 

·
Registered
Joined
·
16 Posts
Discussion Starter #25
I don't think it's bearings, your getting a rattle (lifters) not knocks (bearings).

If it's bearing, try some heavy grade convention oil.

The thicker regular oil will hold the pressure and not drop to zero.

If it drops to zero (and it rattles) you have plugged passages not bearing problems.
What weight oil do you suggest
 

·
Registered
Joined
·
13,592 Posts
What weight oil do you suggest
It's just a short term test, try a 10W40
Remember, a multi-weight oil is designed to act like the 1st number cold and the 2nd number hot.
The bearings expand when hot, so the 2nd number will keep the pressure high when the clearances are bigger.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #27
What weight oil do you suggest
And any suggestions on flushing out or cleaning while motor still in
It's just a short term test, try a 10W40
Remember, a multi-weight oil is designed to act like the 1st number cold and the 2nd number hot.
The bearings expand when hot, so the 2nd number will keep the pressure high when the clearances are bigger.
I will try this and get back to you ...do you have any suggestions on flushing it out
 

·
Registered
Joined
·
4 Posts
So my 5.3 vortec dropped oil pressure to 0 put new oil pump timing chain pick up tube oring it was really gunked up so cleaned all that put new sending unit in with screen started it up it went up to 60pounds then after driving it 15 or 20 miles it goes to 0 I took off intake and valve covers they were gunked up really bad so I cleaned them really good got all cleaned back up let some deisel sit in pan for two days drained it did about 5 oil flushes with some sea foam started it up again after all that and new gaskets up top it jumped to 60 after about 30 min on 0 again it's not smoking or knocking
I had a similar problem around 160,000 miles and it was the o-ring on the oil pick up tube causing the problem. I had good pressure when motor was cold, but pressure dropped very low when it warmed up, not quite to zero, and the clattering would begin. Changed the o-ring and problem solved.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #29
I had a similar problem around 160,000 miles and it was the o-ring on the oil pick up tube causing the problem. I had good pressure when motor was cold, but pressure dropped very low when it warmed up, not quite to zero, and the clattering would begin. Changed the o-ring and problem solved.
I put new pump and tube and oring
 

·
Registered
Joined
·
3 Posts
So my 5.3 vortec dropped oil pressure to 0 put new oil pump timing chain pick up tube oring it was really gunked up so cleaned all that put new sending unit in with screen started it up it went up to 60pounds then after driving it 15 or 20 miles it goes to 0 I took off intake and valve covers they were gunked up really bad so I cleaned them really good got all cleaned back up let some deisel sit in pan for two days drained it did about 5 oil flushes with some sea foam started it up again after all that and new gaskets up top it jumped to 60 after about 30 min on 0 again it's not smoking or knocking
When I first bought my truck we had the oil pressure issue. I actually at one point thought the motor died on us cuz that's how our luck runs. But we changed the sending unit and started using an acdelco 61 oil filter with full synthetic oil and it hasn't happened anymore. We were also using wix but for the 5.3 the acdelco seems best I don't care what anyone says, that's what helped us. And I hate seafoam, it ruined my husband's 97 S10 years ago it had the 4.3 Vortec. It never ran the same gas mileage sucked, had to replace the spider several times, it ruined it. But I know we all have different experiences so if it works for you, great. But try the filter and hopefully it will fix this for you .
 

·
Registered
Joined
·
3 Posts
So my 5.3 vortec dropped oil pressure to 0 put new oil pump timing chain pick up tube oring it was really gunked up so cleaned all that put new sending unit in with screen started it up it went up to 60pounds then after driving it 15 or 20 miles it goes to 0 I took off intake and valve covers they were gunked up really bad so I cleaned them really good got all cleaned back up let some deisel sit in pan for two days drained it did about 5 oil flushes with some sea foam started it up again after all that and new gaskets up top it jumped to 60 after about 30 min on 0 again it's not smoking or knocking
Sorry it's an AC Delco PF61..
 

·
Registered
Joined
·
4 Posts
I put new pump and tube and oring
O ring was my first though. If you go back in I’d put a new one in just because it’s a very inexpensive part, install the best you can find. I have a 5.3L with 224,000 miles on it. I sometimes put a pint of Mystery Oil in a few hundred mile before an oil change just to clean the sludge out. I also hate Sea Foam it can cause major problems in the engine and transmission.
 

