Loss of oil pressure on TV

[Chief T]

Hello all, need some advise...

Only been able to take out the TT a few times since purchased this past summer. On our first journey, the oil pressure gauge went to zero on grades when the RPM went up. Once I took my foot off the gas, the pressure was back to normal. It happened again when the RPM got up again.

Any idea what could be causing this? I had a lot of work done on the TV when we knew we were getting a TT.

Any advise would be greatly appreciated.

Safe and happy travels.

[TheWolfPaq82]

If the TV is running fine otherwise, I'd first look at the oil pressure sending unit. Been a few years, but my 79 F150 had a similar issue and it came down to dirt in the sending unit and under a high load it would clog up and not register.
Got rid of that truck in 1998...it served me very well.

[llr]

Are you sure the oil level is at the full mark? If so it sounds like the oil return passages in the rear or the head are not letting the oil return to the pan quick enough. not sure if they could be clogged or a design issue. Back in the old sludgy oil days it was not uncommon for passages to get plugged, I have not heard of this in a long time.

[rracer5]

Originally Posted by Chief T

Hello all, need some advise...

Only been able to take out the TT a few times since purchased this past summer. On our first journey, the oil pressure gauge went to zero on grades when the RPM went up. Once I took my foot off the gas, the pressure was back to normal. It happened again when the RPM got up again.

Any idea what could be causing this? I had a lot of work done on the TV when we knew we were getting a TT.

Any advise would be greatly appreciated.

Safe and happy travels.

1- How many miles on the TV?
2- Oil level up to spec. on dipstick?
3- Engine temp. (water) also high when this happens?
4- Do you have an auxiliary oil cooler installed?
BTW - an auxiliary trans. cooler would also help save the transmission.


It could be a combination of all above. If you have high mileage on the TV the oil pump tolerances may have worn and therefore can not maintain pressure at high RPM. Oil that is also hotter than normal will thin out and cause low pressure also (sometimes just using a "high mileage" oil or next viscosity heavier will get you through but, not a cure). Low oil level can cause the oil pan to be "sucked dry" at high RPM and so could sludge in the pan and/or a partially blocked oil pump screen.
Engine temp. in general can contribute to high oil temp (which you probably don't have a guage for) as well as high trans. fluid temp. (also no guage) since trans. fluid is cooled through a separate side tank built into the radiator.

You don't mention what kind of work was done to the TV so, what I've discussed above is a general "guess" of what could be going on in a TV of this age without knowing any other details.

Let us know.....we'd all be happy to help you figure it out.

[rracer5]

Originally Posted by TheWolfPaq82

If the TV is running fine otherwise, I'd first look at the oil pressure sending unit. Been a few years, but my 79 F150 had a similar issue and it came down to dirt in the sending unit and under a high load it would clog up and not register.
Got rid of that truck in 1998...it served me very well.

X2

Originally Posted by llr

Are you sure the oil level is at the full mark? If so it sounds like the oil return passages in the rear or the head are not letting the oil return to the pan quick enough. not sure if they could be clogged or a design issue. Back in the old sludgy oil days it was not uncommon for passages to get plugged, I have not heard of this in a long time.

X2 Not very common anymore with today's advanced technology engine oils as long as it was changed as recommended.

[Chief T]

Originally Posted by rracer5

1- How many miles on the TV?
2- Oil level up to spec. on dipstick?
3- Engine temp. (water) also high when this happens?
4- Do you have an auxiliary oil cooler installed?
BTW - an auxiliary trans. cooler would also help save the transmission.


It could be a combination of all above. If you have high mileage on the TV the oil pump tolerances may have worn and therefore can not maintain pressure at high RPM. Oil that is also hotter than normal will thin out and cause low pressure also (sometimes just using a "high mileage" oil or next viscosity heavier will get you through but, not a cure). Low oil level can cause the oil pan to be "sucked dry" at high RPM and so could sludge in the pan and/or a partially blocked oil pump screen.
Engine temp. in general can contribute to high oil temp (which you probably don't have a guage for) as well as high trans. fluid temp. (also no guage) since trans. fluid is cooled through a separate side tank built into the radiator.

You don't mention what kind of work was done to the TV so, what I've discussed above is a general "guess" of what could be going on in a TV of this age without knowing any other details.

Let us know.....we'd all be happy to help you figure it out.

Much appreciated. Here's some info you requested...

1- How many miles on the TV? 165,000, Use “high mileage oil”
2- Oil level up to spec. on dipstick? Yes
3- Engine temp. (water) also high when this happens? No
4- Do you have an auxiliary oil cooler installed? No
BTW - an auxiliary trans. cooler would also help save the transmission. Have one.

Work done June 2017: Transmission serviced, cooling system, new thermostat, rear diff. fluid, clean-out throttle body, new spark plugs & wires, and a couple minor leaks.

