1994 K2500 454 7.4L Proper Oil Pressure When Hot?

[cc333]

OK, so it's looking like one of three things can be true:

• The gauge is defective (unlikely, since I've checked two and they both read identically)
• The engine's oil pump is worn out (possible (engine has at least 105k miles on it, assuming the odometer is accurate), but probably also unlikely, since the engine seems to run very well when hot with no unusual knocking or any other noises that I've noticed)
• The sendier is failing (seems most likely, but we can't know for sure until it's been cross-checked with a known-accurate external gauge)

If the sensor is high on the engine, that probably means I don't need to worry about draining the oil out to change it, correct?

I'm tempted to change it, because why not?

So, to that end, what is the special tool I need? Is the same part used across all the various GMT400 engines?

c

 

[454cid]

An oil pump shouldn't be worn out at that low of mileage.

I'm not sure what special tool your after.

 

[Schurkey]

So far as I know, the sending unit for oil pressure is NOT on the front of the engine, it's next-door to the distributor. Buried, invisible, pain in the tuckus.

Don't forget the wire harness between sending unit and gauge. High resistance will lead to a low reading on the gauge.

The "special tool" is an oil pressure sending unit socket. I had to buy a second one, because the sending unit is too long for my original, decades-old MATCO socket.

I picked up one of these, because I wasn't committed enough to get the Snap-On version.
www.amazon.com/gp/product/B0002SR2RY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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Which I will be using this spring for exactly the same reason--low oil pressure at idle, adequate but not great oil pressure at cruise on my '97 K2500 7.4L.

 

[someotherguy]

Can't remember the last one I did on a TBI 7.4, but on the Vortec 7.4 they sit upright, not in that brittle brass elbow a TBI small block has.

Here's a '96 Vortec 7.4 oil sender location - straight up, threaded into the top rear of the block. Oil sending unit socket would be wise for removal/install; most tool supply stores and some auto parts stores will have them. They're not all the same. Just because it says it's a GM oil pressure sender socket, it may still be the wrong one. Get your new sending unit in hand and try the socket to be sure it goes over the body of it to the flats.

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Richard

 

[packer0440]

So far as I know, the sending unit for oil pressure is NOT on the front of the engine, it's next-door to the distributor. Buried, invisible, pain in the tuckus.

Don't forget the wire harness between sending unit and gauge. High resistance will lead to a low reading on the gauge.

The "special tool" is an oil pressure sending unit socket. I had to buy a second one, because the sending unit is too long for my original, decades-old MATCO socket.

I picked up one of these, because I wasn't committed enough to get the Snap-On version.
www.amazon.com/gp/product/B0002SR2RY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

xc_hide_links_from_guests_guests_error_hide_media

Which I will be using this spring for exactly the same reason--low oil pressure at idle, adequate but not great oil pressure at cruise on my '97 K2500 7.4L.

On the 454 TBI it is on the front of the block, drivers side. Like mentioned above, Vortec models have it in the back location like small blocks.

 

[cc333]

I'm glad I have a TBI 454, then, as I don't much care to climb up to reach behind the distributor (I've had to reach back there to reconnect the ignition coil wire, which popped off one time (since fixed)).

c

 

[Schurkey]

On the 454 TBI it is on the front of the block, drivers side. Like mentioned above, Vortec models have it in the back location like small blocks.

Thanks. I learn something new every day.

 

[454cid]

I'm glad I have a TBI 454, then, as I don't much care to climb up to reach behind the distributor (I've had to reach back there to reconnect the ignition coil wire, which popped off one time (since fixed)).

c

Oh it's easy to see/reach the coil. The oil pressure sensor takes awhile since you have to do it by feel. It's actually below the distributor, but more towards the driver's side. I replaced mine last year. I struggled with the plug for a bit, since the pin didn't want to line up at first.

 

[brian00gmck3500]

i got an 00 k3500 7.4 l same issue , it was a spun main bearing , unfortunatly not uncommon

 

[wb292]

Is the factory oil cooler installed? there is a pressure relief valve in the cooler connection in the block. If this was removed and blocked off, oil will bleed by and go back to the pan lowering oil pressure. This is on Gen V and Vi blocks. They also have the oil pressure sending unit on the drivers side of the block very close to the timing chain cover. under the #1 cylinder exhaust port. Very easy to get to. The sender is about 3/4 inch diameter and about 3 inches long.