·
Registered
Joined
·
1 Posts
My 96 chevy 1500 5.7 304k miles. Oil gage does the same thing but the gage only reads 0 in gear with foot on the brake and once I get moving it shoots up to 20 and it's only when the engine is warmed up but I think mine is the sensor because it doesn't make noise and if I put it in park or neutral the oil pressure jumps back up
 

·
Registered
Joined
·
676 Posts
This problem started by the previous owner never changing the oil. It means everything has a coating of varnish and gunk in all passages ways. Flushing it with Seafoam loosens the junk but not all at once. Clean oil with detergents also does the same. Going to thicker oil will not solve it. Use only the oil viscosity the engine was designed for. Heavier oil will not fix a worn out engine.

When the pressure drops to zero, have you tried just changing the oil filter? Have you check the height of the pickup screen? It might be too low into the oil pan.
 

·
Registered
Joined
·
13,592 Posts
Worth, changing to heavier oil wasn't a suggestion.
The suggestion was to use heavier oil to do a bearing test.
The OP thinks the bearings are worn enough that the pressure falls to zero when the oil is hot.
Trying to show him that that wasn't what was happening, I suggested heavier oil for a quick test.

And just as a note, worn bearings will let the pressure fall; but not to zero.

This was just a test
 

·
Registered
Joined
·
676 Posts
Thanks for the clarity. If STP oil treatment is still around that will turn the oil into molassies. Looks like it's time for a rebuilt. I know an auto repair shop manager for over twenty years and he had a customer come in with a leased vehicle (a car) who never changed the oil and before the lease was up, the engine rattled like no tomorrow. Less than 36K on the clock.
 

·
Registered
Joined
·
5,791 Posts
Thanks for your posting on your engine problems ... you used conventional engine oils well this will instruct many reading your engine problems. alcohol in the gasoline has water in it.. then the engine oil gets mucked up..
decades ago gas had no alcohol so conventional oils worked.. back in the old days I put in marvel mystery oil a few hundred miles prior to my oil changes.. my 1983 GM sedan had 380K miles on it and that engine never had any problems . sold it in 2000...
what I might do with this mess you created I would use 10-30-40wt diesel engine oil .. this shell oil conventional has a load of additives that cleans up the engine.. then put a qt of diesel fuel in the oil. run it for 15 min at idle then drain it out and replace the oil filter.. cut open the oil filter and if its mucked up repeat again.
the oil pressure sensor probably still works because then the pressure drops and then the engine ticks ..

if the muck is gone from the oil filters then use the purolator pure one or a wix filter and use the 10-30wt engine oil...if the engine has wear and a lower oil pressure use the 10-40wt ..change your oil when it is hot .. do not change the engine when cold..
 

·
Registered
Joined
·
5,791 Posts
Thanks for your posting on your engine problems ... you used conventional engine oils well this will instruct many reading your engine problems. alcohol in the gasoline has water in it.. then the engine oil gets mucked up..
decades ago gas had no alcohol so conventional oils worked.. back in the old days I put in marvel mystery oil a few hundred miles prior to my oil changes.. my 1983 GM sedan had 380K miles on it and that engine never had any problems . sold it in 2000...
what I might do with this mess you created I would use 10-30-40wt diesel engine oil .. this shell oil conventional has a load of additives that cleans up the engine.. then put a qt of diesel fuel in the oil. run it for 15 min at idle then drain it out and replace the oil filter.. cut open the oil filter and if its mucked up repeat again.
the oil pressure sensor probably still works because then the pressure drops and then the engine ticks ..

if the muck is gone from the oil filters then use the purolator pure one or a wix filter and use the 10-30wt engine oil...if the engine has wear and a lower oil pressure use the 10-40wt ..change your oil when it is hot .. do not change the engine oil
Thanks for your posting on your engine problems ... you used conventional engine oils well this will instruct many reading your engine problems. alcohol in the gasoline has water in it.. then the engine oil gets mucked up..
decades ago gas had no alcohol so conventional oils worked.. back in the old days I put in marvel mystery oil a few hundred miles prior to my oil changes.. my 1983 GM sedan had 380K miles on it and that engine never had any problems . sold it in 2000...
what I might do with this mess you created I would use 10-30-40wt diesel engine oil .. this shell oil conventional has a load of additives that cleans up the engine.. then put a qt of diesel fuel in the oil. run it for 15 min at idle then drain it out and replace the oil filter.. cut open the oil filter and if its mucked up repeat again.
the oil pressure sensor probably still works because then the pressure drops and then the engine ticks ..

if the muck is gone from the oil filters then use the purolator pure one or a wix filter and use the 10-30wt engine oil...if the engine has wear and a lower oil pressure use the 10-40wt ..change your oil when it is hot .. do not change the engine when cold..
when cold..
 
21 - 38 of 38 Posts
Top