Truck runs like it’s brand new. This is my DW daily driver and we average around 3-5k a year since we got it a few years back.

[bshort]

If oil pressure was truly zero at higher rpm's, you'd know it in a hurry by the awful sounds. Sending unit or gauge issue.

[Brother Les]

You have been given some good advice.

Your TV is a 2003 GMC?

My advice....

I belong to this 'site' to talk about campers and camping.
I belong to a Ford 'site' to talk about my F-250 7.3 Ford.

Go to a good 'site' for your make and model GMC and ask them directly.
I have a 2001 Ford, so I will not give advice on your 2003 GMC.

Some members here will give you some suggestions on a good site and they on that site will walk you through what is going on, step by step.


Car/truck sites are just as friendly and mean as camping sites.....

[D W]

If you lost actual oil pressure like that you would know in a hurry. The sound would start in the hydraulic lifters devoid of oil. I would look into the oil pressure sending unit and/or the electronically controlled step motor that controls the gauge.

[rsdata]

Go to a good 'site' for your make and model GMC and ask them directly.
I have a 2001 Ford, so I will not give advice on your 2003 GMC.

X2...

google "GMC forum" join and ask the question there

[Mike ONeill]

I have a 2008 Sierra all terrain and the oil sending unit screen filter clogged and gauge showed no oil pressure, mine did not come and go though?

[Cowracer]

My guess is a wire or connector on the sending unit that loses its connection going up a hill with a load on the engine (making the engine twist on its motor mounts)

Tim

[KansasJohn]

Just wanted to say that SilveradoSierra.com • Chevy Truck Forum | Silverado Sierra GMC Truck Forums is a great Chevy/GMC truck forum. They may be able to answer better than anyone here.

[Crusadernoob]

Knowing that engine pretty good my first “guess” is a sending unit, fwiw, pull the screen out and make sure it’s clean. Quick job to do. As stated, valve train noise would creep up on you quickly if it lost all psi. On a bad note, cam bearings have been known to spin also.

[OldCoot]

Originally Posted by Crusadernoob

Knowing that engine pretty good my first “guess” is a sending unit, fwiw, pull the screen out and make sure it’s clean. Quick job to do. As stated, valve train noise would creep up on you quickly if it lost all psi. On a bad note, cam bearings have been known to spin also.

Don't understand how a spun cam brg could influence spastic oil pressure. Cam brgs have holes in them that get oil from the grooves in the block. Have never heard of a cam brg spinning. Rod brgs and main brgs are known to spin, but not cam brgs. JMO

[SC for Huskers]

I also had a similar trouble with 95 f150 and Rpod 172, but i was pulling up grade from Charleston SC to KS, and in 4th gear. I pulled off next exit and my gages were reading water hot, oil low. I checked the oil and running high use semi synthetic, 10w30w and it checked full+ but thin as water. I became worried that I blew a gasket and water was in the oil. Waited about 15 min and started engine, everything looked good. Never did it again. Traded the 6cyl. in for 2011 F150 V8. Hope this automatic will do better. Good Luck finding problem.

[Dabmeb]

I have run into a similar situation before on an old ford 400 engine. The rods and mains where badly worn and under load the crankshaft is pushed away from the oil gallery hole and pressure drops. On decel the crank is pulled up tight against the oil gallery and pressure increases. Hopefully it’s just a bad sender.

[Crusadernoob]

Originally Posted by OldCoot

Don't understand how a spun cam brg could influence spastic oil pressure. Cam brgs have holes in them that get oil from the grooves in the block. Have never heard of a cam brg spinning. Rod brgs and main brgs are known to spin, but not cam brgs. JMO

Well if it was only one time I saw it I would call it a fluke, twice, bad luck, seen spun cam bearings on more than just GM V8 gas engines, also happens on a Duramax. High rpm’s, it happens, not saying this is the case, just worst case scenario.

Block doesn’t have the groove, some bearings do, and to aid in the oiling, some cam journals do.

I’d still check the screen and install a new sending unit

[OldCoot]

Originally Posted by Crusadernoob

Well if it was only one time I saw it I would call it a fluke, twice, bad luck, seen spun cam bearings on more than just GM V8 gas engines, also happens on a Duramax. High rpm’s, it happens, not saying this is the case, just worst case scenario.

Block doesn’t have the groove, some bearings do, and to aid in the oiling, some cam journals do.

I’d still check the screen and install a new sending unit

The cast iron block GM V8's have grooves in the block and holes in the cam brgs. Have rebuilt many, many sb Chevy's and raced them. NEVER seen a cam brg spin in one!

[aceinspp]

Sounds more like a defective sending unit. If you have not heard any unusual noises from the engine and the oil level reads full then it most likly the sending unit. Later RJD