Problem: Very high oil pressure

[chestand]

Many GM vehicles of this vintage use stepper motors to drive all the "analog" gauges in the gauge cluster. I've replaced an oil pressure gauge motor on a 2004 Tahoe and a speedometer motor on 2005 Tahoe. Both were bad and the new units restored operation. BTW the 2004 had the same symptom - full deflection of the oil pressure reading in operation.

The motors are available for less than $10 from Amazon.com. It requires pulling the gauge cluster and some skill with a soldering iron.

 

[dailydriver]

Originally Posted By: yonyon
Glad to hear it's fixed.

That's one of those jobs where you really need the right tool. If you have the specific socket that's made specifically for that oil pressure sender it's a ten minute thing: unplug two connectors, unscrew it, repeat in reverse. Alright, if you have big hands or thick forearms maybe a half hour. If you don't have the specific tool then you get what your friend and his son just went through.

Edit:
Of course, he probably could have shaved a couple hours off by removing the intake (very easy to get off and on) but that's one of those things that looks like such a big deal to do you end up killing yourself to avoid it.


Actually, if the engine sits halfway under the cowl on the trucks, like it does on my car, it is STILL a MANY hour job since it is almost IMPOSSIBLE to re-connect all of the little vacuum fittings, and harness electrical connectors which will ONLY reach when the manifold is almost all the way in place (since there is NO slack in these lines

), and one must constantly check to make sure that those said harnesses/wiring are not getting crushed by the manifold causing shorts, and vacuum leaks in the process.

Ask me how I know this (on my car the intake manifold MUST, MUST come off to change the; knock sensors, oil pressure sender/switch, and cam position sensor, as there is NO WAY that even a 5 year old could get his hands/forearms back there to get to the OP sender/CP sensor with it in place).

 

[The_Jake]

Originally Posted By: dailydriver
Originally Posted By: yonyon
Glad to hear it's fixed.

That's one of those jobs where you really need the right tool. If you have the specific socket that's made specifically for that oil pressure sender it's a ten minute thing: unplug two connectors, unscrew it, repeat in reverse. Alright, if you have big hands or thick forearms maybe a half hour. If you don't have the specific tool then you get what your friend and his son just went through.

Edit:
Of course, he probably could have shaved a couple hours off by removing the intake (very easy to get off and on) but that's one of those things that looks like such a big deal to do you end up killing yourself to avoid it.


Actually, if the engine sits halfway under the cowl on the trucks, like it does on my car, it is STILL a MANY hour job since it is almost IMPOSSIBLE to re-connect all of the little vacuum fittings, and harness electrical connectors which will ONLY reach when the manifold is almost all the way in place (since there is NO slack in these lines

), and one must constantly check to make sure that those said harnesses/wiring are not getting crushed by the manifold causing shorts, and vacuum leaks in the process.

Ask me how I know this (on my car the intake manifold MUST, MUST come off to change the; knock sensors, oil pressure sender/switch, and cam position sensor, as there is NO WAY that even a 5 year old could get his hands/forearms back there to get to the OP sender/CP sensor with it in place).

Tip: Many times I will pull off all the lines and mark them with numbered stickers to make re-assembly easier/faster. This is especially helpful if you get interruptions while doing the job. I get stickers here:

http://www.mapshop.com/sticker_dots/sticker-dots-numbered-f.htm

 

[3311]

I just so happen to be in the middle of pulling one of these engines in the 04 below. In the first pic I'm pointing to the sender and in the second is a pic already partially dissembled and still wouldn't be close to removing the sender.
It took me 2+ hours just to unplug and label everything.

Edit: The top bellhousing bolt is behind the sender.

 

[Klutch9]

Originally Posted By: Brons2
probably a bad oil pressure sending unit. I've had it on GMs also.


This is a common problem on GM trucks of that era. Not just for the OP gauge, but for all of the gauges. They register incorrectly, fluctuate oddly, etc. Sometimes they stop working altogether. The potentiometers that control the gauge needles go bad. The fix isn't too hard, IIRC.

 

[SteveSRT8]

It's a common problem on anything with an electric gauge, certainly not just a GM problem!

And who needs stickers, duct tape and a magic marker does just fine and won't come off easily. I also like a couple of pics before disassembly to make sure everything gets back where it should be.

On a van body the dashboard can be taken apart and the engine cover removed, which is a little bit easier than a pickup, but pulling the engine is much more problematic in a van.

 

[3311]

Originally Posted By: SteveSRT8
It's a common problem on anything with an electric gauge, certainly not just a GM problem!

And who needs stickers, duct tape and a magic marker does just fine and won't come off easily. I also like a couple of pics before disassembly to make sure everything gets back where it should be.

On a van body the dashboard can be taken apart and the engine cover removed, which is a little bit easier than a pickup, but pulling the engine is much more problematic in a van.
All I had handy when I got a wild hair was string tags that we use on equipment. It's all down hill now. Should have it out next week. It's in my shop at work so I only have time to work on here and there.