So, I've my car on the road about 4 times this spring after sitting for the last 5 months. I have about 1000 miles on a new rebuilt engine, still running minimum boost for break in. Yesterday I'm driving and my oil pressure drops all the way to about 15lbs - I was not abusing the car in any way, just kinda cursing along. I replaced the oil pump with a high-flow pump from Exlie Racing when I did the rebuild, I'm still getting oil to the trubo through the fed line, although it's weak. I don't hear any valve tapping or chatter so I *think* the head is getting oil, but of course I'm scared to death to drive it at all. Any thoughts? I'm thinking maybe a block in the sending unit?? ... but I wanted to see what you guys think before I rip into tomorrow night. Oh, and the oil level is fine too, but just to be safe I changed the oil last night and put in fresh synethic, but it didn't fix the problem.

Glad to see this thread is so popular :)

I brainstormed with my boys tonight and I've got everything from blown ring, clogged sump, some internal engine problem, doing a compression check to having and oil analysis done. I guess I'll tackle these one at a time and let you know what I find. Hopefully it's something dumb, small, and cheap.

The first thing that I would look at would be the oil pressure gauge. I keep a cheap mechanical oil pressure gauge around for testing.

Hook up another oil guage and see what it says. If it reads low then you know it is in the engine for sure. Also sometimes with high volume oil pumps if the pickup tube is right on the bottom of the pan it will starve the pump for oil.

Yeah, but the oil pressure was fine for a while, and suddenly dropped. Still not a bad idea to make sure you have adaquate clearance between the pickup and the bottom of the pan. I'd check the obvious first, drop the oil pan and look at the pick up screen and see if by chance anything got in there.

Brian

Yeah, I mean that's exactly the thing ... I got about 1000 miles on my car since my rebuild and it's been fine the whole time, great oil pressure. Then Wednesday happened. I'm going to check the oil sending unit, guage, turbo feed/return line ... and if I have to, drop the oil pan tonight. Start with the simple things.

My biggest concern at this point is that when I changed my oil on Wed. after this happened it looked really "milky." It def. wasn't water b/c it wasn't beaded up. It almost looked metallic - which would be really bad .... My engine "taps" a little bit when it runs, (kinda sounds like a desiel) but I've always been told that was "piston slap" from the forged internals so I've never been concerned about it. With this oil pressure problem though I'm wondering if something was hitting or grinding or something like that and just finally broke. I'm real nervous about this guys .... :scratch

oil pressure dropping could mean you have excessive clearance problems on the main or rod bearings, who built your engine?

edit: 1000 miles on the motor and you have synthetic in it? get that crap put of there!

your ticking diesel sound is piston slap, most forged internals will sound like that until they fully expand from my understanding. you also shouldnt be using synthetic yet during a break in like turby said.

I'm not running full synethic ... I'm running the Q-State synthetic blend.

Short block was built by a performance shop in NJ. I did all other work myself.

After working on it all night tonight, I think it's the gauge. I have a mechanical oil pressure gauge. Everytime I try to *just* tighten in down it leaks, when I tighten it good the pressure fitting krimps the nylon line - I think that's why my readings are low. I can't be 100% sure, but I'm hoping it's that and not the engine.

I was looking on Summit tonight at electrical oil pressure guages and I did some searching on here about them, but I didn't find much. How exactly do they work? Sounds like there is some sort of unit that installs at the oil sending unit and then electrically reads the pressure?

Originally posted by techboy
I was looking on Summit tonight at electrical oil pressure guages and I did some searching on here about them, but I didn't find much. How exactly do they work? Sounds like there is some sort of unit that installs at the oil sending unit and then electrically reads the pressure?

exactly, just like a electronic fuel pressure gauge or something...it goes into a sending unit that reads pressure and sends a voltage signal to the gauge in the cab

i bet its your gauge too man, dont worry about your engine im sure its ok

Turbo8u - I hope your right, I ordered the new gauge already ... the only thing that makes me a skeptic was look of my oil. I'm going to take my OP gauge out this weekend and put the idiot light back on and start er up and see what happens. Anybody know how low your oil pressure has to be to trip the idiot light? I figure that should tell me for sure whether it's the guage or the car.

I'm concerned about the condition of the oil too man. How does the coolant look? You burning any oil? Is it possible the head gasket blew and some of the oil pressure was relieved by either finding a way into the coolant or going into the combustion chamber?

I hate to be the cynic, I sure hope it's just the gauge, but the gauge really doesn't explain the "milky" condition of the oil :(

Brian

Oil pressure light usually comes on between 7 to 8psi. The condition of your oil has caught my eye. If indeed it has a metallic greyish look to it sounds like either bearings or even possibly the bore size wasn't taken into account for forged internals. example: .020 over cast pistons can have a tighter tolerance than the same .020 forged piston because the cast dosen't expand as much as the forged one. After you changed the oil and ran it how does the oil look now? Did you plastigauge the mains and rods before you did your final assembly?

Originally posted by techboy
Turbo8u - I hope your right, I ordered the new gauge already ... the only thing that makes me a skeptic was look of my oil. I'm going to take my OP gauge out this weekend and put the idiot light back on and start er up and see what happens. Anybody know how low your oil pressure has to be to trip the idiot light? I figure that should tell me for sure whether it's the guage or the car.

less than 5psi at idle will usually trip the light.

15psi hot idle is within factory spec. mine was lower than that for a long, long time.

Thanks, that's good info. Luckily, I know a guy who works at an airport and get me an oil anlysis for about 15 bucks. The have some fancy computer database that can give a complete read out of all impurities, metal shavings, and grim that's in your oil. So, I'm taking my last batch over there to have it looked at. I'll post up if I find anything out.

I haven't had my oil anlysis done yet, I don't see that guy until Tuesday .... but I do have a MUCH larger problem than the gauge. I disconnected the gauge today and hooked my idiot light back up ... and guess what - it came on in the dash. So, whatever is wrong is wrong with the motor and I have a feeling it's not going to be cheap. I can't even begin to fathom what could have happened. I guess this coming week I'll drop the pan and check the sump and do a compression test on each cylinder ... but I have a funny feeling my car is going to up for sale soon - I can't deal with all this downtime anymore, it's been close to 2 years.