2 weeks ago I was coming home from work and when I put my truck in reverse the warning chime came on and so did the check gauges light. I noticed the oil pressure gauge dropped down to zero. Of course that scared the crap out of me so I jumped out of the truck right away to listen to the engine and everything sounded fine. When I went back in teh truck the gauge was where it was supposed to be and then started jumping from zero to regular pressure numerous times.

I check the oil and it was low and I was pas the oil change date by a month. So I decided to do an oil change and after that everything seemed fine. Now last night I got back from work and the same thing happened. The gauge started jumping from 0 to around 40 numerous times. I again go out of the truck and all seemed fine. I also just checked the oil in the morning and it was at a full level with a good color.

I am thinking this might be the oil pressure sending unit. What do you guys think? Also I tried looking up the oil pressure sending unit on the Autozone website and the closest thing I found was the Oil pressure switch. Is that the same thing?

Any help or ideas would be appreciated.

 

Had the same exact thing happen to Betty. Turned out to be a bad plenum gasket.

If this is your problem, symptons may include, but are not limited too: oil pressure dropping to zero and returning to normal, burning or using oil (not leaking), squealing or various noises.

To check: Pull off the filter housing, climb on top of the engine, then look down into your throttle body to see if you have any pooling of oil in the intake manifold. Sometimes there will be oil in there, but you can't see it. If your truck has a good amount of miles and the plenum hasn't been fixed, you have very good chances of this being the root cause of the problem.

The good news is that a new Hughes plenum plate kit is only $200 at their website, and a DIY will take around 5-8 hrs depending on you mech. skills.

Hope this helps, keep us updated....

 

It is possible, for it to be something else. But this is a common problem among the magnum engines. Chances are more than likely you have a bad plenum.

 

Thanks for your input. I made sure to check and there is no oil in the intake. The engine sounds terrific so I am not thinking that is the issue. At least not that I can see at this point.

I have been doing some searching on the web and it sounds like a lot of people had similar issues and it was the pressure switch. So i think I will start with the cheapest first and go from there.

 

The engine will sound perfectly fine in most cases of bad plenums. Don't let that fool you. Mine sounded perfect too... also just cause you can't see the oil don't mean it isn't there...

 

Is there any way to test for a bad plenum? The more research I am doing on the web seems to point to the pressure switch. I still think it would be best to start with the switch since it is the cheapest possible fix costing only around $30 vs taking it to the shop to have the plenum checked and possibly replaced.

 

Again, my situation was very very similar. I would change my oil, and within two days it was back to bouncing around. Still had clean color, and correct amount of fluid. (It was barely burning oil, but burning oil none the less)

The only way to be 100% sure is to pull off the manifold.

 

It is possible it could be the pressure switch, but you could also just be wasting time and money at a problem that you are not correctly diagnosing. If you just throw new parts in it hoping for the best, chances are you will not have good results.

Make a correct diagnosis before putting in new stuff.

 

I don't see how a bad gasket on the plenum would affect oil pressure.

 

because the manifold is not making a correct seal, allowing the oil to get in the kegger. Thus the oil pressure dropping at idle. My truck did this, and when the plenum was fixed, oil pressure never dropped back down. Not even once.